1.. SPDX-License-Identifier: GPL-2.0 2 3==================== 4The /proc Filesystem 5==================== 6 7===================== ======================================= ================ 8/proc/sys Terrehon Bowden <terrehon@pacbell.net>, October 7 1999 9 Bodo Bauer <bb@ricochet.net> 102.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 11move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 12fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 13===================== ======================================= ================ 14 15 16 17.. Table of Contents 18 19 0 Preface 20 0.1 Introduction/Credits 21 0.2 Legal Stuff 22 23 1 Collecting System Information 24 1.1 Process-Specific Subdirectories 25 1.2 Kernel data 26 1.3 IDE devices in /proc/ide 27 1.4 Networking info in /proc/net 28 1.5 SCSI info 29 1.6 Parallel port info in /proc/parport 30 1.7 TTY info in /proc/tty 31 1.8 Miscellaneous kernel statistics in /proc/stat 32 1.9 Ext4 file system parameters 33 34 2 Modifying System Parameters 35 36 3 Per-Process Parameters 37 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer 38 score 39 3.2 /proc/<pid>/oom_score - Display current oom-killer score 40 3.3 /proc/<pid>/io - Display the IO accounting fields 41 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 42 3.5 /proc/<pid>/mountinfo - Information about mounts 43 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 44 3.7 /proc/<pid>/task/<tid>/children - Information about task children 45 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 46 3.9 /proc/<pid>/map_files - Information about memory mapped files 47 3.10 /proc/<pid>/timerslack_ns - Task timerslack value 48 3.11 /proc/<pid>/patch_state - Livepatch patch operation state 49 3.12 /proc/<pid>/arch_status - Task architecture specific information 50 51 4 Configuring procfs 52 4.1 Mount options 53 54 5 Filesystem behavior 55 56Preface 57======= 58 590.1 Introduction/Credits 60------------------------ 61 62This documentation is part of a soon (or so we hope) to be released book on 63the SuSE Linux distribution. As there is no complete documentation for the 64/proc file system and we've used many freely available sources to write these 65chapters, it seems only fair to give the work back to the Linux community. 66This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 67afraid it's still far from complete, but we hope it will be useful. As far as 68we know, it is the first 'all-in-one' document about the /proc file system. It 69is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 70SPARC, AXP, etc., features, you probably won't find what you are looking for. 71It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 72additions and patches are welcome and will be added to this document if you 73mail them to Bodo. 74 75We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 76other people for help compiling this documentation. We'd also like to extend a 77special thank you to Andi Kleen for documentation, which we relied on heavily 78to create this document, as well as the additional information he provided. 79Thanks to everybody else who contributed source or docs to the Linux kernel 80and helped create a great piece of software... :) 81 82If you have any comments, corrections or additions, please don't hesitate to 83contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 84document. 85 86The latest version of this document is available online at 87http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 88 89If the above direction does not works for you, you could try the kernel 90mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 91comandante@zaralinux.com. 92 930.2 Legal Stuff 94--------------- 95 96We don't guarantee the correctness of this document, and if you come to us 97complaining about how you screwed up your system because of incorrect 98documentation, we won't feel responsible... 99 100Chapter 1: Collecting System Information 101======================================== 102 103In This Chapter 104--------------- 105* Investigating the properties of the pseudo file system /proc and its 106 ability to provide information on the running Linux system 107* Examining /proc's structure 108* Uncovering various information about the kernel and the processes running 109 on the system 110 111------------------------------------------------------------------------------ 112 113The proc file system acts as an interface to internal data structures in the 114kernel. It can be used to obtain information about the system and to change 115certain kernel parameters at runtime (sysctl). 116 117First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 118show you how you can use /proc/sys to change settings. 119 1201.1 Process-Specific Subdirectories 121----------------------------------- 122 123The directory /proc contains (among other things) one subdirectory for each 124process running on the system, which is named after the process ID (PID). 125 126The link 'self' points to the process reading the file system. Each process 127subdirectory has the entries listed in Table 1-1. 128 129Note that an open file descriptor to /proc/<pid> or to any of its 130contained files or subdirectories does not prevent <pid> being reused 131for some other process in the event that <pid> exits. Operations on 132open /proc/<pid> file descriptors corresponding to dead processes 133never act on any new process that the kernel may, through chance, have 134also assigned the process ID <pid>. Instead, operations on these FDs 135usually fail with ESRCH. 136 137.. table:: Table 1-1: Process specific entries in /proc 138 139 ============= =============================================================== 140 File Content 141 ============= =============================================================== 142 clear_refs Clears page referenced bits shown in smaps output 143 cmdline Command line arguments 144 cpu Current and last cpu in which it was executed (2.4)(smp) 145 cwd Link to the current working directory 146 environ Values of environment variables 147 exe Link to the executable of this process 148 fd Directory, which contains all file descriptors 149 maps Memory maps to executables and library files (2.4) 150 mem Memory held by this process 151 root Link to the root directory of this process 152 stat Process status 153 statm Process memory status information 154 status Process status in human readable form 155 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function 156 symbol the task is blocked in - or "0" if not blocked. 157 pagemap Page table 158 stack Report full stack trace, enable via CONFIG_STACKTRACE 159 smaps An extension based on maps, showing the memory consumption of 160 each mapping and flags associated with it 161 smaps_rollup Accumulated smaps stats for all mappings of the process. This 162 can be derived from smaps, but is faster and more convenient 163 numa_maps An extension based on maps, showing the memory locality and 164 binding policy as well as mem usage (in pages) of each mapping. 165 ============= =============================================================== 166 167For example, to get the status information of a process, all you have to do is 168read the file /proc/PID/status:: 169 170 >cat /proc/self/status 171 Name: cat 172 State: R (running) 173 Tgid: 5452 174 Pid: 5452 175 PPid: 743 176 TracerPid: 0 (2.4) 177 Uid: 501 501 501 501 178 Gid: 100 100 100 100 179 FDSize: 256 180 Groups: 100 14 16 181 VmPeak: 5004 kB 182 VmSize: 5004 kB 183 VmLck: 0 kB 184 VmHWM: 476 kB 185 VmRSS: 476 kB 186 RssAnon: 352 kB 187 RssFile: 120 kB 188 RssShmem: 4 kB 189 VmData: 156 kB 190 VmStk: 88 kB 191 VmExe: 68 kB 192 VmLib: 1412 kB 193 VmPTE: 20 kb 194 VmSwap: 0 kB 195 HugetlbPages: 0 kB 196 CoreDumping: 0 197 THP_enabled: 1 198 Threads: 1 199 SigQ: 0/28578 200 SigPnd: 0000000000000000 201 ShdPnd: 0000000000000000 202 SigBlk: 0000000000000000 203 SigIgn: 0000000000000000 204 SigCgt: 0000000000000000 205 CapInh: 00000000fffffeff 206 CapPrm: 0000000000000000 207 CapEff: 0000000000000000 208 CapBnd: ffffffffffffffff 209 CapAmb: 0000000000000000 210 NoNewPrivs: 0 211 Seccomp: 0 212 Speculation_Store_Bypass: thread vulnerable 213 SpeculationIndirectBranch: conditional enabled 214 voluntary_ctxt_switches: 0 215 nonvoluntary_ctxt_switches: 1 216 217This shows you nearly the same information you would get if you viewed it with 218the ps command. In fact, ps uses the proc file system to obtain its 219information. But you get a more detailed view of the process by reading the 220file /proc/PID/status. It fields are described in table 1-2. 221 222The statm file contains more detailed information about the process 223memory usage. Its seven fields are explained in Table 1-3. The stat file 224contains detailed information about the process itself. Its fields are 225explained in Table 1-4. 226 227(for SMP CONFIG users) 228 229For making accounting scalable, RSS related information are handled in an 230asynchronous manner and the value may not be very precise. To see a precise 231snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 232It's slow but very precise. 233 234.. table:: Table 1-2: Contents of the status files (as of 4.19) 235 236 ========================== =================================================== 237 Field Content 238 ========================== =================================================== 239 Name filename of the executable 240 Umask file mode creation mask 241 State state (R is running, S is sleeping, D is sleeping 242 in an uninterruptible wait, Z is zombie, 243 T is traced or stopped) 244 Tgid thread group ID 245 Ngid NUMA group ID (0 if none) 246 Pid process id 247 PPid process id of the parent process 248 TracerPid PID of process tracing this process (0 if not) 249 Uid Real, effective, saved set, and file system UIDs 250 Gid Real, effective, saved set, and file system GIDs 251 FDSize number of file descriptor slots currently allocated 252 Groups supplementary group list 253 NStgid descendant namespace thread group ID hierarchy 254 NSpid descendant namespace process ID hierarchy 255 NSpgid descendant namespace process group ID hierarchy 256 NSsid descendant namespace session ID hierarchy 257 VmPeak peak virtual memory size 258 VmSize total program size 259 VmLck locked memory size 260 VmPin pinned memory size 261 VmHWM peak resident set size ("high water mark") 262 VmRSS size of memory portions. It contains the three 263 following parts 264 (VmRSS = RssAnon + RssFile + RssShmem) 265 RssAnon size of resident anonymous memory 266 RssFile size of resident file mappings 267 RssShmem size of resident shmem memory (includes SysV shm, 268 mapping of tmpfs and shared anonymous mappings) 269 VmData size of private data segments 270 VmStk size of stack segments 271 VmExe size of text segment 272 VmLib size of shared library code 273 VmPTE size of page table entries 274 VmSwap amount of swap used by anonymous private data 275 (shmem swap usage is not included) 276 HugetlbPages size of hugetlb memory portions 277 CoreDumping process's memory is currently being dumped 278 (killing the process may lead to a corrupted core) 279 THP_enabled process is allowed to use THP (returns 0 when 280 PR_SET_THP_DISABLE is set on the process 281 Threads number of threads 282 SigQ number of signals queued/max. number for queue 283 SigPnd bitmap of pending signals for the thread 284 ShdPnd bitmap of shared pending signals for the process 285 SigBlk bitmap of blocked signals 286 SigIgn bitmap of ignored signals 287 SigCgt bitmap of caught signals 288 CapInh bitmap of inheritable capabilities 289 CapPrm bitmap of permitted capabilities 290 CapEff bitmap of effective capabilities 291 CapBnd bitmap of capabilities bounding set 292 CapAmb bitmap of ambient capabilities 293 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...) 