1config ARCH 2 string 3 option env="ARCH" 4 5config KERNELVERSION 6 string 7 option env="KERNELVERSION" 8 9config DEFCONFIG_LIST 10 string 11 depends on !UML 12 option defconfig_list 13 default "/lib/modules/$UNAME_RELEASE/.config" 14 default "/etc/kernel-config" 15 default "/boot/config-$UNAME_RELEASE" 16 default "$ARCH_DEFCONFIG" 17 default "arch/$ARCH/defconfig" 18 19config CONSTRUCTORS 20 bool 21 depends on !UML 22 23config IRQ_WORK 24 bool 25 26config BUILDTIME_EXTABLE_SORT 27 bool 28 29menu "General setup" 30 31config BROKEN 32 bool 33 34config BROKEN_ON_SMP 35 bool 36 depends on BROKEN || !SMP 37 default y 38 39config INIT_ENV_ARG_LIMIT 40 int 41 default 32 if !UML 42 default 128 if UML 43 help 44 Maximum of each of the number of arguments and environment 45 variables passed to init from the kernel command line. 46 47 48config CROSS_COMPILE 49 string "Cross-compiler tool prefix" 50 help 51 Same as running 'make CROSS_COMPILE=prefix-' but stored for 52 default make runs in this kernel build directory. You don't 53 need to set this unless you want the configured kernel build 54 directory to select the cross-compiler automatically. 55 56config COMPILE_TEST 57 bool "Compile also drivers which will not load" 58 default n 59 help 60 Some drivers can be compiled on a different platform than they are 61 intended to be run on. Despite they cannot be loaded there (or even 62 when they load they cannot be used due to missing HW support), 63 developers still, opposing to distributors, might want to build such 64 drivers to compile-test them. 65 66 If you are a developer and want to build everything available, say Y 67 here. If you are a user/distributor, say N here to exclude useless 68 drivers to be distributed. 69 70config LOCALVERSION 71 string "Local version - append to kernel release" 72 help 73 Append an extra string to the end of your kernel version. 74 This will show up when you type uname, for example. 75 The string you set here will be appended after the contents of 76 any files with a filename matching localversion* in your 77 object and source tree, in that order. Your total string can 78 be a maximum of 64 characters. 79 80config LOCALVERSION_AUTO 81 bool "Automatically append version information to the version string" 82 default y 83 help 84 This will try to automatically determine if the current tree is a 85 release tree by looking for git tags that belong to the current 86 top of tree revision. 87 88 A string of the format -gxxxxxxxx will be added to the localversion 89 if a git-based tree is found. The string generated by this will be 90 appended after any matching localversion* files, and after the value 91 set in CONFIG_LOCALVERSION. 92 93 (The actual string used here is the first eight characters produced 94 by running the command: 95 96 $ git rev-parse --verify HEAD 97 98 which is done within the script "scripts/setlocalversion".) 99 100config HAVE_KERNEL_GZIP 101 bool 102 103config HAVE_KERNEL_BZIP2 104 bool 105 106config HAVE_KERNEL_LZMA 107 bool 108 109config HAVE_KERNEL_XZ 110 bool 111 112config HAVE_KERNEL_LZO 113 bool 114 115config HAVE_KERNEL_LZ4 116 bool 117 118choice 119 prompt "Kernel compression mode" 120 default KERNEL_GZIP 121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 122 help 123 The linux kernel is a kind of self-extracting executable. 124 Several compression algorithms are available, which differ 125 in efficiency, compression and decompression speed. 126 Compression speed is only relevant when building a kernel. 127 Decompression speed is relevant at each boot. 128 129 If you have any problems with bzip2 or lzma compressed 130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 131 version of this functionality (bzip2 only), for 2.4, was 132 supplied by Christian Ludwig) 133 134 High compression options are mostly useful for users, who 135 are low on disk space (embedded systems), but for whom ram 136 size matters less. 137 138 If in doubt, select 'gzip' 139 140config KERNEL_GZIP 141 bool "Gzip" 142 depends on HAVE_KERNEL_GZIP 143 help 144 The old and tried gzip compression. It provides a good balance 145 between compression ratio and decompression speed. 146 147config KERNEL_BZIP2 148 bool "Bzip2" 149 depends on HAVE_KERNEL_BZIP2 150 help 151 Its compression ratio and speed is intermediate. 152 Decompression speed is slowest among the choices. The kernel 153 size is about 10% smaller with bzip2, in comparison to gzip. 154 Bzip2 uses a large amount of memory. For modern kernels you 155 will need at least 8MB RAM or more for booting. 156 157config KERNEL_LZMA 158 bool "LZMA" 159 depends on HAVE_KERNEL_LZMA 160 help 161 This compression algorithm's ratio is best. Decompression speed 162 is between gzip and bzip2. Compression is slowest. 163 The kernel size is about 33% smaller with LZMA in comparison to gzip. 164 165config KERNEL_XZ 166 bool "XZ" 167 depends on HAVE_KERNEL_XZ 168 help 169 XZ uses the LZMA2 algorithm and instruction set specific 170 BCJ filters which can improve compression ratio of executable 171 code. The size of the kernel is about 30% smaller with XZ in 172 comparison to gzip. On architectures for which there is a BCJ 173 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 174 will create a few percent smaller kernel than plain LZMA. 175 176 The speed is about the same as with LZMA: The decompression 177 speed of XZ is better than that of bzip2 but worse than gzip 178 and LZO. Compression is slow. 179 180config KERNEL_LZO 181 bool "LZO" 182 depends on HAVE_KERNEL_LZO 183 help 184 Its compression ratio is the poorest among the choices. The kernel 185 size is about 10% bigger than gzip; however its speed 186 (both compression and decompression) is the fastest. 187 188config KERNEL_LZ4 189 bool "LZ4" 190 depends on HAVE_KERNEL_LZ4 191 help 192 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 193 A preliminary version of LZ4 de/compression tool is available at 194 <https://code.google.com/p/lz4/>. 195 196 Its compression ratio is worse than LZO. The size of the kernel 197 is about 8% bigger than LZO. But the decompression speed is 198 faster than LZO. 199 200endchoice 201 202config DEFAULT_HOSTNAME 203 string "Default hostname" 204 default "(none)" 205 help 206 This option determines the default system hostname before userspace 207 calls sethostname(2). The kernel traditionally uses "(none)" here, 208 but you may wish to use a different default here to make a minimal 209 system more usable with less configuration. 210 211config SWAP 212 bool "Support for paging of anonymous memory (swap)" 213 depends on MMU && BLOCK 214 default y 215 help 216 This option allows you to choose whether you want to have support 217 for so called swap devices or swap files in your kernel that are 218 used to provide more virtual memory than the actual RAM present 219 in your computer. If unsure say Y. 220 221config SYSVIPC 222 bool "System V IPC" 223 ---help--- 224 Inter Process Communication is a suite of library functions and 225 system calls which let processes (running programs) synchronize and 226 exchange information. It is generally considered to be a good thing, 227 and some programs won't run unless you say Y here. In particular, if 228 you want to run the DOS emulator dosemu under Linux (read the 229 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 230 you'll need to say Y here. 231 232 You can find documentation about IPC with "info ipc" and also in 233 section 6.4 of the Linux Programmer's Guide, available from 234 <http://www.tldp.org/guides.html>. 235 236config SYSVIPC_SYSCTL 237 bool 238 depends on SYSVIPC 239 depends on SYSCTL 240 default y 241 242config POSIX_MQUEUE 243 bool "POSIX Message Queues" 244 depends on NET 245 ---help--- 246 POSIX variant of message queues is a part of IPC. In POSIX message 247 queues every message has a priority which decides about succession 248 of receiving it by a process. If you want to compile and run 249 programs written e.g. for Solaris with use of its POSIX message 250 queues (functions mq_*) say Y here. 251 252 POSIX message queues are visible as a filesystem called 'mqueue' 253 and can be mounted somewhere if you want to do filesystem 254 operations on message queues. 255 256 If unsure, say Y. 257 258config POSIX_MQUEUE_SYSCTL 259 bool 260 depends on POSIX_MQUEUE 261 depends on SYSCTL 262 default y 263 264config CROSS_MEMORY_ATTACH 265 bool "Enable process_vm_readv/writev syscalls" 266 depends on MMU 267 default y 268 help 269 Enabling this option adds the system calls process_vm_readv and 270 process_vm_writev which allow a process with the correct privileges 271 to directly read from or write to another process' address space. 272 See the man page for more details. 273 274config FHANDLE 275 bool "open by fhandle syscalls" 276 select EXPORTFS 277 help 278 If you say Y here, a user level program will be able to map 279 file names to handle and then later use the handle for 280 different file system operations. This is useful in implementing 281 userspace file servers, which now track files using handles instead 282 of names. The handle would remain the same even if file names 283 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 284 syscalls. 