| blob | d42dc7c6ba649145a2ac3c13f4d071c5303e38da |
1 config ARCH
2 string
3 option env="ARCH"
5 config KERNELVERSION
6 string
7 option env="KERNELVERSION"
9 config 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"
19 config CONSTRUCTORS
20 bool
21 depends on !UML
23 config IRQ_WORK
24 bool
26 config BUILDTIME_EXTABLE_SORT
27 bool
29 menu "General setup"
31 config BROKEN
32 bool
34 config BROKEN_ON_SMP
35 bool
36 depends on BROKEN || !SMP
37 default y
39 config 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.
48 config 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.
56 config 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.
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.
70 config 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.
80 config 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.
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.
93 (The actual string used here is the first eight characters produced
94 by running the command:
96 $ git rev-parse --verify HEAD
98 which is done within the script "scripts/setlocalversion".)
100 config HAVE_KERNEL_GZIP
101 bool
103 config HAVE_KERNEL_BZIP2
104 bool
106 config HAVE_KERNEL_LZMA
107 bool
109 config HAVE_KERNEL_XZ
110 bool
112 config HAVE_KERNEL_LZO
113 bool
115 config HAVE_KERNEL_LZ4
116 bool
118 choice
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.
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)
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.
138 If in doubt, select 'gzip'
140 config 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.
147 config 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.
157 config 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.
165 config 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.
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.
180 config 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.
188 config 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/>.
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.
200 endchoice
202 config 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.
211 config 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.
221 config 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.
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>.
236 config SYSVIPC_SYSCTL
237 bool
238 depends on SYSVIPC
239 depends on SYSCTL
240 default y
242 config 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.
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.
256 If unsure, say Y.
258 config POSIX_MQUEUE_SYSCTL
259 bool
260 depends on POSIX_MQUEUE
261 depends on SYSCTL
262 default y
264 config FHANDLE
265 bool "open by fhandle syscalls"
266 select EXPORTFS
267 help
268 If you say Y here, a user level program will be able to map
269 file names to handle and then later use the handle for
270 different file system operations. This is useful in implementing
271 userspace file servers, which now track files using handles instead
272 of names. The handle would remain the same even if file names
273 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
274 syscalls.
276 config AUDIT
277 bool "Auditing support"
278 depends on NET
279 help
280 Enable auditing infrastructure that can be used with another
281 kernel subsystem, such as SELinux (which requires this for
282 logging of avc messages output). Does not do system-call
283 auditing without CONFIG_AUDITSYSCALL.
285 config AUDITSYSCALL
286 bool "Enable system-call auditing support"
287 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
288 default y if SECURITY_SELINUX
289 help
290 Enable low-overhead system-call auditing infrastructure that
291 can be used independently or with another kernel subsystem,
292 such as SELinux.
294 config AUDIT_WATCH
295 def_bool y
296 depends on AUDITSYSCALL
297 select FSNOTIFY
299 config AUDIT_TREE
300 def_bool y
301 depends on AUDITSYSCALL
302 select FSNOTIFY
304 config AUDIT_LOGINUID_IMMUTABLE
305 bool "Make audit loginuid immutable"
306 depends on AUDIT
307 help
308 The config option toggles if a task setting its loginuid requires
309 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
310 but should instead only allow setting its loginuid if it was never
311 previously set. On systems which use systemd or a similar central
312 process to restart login services this should be set to true. On older
313 systems in which an admin would typically have to directly stop and
314 start processes this should be set to false. Setting this to true allows
315 one to drop potentially dangerous capabilites from the login tasks,
316 but may not be backwards compatible with older init systems.
318 source "kernel/irq/Kconfig"
319 source "kernel/time/Kconfig"
321 menu "CPU/Task time and stats accounting"
323 config VIRT_CPU_ACCOUNTING
324 bool
326 choice
327 prompt "Cputime accounting"
328 default TICK_CPU_ACCOUNTING if !PPC64
329 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
331 # Kind of a stub config for the pure tick based cputime accounting
332 config TICK_CPU_ACCOUNTING
333 bool "Simple tick based cputime accounting"
334 depends on !S390 && !NO_HZ_FULL
335 help
336 This is the basic tick based cputime accounting that maintains
337 statistics about user, system and idle time spent on per jiffies
338 granularity.
340 If unsure, say Y.
342 config VIRT_CPU_ACCOUNTING_NATIVE
343 bool "Deterministic task and CPU time accounting"
344 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
345 select VIRT_CPU_ACCOUNTING
346 help
347 Select this option to enable more accurate task and CPU time
348 accounting. This is done by reading a CPU counter on each
349 kernel entry and exit and on transitions within the kernel
350 between system, softirq and hardirq state, so there is a
351 small performance impact. In the case of s390 or IBM POWER > 5,
352 this also enables accounting of stolen time on logically-partitioned
353 systems.