294 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) 295 Speculation_Store_Bypass speculative store bypass mitigation status 296 SpeculationIndirectBranch indirect branch speculation mode 297 Cpus_allowed mask of CPUs on which this process may run 298 Cpus_allowed_list Same as previous, but in "list format" 299 Mems_allowed mask of memory nodes allowed to this process 300 Mems_allowed_list Same as previous, but in "list format" 301 voluntary_ctxt_switches number of voluntary context switches 302 nonvoluntary_ctxt_switches number of non voluntary context switches 303 ========================== =================================================== 304 305 306.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 307 308 ======== =============================== ============================== 309 Field Content 310 ======== =============================== ============================== 311 size total program size (pages) (same as VmSize in status) 312 resident size of memory portions (pages) (same as VmRSS in status) 313 shared number of pages that are shared (i.e. backed by a file, same 314 as RssFile+RssShmem in status) 315 trs number of pages that are 'code' (not including libs; broken, 316 includes data segment) 317 lrs number of pages of library (always 0 on 2.6) 318 drs number of pages of data/stack (including libs; broken, 319 includes library text) 320 dt number of dirty pages (always 0 on 2.6) 321 ======== =============================== ============================== 322 323 324.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 325 326 ============= =============================================================== 327 Field Content 328 ============= =============================================================== 329 pid process id 330 tcomm filename of the executable 331 state state (R is running, S is sleeping, D is sleeping in an 332 uninterruptible wait, Z is zombie, T is traced or stopped) 333 ppid process id of the parent process 334 pgrp pgrp of the process 335 sid session id 336 tty_nr tty the process uses 337 tty_pgrp pgrp of the tty 338 flags task flags 339 min_flt number of minor faults 340 cmin_flt number of minor faults with child's 341 maj_flt number of major faults 342 cmaj_flt number of major faults with child's 343 utime user mode jiffies 344 stime kernel mode jiffies 345 cutime user mode jiffies with child's 346 cstime kernel mode jiffies with child's 347 priority priority level 348 nice nice level 349 num_threads number of threads 350 it_real_value (obsolete, always 0) 351 start_time time the process started after system boot 352 vsize virtual memory size 353 rss resident set memory size 354 rsslim current limit in bytes on the rss 355 start_code address above which program text can run 356 end_code address below which program text can run 357 start_stack address of the start of the main process stack 358 esp current value of ESP 359 eip current value of EIP 360 pending bitmap of pending signals 361 blocked bitmap of blocked signals 362 sigign bitmap of ignored signals 363 sigcatch bitmap of caught signals 364 0 (place holder, used to be the wchan address, 365 use /proc/PID/wchan instead) 366 0 (place holder) 367 0 (place holder) 368 exit_signal signal to send to parent thread on exit 369 task_cpu which CPU the task is scheduled on 370 rt_priority realtime priority 371 policy scheduling policy (man sched_setscheduler) 372 blkio_ticks time spent waiting for block IO 373 gtime guest time of the task in jiffies 374 cgtime guest time of the task children in jiffies 375 start_data address above which program data+bss is placed 376 end_data address below which program data+bss is placed 377 start_brk address above which program heap can be expanded with brk() 378 arg_start address above which program command line is placed 379 arg_end address below which program command line is placed 380 env_start address above which program environment is placed 381 env_end address below which program environment is placed 382 exit_code the thread's exit_code in the form reported by the waitpid 383 system call 384 ============= =============================================================== 385 386The /proc/PID/maps file contains the currently mapped memory regions and 387their access permissions. 388 389The format is:: 390 391 address perms offset dev inode pathname 392 393 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test 394 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 395 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] 396 a7cb1000-a7cb2000 ---p 00000000 00:00 0 397 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 398 a7eb2000-a7eb3000 ---p 00000000 00:00 0 399 a7eb3000-a7ed5000 rw-p 00000000 00:00 0 400 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 401 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 402 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 403 a800b000-a800e000 rw-p 00000000 00:00 0 404 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 405 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 406 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 407 a8024000-a8027000 rw-p 00000000 00:00 0 408 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 409 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 410 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 411 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 412 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 413 414where "address" is the address space in the process that it occupies, "perms" 415is a set of permissions:: 416 417 r = read 418 w = write 419 x = execute 420 s = shared 421 p = private (copy on write) 422 423"offset" is the offset into the mapping, "dev" is the device (major:minor), and 424"inode" is the inode on that device. 0 indicates that no inode is associated 425with the memory region, as the case would be with BSS (uninitialized data). 426The "pathname" shows the name associated file for this mapping. If the mapping 427is not associated with a file: 428 429 ======= ==================================== 430 [heap] the heap of the program 431 [stack] the stack of the main process 432 [vdso] the "virtual dynamic shared object", 433 the kernel system call handler 434 ======= ==================================== 435 436 or if empty, the mapping is anonymous. 437 438The /proc/PID/smaps is an extension based on maps, showing the memory 439consumption for each of the process's mappings. For each mapping (aka Virtual 440Memory Area, or VMA) there is a series of lines such as the following:: 441 442 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 443 444 Size: 1084 kB 445 KernelPageSize: 4 kB 446 MMUPageSize: 4 kB 447 Rss: 892 kB 448 Pss: 374 kB 449 Shared_Clean: 892 kB 450 Shared_Dirty: 0 kB 451 Private_Clean: 0 kB 452 Private_Dirty: 0 kB 453 Referenced: 892 kB 454 Anonymous: 0 kB 455 LazyFree: 0 kB 456 AnonHugePages: 0 kB 457 ShmemPmdMapped: 0 kB 458 Shared_Hugetlb: 0 kB 459 Private_Hugetlb: 0 kB 460 Swap: 0 kB 461 SwapPss: 0 kB 462 KernelPageSize: 4 kB 463 MMUPageSize: 4 kB 464 Locked: 0 kB 465 THPeligible: 0 466 VmFlags: rd ex mr mw me dw 467 468The first of these lines shows the same information as is displayed for the 469mapping in /proc/PID/maps. Following lines show the size of the mapping 470(size); the size of each page allocated when backing a VMA (KernelPageSize), 471which is usually the same as the size in the page table entries; the page size 472used by the MMU when backing a VMA (in most cases, the same as KernelPageSize); 473the amount of the mapping that is currently resident in RAM (RSS); the 474process' proportional share of this mapping (PSS); and the number of clean and 475dirty shared and private pages in the mapping. 476 477The "proportional set size" (PSS) of a process is the count of pages it has 478in memory, where each page is divided by the number of processes sharing it. 479So if a process has 1000 pages all to itself, and 1000 shared with one other 480process, its PSS will be 1500. 481 482Note that even a page which is part of a MAP_SHARED mapping, but has only 483a single pte mapped, i.e. is currently used by only one process, is accounted 484as private and not as shared. 485 486"Referenced" indicates the amount of memory currently marked as referenced or 487accessed. 488 489"Anonymous" shows the amount of memory that does not belong to any file. Even 490a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 491and a page is modified, the file page is replaced by a private anonymous copy. 492 493"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE). 494The memory isn't freed immediately with madvise(). It's freed in memory 495pressure if the memory is clean. Please note that the printed value might 496be lower than the real value due to optimizations used in the current 497implementation. If this is not desirable please file a bug report. 498 499"AnonHugePages" shows the ammount of memory backed by transparent hugepage. 500 501"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by 502huge pages. 503 504"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by 505hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical 506reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field. 507 508"Swap" shows how much would-be-anonymous memory is also used, but out on swap. 509 510For shmem mappings, "Swap" includes also the size of the mapped (and not 511replaced by copy-on-write) part of the underlying shmem object out on swap. 512"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this 513does not take into account swapped out page of underlying shmem objects. 514"Locked" indicates whether the mapping is locked in memory or not. 515"THPeligible" indicates whether the mapping is eligible for allocating THP 516pages - 1 if true, 0 otherwise. It just shows the current status. 517 518"VmFlags" field deserves a separate description. This member represents the 519kernel flags associated with the particular virtual memory area in two letter 520encoded manner. The codes are the following: 521 522 == ======================================= 523 rd readable 524 wr writeable 525 ex executable 526 sh shared 527 mr may read 528 mw may write 529 me may execute 530 ms may share 531 gd stack segment growns down 532 pf pure PFN range 533 dw disabled write to the mapped file 534 lo pages are locked in memory 535 io memory mapped I/O area 536 sr sequential read advise provided 537 rr random read advise provided 538 dc do not copy area on fork 539 de do not expand area on remapping 540 ac area is accountable 541 nr swap space is not reserved for the area 542 ht area uses huge tlb pages 543 ar architecture specific flag 544 dd do not include area into core dump 545 sd soft dirty flag 546 mm mixed map area 547 hg huge page advise flag 548 nh no huge page advise flag 549 mg mergable advise flag 550 bt arm64 BTI guarded page 551 mt arm64 MTE allocation tags are enabled 552 == ======================================= 553 554Note that there is no guarantee that every flag and associated mnemonic will 555be present in all further kernel releases. Things get changed, the flags may 556be vanished or the reverse -- new added. Interpretation of their meaning 557might change in future as well. So each consumer of these flags has to 558follow each specific kernel version for the exact semantic. 