285 286config USELIB 287 bool "uselib syscall" 288 default y 289 help 290 This option enables the uselib syscall, a system call used in the 291 dynamic linker from libc5 and earlier. glibc does not use this 292 system call. If you intend to run programs built on libc5 or 293 earlier, you may need to enable this syscall. Current systems 294 running glibc can safely disable this. 295 296config AUDIT 297 bool "Auditing support" 298 depends on NET 299 help 300 Enable auditing infrastructure that can be used with another 301 kernel subsystem, such as SELinux (which requires this for 302 logging of avc messages output). Does not do system-call 303 auditing without CONFIG_AUDITSYSCALL. 304 305config HAVE_ARCH_AUDITSYSCALL 306 bool 307 308config AUDITSYSCALL 309 bool "Enable system-call auditing support" 310 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 311 default y if SECURITY_SELINUX 312 help 313 Enable low-overhead system-call auditing infrastructure that 314 can be used independently or with another kernel subsystem, 315 such as SELinux. 316 317config AUDIT_WATCH 318 def_bool y 319 depends on AUDITSYSCALL 320 select FSNOTIFY 321 322config AUDIT_TREE 323 def_bool y 324 depends on AUDITSYSCALL 325 select FSNOTIFY 326 327source "kernel/irq/Kconfig" 328source "kernel/time/Kconfig" 329 330menu "CPU/Task time and stats accounting" 331 332config VIRT_CPU_ACCOUNTING 333 bool 334 335choice 336 prompt "Cputime accounting" 337 default TICK_CPU_ACCOUNTING if !PPC64 338 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 339 340# Kind of a stub config for the pure tick based cputime accounting 341config TICK_CPU_ACCOUNTING 342 bool "Simple tick based cputime accounting" 343 depends on !S390 && !NO_HZ_FULL 344 help 345 This is the basic tick based cputime accounting that maintains 346 statistics about user, system and idle time spent on per jiffies 347 granularity. 348 349 If unsure, say Y. 350 351config VIRT_CPU_ACCOUNTING_NATIVE 352 bool "Deterministic task and CPU time accounting" 353 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 354 select VIRT_CPU_ACCOUNTING 355 help 356 Select this option to enable more accurate task and CPU time 357 accounting. This is done by reading a CPU counter on each 358 kernel entry and exit and on transitions within the kernel 359 between system, softirq and hardirq state, so there is a 360 small performance impact. In the case of s390 or IBM POWER > 5, 361 this also enables accounting of stolen time on logically-partitioned 362 systems. 363 364config VIRT_CPU_ACCOUNTING_GEN 365 bool "Full dynticks CPU time accounting" 366 depends on HAVE_CONTEXT_TRACKING 367 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 368 select VIRT_CPU_ACCOUNTING 369 select CONTEXT_TRACKING 370 help 371 Select this option to enable task and CPU time accounting on full 372 dynticks systems. This accounting is implemented by watching every 373 kernel-user boundaries using the context tracking subsystem. 374 The accounting is thus performed at the expense of some significant 375 overhead. 376 377 For now this is only useful if you are working on the full 378 dynticks subsystem development. 379 380 If unsure, say N. 381 382config IRQ_TIME_ACCOUNTING 383 bool "Fine granularity task level IRQ time accounting" 384 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL 385 help 386 Select this option to enable fine granularity task irq time 387 accounting. This is done by reading a timestamp on each 388 transitions between softirq and hardirq state, so there can be a 389 small performance impact. 390 391 If in doubt, say N here. 392 393endchoice 394 395config BSD_PROCESS_ACCT 396 bool "BSD Process Accounting" 397 depends on MULTIUSER 398 help 399 If you say Y here, a user level program will be able to instruct the 400 kernel (via a special system call) to write process accounting 401 information to a file: whenever a process exits, information about 402 that process will be appended to the file by the kernel. The 403 information includes things such as creation time, owning user, 404 command name, memory usage, controlling terminal etc. (the complete 405 list is in the struct acct in <file:include/linux/acct.h>). It is 406 up to the user level program to do useful things with this 407 information. This is generally a good idea, so say Y. 408 409config BSD_PROCESS_ACCT_V3 410 bool "BSD Process Accounting version 3 file format" 411 depends on BSD_PROCESS_ACCT 412 default n 413 help 414 If you say Y here, the process accounting information is written 415 in a new file format that also logs the process IDs of each 416 process and it's parent. Note that this file format is incompatible 417 with previous v0/v1/v2 file formats, so you will need updated tools 418 for processing it. A preliminary version of these tools is available 419 at <http://www.gnu.org/software/acct/>. 420 421config TASKSTATS 422 bool "Export task/process statistics through netlink" 423 depends on NET 424 depends on MULTIUSER 425 default n 426 help 427 Export selected statistics for tasks/processes through the 428 generic netlink interface. Unlike BSD process accounting, the 429 statistics are available during the lifetime of tasks/processes as 430 responses to commands. Like BSD accounting, they are sent to user 431 space on task exit. 432 433 Say N if unsure. 434 435config TASK_DELAY_ACCT 436 bool "Enable per-task delay accounting" 437 depends on TASKSTATS 438 select SCHED_INFO 439 help 440 Collect information on time spent by a task waiting for system 441 resources like cpu, synchronous block I/O completion and swapping 442 in pages. Such statistics can help in setting a task's priorities 443 relative to other tasks for cpu, io, rss limits etc. 444 445 Say N if unsure. 446 447config TASK_XACCT 448 bool "Enable extended accounting over taskstats" 449 depends on TASKSTATS 450 help 451 Collect extended task accounting data and send the data 452 to userland for processing over the taskstats interface. 453 454 Say N if unsure. 455 456config TASK_IO_ACCOUNTING 457 bool "Enable per-task storage I/O accounting" 458 depends on TASK_XACCT 459 help 460 Collect information on the number of bytes of storage I/O which this 461 task has caused. 462 463 Say N if unsure. 464 465endmenu # "CPU/Task time and stats accounting" 466 467menu "RCU Subsystem" 468 469config TREE_RCU 470 bool 471 default y if !PREEMPT && SMP 472 help 473 This option selects the RCU implementation that is 474 designed for very large SMP system with hundreds or 475 thousands of CPUs. It also scales down nicely to 476 smaller systems. 477 478config PREEMPT_RCU 479 bool 480 default y if PREEMPT 481 help 482 This option selects the RCU implementation that is 483 designed for very large SMP systems with hundreds or 484 thousands of CPUs, but for which real-time response 485 is also required. It also scales down nicely to 486 smaller systems. 487 488 Select this option if you are unsure. 489 490config TINY_RCU 491 bool 492 default y if !PREEMPT && !SMP 493 help 494 This option selects the RCU implementation that is 495 designed for UP systems from which real-time response 496 is not required. This option greatly reduces the 497 memory footprint of RCU. 498 499config RCU_EXPERT 500 bool "Make expert-level adjustments to RCU configuration" 501 default n 502 help 503 This option needs to be enabled if you wish to make 504 expert-level adjustments to RCU configuration. By default, 505 no such adjustments can be made, which has the often-beneficial 506 side-effect of preventing "make oldconfig" from asking you all 507 sorts of detailed questions about how you would like numerous 508 obscure RCU options to be set up. 509 510 Say Y if you need to make expert-level adjustments to RCU. 511 512 Say N if you are unsure. 513 514config SRCU 515 bool 516 help 517 This option selects the sleepable version of RCU. This version 518 permits arbitrary sleeping or blocking within RCU read-side critical 519 sections. 520 521config TASKS_RCU 522 bool 523 default n 524 select SRCU 525 help 526 This option enables a task-based RCU implementation that uses 527 only voluntary context switch (not preemption!), idle, and 528 user-mode execution as quiescent states. 529 530config RCU_STALL_COMMON 531 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE ) 532 help 533 This option enables RCU CPU stall code that is common between 534 the TINY and TREE variants of RCU. The purpose is to allow 535 the tiny variants to disable RCU CPU stall warnings, while 536 making these warnings mandatory for the tree variants. 537 538config CONTEXT_TRACKING 539 bool 540 541config CONTEXT_TRACKING_FORCE 542 bool "Force context tracking" 543 depends on CONTEXT_TRACKING 544 default y if !NO_HZ_FULL 545 help 546 The major pre-requirement for full dynticks to work is to 547 support the context tracking subsystem. But there are also 548 other dependencies to provide in order to make the full 549 dynticks working. 