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 help 439 Collect information on time spent by a task waiting for system 440 resources like cpu, synchronous block I/O completion and swapping 441 in pages. Such statistics can help in setting a task's priorities 442 relative to other tasks for cpu, io, rss limits etc. 443 444 Say N if unsure. 445 446config TASK_XACCT 447 bool "Enable extended accounting over taskstats" 448 depends on TASKSTATS 449 help 450 Collect extended task accounting data and send the data 451 to userland for processing over the taskstats interface. 452 453 Say N if unsure. 454 455config TASK_IO_ACCOUNTING 456 bool "Enable per-task storage I/O accounting" 457 depends on TASK_XACCT 458 help 459 Collect information on the number of bytes of storage I/O which this 460 task has caused. 461 462 Say N if unsure. 463 464endmenu # "CPU/Task time and stats accounting" 465 466menu "RCU Subsystem" 467 468choice 469 prompt "RCU Implementation" 470 default TREE_RCU 471 472config TREE_RCU 473 bool "Tree-based hierarchical RCU" 474 depends on !PREEMPT && SMP 475 help 476 This option selects the RCU implementation that is 477 designed for very large SMP system with hundreds or 478 thousands of CPUs. It also scales down nicely to 479 smaller systems. 480 481config PREEMPT_RCU 482 bool "Preemptible tree-based hierarchical RCU" 483 depends on PREEMPT 484 help 485 This option selects the RCU implementation that is 486 designed for very large SMP systems with hundreds or 487 thousands of CPUs, but for which real-time response 488 is also required. It also scales down nicely to 489 smaller systems. 490 491 Select this option if you are unsure. 492 493config TINY_RCU 494 bool "UP-only small-memory-footprint RCU" 495 depends on !PREEMPT && !SMP 496 help 497 This option selects the RCU implementation that is 498 designed for UP systems from which real-time response 499 is not required. This option greatly reduces the 500 memory footprint of RCU. 501 502endchoice 503 504config SRCU 505 bool 506 help 507 This option selects the sleepable version of RCU. This version 508 permits arbitrary sleeping or blocking within RCU read-side critical 509 sections. 510 511config TASKS_RCU 512 bool "Task_based RCU implementation using voluntary context switch" 513 default n 514 select SRCU 515 help 516 This option enables a task-based RCU implementation that uses 517 only voluntary context switch (not preemption!), idle, and 518 user-mode execution as quiescent states. 519 520 If unsure, say N. 521 522config RCU_STALL_COMMON 523 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE ) 524 help 525 This option enables RCU CPU stall code that is common between 526 the TINY and TREE variants of RCU. The purpose is to allow 527 the tiny variants to disable RCU CPU stall warnings, while 528 making these warnings mandatory for the tree variants. 529 530config CONTEXT_TRACKING 531 bool 532 533config RCU_USER_QS 534 bool "Consider userspace as in RCU extended quiescent state" 535 depends on HAVE_CONTEXT_TRACKING && SMP 536 select CONTEXT_TRACKING 537 help 538 This option sets hooks on kernel / userspace boundaries and 539 puts RCU in extended quiescent state when the CPU runs in 540 userspace. It means that when a CPU runs in userspace, it is 541 excluded from the global RCU state machine and thus doesn't 542 try to keep the timer tick on for RCU. 543 544 Unless you want to hack and help the development of the full 545 dynticks mode, you shouldn't enable this option. It also 546 adds unnecessary overhead. 547 548 If unsure say N 549 550config CONTEXT_TRACKING_FORCE 551 bool "Force context tracking" 552 depends on CONTEXT_TRACKING 553 default y if !NO_HZ_FULL 554 help 555 The major pre-requirement for full dynticks to work is to 556 support the context tracking subsystem. But there are also 557 other dependencies to provide in order to make the full 558 dynticks working. 559 560 This option stands for testing when an arch implements the 561 context tracking backend but doesn't yet fullfill all the 562 requirements to make the full dynticks feature working. 563 Without the full dynticks, there is no way to test the support 564 for context tracking and the subsystems that rely on it: RCU 565 userspace extended quiescent state and tickless cputime 566 accounting. This option copes with the absence of the full 567 dynticks subsystem by forcing the context tracking on all 568 CPUs in the system. 569 570 Say Y only if you're working on the development of an 571 architecture backend for the context tracking. 572 573 Say N otherwise, this option brings an overhead that you 574 don't want in production. 575 576 577config RCU_FANOUT 578 int "Tree-based hierarchical RCU fanout value" 579 range 2 64 if 64BIT 580 range 2 32 if !64BIT 581 depends on TREE_RCU || PREEMPT_RCU 582 default 64 if 64BIT 583 default 32 if !64BIT 584 help 585 This option controls the fanout of hierarchical implementations 586 of RCU, allowing RCU to work efficiently on machines with 587 large numbers of CPUs. This value must be at least the fourth 588 root of NR_CPUS, which allows NR_CPUS to be insanely large. 589 The default value of RCU_FANOUT should be used for production 590 systems, but if you are stress-testing the RCU implementation 591 itself, small RCU_FANOUT values allow you to test large-system 592 code paths on small(er) systems. 593 594 Select a specific number if testing RCU itself. 595 Take the default if unsure. 596 597config RCU_FANOUT_LEAF 598 int "Tree-based hierarchical RCU leaf-level fanout value" 599 range 2 RCU_FANOUT if 64BIT 600 range 2 RCU_FANOUT if !64BIT 601 depends on TREE_RCU || PREEMPT_RCU 602 default 16 603 help 604 This option controls the leaf-level fanout of hierarchical 605 implementations of RCU, and allows trading off cache misses 606 against lock contention. Systems that synchronize their 607 scheduling-clock interrupts for energy-efficiency reasons will 608 want the default because the smaller leaf-level fanout keeps 609 lock contention levels acceptably low. Very large systems 610 (hundreds or thousands of CPUs) will instead want to set this 611 value to the maximum value possible in order to reduce the 612 number of cache misses incurred during RCU's grace-period 613 initialization. These systems tend to run CPU-bound, and thus 614 are not helped by synchronized interrupts, and thus tend to 615 skew them, which reduces lock contention enough that large 616 leaf-level fanouts work well. 617 618 Select a specific number if testing RCU itself. 619 620 Select the maximum permissible value for large systems. 621 622 Take the default if unsure. 623 624config RCU_FANOUT_EXACT 625 bool "Disable tree-based hierarchical RCU auto-balancing" 626 depends on TREE_RCU || PREEMPT_RCU 627 default n 628 help 629 This option forces use of the exact RCU_FANOUT value specified, 630 regardless of imbalances in the hierarchy. This is useful for 631 testing RCU itself, and might one day be useful on systems with 632 strong NUMA behavior. 