355 config VIRT_CPU_ACCOUNTING_GEN
356 bool "Full dynticks CPU time accounting"
357 depends on HAVE_CONTEXT_TRACKING && 64BIT
358 select VIRT_CPU_ACCOUNTING
359 select CONTEXT_TRACKING
360 help
361 Select this option to enable task and CPU time accounting on full
362 dynticks systems. This accounting is implemented by watching every
363 kernel-user boundaries using the context tracking subsystem.
364 The accounting is thus performed at the expense of some significant
365 overhead.
367 For now this is only useful if you are working on the full
368 dynticks subsystem development.
370 If unsure, say N.
372 config IRQ_TIME_ACCOUNTING
373 bool "Fine granularity task level IRQ time accounting"
374 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
375 help
376 Select this option to enable fine granularity task irq time
377 accounting. This is done by reading a timestamp on each
378 transitions between softirq and hardirq state, so there can be a
379 small performance impact.
381 If in doubt, say N here.
383 endchoice
385 config BSD_PROCESS_ACCT
386 bool "BSD Process Accounting"
387 help
388 If you say Y here, a user level program will be able to instruct the
389 kernel (via a special system call) to write process accounting
390 information to a file: whenever a process exits, information about
391 that process will be appended to the file by the kernel. The
392 information includes things such as creation time, owning user,
393 command name, memory usage, controlling terminal etc. (the complete
394 list is in the struct acct in <file:include/linux/acct.h>). It is
395 up to the user level program to do useful things with this
396 information. This is generally a good idea, so say Y.
398 config BSD_PROCESS_ACCT_V3
399 bool "BSD Process Accounting version 3 file format"
400 depends on BSD_PROCESS_ACCT
401 default n
402 help
403 If you say Y here, the process accounting information is written
404 in a new file format that also logs the process IDs of each
405 process and it's parent. Note that this file format is incompatible
406 with previous v0/v1/v2 file formats, so you will need updated tools
407 for processing it. A preliminary version of these tools is available
408 at <http://www.gnu.org/software/acct/>.
410 config TASKSTATS
411 bool "Export task/process statistics through netlink"
412 depends on NET
413 default n
414 help
415 Export selected statistics for tasks/processes through the
416 generic netlink interface. Unlike BSD process accounting, the
417 statistics are available during the lifetime of tasks/processes as
418 responses to commands. Like BSD accounting, they are sent to user
419 space on task exit.
421 Say N if unsure.
423 config TASK_DELAY_ACCT
424 bool "Enable per-task delay accounting"
425 depends on TASKSTATS
426 help
427 Collect information on time spent by a task waiting for system
428 resources like cpu, synchronous block I/O completion and swapping
429 in pages. Such statistics can help in setting a task's priorities
430 relative to other tasks for cpu, io, rss limits etc.
432 Say N if unsure.
434 config TASK_XACCT
435 bool "Enable extended accounting over taskstats"
436 depends on TASKSTATS
437 help
438 Collect extended task accounting data and send the data
439 to userland for processing over the taskstats interface.
441 Say N if unsure.
443 config TASK_IO_ACCOUNTING
444 bool "Enable per-task storage I/O accounting"
445 depends on TASK_XACCT
446 help
447 Collect information on the number of bytes of storage I/O which this
448 task has caused.
450 Say N if unsure.
452 endmenu # "CPU/Task time and stats accounting"
454 menu "RCU Subsystem"
456 choice
457 prompt "RCU Implementation"
458 default TREE_RCU
460 config TREE_RCU
461 bool "Tree-based hierarchical RCU"
462 depends on !PREEMPT && SMP
463 select IRQ_WORK
464 help
465 This option selects the RCU implementation that is
466 designed for very large SMP system with hundreds or
467 thousands of CPUs. It also scales down nicely to
468 smaller systems.
470 config TREE_PREEMPT_RCU
471 bool "Preemptible tree-based hierarchical RCU"
472 depends on PREEMPT
473 select IRQ_WORK
474 help
475 This option selects the RCU implementation that is
476 designed for very large SMP systems with hundreds or
477 thousands of CPUs, but for which real-time response
478 is also required. It also scales down nicely to
479 smaller systems.
481 Select this option if you are unsure.
483 config TINY_RCU
484 bool "UP-only small-memory-footprint RCU"
485 depends on !PREEMPT && !SMP
486 help
487 This option selects the RCU implementation that is
488 designed for UP systems from which real-time response
489 is not required. This option greatly reduces the
490 memory footprint of RCU.