550 551 This option stands for testing when an arch implements the 552 context tracking backend but doesn't yet fullfill all the 553 requirements to make the full dynticks feature working. 554 Without the full dynticks, there is no way to test the support 555 for context tracking and the subsystems that rely on it: RCU 556 userspace extended quiescent state and tickless cputime 557 accounting. This option copes with the absence of the full 558 dynticks subsystem by forcing the context tracking on all 559 CPUs in the system. 560 561 Say Y only if you're working on the development of an 562 architecture backend for the context tracking. 563 564 Say N otherwise, this option brings an overhead that you 565 don't want in production. 566 567 568config RCU_FANOUT 569 int "Tree-based hierarchical RCU fanout value" 570 range 2 64 if 64BIT 571 range 2 32 if !64BIT 572 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 573 default 64 if 64BIT 574 default 32 if !64BIT 575 help 576 This option controls the fanout of hierarchical implementations 577 of RCU, allowing RCU to work efficiently on machines with 578 large numbers of CPUs. This value must be at least the fourth 579 root of NR_CPUS, which allows NR_CPUS to be insanely large. 580 The default value of RCU_FANOUT should be used for production 581 systems, but if you are stress-testing the RCU implementation 582 itself, small RCU_FANOUT values allow you to test large-system 583 code paths on small(er) systems. 584 585 Select a specific number if testing RCU itself. 586 Take the default if unsure. 587 588config RCU_FANOUT_LEAF 589 int "Tree-based hierarchical RCU leaf-level fanout value" 590 range 2 64 if 64BIT 591 range 2 32 if !64BIT 592 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 593 default 16 594 help 595 This option controls the leaf-level fanout of hierarchical 596 implementations of RCU, and allows trading off cache misses 597 against lock contention. Systems that synchronize their 598 scheduling-clock interrupts for energy-efficiency reasons will 599 want the default because the smaller leaf-level fanout keeps 600 lock contention levels acceptably low. Very large systems 601 (hundreds or thousands of CPUs) will instead want to set this 602 value to the maximum value possible in order to reduce the 603 number of cache misses incurred during RCU's grace-period 604 initialization. These systems tend to run CPU-bound, and thus 605 are not helped by synchronized interrupts, and thus tend to 606 skew them, which reduces lock contention enough that large 607 leaf-level fanouts work well. 608 609 Select a specific number if testing RCU itself. 610 611 Select the maximum permissible value for large systems. 612 613 Take the default if unsure. 614 615config RCU_FAST_NO_HZ 616 bool "Accelerate last non-dyntick-idle CPU's grace periods" 617 depends on NO_HZ_COMMON && SMP && RCU_EXPERT 618 default n 619 help 620 This option permits CPUs to enter dynticks-idle state even if 621 they have RCU callbacks queued, and prevents RCU from waking 622 these CPUs up more than roughly once every four jiffies (by 623 default, you can adjust this using the rcutree.rcu_idle_gp_delay 624 parameter), thus improving energy efficiency. On the other 625 hand, this option increases the duration of RCU grace periods, 626 for example, slowing down synchronize_rcu(). 627 628 Say Y if energy efficiency is critically important, and you 629 don't care about increased grace-period durations. 630 631 Say N if you are unsure. 632 633config TREE_RCU_TRACE 634 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) 635 select DEBUG_FS 636 help 637 This option provides tracing for the TREE_RCU and 638 PREEMPT_RCU implementations, permitting Makefile to 639 trivially select kernel/rcutree_trace.c. 640 641config RCU_BOOST 642 bool "Enable RCU priority boosting" 643 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT 644 default n 645 help 646 This option boosts the priority of preempted RCU readers that 647 block the current preemptible RCU grace period for too long. 648 This option also prevents heavy loads from blocking RCU 649 callback invocation for all flavors of RCU. 650 651 Say Y here if you are working with real-time apps or heavy loads 652 Say N here if you are unsure. 653 654config RCU_KTHREAD_PRIO 655 int "Real-time priority to use for RCU worker threads" 656 range 1 99 if RCU_BOOST 657 range 0 99 if !RCU_BOOST 658 default 1 if RCU_BOOST 659 default 0 if !RCU_BOOST 660 depends on RCU_EXPERT 661 help 662 This option specifies the SCHED_FIFO priority value that will be 663 assigned to the rcuc/n and rcub/n threads and is also the value 664 used for RCU_BOOST (if enabled). If you are working with a 665 real-time application that has one or more CPU-bound threads 666 running at a real-time priority level, you should set 667 RCU_KTHREAD_PRIO to a priority higher than the highest-priority 668 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO 669 value of 1 is appropriate in the common case, which is real-time 670 applications that do not have any CPU-bound threads. 671 672 Some real-time applications might not have a single real-time 673 thread that saturates a given CPU, but instead might have 674 multiple real-time threads that, taken together, fully utilize 675 that CPU. In this case, you should set RCU_KTHREAD_PRIO to 676 a priority higher than the lowest-priority thread that is 677 conspiring to prevent the CPU from running any non-real-time 678 tasks. For example, if one thread at priority 10 and another 679 thread at priority 5 are between themselves fully consuming 680 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be 681 set to priority 6 or higher. 682 683 Specify the real-time priority, or take the default if unsure. 684 685config RCU_BOOST_DELAY 686 int "Milliseconds to delay boosting after RCU grace-period start" 687 range 0 3000 688 depends on RCU_BOOST 689 default 500 690 help 691 This option specifies the time to wait after the beginning of 692 a given grace period before priority-boosting preempted RCU 693 readers blocking that grace period. Note that any RCU reader 694 blocking an expedited RCU grace period is boosted immediately. 695 696 Accept the default if unsure. 697 698config RCU_NOCB_CPU 699 bool "Offload RCU callback processing from boot-selected CPUs" 700 depends on TREE_RCU || PREEMPT_RCU 701 depends on RCU_EXPERT || NO_HZ_FULL 702 default n 703 help 704 Use this option to reduce OS jitter for aggressive HPC or 705 real-time workloads. It can also be used to offload RCU 706 callback invocation to energy-efficient CPUs in battery-powered 707 asymmetric multiprocessors. 708 709 This option offloads callback invocation from the set of 710 CPUs specified at boot time by the rcu_nocbs parameter. 711 For each such CPU, a kthread ("rcuox/N") will be created to 712 invoke callbacks, where the "N" is the CPU being offloaded, 713 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 714 "s" for RCU-sched. Nothing prevents this kthread from running 715 on the specified CPUs, but (1) the kthreads may be preempted 716 between each callback, and (2) affinity or cgroups can be used 717 to force the kthreads to run on whatever set of CPUs is desired. 718 719 Say Y here if you want to help to debug reduced OS jitter. 720 Say N here if you are unsure. 721 722choice 723 prompt "Build-forced no-CBs CPUs" 724 default RCU_NOCB_CPU_NONE 725 depends on RCU_NOCB_CPU 726 help 727 This option allows no-CBs CPUs (whose RCU callbacks are invoked 728 from kthreads rather than from softirq context) to be specified 729 at build time. Additional no-CBs CPUs may be specified by 730 the rcu_nocbs= boot parameter. 731 732config RCU_NOCB_CPU_NONE 733 bool "No build_forced no-CBs CPUs" 734 help 735 This option does not force any of the CPUs to be no-CBs CPUs. 736 Only CPUs designated by the rcu_nocbs= boot parameter will be 737 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 738 kthreads whose names begin with "rcuo". All other CPUs will 739 invoke their own RCU callbacks in softirq context. 740 741 Select this option if you want to choose no-CBs CPUs at 742 boot time, for example, to allow testing of different no-CBs 743 configurations without having to rebuild the kernel each time. 744 745config RCU_NOCB_CPU_ZERO 746 bool "CPU 0 is a build_forced no-CBs CPU" 747 help 748 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 749 callbacks are invoked by a per-CPU kthread whose name begins 750 with "rcuo". Additional CPUs may be designated as no-CBs 751 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 752 All other CPUs will invoke their own RCU callbacks in softirq 753 context. 754 755 Select this if CPU 0 needs to be a no-CBs CPU for real-time 756 or energy-efficiency reasons, but the real reason it exists 757 is to ensure that randconfig testing covers mixed systems. 