633 634 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 635 636 Say N if unsure. 637 638config RCU_FAST_NO_HZ 639 bool "Accelerate last non-dyntick-idle CPU's grace periods" 640 depends on NO_HZ_COMMON && SMP 641 default n 642 help 643 This option permits CPUs to enter dynticks-idle state even if 644 they have RCU callbacks queued, and prevents RCU from waking 645 these CPUs up more than roughly once every four jiffies (by 646 default, you can adjust this using the rcutree.rcu_idle_gp_delay 647 parameter), thus improving energy efficiency. On the other 648 hand, this option increases the duration of RCU grace periods, 649 for example, slowing down synchronize_rcu(). 650 651 Say Y if energy efficiency is critically important, and you 652 don't care about increased grace-period durations. 653 654 Say N if you are unsure. 655 656config TREE_RCU_TRACE 657 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) 658 select DEBUG_FS 659 help 660 This option provides tracing for the TREE_RCU and 661 PREEMPT_RCU implementations, permitting Makefile to 662 trivially select kernel/rcutree_trace.c. 663 664config RCU_BOOST 665 bool "Enable RCU priority boosting" 666 depends on RT_MUTEXES && PREEMPT_RCU 667 default n 668 help 669 This option boosts the priority of preempted RCU readers that 670 block the current preemptible RCU grace period for too long. 671 This option also prevents heavy loads from blocking RCU 672 callback invocation for all flavors of RCU. 673 674 Say Y here if you are working with real-time apps or heavy loads 675 Say N here if you are unsure. 676 677config RCU_KTHREAD_PRIO 678 int "Real-time priority to use for RCU worker threads" 679 range 1 99 if RCU_BOOST 680 range 0 99 if !RCU_BOOST 681 default 1 if RCU_BOOST 682 default 0 if !RCU_BOOST 683 help 684 This option specifies the SCHED_FIFO priority value that will be 685 assigned to the rcuc/n and rcub/n threads and is also the value 686 used for RCU_BOOST (if enabled). If you are working with a 687 real-time application that has one or more CPU-bound threads 688 running at a real-time priority level, you should set 689 RCU_KTHREAD_PRIO to a priority higher than the highest-priority 690 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO 691 value of 1 is appropriate in the common case, which is real-time 692 applications that do not have any CPU-bound threads. 693 694 Some real-time applications might not have a single real-time 695 thread that saturates a given CPU, but instead might have 696 multiple real-time threads that, taken together, fully utilize 697 that CPU. In this case, you should set RCU_KTHREAD_PRIO to 698 a priority higher than the lowest-priority thread that is 699 conspiring to prevent the CPU from running any non-real-time 700 tasks. For example, if one thread at priority 10 and another 701 thread at priority 5 are between themselves fully consuming 702 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be 703 set to priority 6 or higher. 704 705 Specify the real-time priority, or take the default if unsure. 706 707config RCU_BOOST_DELAY 708 int "Milliseconds to delay boosting after RCU grace-period start" 709 range 0 3000 710 depends on RCU_BOOST 711 default 500 712 help 713 This option specifies the time to wait after the beginning of 714 a given grace period before priority-boosting preempted RCU 715 readers blocking that grace period. Note that any RCU reader 716 blocking an expedited RCU grace period is boosted immediately. 717 718 Accept the default if unsure. 719 720config RCU_NOCB_CPU 721 bool "Offload RCU callback processing from boot-selected CPUs" 722 depends on TREE_RCU || PREEMPT_RCU 723 default n 724 help 725 Use this option to reduce OS jitter for aggressive HPC or 726 real-time workloads. It can also be used to offload RCU 727 callback invocation to energy-efficient CPUs in battery-powered 728 asymmetric multiprocessors. 729 730 This option offloads callback invocation from the set of 731 CPUs specified at boot time by the rcu_nocbs parameter. 732 For each such CPU, a kthread ("rcuox/N") will be created to 733 invoke callbacks, where the "N" is the CPU being offloaded, 734 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 735 "s" for RCU-sched. Nothing prevents this kthread from running 736 on the specified CPUs, but (1) the kthreads may be preempted 737 between each callback, and (2) affinity or cgroups can be used 738 to force the kthreads to run on whatever set of CPUs is desired. 739 740 Say Y here if you want to help to debug reduced OS jitter. 741 Say N here if you are unsure. 742 743choice 744 prompt "Build-forced no-CBs CPUs" 745 default RCU_NOCB_CPU_NONE 746 depends on RCU_NOCB_CPU 747 help 748 This option allows no-CBs CPUs (whose RCU callbacks are invoked 749 from kthreads rather than from softirq context) to be specified 750 at build time. Additional no-CBs CPUs may be specified by 751 the rcu_nocbs= boot parameter. 752 753config RCU_NOCB_CPU_NONE 754 bool "No build_forced no-CBs CPUs" 755 help 756 This option does not force any of the CPUs to be no-CBs CPUs. 757 Only CPUs designated by the rcu_nocbs= boot parameter will be 758 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 759 kthreads whose names begin with "rcuo". All other CPUs will 760 invoke their own RCU callbacks in softirq context. 761 762 Select this option if you want to choose no-CBs CPUs at 763 boot time, for example, to allow testing of different no-CBs 764 configurations without having to rebuild the kernel each time. 765 766config RCU_NOCB_CPU_ZERO 767 bool "CPU 0 is a build_forced no-CBs CPU" 768 help 769 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 770 callbacks are invoked by a per-CPU kthread whose name begins 771 with "rcuo". Additional CPUs may be designated as no-CBs 772 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 773 All other CPUs will invoke their own RCU callbacks in softirq 774 context. 775 776 Select this if CPU 0 needs to be a no-CBs CPU for real-time 777 or energy-efficiency reasons, but the real reason it exists 778 is to ensure that randconfig testing covers mixed systems. 779 780config RCU_NOCB_CPU_ALL 781 bool "All CPUs are build_forced no-CBs CPUs" 782 help 783 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 784 boot parameter will be ignored. All CPUs' RCU callbacks will 785 be executed in the context of per-CPU rcuo kthreads created for 786 this purpose. Assuming that the kthreads whose names start with 787 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 788 on the remaining CPUs, but might decrease memory locality during 789 RCU-callback invocation, thus potentially degrading throughput. 790 791 Select this if all CPUs need to be no-CBs CPUs for real-time 792 or energy-efficiency reasons. 793 794endchoice 795 796config RCU_EXPEDITE_BOOT 797 bool 798 default n 799 help 800 This option enables expedited grace periods at boot time, 801 as if rcu_expedite_gp() had been invoked early in boot. 802 The corresponding rcu_unexpedite_gp() is invoked from 803 rcu_end_inkernel_boot(), which is intended to be invoked 804 at the end of the kernel-only boot sequence, just before 805 init is exec'ed. 806 807 Accept the default if unsure. 