559 560This file is only present if the CONFIG_MMU kernel configuration option is 561enabled. 562 563Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent 564output can be achieved only in the single read call). 565 566This typically manifests when doing partial reads of these files while the 567memory map is being modified. Despite the races, we do provide the following 568guarantees: 569 5701) The mapped addresses never go backwards, which implies no two 571 regions will ever overlap. 5722) If there is something at a given vaddr during the entirety of the 573 life of the smaps/maps walk, there will be some output for it. 574 575The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps, 576but their values are the sums of the corresponding values for all mappings of 577the process. Additionally, it contains these fields: 578 579- Pss_Anon 580- Pss_File 581- Pss_Shmem 582 583They represent the proportional shares of anonymous, file, and shmem pages, as 584described for smaps above. These fields are omitted in smaps since each 585mapping identifies the type (anon, file, or shmem) of all pages it contains. 586Thus all information in smaps_rollup can be derived from smaps, but at a 587significantly higher cost. 588 589The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 590bits on both physical and virtual pages associated with a process, and the 591soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst 592for details). 593To clear the bits for all the pages associated with the process:: 594 595 > echo 1 > /proc/PID/clear_refs 596 597To clear the bits for the anonymous pages associated with the process:: 598 599 > echo 2 > /proc/PID/clear_refs 600 601To clear the bits for the file mapped pages associated with the process:: 602 603 > echo 3 > /proc/PID/clear_refs 604 605To clear the soft-dirty bit:: 606 607 > echo 4 > /proc/PID/clear_refs 608 609To reset the peak resident set size ("high water mark") to the process's 610current value:: 611 612 > echo 5 > /proc/PID/clear_refs 613 614Any other value written to /proc/PID/clear_refs will have no effect. 615 616The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 617using /proc/kpageflags and number of times a page is mapped using 618/proc/kpagecount. For detailed explanation, see 619Documentation/admin-guide/mm/pagemap.rst. 620 621The /proc/pid/numa_maps is an extension based on maps, showing the memory 622locality and binding policy, as well as the memory usage (in pages) of 623each mapping. The output follows a general format where mapping details get 624summarized separated by blank spaces, one mapping per each file line:: 625 626 address policy mapping details 627 628 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 629 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 630 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 631 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 632 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 633 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 634 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 635 320698b000 default file=/lib64/libc-2.12.so 636 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 637 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 638 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 639 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 640 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 641 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 642 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 643 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 644 645Where: 646 647"address" is the starting address for the mapping; 648 649"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst); 650 651"mapping details" summarizes mapping data such as mapping type, page usage counters, 652node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page 653size, in KB, that is backing the mapping up. 654 6551.2 Kernel data 656--------------- 657 658Similar to the process entries, the kernel data files give information about 659the running kernel. The files used to obtain this information are contained in 660/proc and are listed in Table 1-5. Not all of these will be present in your 661system. It depends on the kernel configuration and the loaded modules, which 662files are there, and which are missing. 663 664.. table:: Table 1-5: Kernel info in /proc 665 666 ============ =============================================================== 667 File Content 668 ============ =============================================================== 669 apm Advanced power management info 670 buddyinfo Kernel memory allocator information (see text) (2.5) 671 bus Directory containing bus specific information 672 cmdline Kernel command line 673 cpuinfo Info about the CPU 674 devices Available devices (block and character) 675 dma Used DMS channels 676 filesystems Supported filesystems 677 driver Various drivers grouped here, currently rtc (2.4) 678 execdomains Execdomains, related to security (2.4) 679 fb Frame Buffer devices (2.4) 680 fs File system parameters, currently nfs/exports (2.4) 681 ide Directory containing info about the IDE subsystem 682 interrupts Interrupt usage 683 iomem Memory map (2.4) 684 ioports I/O port usage 685 irq Masks for irq to cpu affinity (2.4)(smp?) 686 isapnp ISA PnP (Plug&Play) Info (2.4) 687 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 688 kmsg Kernel messages 689 ksyms Kernel symbol table 690 loadavg Load average of last 1, 5 & 15 minutes 691 locks Kernel locks 692 meminfo Memory info 693 misc Miscellaneous 694 modules List of loaded modules 695 mounts Mounted filesystems 696 net Networking info (see text) 697 pagetypeinfo Additional page allocator information (see text) (2.5) 698 partitions Table of partitions known to the system 699 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 700 decoupled by lspci (2.4) 701 rtc Real time clock 702 scsi SCSI info (see text) 703 slabinfo Slab pool info 704 softirqs softirq usage 705 stat Overall statistics 706 swaps Swap space utilization 707 sys See chapter 2 708 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 709 tty Info of tty drivers 710 uptime Wall clock since boot, combined idle time of all cpus 711 version Kernel version 712 video bttv info of video resources (2.4) 713 vmallocinfo Show vmalloced areas 714 ============ =============================================================== 715 716You can, for example, check which interrupts are currently in use and what 717they are used for by looking in the file /proc/interrupts:: 718 719 > cat /proc/interrupts 720 CPU0 721 0: 8728810 XT-PIC timer 722 1: 895 XT-PIC keyboard 723 2: 0 XT-PIC cascade 724 3: 531695 XT-PIC aha152x 725 4: 2014133 XT-PIC serial 726 5: 44401 XT-PIC pcnet_cs 727 8: 2 XT-PIC rtc 728 11: 8 XT-PIC i82365 729 12: 182918 XT-PIC PS/2 Mouse 730 13: 1 XT-PIC fpu 731 14: 1232265 XT-PIC ide0 732 15: 7 XT-PIC ide1 733 NMI: 0 734 735In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 736output of a SMP machine):: 737 738 > cat /proc/interrupts 739 740 CPU0 CPU1 741 0: 1243498 1214548 IO-APIC-edge timer 742 1: 8949 8958 IO-APIC-edge keyboard 743 2: 0 0 XT-PIC cascade 744 5: 11286 10161 IO-APIC-edge soundblaster 745 8: 1 0 IO-APIC-edge rtc 746 9: 27422 27407 IO-APIC-edge 3c503 747 12: 113645 113873 IO-APIC-edge PS/2 Mouse 748 13: 0 0 XT-PIC fpu 749 14: 22491 24012 IO-APIC-edge ide0 750 15: 2183 2415 IO-APIC-edge ide1 751 17: 30564 30414 IO-APIC-level eth0 752 18: 177 164 IO-APIC-level bttv 753 NMI: 2457961 2457959 754 LOC: 2457882 2457881 755 ERR: 2155 756 757NMI is incremented in this case because every timer interrupt generates a NMI 758(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 759 760LOC is the local interrupt counter of the internal APIC of every CPU. 761 762ERR is incremented in the case of errors in the IO-APIC bus (the bus that 763connects the CPUs in a SMP system. This means that an error has been detected, 764the IO-APIC automatically retry the transmission, so it should not be a big 765problem, but you should read the SMP-FAQ. 766 767In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 768/proc/interrupts to display every IRQ vector in use by the system, not 769just those considered 'most important'. The new vectors are: 770 771THR 772 interrupt raised when a machine check threshold counter 773 (typically counting ECC corrected errors of memory or cache) exceeds 774 a configurable threshold. Only available on some systems. 775 776TRM 777 a thermal event interrupt occurs when a temperature threshold 778 has been exceeded for the CPU. This interrupt may also be generated 779 when the temperature drops back to normal. 780 781SPU 782 a spurious interrupt is some interrupt that was raised then lowered 783 by some IO device before it could be fully processed by the APIC. Hence 784 the APIC sees the interrupt but does not know what device it came from. 785 For this case the APIC will generate the interrupt with a IRQ vector 786 of 0xff. This might also be generated by chipset bugs. 787 788RES, CAL, TLB 789 rescheduling, call and TLB flush interrupts are 790 sent from one CPU to another per the needs of the OS. Typically, 791 their statistics are used by kernel developers and interested users to 792 determine the occurrence of interrupts of the given type. 793 794The above IRQ vectors are displayed only when relevant. For example, 795the threshold vector does not exist on x86_64 platforms. Others are 796suppressed when the system is a uniprocessor. As of this writing, only 797i386 and x86_64 platforms support the new IRQ vector displays. 798 799Of some interest is the introduction of the /proc/irq directory to 2.4. 800It could be used to set IRQ to CPU affinity. This means that you can "hook" an 801IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 802irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 803prof_cpu_mask. 804 805For example:: 806 807 > ls /proc/irq/ 808 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 809 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 810 > ls /proc/irq/0/ 811 smp_affinity 812 813smp_affinity is a bitmask, in which you can specify which CPUs can handle the 814IRQ. You can set it by doing:: 815 816 > echo 1 > /proc/irq/10/smp_affinity 817 818This means that only the first CPU will handle the IRQ, but you can also echo 8195 which means that only the first and third CPU can handle the IRQ. 820 821The contents of each smp_affinity file is the same by default:: 822 823 > cat /proc/irq/0/smp_affinity 824 ffffffff 825 826There is an alternate interface, smp_affinity_list which allows specifying 827a CPU range instead of a bitmask:: 828 829 > cat /proc/irq/0/smp_affinity_list 830 1024-1031 831 832The default_smp_affinity mask applies to all non-active IRQs, which are the 833IRQs which have not yet been allocated/activated, and hence which lack a 834/proc/irq/[0-9]* directory. 