758 759config RCU_NOCB_CPU_ALL 760 bool "All CPUs are build_forced no-CBs CPUs" 761 help 762 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 763 boot parameter will be ignored. All CPUs' RCU callbacks will 764 be executed in the context of per-CPU rcuo kthreads created for 765 this purpose. Assuming that the kthreads whose names start with 766 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 767 on the remaining CPUs, but might decrease memory locality during 768 RCU-callback invocation, thus potentially degrading throughput. 769 770 Select this if all CPUs need to be no-CBs CPUs for real-time 771 or energy-efficiency reasons. 772 773endchoice 774 775config RCU_EXPEDITE_BOOT 776 bool 777 default n 778 help 779 This option enables expedited grace periods at boot time, 780 as if rcu_expedite_gp() had been invoked early in boot. 781 The corresponding rcu_unexpedite_gp() is invoked from 782 rcu_end_inkernel_boot(), which is intended to be invoked 783 at the end of the kernel-only boot sequence, just before 784 init is exec'ed. 785 786 Accept the default if unsure. 787 788endmenu # "RCU Subsystem" 789 790config BUILD_BIN2C 791 bool 792 default n 793 794config IKCONFIG 795 tristate "Kernel .config support" 796 select BUILD_BIN2C 797 ---help--- 798 This option enables the complete Linux kernel ".config" file 799 contents to be saved in the kernel. It provides documentation 800 of which kernel options are used in a running kernel or in an 801 on-disk kernel. This information can be extracted from the kernel 802 image file with the script scripts/extract-ikconfig and used as 803 input to rebuild the current kernel or to build another kernel. 804 It can also be extracted from a running kernel by reading 805 /proc/config.gz if enabled (below). 806 807config IKCONFIG_PROC 808 bool "Enable access to .config through /proc/config.gz" 809 depends on IKCONFIG && PROC_FS 810 ---help--- 811 This option enables access to the kernel configuration file 812 through /proc/config.gz. 813 814config LOG_BUF_SHIFT 815 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 816 range 12 25 817 default 17 818 depends on PRINTK 819 help 820 Select the minimal kernel log buffer size as a power of 2. 821 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 822 parameter, see below. Any higher size also might be forced 823 by "log_buf_len" boot parameter. 824 825 Examples: 826 17 => 128 KB 827 16 => 64 KB 828 15 => 32 KB 829 14 => 16 KB 830 13 => 8 KB 831 12 => 4 KB 832 833config LOG_CPU_MAX_BUF_SHIFT 834 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 835 depends on SMP 836 range 0 21 837 default 12 if !BASE_SMALL 838 default 0 if BASE_SMALL 839 depends on PRINTK 840 help 841 This option allows to increase the default ring buffer size 842 according to the number of CPUs. The value defines the contribution 843 of each CPU as a power of 2. The used space is typically only few 844 lines however it might be much more when problems are reported, 845 e.g. backtraces. 846 847 The increased size means that a new buffer has to be allocated and 848 the original static one is unused. It makes sense only on systems 849 with more CPUs. Therefore this value is used only when the sum of 850 contributions is greater than the half of the default kernel ring 851 buffer as defined by LOG_BUF_SHIFT. The default values are set 852 so that more than 64 CPUs are needed to trigger the allocation. 853 854 Also this option is ignored when "log_buf_len" kernel parameter is 855 used as it forces an exact (power of two) size of the ring buffer. 856 857 The number of possible CPUs is used for this computation ignoring 858 hotplugging making the compuation optimal for the the worst case 859 scenerio while allowing a simple algorithm to be used from bootup. 860 861 Examples shift values and their meaning: 862 17 => 128 KB for each CPU 863 16 => 64 KB for each CPU 864 15 => 32 KB for each CPU 865 14 => 16 KB for each CPU 866 13 => 8 KB for each CPU 867 12 => 4 KB for each CPU 868 869# 870# Architectures with an unreliable sched_clock() should select this: 871# 872config HAVE_UNSTABLE_SCHED_CLOCK 873 bool 874 875config GENERIC_SCHED_CLOCK 876 bool 877 878# 879# For architectures that want to enable the support for NUMA-affine scheduler 880# balancing logic: 881# 882config ARCH_SUPPORTS_NUMA_BALANCING 883 bool 884 885# 886# For architectures that prefer to flush all TLBs after a number of pages 887# are unmapped instead of sending one IPI per page to flush. The architecture 888# must provide guarantees on what happens if a clean TLB cache entry is 889# written after the unmap. Details are in mm/rmap.c near the check for 890# should_defer_flush. The architecture should also consider if the full flush 891# and the refill costs are offset by the savings of sending fewer IPIs. 892config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 893 bool 894 895# 896# For architectures that know their GCC __int128 support is sound 897# 898config ARCH_SUPPORTS_INT128 899 bool 900 901# For architectures that (ab)use NUMA to represent different memory regions 902# all cpu-local but of different latencies, such as SuperH. 903# 904config ARCH_WANT_NUMA_VARIABLE_LOCALITY 905 bool 906 907config NUMA_BALANCING 908 bool "Memory placement aware NUMA scheduler" 909 depends on ARCH_SUPPORTS_NUMA_BALANCING 910 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 911 depends on SMP && NUMA && MIGRATION 912 help 913 This option adds support for automatic NUMA aware memory/task placement. 914 The mechanism is quite primitive and is based on migrating memory when 915 it has references to the node the task is running on. 916 917 This system will be inactive on UMA systems. 918 919config NUMA_BALANCING_DEFAULT_ENABLED 920 bool "Automatically enable NUMA aware memory/task placement" 921 default y 922 depends on NUMA_BALANCING 923 help 924 If set, automatic NUMA balancing will be enabled if running on a NUMA 925 machine. 926 927menuconfig CGROUPS 928 bool "Control Group support" 929 select KERNFS 930 help 931 This option adds support for grouping sets of processes together, for 932 use with process control subsystems such as Cpusets, CFS, memory 933 controls or device isolation. 934 See 935 - Documentation/scheduler/sched-design-CFS.txt (CFS) 936 - Documentation/cgroups/ (features for grouping, isolation 937 and resource control) 938 939 Say N if unsure. 940 941if CGROUPS 942 943config CGROUP_DEBUG 944 bool "Example debug cgroup subsystem" 945 default n 946 help 947 This option enables a simple cgroup subsystem that 948 exports useful debugging information about the cgroups 949 framework. 950 951 Say N if unsure. 952 953config CGROUP_FREEZER 954 bool "Freezer cgroup subsystem" 955 help 956 Provides a way to freeze and unfreeze all tasks in a 957 cgroup. 958 959config CGROUP_PIDS 960 bool "PIDs cgroup subsystem" 961 help 962 Provides enforcement of process number limits in the scope of a 963 cgroup. Any attempt to fork more processes than is allowed in the 964 cgroup will fail. PIDs are fundamentally a global resource because it 965 is fairly trivial to reach PID exhaustion before you reach even a 966 conservative kmemcg limit. As a result, it is possible to grind a 967 system to halt without being limited by other cgroup policies. The 968 PIDs cgroup subsystem is designed to stop this from happening. 969 970 It should be noted that organisational operations (such as attaching 971 to a cgroup hierarchy will *not* be blocked by the PIDs subsystem), 972 since the PIDs limit only affects a process's ability to fork, not to 973 attach to a cgroup. 974 975config CGROUP_DEVICE 976 bool "Device controller for cgroups" 977 help 978 Provides a cgroup implementing whitelists for devices which 979 a process in the cgroup can mknod or open. 980 981config CPUSETS 982 bool "Cpuset support" 983 help 984 This option will let you create and manage CPUSETs which 985 allow dynamically partitioning a system into sets of CPUs and 986 Memory Nodes and assigning tasks to run only within those sets. 987 This is primarily useful on large SMP or NUMA systems. 988 989 Say N if unsure. 990 991config PROC_PID_CPUSET 992 bool "Include legacy /proc/<pid>/cpuset file" 993 depends on CPUSETS 994 default y 995 996config CGROUP_CPUACCT 997 bool "Simple CPU accounting cgroup subsystem" 998 help 999 Provides a simple Resource Controller for monitoring the 1000 total CPU consumed by the tasks in a cgroup. 1001 1002config PAGE_COUNTER 1003 bool 1004 1005config MEMCG 1006 bool "Memory Resource Controller for Control Groups" 1007 select PAGE_COUNTER 1008 select EVENTFD 1009 help 1010 Provides a memory resource controller that manages both anonymous 1011 memory and page cache. (See Documentation/cgroups/memory.txt) 1012 1013config MEMCG_SWAP 1014 bool "Memory Resource Controller Swap Extension" 1015 depends on MEMCG && SWAP 1016 help 1017 Add swap management feature to memory resource controller. When you 1018 enable this, you can limit mem+swap usage per cgroup. In other words, 1019 when you disable this, memory resource controller has no cares to 1020 usage of swap...a process can exhaust all of the swap. This extension 1021 is useful when you want to avoid exhaustion swap but this itself 1022 adds more overheads and consumes memory for remembering information. 