808 809endmenu # "RCU Subsystem" 810 811config BUILD_BIN2C 812 bool 813 default n 814 815config IKCONFIG 816 tristate "Kernel .config support" 817 select BUILD_BIN2C 818 ---help--- 819 This option enables the complete Linux kernel ".config" file 820 contents to be saved in the kernel. It provides documentation 821 of which kernel options are used in a running kernel or in an 822 on-disk kernel. This information can be extracted from the kernel 823 image file with the script scripts/extract-ikconfig and used as 824 input to rebuild the current kernel or to build another kernel. 825 It can also be extracted from a running kernel by reading 826 /proc/config.gz if enabled (below). 827 828config IKCONFIG_PROC 829 bool "Enable access to .config through /proc/config.gz" 830 depends on IKCONFIG && PROC_FS 831 ---help--- 832 This option enables access to the kernel configuration file 833 through /proc/config.gz. 834 835config LOG_BUF_SHIFT 836 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 837 range 12 21 838 default 17 839 depends on PRINTK 840 help 841 Select the minimal kernel log buffer size as a power of 2. 842 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 843 parameter, see below. Any higher size also might be forced 844 by "log_buf_len" boot parameter. 845 846 Examples: 847 17 => 128 KB 848 16 => 64 KB 849 15 => 32 KB 850 14 => 16 KB 851 13 => 8 KB 852 12 => 4 KB 853 854config LOG_CPU_MAX_BUF_SHIFT 855 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 856 depends on SMP 857 range 0 21 858 default 12 if !BASE_SMALL 859 default 0 if BASE_SMALL 860 depends on PRINTK 861 help 862 This option allows to increase the default ring buffer size 863 according to the number of CPUs. The value defines the contribution 864 of each CPU as a power of 2. The used space is typically only few 865 lines however it might be much more when problems are reported, 866 e.g. backtraces. 867 868 The increased size means that a new buffer has to be allocated and 869 the original static one is unused. It makes sense only on systems 870 with more CPUs. Therefore this value is used only when the sum of 871 contributions is greater than the half of the default kernel ring 872 buffer as defined by LOG_BUF_SHIFT. The default values are set 873 so that more than 64 CPUs are needed to trigger the allocation. 874 875 Also this option is ignored when "log_buf_len" kernel parameter is 876 used as it forces an exact (power of two) size of the ring buffer. 877 878 The number of possible CPUs is used for this computation ignoring 879 hotplugging making the compuation optimal for the the worst case 880 scenerio while allowing a simple algorithm to be used from bootup. 881 882 Examples shift values and their meaning: 883 17 => 128 KB for each CPU 884 16 => 64 KB for each CPU 885 15 => 32 KB for each CPU 886 14 => 16 KB for each CPU 887 13 => 8 KB for each CPU 888 12 => 4 KB for each CPU 889 890# 891# Architectures with an unreliable sched_clock() should select this: 892# 893config HAVE_UNSTABLE_SCHED_CLOCK 894 bool 895 896config GENERIC_SCHED_CLOCK 897 bool 898 899# 900# For architectures that want to enable the support for NUMA-affine scheduler 901# balancing logic: 902# 903config ARCH_SUPPORTS_NUMA_BALANCING 904 bool 905 906# 907# For architectures that know their GCC __int128 support is sound 908# 909config ARCH_SUPPORTS_INT128 910 bool 911 912# For architectures that (ab)use NUMA to represent different memory regions 913# all cpu-local but of different latencies, such as SuperH. 914# 915config ARCH_WANT_NUMA_VARIABLE_LOCALITY 916 bool 917 918config NUMA_BALANCING 919 bool "Memory placement aware NUMA scheduler" 920 depends on ARCH_SUPPORTS_NUMA_BALANCING 921 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 922 depends on SMP && NUMA && MIGRATION 923 help 924 This option adds support for automatic NUMA aware memory/task placement. 925 The mechanism is quite primitive and is based on migrating memory when 926 it has references to the node the task is running on. 927 928 This system will be inactive on UMA systems. 929 930config NUMA_BALANCING_DEFAULT_ENABLED 931 bool "Automatically enable NUMA aware memory/task placement" 932 default y 933 depends on NUMA_BALANCING 934 help 935 If set, automatic NUMA balancing will be enabled if running on a NUMA 936 machine. 937 938menuconfig CGROUPS 939 bool "Control Group support" 940 select KERNFS 941 help 942 This option adds support for grouping sets of processes together, for 943 use with process control subsystems such as Cpusets, CFS, memory 944 controls or device isolation. 945 See 946 - Documentation/scheduler/sched-design-CFS.txt (CFS) 947 - Documentation/cgroups/ (features for grouping, isolation 948 and resource control) 949 950 Say N if unsure. 951 952if CGROUPS 953 954config CGROUP_DEBUG 955 bool "Example debug cgroup subsystem" 956 default n 957 help 958 This option enables a simple cgroup subsystem that 959 exports useful debugging information about the cgroups 960 framework. 961 962 Say N if unsure. 963 964config CGROUP_FREEZER 965 bool "Freezer cgroup subsystem" 966 help 967 Provides a way to freeze and unfreeze all tasks in a 968 cgroup. 969 970config CGROUP_DEVICE 971 bool "Device controller for cgroups" 972 help 973 Provides a cgroup implementing whitelists for devices which 974 a process in the cgroup can mknod or open. 975 976config CPUSETS 977 bool "Cpuset support" 978 help 979 This option will let you create and manage CPUSETs which 980 allow dynamically partitioning a system into sets of CPUs and 981 Memory Nodes and assigning tasks to run only within those sets. 982 This is primarily useful on large SMP or NUMA systems. 983 984 Say N if unsure. 985 986config PROC_PID_CPUSET 987 bool "Include legacy /proc/<pid>/cpuset file" 988 depends on CPUSETS 989 default y 990 991config CGROUP_CPUACCT 992 bool "Simple CPU accounting cgroup subsystem" 993 help 994 Provides a simple Resource Controller for monitoring the 995 total CPU consumed by the tasks in a cgroup. 996 997config PAGE_COUNTER 998 bool 999 1000config MEMCG 1001 bool "Memory Resource Controller for Control Groups" 1002 select PAGE_COUNTER 1003 select EVENTFD 1004 help 1005 Provides a memory resource controller that manages both anonymous 1006 memory and page cache. (See Documentation/cgroups/memory.txt) 1007 1008config MEMCG_SWAP 1009 bool "Memory Resource Controller Swap Extension" 1010 depends on MEMCG && SWAP 1011 help 1012 Add swap management feature to memory resource controller. When you 1013 enable this, you can limit mem+swap usage per cgroup. In other words, 1014 when you disable this, memory resource controller has no cares to 1015 usage of swap...a process can exhaust all of the swap. This extension 1016 is useful when you want to avoid exhaustion swap but this itself 1017 adds more overheads and consumes memory for remembering information. 