835 836The node file on an SMP system shows the node to which the device using the IRQ 837reports itself as being attached. This hardware locality information does not 838include information about any possible driver locality preference. 839 840prof_cpu_mask specifies which CPUs are to be profiled by the system wide 841profiler. Default value is ffffffff (all CPUs if there are only 32 of them). 842 843The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 844between all the CPUs which are allowed to handle it. As usual the kernel has 845more info than you and does a better job than you, so the defaults are the 846best choice for almost everyone. [Note this applies only to those IO-APIC's 847that support "Round Robin" interrupt distribution.] 848 849There are three more important subdirectories in /proc: net, scsi, and sys. 850The general rule is that the contents, or even the existence of these 851directories, depend on your kernel configuration. If SCSI is not enabled, the 852directory scsi may not exist. The same is true with the net, which is there 853only when networking support is present in the running kernel. 854 855The slabinfo file gives information about memory usage at the slab level. 856Linux uses slab pools for memory management above page level in version 2.2. 857Commonly used objects have their own slab pool (such as network buffers, 858directory cache, and so on). 859 860:: 861 862 > cat /proc/buddyinfo 863 864 Node 0, zone DMA 0 4 5 4 4 3 ... 865 Node 0, zone Normal 1 0 0 1 101 8 ... 866 Node 0, zone HighMem 2 0 0 1 1 0 ... 867 868External fragmentation is a problem under some workloads, and buddyinfo is a 869useful tool for helping diagnose these problems. Buddyinfo will give you a 870clue as to how big an area you can safely allocate, or why a previous 871allocation failed. 872 873Each column represents the number of pages of a certain order which are 874available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 875ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 876available in ZONE_NORMAL, etc... 877 878More information relevant to external fragmentation can be found in 879pagetypeinfo:: 880 881 > cat /proc/pagetypeinfo 882 Page block order: 9 883 Pages per block: 512 884 885 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 886 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 887 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 888 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 889 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 890 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 891 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 892 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 893 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 894 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 895 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 896 897 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 898 Node 0, zone DMA 2 0 5 1 0 899 Node 0, zone DMA32 41 6 967 2 0 900 901Fragmentation avoidance in the kernel works by grouping pages of different 902migrate types into the same contiguous regions of memory called page blocks. 903A page block is typically the size of the default hugepage size, e.g. 2MB on 904X86-64. By keeping pages grouped based on their ability to move, the kernel 905can reclaim pages within a page block to satisfy a high-order allocation. 906 907The pagetypinfo begins with information on the size of a page block. It 908then gives the same type of information as buddyinfo except broken down 909by migrate-type and finishes with details on how many page blocks of each 910type exist. 911 912If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 913from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can 914make an estimate of the likely number of huge pages that can be allocated 915at a given point in time. All the "Movable" blocks should be allocatable 916unless memory has been mlock()'d. Some of the Reclaimable blocks should 917also be allocatable although a lot of filesystem metadata may have to be 918reclaimed to achieve this. 919 920 921meminfo 922~~~~~~~ 923 924Provides information about distribution and utilization of memory. This 925varies by architecture and compile options. The following is from a 92616GB PIII, which has highmem enabled. You may not have all of these fields. 927 928:: 929 930 > cat /proc/meminfo 931 932 MemTotal: 16344972 kB 933 MemFree: 13634064 kB 934 MemAvailable: 14836172 kB 935 Buffers: 3656 kB 936 Cached: 1195708 kB 937 SwapCached: 0 kB 938 Active: 891636 kB 939 Inactive: 1077224 kB 940 HighTotal: 15597528 kB 941 HighFree: 13629632 kB 942 LowTotal: 747444 kB 943 LowFree: 4432 kB 944 SwapTotal: 0 kB 945 SwapFree: 0 kB 946 Dirty: 968 kB 947 Writeback: 0 kB 948 AnonPages: 861800 kB 949 Mapped: 280372 kB 950 Shmem: 644 kB 951 KReclaimable: 168048 kB 952 Slab: 284364 kB 953 SReclaimable: 159856 kB 954 SUnreclaim: 124508 kB 955 PageTables: 24448 kB 956 NFS_Unstable: 0 kB 957 Bounce: 0 kB 958 WritebackTmp: 0 kB 959 CommitLimit: 7669796 kB 960 Committed_AS: 100056 kB 961 VmallocTotal: 112216 kB 962 VmallocUsed: 428 kB 963 VmallocChunk: 111088 kB 964 Percpu: 62080 kB 965 HardwareCorrupted: 0 kB 966 AnonHugePages: 49152 kB 967 ShmemHugePages: 0 kB 968 ShmemPmdMapped: 0 kB 969 970MemTotal 971 Total usable RAM (i.e. physical RAM minus a few reserved 972 bits and the kernel binary code) 973MemFree 974 The sum of LowFree+HighFree 975MemAvailable 976 An estimate of how much memory is available for starting new 977 applications, without swapping. Calculated from MemFree, 978 SReclaimable, the size of the file LRU lists, and the low 979 watermarks in each zone. 980 The estimate takes into account that the system needs some 981 page cache to function well, and that not all reclaimable 982 slab will be reclaimable, due to items being in use. The 983 impact of those factors will vary from system to system. 984Buffers 985 Relatively temporary storage for raw disk blocks 986 shouldn't get tremendously large (20MB or so) 987Cached 988 in-memory cache for files read from the disk (the 989 pagecache). Doesn't include SwapCached 990SwapCached 991 Memory that once was swapped out, is swapped back in but 992 still also is in the swapfile (if memory is needed it 993 doesn't need to be swapped out AGAIN because it is already 994 in the swapfile. This saves I/O) 995Active 996 Memory that has been used more recently and usually not 997 reclaimed unless absolutely necessary. 998Inactive 999 Memory which has been less recently used. It is more 1000 eligible to be reclaimed for other purposes 1001HighTotal, HighFree 1002 Highmem is all memory above ~860MB of physical memory. 1003 Highmem areas are for use by userspace programs, or 1004 for the pagecache. The kernel must use tricks to access 1005 this memory, making it slower to access than lowmem. 1006LowTotal, LowFree 1007 Lowmem is memory which can be used for everything that 1008 highmem can be used for, but it is also available for the 1009 kernel's use for its own data structures. Among many 1010 other things, it is where everything from the Slab is 1011 allocated. Bad things happen when you're out of lowmem. 1012SwapTotal 1013 total amount of swap space available 1014SwapFree 1015 Memory which has been evicted from RAM, and is temporarily 1016 on the disk 1017Dirty 1018 Memory which is waiting to get written back to the disk 1019Writeback 1020 Memory which is actively being written back to the disk 1021AnonPages 1022 Non-file backed pages mapped into userspace page tables 1023HardwareCorrupted 1024 The amount of RAM/memory in KB, the kernel identifies as 1025 corrupted. 1026AnonHugePages 1027 Non-file backed huge pages mapped into userspace page tables 1028Mapped 1029 files which have been mmaped, such as libraries 1030Shmem 1031 Total memory used by shared memory (shmem) and tmpfs 1032ShmemHugePages 1033 Memory used by shared memory (shmem) and tmpfs allocated 1034 with huge pages 1035ShmemPmdMapped 1036 Shared memory mapped into userspace with huge pages 1037KReclaimable 1038 Kernel allocations that the kernel will attempt to reclaim 1039 under memory pressure. Includes SReclaimable (below), and other 1040 direct allocations with a shrinker. 1041Slab 1042 in-kernel data structures cache 1043SReclaimable 1044 Part of Slab, that might be reclaimed, such as caches 1045SUnreclaim 1046 Part of Slab, that cannot be reclaimed on memory pressure 1047PageTables 1048 amount of memory dedicated to the lowest level of page 1049 tables. 1050NFS_Unstable 1051 Always zero. Previous counted pages which had been written to 1052 the server, but has not been committed to stable storage. 1053Bounce 1054 Memory used for block device "bounce buffers" 1055WritebackTmp 1056 Memory used by FUSE for temporary writeback buffers 1057CommitLimit 1058 Based on the overcommit ratio ('vm.overcommit_ratio'), 1059 this is the total amount of memory currently available to 1060 be allocated on the system. This limit is only adhered to 1061 if strict overcommit accounting is enabled (mode 2 in 1062 'vm.overcommit_memory'). 1063 1064 The CommitLimit is calculated with the following formula:: 1065 1066 CommitLimit = ([total RAM pages] - [total huge TLB pages]) * 1067 overcommit_ratio / 100 + [total swap pages] 1068 1069 For example, on a system with 1G of physical RAM and 7G 1070 of swap with a `vm.overcommit_ratio` of 30 it would 1071 yield a CommitLimit of 7.3G. 1072 1073 For more details, see the memory overcommit documentation 1074 in vm/overcommit-accounting. 1075Committed_AS 1076 The amount of memory presently allocated on the system. 1077 The committed memory is a sum of all of the memory which 1078 has been allocated by processes, even if it has not been 1079 "used" by them as of yet. A process which malloc()'s 1G 1080 of memory, but only touches 300M of it will show up as 1081 using 1G. This 1G is memory which has been "committed" to 1082 by the VM and can be used at any time by the allocating 1083 application. With strict overcommit enabled on the system 1084 (mode 2 in 'vm.overcommit_memory'), allocations which would 1085 exceed the CommitLimit (detailed above) will not be permitted. 1086 This is useful if one needs to guarantee that processes will 1087 not fail due to lack of memory once that memory has been 1088 successfully allocated. 1089VmallocTotal 1090 total size of vmalloc memory area 1091VmallocUsed 1092 amount of vmalloc area which is used 1093VmallocChunk 1094 largest contiguous block of vmalloc area which is free 1095Percpu 1096 Memory allocated to the percpu allocator used to back percpu 1097 allocations. This stat excludes the cost of metadata. 