1023 Especially if you use 32bit system or small memory system, please 1024 be careful about enabling this. When memory resource controller 1025 is disabled by boot option, this will be automatically disabled and 1026 there will be no overhead from this. Even when you set this config=y, 1027 if boot option "swapaccount=0" is set, swap will not be accounted. 1028 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 1029 size is 4096bytes, 512k per 1Gbytes of swap. 1030config MEMCG_SWAP_ENABLED 1031 bool "Memory Resource Controller Swap Extension enabled by default" 1032 depends on MEMCG_SWAP 1033 default y 1034 help 1035 Memory Resource Controller Swap Extension comes with its price in 1036 a bigger memory consumption. General purpose distribution kernels 1037 which want to enable the feature but keep it disabled by default 1038 and let the user enable it by swapaccount=1 boot command line 1039 parameter should have this option unselected. 1040 For those who want to have the feature enabled by default should 1041 select this option (if, for some reason, they need to disable it 1042 then swapaccount=0 does the trick). 1043config MEMCG_KMEM 1044 bool "Memory Resource Controller Kernel Memory accounting" 1045 depends on MEMCG 1046 depends on SLUB || SLAB 1047 help 1048 The Kernel Memory extension for Memory Resource Controller can limit 1049 the amount of memory used by kernel objects in the system. Those are 1050 fundamentally different from the entities handled by the standard 1051 Memory Controller, which are page-based, and can be swapped. Users of 1052 the kmem extension can use it to guarantee that no group of processes 1053 will ever exhaust kernel resources alone. 1054 1055config CGROUP_HUGETLB 1056 bool "HugeTLB Resource Controller for Control Groups" 1057 depends on HUGETLB_PAGE 1058 select PAGE_COUNTER 1059 default n 1060 help 1061 Provides a cgroup Resource Controller for HugeTLB pages. 1062 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1063 The limit is enforced during page fault. Since HugeTLB doesn't 1064 support page reclaim, enforcing the limit at page fault time implies 1065 that, the application will get SIGBUS signal if it tries to access 1066 HugeTLB pages beyond its limit. This requires the application to know 1067 beforehand how much HugeTLB pages it would require for its use. The 1068 control group is tracked in the third page lru pointer. This means 1069 that we cannot use the controller with huge page less than 3 pages. 1070 1071config CGROUP_PERF 1072 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 1073 depends on PERF_EVENTS && CGROUPS 1074 help 1075 This option extends the per-cpu mode to restrict monitoring to 1076 threads which belong to the cgroup specified and run on the 1077 designated cpu. 1078 1079 Say N if unsure. 1080 1081menuconfig CGROUP_SCHED 1082 bool "Group CPU scheduler" 1083 default n 1084 help 1085 This feature lets CPU scheduler recognize task groups and control CPU 1086 bandwidth allocation to such task groups. It uses cgroups to group 1087 tasks. 1088 1089if CGROUP_SCHED 1090config FAIR_GROUP_SCHED 1091 bool "Group scheduling for SCHED_OTHER" 1092 depends on CGROUP_SCHED 1093 default CGROUP_SCHED 1094 1095config CFS_BANDWIDTH 1096 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1097 depends on FAIR_GROUP_SCHED 1098 default n 1099 help 1100 This option allows users to define CPU bandwidth rates (limits) for 1101 tasks running within the fair group scheduler. Groups with no limit 1102 set are considered to be unconstrained and will run with no 1103 restriction. 1104 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1105 1106config RT_GROUP_SCHED 1107 bool "Group scheduling for SCHED_RR/FIFO" 1108 depends on CGROUP_SCHED 1109 default n 1110 help 1111 This feature lets you explicitly allocate real CPU bandwidth 1112 to task groups. If enabled, it will also make it impossible to 1113 schedule realtime tasks for non-root users until you allocate 1114 realtime bandwidth for them. 1115 See Documentation/scheduler/sched-rt-group.txt for more information. 1116 1117endif #CGROUP_SCHED 1118 1119config BLK_CGROUP 1120 bool "Block IO controller" 1121 depends on BLOCK 1122 default n 1123 ---help--- 1124 Generic block IO controller cgroup interface. This is the common 1125 cgroup interface which should be used by various IO controlling 1126 policies. 1127 1128 Currently, CFQ IO scheduler uses it to recognize task groups and 1129 control disk bandwidth allocation (proportional time slice allocation) 1130 to such task groups. It is also used by bio throttling logic in 1131 block layer to implement upper limit in IO rates on a device. 1132 1133 This option only enables generic Block IO controller infrastructure. 1134 One needs to also enable actual IO controlling logic/policy. For 1135 enabling proportional weight division of disk bandwidth in CFQ, set 1136 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1137 CONFIG_BLK_DEV_THROTTLING=y. 1138 1139 See Documentation/cgroups/blkio-controller.txt for more information. 1140 1141config DEBUG_BLK_CGROUP 1142 bool "Enable Block IO controller debugging" 1143 depends on BLK_CGROUP 1144 default n 1145 ---help--- 1146 Enable some debugging help. Currently it exports additional stat 1147 files in a cgroup which can be useful for debugging. 1148 1149config CGROUP_WRITEBACK 1150 bool 1151 depends on MEMCG && BLK_CGROUP 1152 default y 1153 1154endif # CGROUPS 1155 1156config CHECKPOINT_RESTORE 1157 bool "Checkpoint/restore support" if EXPERT 1158 select PROC_CHILDREN 1159 default n 1160 help 1161 Enables additional kernel features in a sake of checkpoint/restore. 1162 In particular it adds auxiliary prctl codes to setup process text, 1163 data and heap segment sizes, and a few additional /proc filesystem 1164 entries. 1165 1166 If unsure, say N here. 1167 1168menuconfig NAMESPACES 1169 bool "Namespaces support" if EXPERT 1170 depends on MULTIUSER 1171 default !EXPERT 1172 help 1173 Provides the way to make tasks work with different objects using 1174 the same id. For example same IPC id may refer to different objects 1175 or same user id or pid may refer to different tasks when used in 1176 different namespaces. 1177 1178if NAMESPACES 1179 1180config UTS_NS 1181 bool "UTS namespace" 1182 default y 1183 help 1184 In this namespace tasks see different info provided with the 1185 uname() system call 1186 1187config IPC_NS 1188 bool "IPC namespace" 1189 depends on (SYSVIPC || POSIX_MQUEUE) 1190 default y 1191 help 1192 In this namespace tasks work with IPC ids which correspond to 1193 different IPC objects in different namespaces. 1194 1195config USER_NS 1196 bool "User namespace" 1197 default n 1198 help 1199 This allows containers, i.e. vservers, to use user namespaces 1200 to provide different user info for different servers. 1201 1202 When user namespaces are enabled in the kernel it is 1203 recommended that the MEMCG and MEMCG_KMEM options also be 1204 enabled and that user-space use the memory control groups to 1205 limit the amount of memory a memory unprivileged users can 1206 use. 1207 1208 If unsure, say N. 1209 1210config PID_NS 1211 bool "PID Namespaces" 1212 default y 1213 help 1214 Support process id namespaces. This allows having multiple 1215 processes with the same pid as long as they are in different 1216 pid namespaces. This is a building block of containers. 1217 1218config NET_NS 1219 bool "Network namespace" 1220 depends on NET 1221 default y 1222 help 1223 Allow user space to create what appear to be multiple instances 1224 of the network stack. 1225 1226endif # NAMESPACES 1227 1228config SCHED_AUTOGROUP 1229 bool "Automatic process group scheduling" 1230 select CGROUPS 1231 select CGROUP_SCHED 1232 select FAIR_GROUP_SCHED 1233 help 1234 This option optimizes the scheduler for common desktop workloads by 1235 automatically creating and populating task groups. This separation 1236 of workloads isolates aggressive CPU burners (like build jobs) from 1237 desktop applications. Task group autogeneration is currently based 1238 upon task session. 1239 1240config SYSFS_DEPRECATED 1241 bool "Enable deprecated sysfs features to support old userspace tools" 1242 depends on SYSFS 1243 default n 1244 help 1245 This option adds code that switches the layout of the "block" class 1246 devices, to not show up in /sys/class/block/, but only in 1247 /sys/block/. 