1018 Especially if you use 32bit system or small memory system, please 1019 be careful about enabling this. When memory resource controller 1020 is disabled by boot option, this will be automatically disabled and 1021 there will be no overhead from this. Even when you set this config=y, 1022 if boot option "swapaccount=0" is set, swap will not be accounted. 1023 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 1024 size is 4096bytes, 512k per 1Gbytes of swap. 1025config MEMCG_SWAP_ENABLED 1026 bool "Memory Resource Controller Swap Extension enabled by default" 1027 depends on MEMCG_SWAP 1028 default y 1029 help 1030 Memory Resource Controller Swap Extension comes with its price in 1031 a bigger memory consumption. General purpose distribution kernels 1032 which want to enable the feature but keep it disabled by default 1033 and let the user enable it by swapaccount=1 boot command line 1034 parameter should have this option unselected. 1035 For those who want to have the feature enabled by default should 1036 select this option (if, for some reason, they need to disable it 1037 then swapaccount=0 does the trick). 1038config MEMCG_KMEM 1039 bool "Memory Resource Controller Kernel Memory accounting" 1040 depends on MEMCG 1041 depends on SLUB || SLAB 1042 help 1043 The Kernel Memory extension for Memory Resource Controller can limit 1044 the amount of memory used by kernel objects in the system. Those are 1045 fundamentally different from the entities handled by the standard 1046 Memory Controller, which are page-based, and can be swapped. Users of 1047 the kmem extension can use it to guarantee that no group of processes 1048 will ever exhaust kernel resources alone. 1049 1050 WARNING: Current implementation lacks reclaim support. That means 1051 allocation attempts will fail when close to the limit even if there 1052 are plenty of kmem available for reclaim. That makes this option 1053 unusable in real life so DO NOT SELECT IT unless for development 1054 purposes. 1055 1056config CGROUP_HUGETLB 1057 bool "HugeTLB Resource Controller for Control Groups" 1058 depends on HUGETLB_PAGE 1059 select PAGE_COUNTER 1060 default n 1061 help 1062 Provides a cgroup Resource Controller for HugeTLB pages. 1063 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1064 The limit is enforced during page fault. Since HugeTLB doesn't 1065 support page reclaim, enforcing the limit at page fault time implies 1066 that, the application will get SIGBUS signal if it tries to access 1067 HugeTLB pages beyond its limit. This requires the application to know 1068 beforehand how much HugeTLB pages it would require for its use. The 1069 control group is tracked in the third page lru pointer. This means 1070 that we cannot use the controller with huge page less than 3 pages. 1071 1072config CGROUP_PERF 1073 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 1074 depends on PERF_EVENTS && CGROUPS 1075 help 1076 This option extends the per-cpu mode to restrict monitoring to 1077 threads which belong to the cgroup specified and run on the 1078 designated cpu. 1079 1080 Say N if unsure. 1081 1082menuconfig CGROUP_SCHED 1083 bool "Group CPU scheduler" 1084 default n 1085 help 1086 This feature lets CPU scheduler recognize task groups and control CPU 1087 bandwidth allocation to such task groups. It uses cgroups to group 1088 tasks. 1089 1090if CGROUP_SCHED 1091config FAIR_GROUP_SCHED 1092 bool "Group scheduling for SCHED_OTHER" 1093 depends on CGROUP_SCHED 1094 default CGROUP_SCHED 1095 1096config CFS_BANDWIDTH 1097 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1098 depends on FAIR_GROUP_SCHED 1099 default n 1100 help 1101 This option allows users to define CPU bandwidth rates (limits) for 1102 tasks running within the fair group scheduler. Groups with no limit 1103 set are considered to be unconstrained and will run with no 1104 restriction. 1105 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1106 1107config RT_GROUP_SCHED 1108 bool "Group scheduling for SCHED_RR/FIFO" 1109 depends on CGROUP_SCHED 1110 default n 1111 help 1112 This feature lets you explicitly allocate real CPU bandwidth 1113 to task groups. If enabled, it will also make it impossible to 1114 schedule realtime tasks for non-root users until you allocate 1115 realtime bandwidth for them. 1116 See Documentation/scheduler/sched-rt-group.txt for more information. 1117 1118endif #CGROUP_SCHED 1119 1120config BLK_CGROUP 1121 bool "Block IO controller" 1122 depends on BLOCK 1123 default n 1124 ---help--- 1125 Generic block IO controller cgroup interface. This is the common 1126 cgroup interface which should be used by various IO controlling 1127 policies. 1128 1129 Currently, CFQ IO scheduler uses it to recognize task groups and 1130 control disk bandwidth allocation (proportional time slice allocation) 1131 to such task groups. It is also used by bio throttling logic in 1132 block layer to implement upper limit in IO rates on a device. 1133 1134 This option only enables generic Block IO controller infrastructure. 1135 One needs to also enable actual IO controlling logic/policy. For 1136 enabling proportional weight division of disk bandwidth in CFQ, set 1137 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1138 CONFIG_BLK_DEV_THROTTLING=y. 1139 1140 See Documentation/cgroups/blkio-controller.txt for more information. 1141 1142config DEBUG_BLK_CGROUP 1143 bool "Enable Block IO controller debugging" 1144 depends on BLK_CGROUP 1145 default n 1146 ---help--- 1147 Enable some debugging help. Currently it exports additional stat 1148 files in a cgroup which can be useful for debugging. 1149 1150endif # CGROUPS 1151 1152config CHECKPOINT_RESTORE 1153 bool "Checkpoint/restore support" if EXPERT 1154 default n 1155 help 1156 Enables additional kernel features in a sake of checkpoint/restore. 1157 In particular it adds auxiliary prctl codes to setup process text, 1158 data and heap segment sizes, and a few additional /proc filesystem 1159 entries. 1160 1161 If unsure, say N here. 1162 1163menuconfig NAMESPACES 1164 bool "Namespaces support" if EXPERT 1165 depends on MULTIUSER 1166 default !EXPERT 1167 help 1168 Provides the way to make tasks work with different objects using 1169 the same id. For example same IPC id may refer to different objects 1170 or same user id or pid may refer to different tasks when used in 1171 different namespaces. 1172 1173if NAMESPACES 1174 1175config UTS_NS 1176 bool "UTS namespace" 1177 default y 1178 help 1179 In this namespace tasks see different info provided with the 1180 uname() system call 1181 1182config IPC_NS 1183 bool "IPC namespace" 1184 depends on (SYSVIPC || POSIX_MQUEUE) 1185 default y 1186 help 1187 In this namespace tasks work with IPC ids which correspond to 1188 different IPC objects in different namespaces. 1189 1190config USER_NS 1191 bool "User namespace" 1192 default n 1193 help 1194 This allows containers, i.e. vservers, to use user namespaces 1195 to provide different user info for different servers. 