1098 1099vmallocinfo 1100~~~~~~~~~~~ 1101 1102Provides information about vmalloced/vmaped areas. One line per area, 1103containing the virtual address range of the area, size in bytes, 1104caller information of the creator, and optional information depending 1105on the kind of area: 1106 1107 ========== =================================================== 1108 pages=nr number of pages 1109 phys=addr if a physical address was specified 1110 ioremap I/O mapping (ioremap() and friends) 1111 vmalloc vmalloc() area 1112 vmap vmap()ed pages 1113 user VM_USERMAP area 1114 vpages buffer for pages pointers was vmalloced (huge area) 1115 N<node>=nr (Only on NUMA kernels) 1116 Number of pages allocated on memory node <node> 1117 ========== =================================================== 1118 1119:: 1120 1121 > cat /proc/vmallocinfo 1122 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 1123 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 1124 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 1125 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 1126 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 1127 phys=7fee8000 ioremap 1128 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 1129 phys=7fee7000 ioremap 1130 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 1131 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 1132 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 1133 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 1134 pages=2 vmalloc N1=2 1135 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 1136 /0x130 [x_tables] pages=4 vmalloc N0=4 1137 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 1138 pages=14 vmalloc N2=14 1139 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 1140 pages=4 vmalloc N1=4 1141 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 1142 pages=2 vmalloc N1=2 1143 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 1144 pages=10 vmalloc N0=10 1145 1146 1147softirqs 1148~~~~~~~~ 1149 1150Provides counts of softirq handlers serviced since boot time, for each CPU. 1151 1152:: 1153 1154 > cat /proc/softirqs 1155 CPU0 CPU1 CPU2 CPU3 1156 HI: 0 0 0 0 1157 TIMER: 27166 27120 27097 27034 1158 NET_TX: 0 0 0 17 1159 NET_RX: 42 0 0 39 1160 BLOCK: 0 0 107 1121 1161 TASKLET: 0 0 0 290 1162 SCHED: 27035 26983 26971 26746 1163 HRTIMER: 0 0 0 0 1164 RCU: 1678 1769 2178 2250 1165 1166 11671.3 IDE devices in /proc/ide 1168---------------------------- 1169 1170The subdirectory /proc/ide contains information about all IDE devices of which 1171the kernel is aware. There is one subdirectory for each IDE controller, the 1172file drivers and a link for each IDE device, pointing to the device directory 1173in the controller specific subtree. 1174 1175The file 'drivers' contains general information about the drivers used for the 1176IDE devices:: 1177 1178 > cat /proc/ide/drivers 1179 ide-cdrom version 4.53 1180 ide-disk version 1.08 1181 1182More detailed information can be found in the controller specific 1183subdirectories. These are named ide0, ide1 and so on. Each of these 1184directories contains the files shown in table 1-6. 1185 1186 1187.. table:: Table 1-6: IDE controller info in /proc/ide/ide? 1188 1189 ======= ======================================= 1190 File Content 1191 ======= ======================================= 1192 channel IDE channel (0 or 1) 1193 config Configuration (only for PCI/IDE bridge) 1194 mate Mate name 1195 model Type/Chipset of IDE controller 1196 ======= ======================================= 1197 1198Each device connected to a controller has a separate subdirectory in the 1199controllers directory. The files listed in table 1-7 are contained in these 1200directories. 1201 1202 1203.. table:: Table 1-7: IDE device information 1204 1205 ================ ========================================== 1206 File Content 1207 ================ ========================================== 1208 cache The cache 1209 capacity Capacity of the medium (in 512Byte blocks) 1210 driver driver and version 1211 geometry physical and logical geometry 1212 identify device identify block 1213 media media type 1214 model device identifier 1215 settings device setup 1216 smart_thresholds IDE disk management thresholds 1217 smart_values IDE disk management values 1218 ================ ========================================== 1219 1220The most interesting file is ``settings``. This file contains a nice 1221overview of the drive parameters:: 1222 1223 # cat /proc/ide/ide0/hda/settings 1224 name value min max mode 1225 ---- ----- --- --- ---- 1226 bios_cyl 526 0 65535 rw 1227 bios_head 255 0 255 rw 1228 bios_sect 63 0 63 rw 1229 breada_readahead 4 0 127 rw 1230 bswap 0 0 1 r 1231 file_readahead 72 0 2097151 rw 1232 io_32bit 0 0 3 rw 1233 keepsettings 0 0 1 rw 1234 max_kb_per_request 122 1 127 rw 1235 multcount 0 0 8 rw 1236 nice1 1 0 1 rw 1237 nowerr 0 0 1 rw 1238 pio_mode write-only 0 255 w 1239 slow 0 0 1 rw 1240 unmaskirq 0 0 1 rw 1241 using_dma 0 0 1 rw 1242 1243 12441.4 Networking info in /proc/net 1245-------------------------------- 1246 1247The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1248additional values you get for IP version 6 if you configure the kernel to 1249support this. Table 1-9 lists the files and their meaning. 1250 1251 1252.. table:: Table 1-8: IPv6 info in /proc/net 1253 1254 ========== ===================================================== 1255 File Content 1256 ========== ===================================================== 1257 udp6 UDP sockets (IPv6) 1258 tcp6 TCP sockets (IPv6) 1259 raw6 Raw device statistics (IPv6) 1260 igmp6 IP multicast addresses, which this host joined (IPv6) 1261 if_inet6 List of IPv6 interface addresses 1262 ipv6_route Kernel routing table for IPv6 1263 rt6_stats Global IPv6 routing tables statistics 1264 sockstat6 Socket statistics (IPv6) 1265 snmp6 Snmp data (IPv6) 1266 ========== ===================================================== 1267 1268.. table:: Table 1-9: Network info in /proc/net 1269 1270 ============= ================================================================ 1271 File Content 1272 ============= ================================================================ 1273 arp Kernel ARP table 1274 dev network devices with statistics 1275 dev_mcast the Layer2 multicast groups a device is listening too 1276 (interface index, label, number of references, number of bound 1277 addresses). 1278 dev_stat network device status 1279 ip_fwchains Firewall chain linkage 1280 ip_fwnames Firewall chain names 1281 ip_masq Directory containing the masquerading tables 1282 ip_masquerade Major masquerading table 1283 netstat Network statistics 1284 raw raw device statistics 1285 route Kernel routing table 1286 rpc Directory containing rpc info 1287 rt_cache Routing cache 1288 snmp SNMP data 1289 sockstat Socket statistics 1290 tcp TCP sockets 1291 udp UDP sockets 1292 unix UNIX domain sockets 1293 wireless Wireless interface data (Wavelan etc) 1294 igmp IP multicast addresses, which this host joined 1295 psched Global packet scheduler parameters. 1296 netlink List of PF_NETLINK sockets 1297 ip_mr_vifs List of multicast virtual interfaces 1298 ip_mr_cache List of multicast routing cache 1299 ============= ================================================================ 1300 1301You can use this information to see which network devices are available in 1302your system and how much traffic was routed over those devices:: 1303 1304 > cat /proc/net/dev 1305 Inter-|Receive |[... 1306 face |bytes packets errs drop fifo frame compressed multicast|[... 1307 lo: 908188 5596 0 0 0 0 0 0 [... 1308 ppp0:15475140 20721 410 0 0 410 0 0 [... 1309 eth0: 614530 7085 0 0 0 0 0 1 [... 1310 1311 ...] Transmit 1312 ...] bytes packets errs drop fifo colls carrier compressed 1313 ...] 908188 5596 0 0 0 0 0 0 1314 ...] 1375103 17405 0 0 0 0 0 0 1315 ...] 1703981 5535 0 0 0 3 0 0 1316 1317In addition, each Channel Bond interface has its own directory. For 1318example, the bond0 device will have a directory called /proc/net/bond0/. 1319It will contain information that is specific to that bond, such as the 1320current slaves of the bond, the link status of the slaves, and how 1321many times the slaves link has failed. 1322 13231.5 SCSI info 1324------------- 1325 1326If you have a SCSI host adapter in your system, you'll find a subdirectory 1327named after the driver for this adapter in /proc/scsi. You'll also see a list 1328of all recognized SCSI devices in /proc/scsi:: 1329 1330 >cat /proc/scsi/scsi 1331 Attached devices: 1332 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1333 Vendor: IBM Model: DGHS09U Rev: 03E0 1334 Type: Direct-Access ANSI SCSI revision: 03 1335 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1336 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1337 Type: CD-ROM ANSI SCSI revision: 02 1338 1339 1340The directory named after the driver has one file for each adapter found in 1341the system. These files contain information about the controller, including 1342the used IRQ and the IO address range. The amount of information shown is 1343dependent on the adapter you use. The example shows the output for an Adaptec 1344AHA-2940 SCSI adapter:: 1345 1346 > cat /proc/scsi/aic7xxx/0 1347 1348 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1349 Compile Options: 1350 TCQ Enabled By Default : Disabled 1351 AIC7XXX_PROC_STATS : Disabled 1352 AIC7XXX_RESET_DELAY : 5 1353 Adapter Configuration: 1354 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1355 Ultra Wide Controller 1356 PCI MMAPed I/O Base: 0xeb001000 1357 Adapter SEEPROM Config: SEEPROM found and used. 1358 Adaptec SCSI BIOS: Enabled 1359 IRQ: 10 1360 SCBs: Active 0, Max Active 2, 1361 Allocated 15, HW 16, Page 255 1362 Interrupts: 160328 1363 BIOS Control Word: 0x18b6 1364 Adapter Control Word: 0x005b 1365 Extended Translation: Enabled 1366 Disconnect Enable Flags: 0xffff 1367 Ultra Enable Flags: 0x0001 1368 Tag Queue Enable Flags: 0x0000 1369 Ordered Queue Tag Flags: 0x0000 1370 Default Tag Queue Depth: 8 1371 Tagged Queue By Device array for aic7xxx host instance 0: 1372 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1373 Actual queue depth per device for aic7xxx host instance 0: 1374 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1375 Statistics: 1376 (scsi0:0:0:0) 1377 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1378 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1379 Total transfers 160151 (74577 reads and 85574 writes) 1380 (scsi0:0:6:0) 1381 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1382 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1383 Total transfers 0 (0 reads and 0 writes) 1384 1385 13861.6 Parallel port info in /proc/parport 1387--------------------------------------- 1388 1389The directory /proc/parport contains information about the parallel ports of 1390your system. It has one subdirectory for each port, named after the port 1391number (0,1,2,...). 1392 1393These directories contain the four files shown in Table 1-10. 1394 1395 1396.. table:: Table 1-10: Files in /proc/parport 1397 1398 ========= ==================================================================== 1399 File Content 1400 ========= ==================================================================== 1401 autoprobe Any IEEE-1284 device ID information that has been acquired. 1402 devices list of the device drivers using that port. A + will appear by the 1403 name of the device currently using the port (it might not appear 1404 against any). 1405 hardware Parallel port's base address, IRQ line and DMA channel. 1406 irq IRQ that parport is using for that port. This is in a separate 1407 file to allow you to alter it by writing a new value in (IRQ 1408 number or none). 