1248 1249 This switch is only active when the sysfs.deprecated=1 boot option is 1250 passed or the SYSFS_DEPRECATED_V2 option is set. 1251 1252 This option allows new kernels to run on old distributions and tools, 1253 which might get confused by /sys/class/block/. Since 2007/2008 all 1254 major distributions and tools handle this just fine. 1255 1256 Recent distributions and userspace tools after 2009/2010 depend on 1257 the existence of /sys/class/block/, and will not work with this 1258 option enabled. 1259 1260 Only if you are using a new kernel on an old distribution, you might 1261 need to say Y here. 1262 1263config SYSFS_DEPRECATED_V2 1264 bool "Enable deprecated sysfs features by default" 1265 default n 1266 depends on SYSFS 1267 depends on SYSFS_DEPRECATED 1268 help 1269 Enable deprecated sysfs by default. 1270 1271 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1272 option. 1273 1274 Only if you are using a new kernel on an old distribution, you might 1275 need to say Y here. Even then, odds are you would not need it 1276 enabled, you can always pass the boot option if absolutely necessary. 1277 1278config RELAY 1279 bool "Kernel->user space relay support (formerly relayfs)" 1280 help 1281 This option enables support for relay interface support in 1282 certain file systems (such as debugfs). 1283 It is designed to provide an efficient mechanism for tools and 1284 facilities to relay large amounts of data from kernel space to 1285 user space. 1286 1287 If unsure, say N. 1288 1289config BLK_DEV_INITRD 1290 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1291 depends on BROKEN || !FRV 1292 help 1293 The initial RAM filesystem is a ramfs which is loaded by the 1294 boot loader (loadlin or lilo) and that is mounted as root 1295 before the normal boot procedure. It is typically used to 1296 load modules needed to mount the "real" root file system, 1297 etc. See <file:Documentation/initrd.txt> for details. 1298 1299 If RAM disk support (BLK_DEV_RAM) is also included, this 1300 also enables initial RAM disk (initrd) support and adds 1301 15 Kbytes (more on some other architectures) to the kernel size. 1302 1303 If unsure say Y. 1304 1305if BLK_DEV_INITRD 1306 1307source "usr/Kconfig" 1308 1309endif 1310 1311config CC_OPTIMIZE_FOR_SIZE 1312 bool "Optimize for size" 1313 help 1314 Enabling this option will pass "-Os" instead of "-O2" to 1315 your compiler resulting in a smaller kernel. 1316 1317 If unsure, say N. 1318 1319config SYSCTL 1320 bool 1321 1322config ANON_INODES 1323 bool 1324 1325config HAVE_UID16 1326 bool 1327 1328config SYSCTL_EXCEPTION_TRACE 1329 bool 1330 help 1331 Enable support for /proc/sys/debug/exception-trace. 1332 1333config SYSCTL_ARCH_UNALIGN_NO_WARN 1334 bool 1335 help 1336 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1337 Allows arch to define/use @no_unaligned_warning to possibly warn 1338 about unaligned access emulation going on under the hood. 1339 1340config SYSCTL_ARCH_UNALIGN_ALLOW 1341 bool 1342 help 1343 Enable support for /proc/sys/kernel/unaligned-trap 1344 Allows arches to define/use @unaligned_enabled to runtime toggle 1345 the unaligned access emulation. 1346 see arch/parisc/kernel/unaligned.c for reference 1347 1348config HAVE_PCSPKR_PLATFORM 1349 bool 1350 1351# interpreter that classic socket filters depend on 1352config BPF 1353 bool 1354 1355menuconfig EXPERT 1356 bool "Configure standard kernel features (expert users)" 1357 # Unhide debug options, to make the on-by-default options visible 1358 select DEBUG_KERNEL 1359 help 1360 This option allows certain base kernel options and settings 1361 to be disabled or tweaked. This is for specialized 1362 environments which can tolerate a "non-standard" kernel. 1363 Only use this if you really know what you are doing. 1364 1365config UID16 1366 bool "Enable 16-bit UID system calls" if EXPERT 1367 depends on HAVE_UID16 && MULTIUSER 1368 default y 1369 help 1370 This enables the legacy 16-bit UID syscall wrappers. 1371 1372config MULTIUSER 1373 bool "Multiple users, groups and capabilities support" if EXPERT 1374 default y 1375 help 1376 This option enables support for non-root users, groups and 1377 capabilities. 1378 1379 If you say N here, all processes will run with UID 0, GID 0, and all 1380 possible capabilities. Saying N here also compiles out support for 1381 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1382 setgid, and capset. 1383 1384 If unsure, say Y here. 1385 1386config SGETMASK_SYSCALL 1387 bool "sgetmask/ssetmask syscalls support" if EXPERT 1388 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1389 ---help--- 1390 sys_sgetmask and sys_ssetmask are obsolete system calls 1391 no longer supported in libc but still enabled by default in some 1392 architectures. 1393 1394 If unsure, leave the default option here. 1395 1396config SYSFS_SYSCALL 1397 bool "Sysfs syscall support" if EXPERT 1398 default y 1399 ---help--- 1400 sys_sysfs is an obsolete system call no longer supported in libc. 1401 Note that disabling this option is more secure but might break 1402 compatibility with some systems. 1403 1404 If unsure say Y here. 1405 1406config SYSCTL_SYSCALL 1407 bool "Sysctl syscall support" if EXPERT 1408 depends on PROC_SYSCTL 1409 default n 1410 select SYSCTL 1411 ---help--- 1412 sys_sysctl uses binary paths that have been found challenging 1413 to properly maintain and use. The interface in /proc/sys 1414 using paths with ascii names is now the primary path to this 1415 information. 1416 1417 Almost nothing using the binary sysctl interface so if you are 1418 trying to save some space it is probably safe to disable this, 1419 making your kernel marginally smaller. 1420 1421 If unsure say N here. 1422 1423config KALLSYMS 1424 bool "Load all symbols for debugging/ksymoops" if EXPERT 1425 default y 1426 help 1427 Say Y here to let the kernel print out symbolic crash information and 1428 symbolic stack backtraces. This increases the size of the kernel 1429 somewhat, as all symbols have to be loaded into the kernel image. 1430 1431config KALLSYMS_ALL 1432 bool "Include all symbols in kallsyms" 1433 depends on DEBUG_KERNEL && KALLSYMS 1434 help 1435 Normally kallsyms only contains the symbols of functions for nicer 1436 OOPS messages and backtraces (i.e., symbols from the text and inittext 1437 sections). This is sufficient for most cases. And only in very rare 1438 cases (e.g., when a debugger is used) all symbols are required (e.g., 1439 names of variables from the data sections, etc). 1440 1441 This option makes sure that all symbols are loaded into the kernel 1442 image (i.e., symbols from all sections) in cost of increased kernel 1443 size (depending on the kernel configuration, it may be 300KiB or 1444 something like this). 1445 1446 Say N unless you really need all symbols. 1447 1448config PRINTK 1449 default y 1450 bool "Enable support for printk" if EXPERT 1451 select IRQ_WORK 1452 help 1453 This option enables normal printk support. Removing it 1454 eliminates most of the message strings from the kernel image 1455 and makes the kernel more or less silent. As this makes it 1456 very difficult to diagnose system problems, saying N here is 1457 strongly discouraged. 1458 1459config BUG 1460 bool "BUG() support" if EXPERT 1461 default y 1462 help 1463 Disabling this option eliminates support for BUG and WARN, reducing 1464 the size of your kernel image and potentially quietly ignoring 1465 numerous fatal conditions. You should only consider disabling this 1466 option for embedded systems with no facilities for reporting errors. 1467 Just say Y. 1468 1469config ELF_CORE 1470 depends on COREDUMP 1471 default y 1472 bool "Enable ELF core dumps" if EXPERT 1473 help 1474 Enable support for generating core dumps. Disabling saves about 4k. 1475 1476 1477config PCSPKR_PLATFORM 1478 bool "Enable PC-Speaker support" if EXPERT 1479 depends on HAVE_PCSPKR_PLATFORM 1480 select I8253_LOCK 1481 default y 1482 help 1483 This option allows to disable the internal PC-Speaker 1484 support, saving some memory. 1485 1486config BASE_FULL 1487 default y 1488 bool "Enable full-sized data structures for core" if EXPERT 1489 help 1490 Disabling this option reduces the size of miscellaneous core 1491 kernel data structures. This saves memory on small machines, 1492 but may reduce performance. 1493 1494config FUTEX 1495 bool "Enable futex support" if EXPERT 1496 default y 1497 select RT_MUTEXES 1498 help 1499 Disabling this option will cause the kernel to be built without 1500 support for "fast userspace mutexes". The resulting kernel may not 1501 run glibc-based applications correctly. 1502 1503config HAVE_FUTEX_CMPXCHG 1504 bool 1505 depends on FUTEX 1506 help 1507 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1508 is implemented and always working. This removes a couple of runtime 1509 checks. 1510 1511config EPOLL 1512 bool "Enable eventpoll support" if EXPERT 1513 default y 1514 select ANON_INODES 1515 help 1516 Disabling this option will cause the kernel to be built without 1517 support for epoll family of system calls. 