1196 1197 When user namespaces are enabled in the kernel it is 1198 recommended that the MEMCG and MEMCG_KMEM options also be 1199 enabled and that user-space use the memory control groups to 1200 limit the amount of memory a memory unprivileged users can 1201 use. 1202 1203 If unsure, say N. 1204 1205config PID_NS 1206 bool "PID Namespaces" 1207 default y 1208 help 1209 Support process id namespaces. This allows having multiple 1210 processes with the same pid as long as they are in different 1211 pid namespaces. This is a building block of containers. 1212 1213config NET_NS 1214 bool "Network namespace" 1215 depends on NET 1216 default y 1217 help 1218 Allow user space to create what appear to be multiple instances 1219 of the network stack. 1220 1221endif # NAMESPACES 1222 1223config SCHED_AUTOGROUP 1224 bool "Automatic process group scheduling" 1225 select CGROUPS 1226 select CGROUP_SCHED 1227 select FAIR_GROUP_SCHED 1228 help 1229 This option optimizes the scheduler for common desktop workloads by 1230 automatically creating and populating task groups. This separation 1231 of workloads isolates aggressive CPU burners (like build jobs) from 1232 desktop applications. Task group autogeneration is currently based 1233 upon task session. 1234 1235config SYSFS_DEPRECATED 1236 bool "Enable deprecated sysfs features to support old userspace tools" 1237 depends on SYSFS 1238 default n 1239 help 1240 This option adds code that switches the layout of the "block" class 1241 devices, to not show up in /sys/class/block/, but only in 1242 /sys/block/. 1243 1244 This switch is only active when the sysfs.deprecated=1 boot option is 1245 passed or the SYSFS_DEPRECATED_V2 option is set. 1246 1247 This option allows new kernels to run on old distributions and tools, 1248 which might get confused by /sys/class/block/. Since 2007/2008 all 1249 major distributions and tools handle this just fine. 1250 1251 Recent distributions and userspace tools after 2009/2010 depend on 1252 the existence of /sys/class/block/, and will not work with this 1253 option enabled. 1254 1255 Only if you are using a new kernel on an old distribution, you might 1256 need to say Y here. 1257 1258config SYSFS_DEPRECATED_V2 1259 bool "Enable deprecated sysfs features by default" 1260 default n 1261 depends on SYSFS 1262 depends on SYSFS_DEPRECATED 1263 help 1264 Enable deprecated sysfs by default. 1265 1266 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1267 option. 1268 1269 Only if you are using a new kernel on an old distribution, you might 1270 need to say Y here. Even then, odds are you would not need it 1271 enabled, you can always pass the boot option if absolutely necessary. 1272 1273config RELAY 1274 bool "Kernel->user space relay support (formerly relayfs)" 1275 help 1276 This option enables support for relay interface support in 1277 certain file systems (such as debugfs). 1278 It is designed to provide an efficient mechanism for tools and 1279 facilities to relay large amounts of data from kernel space to 1280 user space. 1281 1282 If unsure, say N. 1283 1284config BLK_DEV_INITRD 1285 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1286 depends on BROKEN || !FRV 1287 help 1288 The initial RAM filesystem is a ramfs which is loaded by the 1289 boot loader (loadlin or lilo) and that is mounted as root 1290 before the normal boot procedure. It is typically used to 1291 load modules needed to mount the "real" root file system, 1292 etc. See <file:Documentation/initrd.txt> for details. 1293 1294 If RAM disk support (BLK_DEV_RAM) is also included, this 1295 also enables initial RAM disk (initrd) support and adds 1296 15 Kbytes (more on some other architectures) to the kernel size. 1297 1298 If unsure say Y. 1299 1300if BLK_DEV_INITRD 1301 1302source "usr/Kconfig" 1303 1304endif 1305 1306config CC_OPTIMIZE_FOR_SIZE 1307 bool "Optimize for size" 1308 help 1309 Enabling this option will pass "-Os" instead of "-O2" to 1310 your compiler resulting in a smaller kernel. 1311 1312 If unsure, say N. 1313 1314config SYSCTL 1315 bool 1316 1317config ANON_INODES 1318 bool 1319 1320config HAVE_UID16 1321 bool 1322 1323config SYSCTL_EXCEPTION_TRACE 1324 bool 1325 help 1326 Enable support for /proc/sys/debug/exception-trace. 1327 1328config SYSCTL_ARCH_UNALIGN_NO_WARN 1329 bool 1330 help 1331 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1332 Allows arch to define/use @no_unaligned_warning to possibly warn 1333 about unaligned access emulation going on under the hood. 1334 1335config SYSCTL_ARCH_UNALIGN_ALLOW 1336 bool 1337 help 1338 Enable support for /proc/sys/kernel/unaligned-trap 1339 Allows arches to define/use @unaligned_enabled to runtime toggle 1340 the unaligned access emulation. 1341 see arch/parisc/kernel/unaligned.c for reference 1342 1343config HAVE_PCSPKR_PLATFORM 1344 bool 1345 1346# interpreter that classic socket filters depend on 1347config BPF 1348 bool 1349 1350menuconfig EXPERT 1351 bool "Configure standard kernel features (expert users)" 1352 # Unhide debug options, to make the on-by-default options visible 1353 select DEBUG_KERNEL 1354 help 1355 This option allows certain base kernel options and settings 1356 to be disabled or tweaked. This is for specialized 1357 environments which can tolerate a "non-standard" kernel. 1358 Only use this if you really know what you are doing. 1359 1360config UID16 1361 bool "Enable 16-bit UID system calls" if EXPERT 1362 depends on HAVE_UID16 && MULTIUSER 1363 default y 1364 help 1365 This enables the legacy 16-bit UID syscall wrappers. 1366 1367config MULTIUSER 1368 bool "Multiple users, groups and capabilities support" if EXPERT 1369 default y 1370 help 1371 This option enables support for non-root users, groups and 1372 capabilities. 1373 1374 If you say N here, all processes will run with UID 0, GID 0, and all 1375 possible capabilities. Saying N here also compiles out support for 1376 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1377 setgid, and capset. 1378 1379 If unsure, say Y here. 1380 1381config SGETMASK_SYSCALL 1382 bool "sgetmask/ssetmask syscalls support" if EXPERT 1383 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1384 ---help--- 1385 sys_sgetmask and sys_ssetmask are obsolete system calls 1386 no longer supported in libc but still enabled by default in some 1387 architectures. 1388 1389 If unsure, leave the default option here. 1390 1391config SYSFS_SYSCALL 1392 bool "Sysfs syscall support" if EXPERT 1393 default y 1394 ---help--- 1395 sys_sysfs is an obsolete system call no longer supported in libc. 1396 Note that disabling this option is more secure but might break 1397 compatibility with some systems. 1398 1399 If unsure say Y here. 1400 1401config SYSCTL_SYSCALL 1402 bool "Sysctl syscall support" if EXPERT 1403 depends on PROC_SYSCTL 1404 default n 1405 select SYSCTL 1406 ---help--- 1407 sys_sysctl uses binary paths that have been found challenging 1408 to properly maintain and use. The interface in /proc/sys 1409 using paths with ascii names is now the primary path to this 1410 information. 1411 1412 Almost nothing using the binary sysctl interface so if you are 1413 trying to save some space it is probably safe to disable this, 1414 making your kernel marginally smaller. 