1409 ========= ==================================================================== 1410 14111.7 TTY info in /proc/tty 1412------------------------- 1413 1414Information about the available and actually used tty's can be found in the 1415directory /proc/tty. You'll find entries for drivers and line disciplines in 1416this directory, as shown in Table 1-11. 1417 1418 1419.. table:: Table 1-11: Files in /proc/tty 1420 1421 ============= ============================================== 1422 File Content 1423 ============= ============================================== 1424 drivers list of drivers and their usage 1425 ldiscs registered line disciplines 1426 driver/serial usage statistic and status of single tty lines 1427 ============= ============================================== 1428 1429To see which tty's are currently in use, you can simply look into the file 1430/proc/tty/drivers:: 1431 1432 > cat /proc/tty/drivers 1433 pty_slave /dev/pts 136 0-255 pty:slave 1434 pty_master /dev/ptm 128 0-255 pty:master 1435 pty_slave /dev/ttyp 3 0-255 pty:slave 1436 pty_master /dev/pty 2 0-255 pty:master 1437 serial /dev/cua 5 64-67 serial:callout 1438 serial /dev/ttyS 4 64-67 serial 1439 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1440 /dev/ptmx /dev/ptmx 5 2 system 1441 /dev/console /dev/console 5 1 system:console 1442 /dev/tty /dev/tty 5 0 system:/dev/tty 1443 unknown /dev/tty 4 1-63 console 1444 1445 14461.8 Miscellaneous kernel statistics in /proc/stat 1447------------------------------------------------- 1448 1449Various pieces of information about kernel activity are available in the 1450/proc/stat file. All of the numbers reported in this file are aggregates 1451since the system first booted. For a quick look, simply cat the file:: 1452 1453 > cat /proc/stat 1454 cpu 2255 34 2290 22625563 6290 127 456 0 0 0 1455 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 1456 cpu1 1123 0 849 11313845 2614 0 18 0 0 0 1457 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1458 ctxt 1990473 1459 btime 1062191376 1460 processes 2915 1461 procs_running 1 1462 procs_blocked 0 1463 softirq 183433 0 21755 12 39 1137 231 21459 2263 1464 1465The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1466lines. These numbers identify the amount of time the CPU has spent performing 1467different kinds of work. Time units are in USER_HZ (typically hundredths of a 1468second). The meanings of the columns are as follows, from left to right: 1469 1470- user: normal processes executing in user mode 1471- nice: niced processes executing in user mode 1472- system: processes executing in kernel mode 1473- idle: twiddling thumbs 1474- iowait: In a word, iowait stands for waiting for I/O to complete. But there 1475 are several problems: 1476 1477 1. CPU will not wait for I/O to complete, iowait is the time that a task is 1478 waiting for I/O to complete. When CPU goes into idle state for 1479 outstanding task I/O, another task will be scheduled on this CPU. 1480 2. In a multi-core CPU, the task waiting for I/O to complete is not running 1481 on any CPU, so the iowait of each CPU is difficult to calculate. 1482 3. The value of iowait field in /proc/stat will decrease in certain 1483 conditions. 1484 1485 So, the iowait is not reliable by reading from /proc/stat. 1486- irq: servicing interrupts 1487- softirq: servicing softirqs 1488- steal: involuntary wait 1489- guest: running a normal guest 1490- guest_nice: running a niced guest 1491 1492The "intr" line gives counts of interrupts serviced since boot time, for each 1493of the possible system interrupts. The first column is the total of all 1494interrupts serviced including unnumbered architecture specific interrupts; 1495each subsequent column is the total for that particular numbered interrupt. 1496Unnumbered interrupts are not shown, only summed into the total. 1497 1498The "ctxt" line gives the total number of context switches across all CPUs. 1499 1500The "btime" line gives the time at which the system booted, in seconds since 1501the Unix epoch. 1502 1503The "processes" line gives the number of processes and threads created, which 1504includes (but is not limited to) those created by calls to the fork() and 1505clone() system calls. 1506 1507The "procs_running" line gives the total number of threads that are 1508running or ready to run (i.e., the total number of runnable threads). 1509 1510The "procs_blocked" line gives the number of processes currently blocked, 1511waiting for I/O to complete. 1512 1513The "softirq" line gives counts of softirqs serviced since boot time, for each 1514of the possible system softirqs. The first column is the total of all 1515softirqs serviced; each subsequent column is the total for that particular 1516softirq. 1517 1518 15191.9 Ext4 file system parameters 1520------------------------------- 1521 1522Information about mounted ext4 file systems can be found in 1523/proc/fs/ext4. Each mounted filesystem will have a directory in 1524/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1525/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1526in Table 1-12, below. 1527 1528.. table:: Table 1-12: Files in /proc/fs/ext4/<devname> 1529 1530 ============== ========================================================== 1531 File Content 1532 mb_groups details of multiblock allocator buddy cache of free blocks 1533 ============== ========================================================== 1534 15351.10 /proc/consoles 1536------------------- 1537Shows registered system console lines. 1538 1539To see which character device lines are currently used for the system console 1540/dev/console, you may simply look into the file /proc/consoles:: 1541 1542 > cat /proc/consoles 1543 tty0 -WU (ECp) 4:7 1544 ttyS0 -W- (Ep) 4:64 1545 1546The columns are: 1547 1548+--------------------+-------------------------------------------------------+ 1549| device | name of the device | 1550+====================+=======================================================+ 1551| operations | * R = can do read operations | 1552| | * W = can do write operations | 1553| | * U = can do unblank | 1554+--------------------+-------------------------------------------------------+ 1555| flags | * E = it is enabled | 1556| | * C = it is preferred console | 1557| | * B = it is primary boot console | 1558| | * p = it is used for printk buffer | 1559| | * b = it is not a TTY but a Braille device | 1560| | * a = it is safe to use when cpu is offline | 1561+--------------------+-------------------------------------------------------+ 1562| major:minor | major and minor number of the device separated by a | 1563| | colon | 1564+--------------------+-------------------------------------------------------+ 1565 1566Summary 1567------- 1568 1569The /proc file system serves information about the running system. It not only 1570allows access to process data but also allows you to request the kernel status 1571by reading files in the hierarchy. 1572 1573The directory structure of /proc reflects the types of information and makes 1574it easy, if not obvious, where to look for specific data. 1575 1576Chapter 2: Modifying System Parameters 1577====================================== 1578 1579In This Chapter 1580--------------- 1581 1582* Modifying kernel parameters by writing into files found in /proc/sys 1583* Exploring the files which modify certain parameters 1584* Review of the /proc/sys file tree 1585 1586------------------------------------------------------------------------------ 1587 1588A very interesting part of /proc is the directory /proc/sys. This is not only 1589a source of information, it also allows you to change parameters within the 1590kernel. Be very careful when attempting this. You can optimize your system, 1591but you can also cause it to crash. Never alter kernel parameters on a 1592production system. Set up a development machine and test to make sure that 1593everything works the way you want it to. You may have no alternative but to 1594reboot the machine once an error has been made. 1595 1596To change a value, simply echo the new value into the file. 1597You need to be root to do this. You can create your own boot script 1598to perform this every time your system boots. 1599 1600The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1601general things in the operation of the Linux kernel. Since some of the files 1602can inadvertently disrupt your system, it is advisable to read both 1603documentation and source before actually making adjustments. In any case, be 1604very careful when writing to any of these files. The entries in /proc may 1605change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1606review the kernel documentation in the directory /usr/src/linux/Documentation. 1607This chapter is heavily based on the documentation included in the pre 2.2 1608kernels, and became part of it in version 2.2.1 of the Linux kernel. 1609 1610Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these 1611entries. 1612 1613Summary 1614------- 1615 1616Certain aspects of kernel behavior can be modified at runtime, without the 1617need to recompile the kernel, or even to reboot the system. The files in the 1618/proc/sys tree can not only be read, but also modified. You can use the echo 1619command to write value into these files, thereby changing the default settings 1620of the kernel. 1621 1622 1623Chapter 3: Per-process Parameters 1624================================= 1625 16263.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1627-------------------------------------------------------------------------------- 1628 1629These files can be used to adjust the badness heuristic used to select which 1630process gets killed in out of memory (oom) conditions. 1631 1632The badness heuristic assigns a value to each candidate task ranging from 0 1633(never kill) to 1000 (always kill) to determine which process is targeted. The 1634units are roughly a proportion along that range of allowed memory the process 1635may allocate from based on an estimation of its current memory and swap use. 1636For example, if a task is using all allowed memory, its badness score will be 16371000. If it is using half of its allowed memory, its score will be 500. 1638 1639The amount of "allowed" memory depends on the context in which the oom killer 1640was called. If it is due to the memory assigned to the allocating task's cpuset 1641being exhausted, the allowed memory represents the set of mems assigned to that 1642cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1643memory represents the set of mempolicy nodes. If it is due to a memory 1644limit (or swap limit) being reached, the allowed memory is that configured 1645limit. Finally, if it is due to the entire system being out of memory, the 1646allowed memory represents all allocatable resources. 1647 1648The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1649is used to determine which task to kill. Acceptable values range from -1000 1650(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1651polarize the preference for oom killing either by always preferring a certain 1652task or completely disabling it. The lowest possible value, -1000, is 1653equivalent to disabling oom killing entirely for that task since it will always 1654report a badness score of 0. 