1518 1519config SIGNALFD 1520 bool "Enable signalfd() system call" if EXPERT 1521 select ANON_INODES 1522 default y 1523 help 1524 Enable the signalfd() system call that allows to receive signals 1525 on a file descriptor. 1526 1527 If unsure, say Y. 1528 1529config TIMERFD 1530 bool "Enable timerfd() system call" if EXPERT 1531 select ANON_INODES 1532 default y 1533 help 1534 Enable the timerfd() system call that allows to receive timer 1535 events on a file descriptor. 1536 1537 If unsure, say Y. 1538 1539config EVENTFD 1540 bool "Enable eventfd() system call" if EXPERT 1541 select ANON_INODES 1542 default y 1543 help 1544 Enable the eventfd() system call that allows to receive both 1545 kernel notification (ie. KAIO) or userspace notifications. 1546 1547 If unsure, say Y. 1548 1549# syscall, maps, verifier 1550config BPF_SYSCALL 1551 bool "Enable bpf() system call" 1552 select ANON_INODES 1553 select BPF 1554 default n 1555 help 1556 Enable the bpf() system call that allows to manipulate eBPF 1557 programs and maps via file descriptors. 1558 1559config SHMEM 1560 bool "Use full shmem filesystem" if EXPERT 1561 default y 1562 depends on MMU 1563 help 1564 The shmem is an internal filesystem used to manage shared memory. 1565 It is backed by swap and manages resource limits. It is also exported 1566 to userspace as tmpfs if TMPFS is enabled. Disabling this 1567 option replaces shmem and tmpfs with the much simpler ramfs code, 1568 which may be appropriate on small systems without swap. 1569 1570config AIO 1571 bool "Enable AIO support" if EXPERT 1572 default y 1573 help 1574 This option enables POSIX asynchronous I/O which may by used 1575 by some high performance threaded applications. Disabling 1576 this option saves about 7k. 1577 1578config ADVISE_SYSCALLS 1579 bool "Enable madvise/fadvise syscalls" if EXPERT 1580 default y 1581 help 1582 This option enables the madvise and fadvise syscalls, used by 1583 applications to advise the kernel about their future memory or file 1584 usage, improving performance. If building an embedded system where no 1585 applications use these syscalls, you can disable this option to save 1586 space. 1587 1588config USERFAULTFD 1589 bool "Enable userfaultfd() system call" 1590 select ANON_INODES 1591 depends on MMU 1592 help 1593 Enable the userfaultfd() system call that allows to intercept and 1594 handle page faults in userland. 1595 1596config PCI_QUIRKS 1597 default y 1598 bool "Enable PCI quirk workarounds" if EXPERT 1599 depends on PCI 1600 help 1601 This enables workarounds for various PCI chipset 1602 bugs/quirks. Disable this only if your target machine is 1603 unaffected by PCI quirks. 1604 1605config MEMBARRIER 1606 bool "Enable membarrier() system call" if EXPERT 1607 default y 1608 help 1609 Enable the membarrier() system call that allows issuing memory 1610 barriers across all running threads, which can be used to distribute 1611 the cost of user-space memory barriers asymmetrically by transforming 1612 pairs of memory barriers into pairs consisting of membarrier() and a 1613 compiler barrier. 1614 1615 If unsure, say Y. 1616 1617config EMBEDDED 1618 bool "Embedded system" 1619 option allnoconfig_y 1620 select EXPERT 1621 help 1622 This option should be enabled if compiling the kernel for 1623 an embedded system so certain expert options are available 1624 for configuration. 1625 1626config HAVE_PERF_EVENTS 1627 bool 1628 help 1629 See tools/perf/design.txt for details. 1630 1631config PERF_USE_VMALLOC 1632 bool 1633 help 1634 See tools/perf/design.txt for details 1635 1636menu "Kernel Performance Events And Counters" 1637 1638config PERF_EVENTS 1639 bool "Kernel performance events and counters" 1640 default y if PROFILING 1641 depends on HAVE_PERF_EVENTS 1642 select ANON_INODES 1643 select IRQ_WORK 1644 select SRCU 1645 help 1646 Enable kernel support for various performance events provided 1647 by software and hardware. 1648 1649 Software events are supported either built-in or via the 1650 use of generic tracepoints. 1651 1652 Most modern CPUs support performance events via performance 1653 counter registers. These registers count the number of certain 1654 types of hw events: such as instructions executed, cachemisses 1655 suffered, or branches mis-predicted - without slowing down the 1656 kernel or applications. These registers can also trigger interrupts 1657 when a threshold number of events have passed - and can thus be 1658 used to profile the code that runs on that CPU. 1659 1660 The Linux Performance Event subsystem provides an abstraction of 1661 these software and hardware event capabilities, available via a 1662 system call and used by the "perf" utility in tools/perf/. It 1663 provides per task and per CPU counters, and it provides event 1664 capabilities on top of those. 1665 1666 Say Y if unsure. 1667 1668config DEBUG_PERF_USE_VMALLOC 1669 default n 1670 bool "Debug: use vmalloc to back perf mmap() buffers" 1671 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1672 select PERF_USE_VMALLOC 1673 help 1674 Use vmalloc memory to back perf mmap() buffers. 1675 1676 Mostly useful for debugging the vmalloc code on platforms 1677 that don't require it. 1678 1679 Say N if unsure. 1680 1681endmenu 1682 1683config VM_EVENT_COUNTERS 1684 default y 1685 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1686 help 1687 VM event counters are needed for event counts to be shown. 1688 This option allows the disabling of the VM event counters 1689 on EXPERT systems. /proc/vmstat will only show page counts 1690 if VM event counters are disabled. 1691 1692config SLUB_DEBUG 1693 default y 1694 bool "Enable SLUB debugging support" if EXPERT 1695 depends on SLUB && SYSFS 1696 help 1697 SLUB has extensive debug support features. Disabling these can 1698 result in significant savings in code size. This also disables 1699 SLUB sysfs support. /sys/slab will not exist and there will be 1700 no support for cache validation etc. 1701 1702config COMPAT_BRK 1703 bool "Disable heap randomization" 1704 default y 1705 help 1706 Randomizing heap placement makes heap exploits harder, but it 1707 also breaks ancient binaries (including anything libc5 based). 1708 This option changes the bootup default to heap randomization 1709 disabled, and can be overridden at runtime by setting 1710 /proc/sys/kernel/randomize_va_space to 2. 1711 1712 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1713 1714choice 1715 prompt "Choose SLAB allocator" 1716 default SLUB 1717 help 1718 This option allows to select a slab allocator. 1719 1720config SLAB 1721 bool "SLAB" 1722 help 1723 The regular slab allocator that is established and known to work 1724 well in all environments. It organizes cache hot objects in 1725 per cpu and per node queues. 1726 1727config SLUB 1728 bool "SLUB (Unqueued Allocator)" 1729 help 1730 SLUB is a slab allocator that minimizes cache line usage 1731 instead of managing queues of cached objects (SLAB approach). 1732 Per cpu caching is realized using slabs of objects instead 1733 of queues of objects. SLUB can use memory efficiently 1734 and has enhanced diagnostics. SLUB is the default choice for 1735 a slab allocator. 1736 1737config SLOB 1738 depends on EXPERT 1739 bool "SLOB (Simple Allocator)" 1740 help 1741 SLOB replaces the stock allocator with a drastically simpler 1742 allocator. SLOB is generally more space efficient but 1743 does not perform as well on large systems. 1744 1745endchoice 1746 1747config SLUB_CPU_PARTIAL 1748 default y 1749 depends on SLUB && SMP 1750 bool "SLUB per cpu partial cache" 1751 help 1752 Per cpu partial caches accellerate objects allocation and freeing 1753 that is local to a processor at the price of more indeterminism 1754 in the latency of the free. On overflow these caches will be cleared 1755 which requires the taking of locks that may cause latency spikes. 1756 Typically one would choose no for a realtime system. 1757 1758config MMAP_ALLOW_UNINITIALIZED 1759 bool "Allow mmapped anonymous memory to be uninitialized" 1760 depends on EXPERT && !MMU 1761 default n 1762 help 1763 Normally, and according to the Linux spec, anonymous memory obtained 1764 from mmap() has it's contents cleared before it is passed to 1765 userspace. Enabling this config option allows you to request that 1766 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1767 providing a huge performance boost. If this option is not enabled, 1768 then the flag will be ignored. 1769 1770 This is taken advantage of by uClibc's malloc(), and also by 1771 ELF-FDPIC binfmt's brk and stack allocator. 1772 1773 Because of the obvious security issues, this option should only be 1774 enabled on embedded devices where you control what is run in 1775 userspace. Since that isn't generally a problem on no-MMU systems, 1776 it is normally safe to say Y here. 1777 1778 See Documentation/nommu-mmap.txt for more information. 