1415 1416 If unsure say N here. 1417 1418config KALLSYMS 1419 bool "Load all symbols for debugging/ksymoops" if EXPERT 1420 default y 1421 help 1422 Say Y here to let the kernel print out symbolic crash information and 1423 symbolic stack backtraces. This increases the size of the kernel 1424 somewhat, as all symbols have to be loaded into the kernel image. 1425 1426config KALLSYMS_ALL 1427 bool "Include all symbols in kallsyms" 1428 depends on DEBUG_KERNEL && KALLSYMS 1429 help 1430 Normally kallsyms only contains the symbols of functions for nicer 1431 OOPS messages and backtraces (i.e., symbols from the text and inittext 1432 sections). This is sufficient for most cases. And only in very rare 1433 cases (e.g., when a debugger is used) all symbols are required (e.g., 1434 names of variables from the data sections, etc). 1435 1436 This option makes sure that all symbols are loaded into the kernel 1437 image (i.e., symbols from all sections) in cost of increased kernel 1438 size (depending on the kernel configuration, it may be 300KiB or 1439 something like this). 1440 1441 Say N unless you really need all symbols. 1442 1443config PRINTK 1444 default y 1445 bool "Enable support for printk" if EXPERT 1446 select IRQ_WORK 1447 help 1448 This option enables normal printk support. Removing it 1449 eliminates most of the message strings from the kernel image 1450 and makes the kernel more or less silent. As this makes it 1451 very difficult to diagnose system problems, saying N here is 1452 strongly discouraged. 1453 1454config BUG 1455 bool "BUG() support" if EXPERT 1456 default y 1457 help 1458 Disabling this option eliminates support for BUG and WARN, reducing 1459 the size of your kernel image and potentially quietly ignoring 1460 numerous fatal conditions. You should only consider disabling this 1461 option for embedded systems with no facilities for reporting errors. 1462 Just say Y. 1463 1464config ELF_CORE 1465 depends on COREDUMP 1466 default y 1467 bool "Enable ELF core dumps" if EXPERT 1468 help 1469 Enable support for generating core dumps. Disabling saves about 4k. 1470 1471 1472config PCSPKR_PLATFORM 1473 bool "Enable PC-Speaker support" if EXPERT 1474 depends on HAVE_PCSPKR_PLATFORM 1475 select I8253_LOCK 1476 default y 1477 help 1478 This option allows to disable the internal PC-Speaker 1479 support, saving some memory. 1480 1481config BASE_FULL 1482 default y 1483 bool "Enable full-sized data structures for core" if EXPERT 1484 help 1485 Disabling this option reduces the size of miscellaneous core 1486 kernel data structures. This saves memory on small machines, 1487 but may reduce performance. 1488 1489config FUTEX 1490 bool "Enable futex support" if EXPERT 1491 default y 1492 select RT_MUTEXES 1493 help 1494 Disabling this option will cause the kernel to be built without 1495 support for "fast userspace mutexes". The resulting kernel may not 1496 run glibc-based applications correctly. 1497 1498config HAVE_FUTEX_CMPXCHG 1499 bool 1500 depends on FUTEX 1501 help 1502 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1503 is implemented and always working. This removes a couple of runtime 1504 checks. 1505 1506config EPOLL 1507 bool "Enable eventpoll support" if EXPERT 1508 default y 1509 select ANON_INODES 1510 help 1511 Disabling this option will cause the kernel to be built without 1512 support for epoll family of system calls. 1513 1514config SIGNALFD 1515 bool "Enable signalfd() system call" if EXPERT 1516 select ANON_INODES 1517 default y 1518 help 1519 Enable the signalfd() system call that allows to receive signals 1520 on a file descriptor. 1521 1522 If unsure, say Y. 1523 1524config TIMERFD 1525 bool "Enable timerfd() system call" if EXPERT 1526 select ANON_INODES 1527 default y 1528 help 1529 Enable the timerfd() system call that allows to receive timer 1530 events on a file descriptor. 1531 1532 If unsure, say Y. 1533 1534config EVENTFD 1535 bool "Enable eventfd() system call" if EXPERT 1536 select ANON_INODES 1537 default y 1538 help 1539 Enable the eventfd() system call that allows to receive both 1540 kernel notification (ie. KAIO) or userspace notifications. 1541 1542 If unsure, say Y. 1543 1544# syscall, maps, verifier 1545config BPF_SYSCALL 1546 bool "Enable bpf() system call" 1547 select ANON_INODES 1548 select BPF 1549 default n 1550 help 1551 Enable the bpf() system call that allows to manipulate eBPF 1552 programs and maps via file descriptors. 1553 1554config SHMEM 1555 bool "Use full shmem filesystem" if EXPERT 1556 default y 1557 depends on MMU 1558 help 1559 The shmem is an internal filesystem used to manage shared memory. 1560 It is backed by swap and manages resource limits. It is also exported 1561 to userspace as tmpfs if TMPFS is enabled. Disabling this 1562 option replaces shmem and tmpfs with the much simpler ramfs code, 1563 which may be appropriate on small systems without swap. 1564 1565config AIO 1566 bool "Enable AIO support" if EXPERT 1567 default y 1568 help 1569 This option enables POSIX asynchronous I/O which may by used 1570 by some high performance threaded applications. Disabling 1571 this option saves about 7k. 1572 1573config ADVISE_SYSCALLS 1574 bool "Enable madvise/fadvise syscalls" if EXPERT 1575 default y 1576 help 1577 This option enables the madvise and fadvise syscalls, used by 1578 applications to advise the kernel about their future memory or file 1579 usage, improving performance. If building an embedded system where no 1580 applications use these syscalls, you can disable this option to save 1581 space. 1582 1583config PCI_QUIRKS 1584 default y 1585 bool "Enable PCI quirk workarounds" if EXPERT 1586 depends on PCI 1587 help 1588 This enables workarounds for various PCI chipset 1589 bugs/quirks. Disable this only if your target machine is 1590 unaffected by PCI quirks. 1591 1592config EMBEDDED 1593 bool "Embedded system" 1594 option allnoconfig_y 1595 select EXPERT 1596 help 1597 This option should be enabled if compiling the kernel for 1598 an embedded system so certain expert options are available 1599 for configuration. 1600 1601config HAVE_PERF_EVENTS 1602 bool 1603 help 1604 See tools/perf/design.txt for details. 1605 1606config PERF_USE_VMALLOC 1607 bool 1608 help 1609 See tools/perf/design.txt for details 1610 1611menu "Kernel Performance Events And Counters" 1612 1613config PERF_EVENTS 1614 bool "Kernel performance events and counters" 1615 default y if PROFILING 1616 depends on HAVE_PERF_EVENTS 1617 select ANON_INODES 1618 select IRQ_WORK 1619 select SRCU 1620 help 1621 Enable kernel support for various performance events provided 1622 by software and hardware. 1623 1624 Software events are supported either built-in or via the 1625 use of generic tracepoints. 