1655 1656Consequently, it is very simple for userspace to define the amount of memory to 1657consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1658example, is roughly equivalent to allowing the remainder of tasks sharing the 1659same system, cpuset, mempolicy, or memory controller resources to use at least 166050% more memory. A value of -500, on the other hand, would be roughly 1661equivalent to discounting 50% of the task's allowed memory from being considered 1662as scoring against the task. 1663 1664For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1665be used to tune the badness score. Its acceptable values range from -16 1666(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1667(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1668scaled linearly with /proc/<pid>/oom_score_adj. 1669 1670The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1671value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1672requires CAP_SYS_RESOURCE. 1673 1674 16753.2 /proc/<pid>/oom_score - Display current oom-killer score 1676------------------------------------------------------------- 1677 1678This file can be used to check the current score used by the oom-killer for 1679any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1680process should be killed in an out-of-memory situation. 1681 1682Please note that the exported value includes oom_score_adj so it is 1683effectively in range [0,2000]. 1684 1685 16863.3 /proc/<pid>/io - Display the IO accounting fields 1687------------------------------------------------------- 1688 1689This file contains IO statistics for each running process. 1690 1691Example 1692~~~~~~~ 1693 1694:: 1695 1696 test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1697 [1] 3828 1698 1699 test:/tmp # cat /proc/3828/io 1700 rchar: 323934931 1701 wchar: 323929600 1702 syscr: 632687 1703 syscw: 632675 1704 read_bytes: 0 1705 write_bytes: 323932160 1706 cancelled_write_bytes: 0 1707 1708 1709Description 1710~~~~~~~~~~~ 1711 1712rchar 1713^^^^^ 1714 1715I/O counter: chars read 1716The number of bytes which this task has caused to be read from storage. This 1717is simply the sum of bytes which this process passed to read() and pread(). 1718It includes things like tty IO and it is unaffected by whether or not actual 1719physical disk IO was required (the read might have been satisfied from 1720pagecache). 1721 1722 1723wchar 1724^^^^^ 1725 1726I/O counter: chars written 1727The number of bytes which this task has caused, or shall cause to be written 1728to disk. Similar caveats apply here as with rchar. 1729 1730 1731syscr 1732^^^^^ 1733 1734I/O counter: read syscalls 1735Attempt to count the number of read I/O operations, i.e. syscalls like read() 1736and pread(). 1737 1738 1739syscw 1740^^^^^ 1741 1742I/O counter: write syscalls 1743Attempt to count the number of write I/O operations, i.e. syscalls like 1744write() and pwrite(). 1745 1746 1747read_bytes 1748^^^^^^^^^^ 1749 1750I/O counter: bytes read 1751Attempt to count the number of bytes which this process really did cause to 1752be fetched from the storage layer. Done at the submit_bio() level, so it is 1753accurate for block-backed filesystems. <please add status regarding NFS and 1754CIFS at a later time> 1755 1756 1757write_bytes 1758^^^^^^^^^^^ 1759 1760I/O counter: bytes written 1761Attempt to count the number of bytes which this process caused to be sent to 1762the storage layer. This is done at page-dirtying time. 1763 1764 1765cancelled_write_bytes 1766^^^^^^^^^^^^^^^^^^^^^ 1767 1768The big inaccuracy here is truncate. If a process writes 1MB to a file and 1769then deletes the file, it will in fact perform no writeout. But it will have 1770been accounted as having caused 1MB of write. 1771In other words: The number of bytes which this process caused to not happen, 1772by truncating pagecache. A task can cause "negative" IO too. If this task 1773truncates some dirty pagecache, some IO which another task has been accounted 1774for (in its write_bytes) will not be happening. We _could_ just subtract that 1775from the truncating task's write_bytes, but there is information loss in doing 1776that. 1777 1778 1779.. Note:: 1780 1781 At its current implementation state, this is a bit racy on 32-bit machines: 1782 if process A reads process B's /proc/pid/io while process B is updating one 1783 of those 64-bit counters, process A could see an intermediate result. 1784 1785 1786More information about this can be found within the taskstats documentation in 1787Documentation/accounting. 1788 17893.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1790--------------------------------------------------------------- 1791When a process is dumped, all anonymous memory is written to a core file as 1792long as the size of the core file isn't limited. But sometimes we don't want 1793to dump some memory segments, for example, huge shared memory or DAX. 1794Conversely, sometimes we want to save file-backed memory segments into a core 1795file, not only the individual files. 1796 1797/proc/<pid>/coredump_filter allows you to customize which memory segments 1798will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1799of memory types. If a bit of the bitmask is set, memory segments of the 1800corresponding memory type are dumped, otherwise they are not dumped. 1801 1802The following 9 memory types are supported: 1803 1804 - (bit 0) anonymous private memory 1805 - (bit 1) anonymous shared memory 1806 - (bit 2) file-backed private memory 1807 - (bit 3) file-backed shared memory 1808 - (bit 4) ELF header pages in file-backed private memory areas (it is 1809 effective only if the bit 2 is cleared) 1810 - (bit 5) hugetlb private memory 1811 - (bit 6) hugetlb shared memory 1812 - (bit 7) DAX private memory 1813 - (bit 8) DAX shared memory 1814 1815 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1816 are always dumped regardless of the bitmask status. 1817 1818 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is 1819 only affected by bit 5-6, and DAX is only affected by bits 7-8. 1820 1821The default value of coredump_filter is 0x33; this means all anonymous memory 1822segments, ELF header pages and hugetlb private memory are dumped. 1823 1824If you don't want to dump all shared memory segments attached to pid 1234, 1825write 0x31 to the process's proc file:: 1826 1827 $ echo 0x31 > /proc/1234/coredump_filter 1828 1829When a new process is created, the process inherits the bitmask status from its 1830parent. It is useful to set up coredump_filter before the program runs. 1831For example:: 1832 1833 $ echo 0x7 > /proc/self/coredump_filter 1834 $ ./some_program 1835 18363.5 /proc/<pid>/mountinfo - Information about mounts 1837-------------------------------------------------------- 1838 1839This file contains lines of the form:: 1840 1841 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1842 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1843 1844 (1) mount ID: unique identifier of the mount (may be reused after umount) 1845 (2) parent ID: ID of parent (or of self for the top of the mount tree) 1846 (3) major:minor: value of st_dev for files on filesystem 1847 (4) root: root of the mount within the filesystem 1848 (5) mount point: mount point relative to the process's root 1849 (6) mount options: per mount options 1850 (7) optional fields: zero or more fields of the form "tag[:value]" 1851 (8) separator: marks the end of the optional fields 1852 (9) filesystem type: name of filesystem of the form "type[.subtype]" 1853 (10) mount source: filesystem specific information or "none" 1854 (11) super options: per super block options 1855 1856Parsers should ignore all unrecognised optional fields. Currently the 1857possible optional fields are: 1858 1859================ ============================================================== 1860shared:X mount is shared in peer group X 1861master:X mount is slave to peer group X 1862propagate_from:X mount is slave and receives propagation from peer group X [#]_ 1863unbindable mount is unbindable 1864================ ============================================================== 1865 1866.. [#] X is the closest dominant peer group under the process's root. If 1867 X is the immediate master of the mount, or if there's no dominant peer 1868 group under the same root, then only the "master:X" field is present 1869 and not the "propagate_from:X" field. 1870 1871For more information on mount propagation see: 1872 1873 Documentation/filesystems/sharedsubtree.rst 1874 1875 18763.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1877-------------------------------------------------------- 1878These files provide a method to access a task's comm value. It also allows for 1879a task to set its own or one of its thread siblings comm value. The comm value 1880is limited in size compared to the cmdline value, so writing anything longer 1881then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1882comm value. 1883 1884 18853.7 /proc/<pid>/task/<tid>/children - Information about task children 1886------------------------------------------------------------------------- 1887This file provides a fast way to retrieve first level children pids 1888of a task pointed by <pid>/<tid> pair. The format is a space separated 1889stream of pids. 1890 1891Note the "first level" here -- if a child has its own children they will 1892not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children 1893to obtain the descendants. 1894 1895Since this interface is intended to be fast and cheap it doesn't 1896guarantee to provide precise results and some children might be 1897skipped, especially if they've exited right after we printed their 1898pids, so one needs to either stop or freeze processes being inspected 1899if precise results are needed. 1900 1901 19023.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 1903--------------------------------------------------------------- 1904This file provides information associated with an opened file. The regular 1905files have at least three fields -- 'pos', 'flags' and 'mnt_id'. The 'pos' 1906represents the current offset of the opened file in decimal form [see lseek(2) 1907for details], 'flags' denotes the octal O_xxx mask the file has been 1908created with [see open(2) for details] and 'mnt_id' represents mount ID of 1909the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo 1910for details]. 1911 1912A typical output is:: 1913 1914 pos: 0 1915 flags: 0100002 1916 mnt_id: 19 1917 1918All locks associated with a file descriptor are shown in its fdinfo too:: 1919 1920 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF 1921 1922The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1923pair provide additional information particular to the objects they represent. 1924 1925Eventfd files 1926~~~~~~~~~~~~~ 1927 1928:: 1929 1930 pos: 0 1931 flags: 04002 1932 mnt_id: 9 1933 eventfd-count: 5a 1934 1935where 'eventfd-count' is hex value of a counter. 