1779 1780config SYSTEM_DATA_VERIFICATION 1781 def_bool n 1782 select SYSTEM_TRUSTED_KEYRING 1783 select KEYS 1784 select CRYPTO 1785 select ASYMMETRIC_KEY_TYPE 1786 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1787 select PUBLIC_KEY_ALGO_RSA 1788 select ASN1 1789 select OID_REGISTRY 1790 select X509_CERTIFICATE_PARSER 1791 select PKCS7_MESSAGE_PARSER 1792 help 1793 Provide PKCS#7 message verification using the contents of the system 1794 trusted keyring to provide public keys. This then can be used for 1795 module verification, kexec image verification and firmware blob 1796 verification. 1797 1798config PROFILING 1799 bool "Profiling support" 1800 help 1801 Say Y here to enable the extended profiling support mechanisms used 1802 by profilers such as OProfile. 1803 1804# 1805# Place an empty function call at each tracepoint site. Can be 1806# dynamically changed for a probe function. 1807# 1808config TRACEPOINTS 1809 bool 1810 1811source "arch/Kconfig" 1812 1813endmenu # General setup 1814 1815config HAVE_GENERIC_DMA_COHERENT 1816 bool 1817 default n 1818 1819config SLABINFO 1820 bool 1821 depends on PROC_FS 1822 depends on SLAB || SLUB_DEBUG 1823 default y 1824 1825config RT_MUTEXES 1826 bool 1827 1828config BASE_SMALL 1829 int 1830 default 0 if BASE_FULL 1831 default 1 if !BASE_FULL 1832 1833menuconfig MODULES 1834 bool "Enable loadable module support" 1835 option modules 1836 help 1837 Kernel modules are small pieces of compiled code which can 1838 be inserted in the running kernel, rather than being 1839 permanently built into the kernel. You use the "modprobe" 1840 tool to add (and sometimes remove) them. If you say Y here, 1841 many parts of the kernel can be built as modules (by 1842 answering M instead of Y where indicated): this is most 1843 useful for infrequently used options which are not required 1844 for booting. For more information, see the man pages for 1845 modprobe, lsmod, modinfo, insmod and rmmod. 1846 1847 If you say Y here, you will need to run "make 1848 modules_install" to put the modules under /lib/modules/ 1849 where modprobe can find them (you may need to be root to do 1850 this). 1851 1852 If unsure, say Y. 1853 1854if MODULES 1855 1856config MODULE_FORCE_LOAD 1857 bool "Forced module loading" 1858 default n 1859 help 1860 Allow loading of modules without version information (ie. modprobe 1861 --force). Forced module loading sets the 'F' (forced) taint flag and 1862 is usually a really bad idea. 1863 1864config MODULE_UNLOAD 1865 bool "Module unloading" 1866 help 1867 Without this option you will not be able to unload any 1868 modules (note that some modules may not be unloadable 1869 anyway), which makes your kernel smaller, faster 1870 and simpler. If unsure, say Y. 1871 1872config MODULE_FORCE_UNLOAD 1873 bool "Forced module unloading" 1874 depends on MODULE_UNLOAD 1875 help 1876 This option allows you to force a module to unload, even if the 1877 kernel believes it is unsafe: the kernel will remove the module 1878 without waiting for anyone to stop using it (using the -f option to 1879 rmmod). This is mainly for kernel developers and desperate users. 1880 If unsure, say N. 1881 1882config MODVERSIONS 1883 bool "Module versioning support" 1884 help 1885 Usually, you have to use modules compiled with your kernel. 1886 Saying Y here makes it sometimes possible to use modules 1887 compiled for different kernels, by adding enough information 1888 to the modules to (hopefully) spot any changes which would 1889 make them incompatible with the kernel you are running. If 1890 unsure, say N. 1891 1892config MODULE_SRCVERSION_ALL 1893 bool "Source checksum for all modules" 1894 help 1895 Modules which contain a MODULE_VERSION get an extra "srcversion" 1896 field inserted into their modinfo section, which contains a 1897 sum of the source files which made it. This helps maintainers 1898 see exactly which source was used to build a module (since 1899 others sometimes change the module source without updating 1900 the version). With this option, such a "srcversion" field 1901 will be created for all modules. If unsure, say N. 1902 1903config MODULE_SIG 1904 bool "Module signature verification" 1905 depends on MODULES 1906 select SYSTEM_DATA_VERIFICATION 1907 help 1908 Check modules for valid signatures upon load: the signature 1909 is simply appended to the module. For more information see 1910 Documentation/module-signing.txt. 1911 1912 Note that this option adds the OpenSSL development packages as a 1913 kernel build dependency so that the signing tool can use its crypto 1914 library. 1915 1916 !!!WARNING!!! If you enable this option, you MUST make sure that the 1917 module DOES NOT get stripped after being signed. This includes the 1918 debuginfo strip done by some packagers (such as rpmbuild) and 1919 inclusion into an initramfs that wants the module size reduced. 1920 1921config MODULE_SIG_FORCE 1922 bool "Require modules to be validly signed" 1923 depends on MODULE_SIG 1924 help 1925 Reject unsigned modules or signed modules for which we don't have a 1926 key. Without this, such modules will simply taint the kernel. 1927 1928config MODULE_SIG_ALL 1929 bool "Automatically sign all modules" 1930 default y 1931 depends on MODULE_SIG 1932 help 1933 Sign all modules during make modules_install. Without this option, 1934 modules must be signed manually, using the scripts/sign-file tool. 1935 1936comment "Do not forget to sign required modules with scripts/sign-file" 1937 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1938 1939choice 1940 prompt "Which hash algorithm should modules be signed with?" 1941 depends on MODULE_SIG 1942 help 1943 This determines which sort of hashing algorithm will be used during 1944 signature generation. This algorithm _must_ be built into the kernel 1945 directly so that signature verification can take place. It is not 1946 possible to load a signed module containing the algorithm to check 1947 the signature on that module. 1948 1949config MODULE_SIG_SHA1 1950 bool "Sign modules with SHA-1" 1951 select CRYPTO_SHA1 1952 1953config MODULE_SIG_SHA224 1954 bool "Sign modules with SHA-224" 1955 select CRYPTO_SHA256 1956 1957config MODULE_SIG_SHA256 1958 bool "Sign modules with SHA-256" 1959 select CRYPTO_SHA256 1960 1961config MODULE_SIG_SHA384 1962 bool "Sign modules with SHA-384" 1963 select CRYPTO_SHA512 1964 1965config MODULE_SIG_SHA512 1966 bool "Sign modules with SHA-512" 1967 select CRYPTO_SHA512 1968 1969endchoice 1970 1971config MODULE_SIG_HASH 1972 string 1973 depends on MODULE_SIG 1974 default "sha1" if MODULE_SIG_SHA1 1975 default "sha224" if MODULE_SIG_SHA224 1976 default "sha256" if MODULE_SIG_SHA256 1977 default "sha384" if MODULE_SIG_SHA384 1978 default "sha512" if MODULE_SIG_SHA512 1979 1980config MODULE_COMPRESS 1981 bool "Compress modules on installation" 1982 depends on MODULES 1983 help 1984 1985 Compresses kernel modules when 'make modules_install' is run; gzip or 1986 xz depending on "Compression algorithm" below. 1987 1988 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 1989 1990 Out-of-tree kernel modules installed using Kbuild will also be 1991 compressed upon installation. 1992 1993 Note: for modules inside an initrd or initramfs, it's more efficient 1994 to compress the whole initrd or initramfs instead. 1995 1996 Note: This is fully compatible with signed modules. 1997 1998 If in doubt, say N. 1999 2000choice 2001 prompt "Compression algorithm" 2002 depends on MODULE_COMPRESS 2003 default MODULE_COMPRESS_GZIP 2004 help 2005 This determines which sort of compression will be used during 2006 'make modules_install'. 2007 2008 GZIP (default) and XZ are supported. 2009 2010config MODULE_COMPRESS_GZIP 2011 bool "GZIP" 2012 2013config MODULE_COMPRESS_XZ 2014 bool "XZ" 2015 2016endchoice 2017 2018endif # MODULES 2019 2020config MODULES_TREE_LOOKUP 2021 def_bool y 2022 depends on PERF_EVENTS || TRACING 2023 2024config INIT_ALL_POSSIBLE 2025 bool 2026 help 2027 Back when each arch used to define their own cpu_online_mask and 2028 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2029 with all 1s, and others with all 0s. When they were centralised, 2030 it was better to provide this option than to break all the archs 2031 and have several arch maintainers pursuing me down dark alleys. 2032 2033config STOP_MACHINE 2034 bool 2035 default y 2036 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 2037 help 2038 Need stop_machine() primitive. 2039 2040source "block/Kconfig" 2041 2042config PREEMPT_NOTIFIERS 2043 bool 2044 2045config PADATA 2046 depends on SMP 2047 bool 2048 2049# Can be selected by architectures with broken toolchains 2050# that get confused by correct const<->read_only section 2051# mappings 2052config BROKEN_RODATA 2053 bool 2054 2055config ASN1 2056 tristate 2057 help 2058 Build a simple ASN.1 grammar compiler that produces a bytecode output 2059 that can be interpreted by the ASN.1 stream decoder and used to 2060 inform it as to what tags are to be expected in a stream and what 2061 functions to call on what tags. 2062 2063source "kernel/Kconfig.locks" 2064