1626 1627 Most modern CPUs support performance events via performance 1628 counter registers. These registers count the number of certain 1629 types of hw events: such as instructions executed, cachemisses 1630 suffered, or branches mis-predicted - without slowing down the 1631 kernel or applications. These registers can also trigger interrupts 1632 when a threshold number of events have passed - and can thus be 1633 used to profile the code that runs on that CPU. 1634 1635 The Linux Performance Event subsystem provides an abstraction of 1636 these software and hardware event capabilities, available via a 1637 system call and used by the "perf" utility in tools/perf/. It 1638 provides per task and per CPU counters, and it provides event 1639 capabilities on top of those. 1640 1641 Say Y if unsure. 1642 1643config DEBUG_PERF_USE_VMALLOC 1644 default n 1645 bool "Debug: use vmalloc to back perf mmap() buffers" 1646 depends on PERF_EVENTS && DEBUG_KERNEL 1647 select PERF_USE_VMALLOC 1648 help 1649 Use vmalloc memory to back perf mmap() buffers. 1650 1651 Mostly useful for debugging the vmalloc code on platforms 1652 that don't require it. 1653 1654 Say N if unsure. 1655 1656endmenu 1657 1658config VM_EVENT_COUNTERS 1659 default y 1660 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1661 help 1662 VM event counters are needed for event counts to be shown. 1663 This option allows the disabling of the VM event counters 1664 on EXPERT systems. /proc/vmstat will only show page counts 1665 if VM event counters are disabled. 1666 1667config SLUB_DEBUG 1668 default y 1669 bool "Enable SLUB debugging support" if EXPERT 1670 depends on SLUB && SYSFS 1671 help 1672 SLUB has extensive debug support features. Disabling these can 1673 result in significant savings in code size. This also disables 1674 SLUB sysfs support. /sys/slab will not exist and there will be 1675 no support for cache validation etc. 1676 1677config COMPAT_BRK 1678 bool "Disable heap randomization" 1679 default y 1680 help 1681 Randomizing heap placement makes heap exploits harder, but it 1682 also breaks ancient binaries (including anything libc5 based). 1683 This option changes the bootup default to heap randomization 1684 disabled, and can be overridden at runtime by setting 1685 /proc/sys/kernel/randomize_va_space to 2. 1686 1687 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1688 1689choice 1690 prompt "Choose SLAB allocator" 1691 default SLUB 1692 help 1693 This option allows to select a slab allocator. 1694 1695config SLAB 1696 bool "SLAB" 1697 help 1698 The regular slab allocator that is established and known to work 1699 well in all environments. It organizes cache hot objects in 1700 per cpu and per node queues. 1701 1702config SLUB 1703 bool "SLUB (Unqueued Allocator)" 1704 help 1705 SLUB is a slab allocator that minimizes cache line usage 1706 instead of managing queues of cached objects (SLAB approach). 1707 Per cpu caching is realized using slabs of objects instead 1708 of queues of objects. SLUB can use memory efficiently 1709 and has enhanced diagnostics. SLUB is the default choice for 1710 a slab allocator. 1711 1712config SLOB 1713 depends on EXPERT 1714 bool "SLOB (Simple Allocator)" 1715 help 1716 SLOB replaces the stock allocator with a drastically simpler 1717 allocator. SLOB is generally more space efficient but 1718 does not perform as well on large systems. 1719 1720endchoice 1721 1722config SLUB_CPU_PARTIAL 1723 default y 1724 depends on SLUB && SMP 1725 bool "SLUB per cpu partial cache" 1726 help 1727 Per cpu partial caches accellerate objects allocation and freeing 1728 that is local to a processor at the price of more indeterminism 1729 in the latency of the free. On overflow these caches will be cleared 1730 which requires the taking of locks that may cause latency spikes. 1731 Typically one would choose no for a realtime system. 1732 1733config MMAP_ALLOW_UNINITIALIZED 1734 bool "Allow mmapped anonymous memory to be uninitialized" 1735 depends on EXPERT && !MMU 1736 default n 1737 help 1738 Normally, and according to the Linux spec, anonymous memory obtained 1739 from mmap() has it's contents cleared before it is passed to 1740 userspace. Enabling this config option allows you to request that 1741 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1742 providing a huge performance boost. If this option is not enabled, 1743 then the flag will be ignored. 1744 1745 This is taken advantage of by uClibc's malloc(), and also by 1746 ELF-FDPIC binfmt's brk and stack allocator. 1747 1748 Because of the obvious security issues, this option should only be 1749 enabled on embedded devices where you control what is run in 1750 userspace. Since that isn't generally a problem on no-MMU systems, 1751 it is normally safe to say Y here. 1752 1753 See Documentation/nommu-mmap.txt for more information. 1754 1755config SYSTEM_TRUSTED_KEYRING 1756 bool "Provide system-wide ring of trusted keys" 1757 depends on KEYS 1758 help 1759 Provide a system keyring to which trusted keys can be added. Keys in 1760 the keyring are considered to be trusted. Keys may be added at will 1761 by the kernel from compiled-in data and from hardware key stores, but 1762 userspace may only add extra keys if those keys can be verified by 1763 keys already in the keyring. 1764 1765 Keys in this keyring are used by module signature checking. 1766 1767config PROFILING 1768 bool "Profiling support" 1769 help 1770 Say Y here to enable the extended profiling support mechanisms used 1771 by profilers such as OProfile. 1772 1773# 1774# Place an empty function call at each tracepoint site. Can be 1775# dynamically changed for a probe function. 1776# 1777config TRACEPOINTS 1778 bool 1779 1780source "arch/Kconfig" 1781 1782endmenu # General setup 1783 1784config HAVE_GENERIC_DMA_COHERENT 1785 bool 1786 default n 1787 1788config SLABINFO 1789 bool 1790 depends on PROC_FS 1791 depends on SLAB || SLUB_DEBUG 1792 default y 1793 1794config RT_MUTEXES 1795 bool 1796 1797config BASE_SMALL 1798 int 1799 default 0 if BASE_FULL 1800 default 1 if !BASE_FULL 1801 1802menuconfig MODULES 1803 bool "Enable loadable module support" 1804 option modules 1805 help 1806 Kernel modules are small pieces of compiled code which can 1807 be inserted in the running kernel, rather than being 1808 permanently built into the kernel. You use the "modprobe" 1809 tool to add (and sometimes remove) them. If you say Y here, 1810 many parts of the kernel can be built as modules (by 1811 answering M instead of Y where indicated): this is most 1812 useful for infrequently used options which are not required 1813 for booting. For more information, see the man pages for 1814 modprobe, lsmod, modinfo, insmod and rmmod. 1815 1816 If you say Y here, you will need to run "make 1817 modules_install" to put the modules under /lib/modules/ 1818 where modprobe can find them (you may need to be root to do 1819 this). 