1936 1937Signalfd files 1938~~~~~~~~~~~~~~ 1939 1940:: 1941 1942 pos: 0 1943 flags: 04002 1944 mnt_id: 9 1945 sigmask: 0000000000000200 1946 1947where 'sigmask' is hex value of the signal mask associated 1948with a file. 1949 1950Epoll files 1951~~~~~~~~~~~ 1952 1953:: 1954 1955 pos: 0 1956 flags: 02 1957 mnt_id: 9 1958 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 1959 1960where 'tfd' is a target file descriptor number in decimal form, 1961'events' is events mask being watched and the 'data' is data 1962associated with a target [see epoll(7) for more details]. 1963 1964The 'pos' is current offset of the target file in decimal form 1965[see lseek(2)], 'ino' and 'sdev' are inode and device numbers 1966where target file resides, all in hex format. 1967 1968Fsnotify files 1969~~~~~~~~~~~~~~ 1970For inotify files the format is the following:: 1971 1972 pos: 0 1973 flags: 02000000 1974 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 1975 1976where 'wd' is a watch descriptor in decimal form, i.e. a target file 1977descriptor number, 'ino' and 'sdev' are inode and device where the 1978target file resides and the 'mask' is the mask of events, all in hex 1979form [see inotify(7) for more details]. 1980 1981If the kernel was built with exportfs support, the path to the target 1982file is encoded as a file handle. The file handle is provided by three 1983fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 1984format. 1985 1986If the kernel is built without exportfs support the file handle won't be 1987printed out. 1988 1989If there is no inotify mark attached yet the 'inotify' line will be omitted. 1990 1991For fanotify files the format is:: 1992 1993 pos: 0 1994 flags: 02 1995 mnt_id: 9 1996 fanotify flags:10 event-flags:0 1997 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 1998 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 1999 2000where fanotify 'flags' and 'event-flags' are values used in fanotify_init 2001call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 2002flags associated with mark which are tracked separately from events 2003mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events 2004mask and 'ignored_mask' is the mask of events which are to be ignored. 2005All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 2006provide information about flags and mask used in fanotify_mark 2007call [see fsnotify manpage for details]. 2008 2009While the first three lines are mandatory and always printed, the rest is 2010optional and may be omitted if no marks created yet. 2011 2012Timerfd files 2013~~~~~~~~~~~~~ 2014 2015:: 2016 2017 pos: 0 2018 flags: 02 2019 mnt_id: 9 2020 clockid: 0 2021 ticks: 0 2022 settime flags: 01 2023 it_value: (0, 49406829) 2024 it_interval: (1, 0) 2025 2026where 'clockid' is the clock type and 'ticks' is the number of the timer expirations 2027that have occurred [see timerfd_create(2) for details]. 'settime flags' are 2028flags in octal form been used to setup the timer [see timerfd_settime(2) for 2029details]. 'it_value' is remaining time until the timer expiration. 2030'it_interval' is the interval for the timer. Note the timer might be set up 2031with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' 2032still exhibits timer's remaining time. 2033 20343.9 /proc/<pid>/map_files - Information about memory mapped files 2035--------------------------------------------------------------------- 2036This directory contains symbolic links which represent memory mapped files 2037the process is maintaining. Example output:: 2038 2039 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so 2040 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so 2041 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so 2042 | ... 2043 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 2044 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls 2045 2046The name of a link represents the virtual memory bounds of a mapping, i.e. 2047vm_area_struct::vm_start-vm_area_struct::vm_end. 2048 2049The main purpose of the map_files is to retrieve a set of memory mapped 2050files in a fast way instead of parsing /proc/<pid>/maps or 2051/proc/<pid>/smaps, both of which contain many more records. At the same 2052time one can open(2) mappings from the listings of two processes and 2053comparing their inode numbers to figure out which anonymous memory areas 2054are actually shared. 2055 20563.10 /proc/<pid>/timerslack_ns - Task timerslack value 2057--------------------------------------------------------- 2058This file provides the value of the task's timerslack value in nanoseconds. 2059This value specifies an amount of time that normal timers may be deferred 2060in order to coalesce timers and avoid unnecessary wakeups. 2061 2062This allows a task's interactivity vs power consumption tradeoff to be 2063adjusted. 2064 2065Writing 0 to the file will set the task's timerslack to the default value. 2066 2067Valid values are from 0 - ULLONG_MAX 2068 2069An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level 2070permissions on the task specified to change its timerslack_ns value. 2071 20723.11 /proc/<pid>/patch_state - Livepatch patch operation state 2073----------------------------------------------------------------- 2074When CONFIG_LIVEPATCH is enabled, this file displays the value of the 2075patch state for the task. 2076 2077A value of '-1' indicates that no patch is in transition. 2078 2079A value of '0' indicates that a patch is in transition and the task is 2080unpatched. If the patch is being enabled, then the task hasn't been 2081patched yet. If the patch is being disabled, then the task has already 2082been unpatched. 2083 2084A value of '1' indicates that a patch is in transition and the task is 2085patched. If the patch is being enabled, then the task has already been 2086patched. If the patch is being disabled, then the task hasn't been 2087unpatched yet. 2088 20893.12 /proc/<pid>/arch_status - task architecture specific status 2090------------------------------------------------------------------- 2091When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the 2092architecture specific status of the task. 2093 2094Example 2095~~~~~~~ 2096 2097:: 2098 2099 $ cat /proc/6753/arch_status 2100 AVX512_elapsed_ms: 8 2101 2102Description 2103~~~~~~~~~~~ 2104 2105x86 specific entries 2106~~~~~~~~~~~~~~~~~~~~~ 2107 2108AVX512_elapsed_ms 2109^^^^^^^^^^^^^^^^^^ 2110 2111 If AVX512 is supported on the machine, this entry shows the milliseconds 2112 elapsed since the last time AVX512 usage was recorded. The recording 2113 happens on a best effort basis when a task is scheduled out. This means 2114 that the value depends on two factors: 2115 2116 1) The time which the task spent on the CPU without being scheduled 2117 out. With CPU isolation and a single runnable task this can take 2118 several seconds. 2119 2120 2) The time since the task was scheduled out last. Depending on the 2121 reason for being scheduled out (time slice exhausted, syscall ...) 2122 this can be arbitrary long time. 2123 2124 As a consequence the value cannot be considered precise and authoritative 2125 information. The application which uses this information has to be aware 2126 of the overall scenario on the system in order to determine whether a 2127 task is a real AVX512 user or not. Precise information can be obtained 2128 with performance counters. 2129 2130 A special value of '-1' indicates that no AVX512 usage was recorded, thus 2131 the task is unlikely an AVX512 user, but depends on the workload and the 2132 scheduling scenario, it also could be a false negative mentioned above. 2133 2134Chapter 4: Configuring procfs 2135============================= 2136 21374.1 Mount options 2138--------------------- 2139 2140The following mount options are supported: 2141 2142 ========= ======================================================== 2143 hidepid= Set /proc/<pid>/ access mode. 2144 gid= Set the group authorized to learn processes information. 2145 subset= Show only the specified subset of procfs. 2146 ========= ======================================================== 2147 2148hidepid=off or hidepid=0 means classic mode - everybody may access all 2149/proc/<pid>/ directories (default). 2150 2151hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/ 2152directories but their own. Sensitive files like cmdline, sched*, status are now 2153protected against other users. This makes it impossible to learn whether any 2154user runs specific program (given the program doesn't reveal itself by its 2155behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for 2156other users, poorly written programs passing sensitive information via program 2157arguments are now protected against local eavesdroppers. 2158 2159hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be 2160fully invisible to other users. It doesn't mean that it hides a fact whether a 2161process with a specific pid value exists (it can be learned by other means, e.g. 2162by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by 2163stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of 2164gathering information about running processes, whether some daemon runs with 2165elevated privileges, whether other user runs some sensitive program, whether 2166other users run any program at all, etc. 2167 2168hidepid=ptraceable or hidepid=4 means that procfs should only contain 2169/proc/<pid>/ directories that the caller can ptrace. 2170 2171gid= defines a group authorized to learn processes information otherwise 2172prohibited by hidepid=. If you use some daemon like identd which needs to learn 2173information about processes information, just add identd to this group. 2174 2175subset=pid hides all top level files and directories in the procfs that 2176are not related to tasks. 2177 2178Chapter 5: Filesystem behavior 2179============================== 2180 2181Originally, before the advent of pid namepsace, procfs was a global file 2182system. It means that there was only one procfs instance in the system. 2183 2184When pid namespace was added, a separate procfs instance was mounted in 2185each pid namespace. So, procfs mount options are global among all 2186mountpoints within the same namespace:: 2187 2188 # grep ^proc /proc/mounts 2189 proc /proc proc rw,relatime,hidepid=2 0 0 2190 2191 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc 2192 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0 2193 +++ exited with 0 +++ 2194 2195 # grep ^proc /proc/mounts 2196 proc /proc proc rw,relatime,hidepid=2 0 0 2197 proc /tmp/proc proc rw,relatime,hidepid=2 0 0 2198 2199and only after remounting procfs mount options will change at all 2200mountpoints:: 2201 2202 # mount -o remount,hidepid=1 -t proc proc /tmp/proc 2203 2204 # grep ^proc /proc/mounts 2205 proc /proc proc rw,relatime,hidepid=1 0 0 2206 proc /tmp/proc proc rw,relatime,hidepid=1 0 0 2207 2208This behavior is different from the behavior of other filesystems. 2209 2210The new procfs behavior is more like other filesystems. Each procfs mount 2211creates a new procfs instance. Mount options affect own procfs instance. 2212It means that it became possible to have several procfs instances 2213displaying tasks with different filtering options in one pid namespace:: 2214 2215 # mount -o hidepid=invisible -t proc proc /proc 2216 # mount -o hidepid=noaccess -t proc proc /tmp/proc 2217 # grep ^proc /proc/mounts 2218 proc /proc proc rw,relatime,hidepid=invisible 0 0 2219 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 2220