1820 1821 If unsure, say Y. 1822 1823if MODULES 1824 1825config MODULE_FORCE_LOAD 1826 bool "Forced module loading" 1827 default n 1828 help 1829 Allow loading of modules without version information (ie. modprobe 1830 --force). Forced module loading sets the 'F' (forced) taint flag and 1831 is usually a really bad idea. 1832 1833config MODULE_UNLOAD 1834 bool "Module unloading" 1835 help 1836 Without this option you will not be able to unload any 1837 modules (note that some modules may not be unloadable 1838 anyway), which makes your kernel smaller, faster 1839 and simpler. If unsure, say Y. 1840 1841config MODULE_FORCE_UNLOAD 1842 bool "Forced module unloading" 1843 depends on MODULE_UNLOAD 1844 help 1845 This option allows you to force a module to unload, even if the 1846 kernel believes it is unsafe: the kernel will remove the module 1847 without waiting for anyone to stop using it (using the -f option to 1848 rmmod). This is mainly for kernel developers and desperate users. 1849 If unsure, say N. 1850 1851config MODVERSIONS 1852 bool "Module versioning support" 1853 help 1854 Usually, you have to use modules compiled with your kernel. 1855 Saying Y here makes it sometimes possible to use modules 1856 compiled for different kernels, by adding enough information 1857 to the modules to (hopefully) spot any changes which would 1858 make them incompatible with the kernel you are running. If 1859 unsure, say N. 1860 1861config MODULE_SRCVERSION_ALL 1862 bool "Source checksum for all modules" 1863 help 1864 Modules which contain a MODULE_VERSION get an extra "srcversion" 1865 field inserted into their modinfo section, which contains a 1866 sum of the source files which made it. This helps maintainers 1867 see exactly which source was used to build a module (since 1868 others sometimes change the module source without updating 1869 the version). With this option, such a "srcversion" field 1870 will be created for all modules. If unsure, say N. 1871 1872config MODULE_SIG 1873 bool "Module signature verification" 1874 depends on MODULES 1875 select SYSTEM_TRUSTED_KEYRING 1876 select KEYS 1877 select CRYPTO 1878 select ASYMMETRIC_KEY_TYPE 1879 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1880 select PUBLIC_KEY_ALGO_RSA 1881 select ASN1 1882 select OID_REGISTRY 1883 select X509_CERTIFICATE_PARSER 1884 help 1885 Check modules for valid signatures upon load: the signature 1886 is simply appended to the module. For more information see 1887 Documentation/module-signing.txt. 1888 1889 !!!WARNING!!! If you enable this option, you MUST make sure that the 1890 module DOES NOT get stripped after being signed. This includes the 1891 debuginfo strip done by some packagers (such as rpmbuild) and 1892 inclusion into an initramfs that wants the module size reduced. 1893 1894config MODULE_SIG_FORCE 1895 bool "Require modules to be validly signed" 1896 depends on MODULE_SIG 1897 help 1898 Reject unsigned modules or signed modules for which we don't have a 1899 key. Without this, such modules will simply taint the kernel. 1900 1901config MODULE_SIG_ALL 1902 bool "Automatically sign all modules" 1903 default y 1904 depends on MODULE_SIG 1905 help 1906 Sign all modules during make modules_install. Without this option, 1907 modules must be signed manually, using the scripts/sign-file tool. 1908 1909comment "Do not forget to sign required modules with scripts/sign-file" 1910 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1911 1912choice 1913 prompt "Which hash algorithm should modules be signed with?" 1914 depends on MODULE_SIG 1915 help 1916 This determines which sort of hashing algorithm will be used during 1917 signature generation. This algorithm _must_ be built into the kernel 1918 directly so that signature verification can take place. It is not 1919 possible to load a signed module containing the algorithm to check 1920 the signature on that module. 1921 1922config MODULE_SIG_SHA1 1923 bool "Sign modules with SHA-1" 1924 select CRYPTO_SHA1 1925 1926config MODULE_SIG_SHA224 1927 bool "Sign modules with SHA-224" 1928 select CRYPTO_SHA256 1929 1930config MODULE_SIG_SHA256 1931 bool "Sign modules with SHA-256" 1932 select CRYPTO_SHA256 1933 1934config MODULE_SIG_SHA384 1935 bool "Sign modules with SHA-384" 1936 select CRYPTO_SHA512 1937 1938config MODULE_SIG_SHA512 1939 bool "Sign modules with SHA-512" 1940 select CRYPTO_SHA512 1941 1942endchoice 1943 1944config MODULE_SIG_HASH 1945 string 1946 depends on MODULE_SIG 1947 default "sha1" if MODULE_SIG_SHA1 1948 default "sha224" if MODULE_SIG_SHA224 1949 default "sha256" if MODULE_SIG_SHA256 1950 default "sha384" if MODULE_SIG_SHA384 1951 default "sha512" if MODULE_SIG_SHA512 1952 1953config MODULE_COMPRESS 1954 bool "Compress modules on installation" 1955 depends on MODULES 1956 help 1957 This option compresses the kernel modules when 'make 1958 modules_install' is run. 1959 1960 The modules will be compressed either using gzip or xz depend on the 1961 choice made in "Compression algorithm". 1962 1963 module-init-tools has support for gzip format while kmod handle gzip 1964 and xz compressed modules. 1965 1966 When a kernel module is installed from outside of the main kernel 1967 source and uses the Kbuild system for installing modules then that 1968 kernel module will also be compressed when it is installed. 1969 1970 This option provides little benefit when the modules are to be used inside 1971 an initrd or initramfs, it generally is more efficient to compress the whole 1972 initrd or initramfs instead. 1973 1974 This is fully compatible with signed modules while the signed module is 1975 compressed. module-init-tools or kmod handles decompression and provide to 1976 other layer the uncompressed but signed payload. 1977 1978choice 1979 prompt "Compression algorithm" 1980 depends on MODULE_COMPRESS 1981 default MODULE_COMPRESS_GZIP 1982 help 1983 This determines which sort of compression will be used during 1984 'make modules_install'. 1985 1986 GZIP (default) and XZ are supported. 1987 1988config MODULE_COMPRESS_GZIP 1989 bool "GZIP" 1990 1991config MODULE_COMPRESS_XZ 1992 bool "XZ" 1993 1994endchoice 1995 1996endif # MODULES 1997 1998config INIT_ALL_POSSIBLE 1999 bool 2000 help 2001 Back when each arch used to define their own cpu_online_mask and 2002 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2003 with all 1s, and others with all 0s. When they were centralised, 2004 it was better to provide this option than to break all the archs 2005 and have several arch maintainers pursuing me down dark alleys. 2006 2007config STOP_MACHINE 2008 bool 2009 default y 2010 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 2011 help 2012 Need stop_machine() primitive. 2013 2014source "block/Kconfig" 2015 2016config PREEMPT_NOTIFIERS 2017 bool 2018 2019config PADATA 2020 depends on SMP 2021 bool 2022 2023# Can be selected by architectures with broken toolchains 2024# that get confused by correct const<->read_only section 2025# mappings 2026config BROKEN_RODATA 2027 bool 2028 2029config ASN1 2030 tristate 2031 help 2032 Build a simple ASN.1 grammar compiler that produces a bytecode output 2033 that can be interpreted by the ASN.1 stream decoder and used to 2034 inform it as to what tags are to be expected in a stream and what 2035 functions to call on what tags. 2036 2037source "kernel/Kconfig.locks" 2038