492 endchoice
494 config PREEMPT_RCU
495 def_bool TREE_PREEMPT_RCU
496 help
497 This option enables preemptible-RCU code that is common between
498 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
500 config RCU_STALL_COMMON
501 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
502 help
503 This option enables RCU CPU stall code that is common between
504 the TINY and TREE variants of RCU. The purpose is to allow
505 the tiny variants to disable RCU CPU stall warnings, while
506 making these warnings mandatory for the tree variants.
508 config CONTEXT_TRACKING
509 bool
511 config RCU_USER_QS
512 bool "Consider userspace as in RCU extended quiescent state"
513 depends on HAVE_CONTEXT_TRACKING && SMP
514 select CONTEXT_TRACKING
515 help
516 This option sets hooks on kernel / userspace boundaries and
517 puts RCU in extended quiescent state when the CPU runs in
518 userspace. It means that when a CPU runs in userspace, it is
519 excluded from the global RCU state machine and thus doesn't
520 try to keep the timer tick on for RCU.
522 Unless you want to hack and help the development of the full
523 dynticks mode, you shouldn't enable this option. It also
524 adds unnecessary overhead.
526 If unsure say N
528 config CONTEXT_TRACKING_FORCE
529 bool "Force context tracking"
530 depends on CONTEXT_TRACKING
531 default y if !NO_HZ_FULL
532 help
533 The major pre-requirement for full dynticks to work is to
534 support the context tracking subsystem. But there are also
535 other dependencies to provide in order to make the full
536 dynticks working.
538 This option stands for testing when an arch implements the
539 context tracking backend but doesn't yet fullfill all the
540 requirements to make the full dynticks feature working.
541 Without the full dynticks, there is no way to test the support
542 for context tracking and the subsystems that rely on it: RCU
543 userspace extended quiescent state and tickless cputime
544 accounting. This option copes with the absence of the full
545 dynticks subsystem by forcing the context tracking on all
546 CPUs in the system.
548 Say Y only if you're working on the developpement of an
549 architecture backend for the context tracking.
551 Say N otherwise, this option brings an overhead that you
552 don't want in production.
555 config RCU_FANOUT
556 int "Tree-based hierarchical RCU fanout value"
557 range 2 64 if 64BIT
558 range 2 32 if !64BIT
559 depends on TREE_RCU || TREE_PREEMPT_RCU
560 default 64 if 64BIT
561 default 32 if !64BIT
562 help
563 This option controls the fanout of hierarchical implementations
564 of RCU, allowing RCU to work efficiently on machines with
565 large numbers of CPUs. This value must be at least the fourth
566 root of NR_CPUS, which allows NR_CPUS to be insanely large.
567 The default value of RCU_FANOUT should be used for production
568 systems, but if you are stress-testing the RCU implementation
569 itself, small RCU_FANOUT values allow you to test large-system
570 code paths on small(er) systems.
572 Select a specific number if testing RCU itself.
573 Take the default if unsure.
575 config RCU_FANOUT_LEAF
576 int "Tree-based hierarchical RCU leaf-level fanout value"
577 range 2 RCU_FANOUT if 64BIT
578 range 2 RCU_FANOUT if !64BIT
579 depends on TREE_RCU || TREE_PREEMPT_RCU
580 default 16
581 help
582 This option controls the leaf-level fanout of hierarchical
583 implementations of RCU, and allows trading off cache misses
584 against lock contention. Systems that synchronize their
585 scheduling-clock interrupts for energy-efficiency reasons will
586 want the default because the smaller leaf-level fanout keeps
587 lock contention levels acceptably low. Very large systems
588 (hundreds or thousands of CPUs) will instead want to set this
589 value to the maximum value possible in order to reduce the
590 number of cache misses incurred during RCU's grace-period
591 initialization. These systems tend to run CPU-bound, and thus
592 are not helped by synchronized interrupts, and thus tend to
593 skew them, which reduces lock contention enough that large
594 leaf-level fanouts work well.
596 Select a specific number if testing RCU itself.
598 Select the maximum permissible value for large systems.
600 Take the default if unsure.
602 config RCU_FANOUT_EXACT
603 bool "Disable tree-based hierarchical RCU auto-balancing"
604 depends on TREE_RCU || TREE_PREEMPT_RCU
605 default n
606 help
607 This option forces use of the exact RCU_FANOUT value specified,
608 regardless of imbalances in the hierarchy. This is useful for
609 testing RCU itself, and might one day be useful on systems with
610 strong NUMA behavior.
612 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
614 Say N if unsure.
616 config RCU_FAST_NO_HZ
617 bool "Accelerate last non-dyntick-idle CPU's grace periods"
618 depends on NO_HZ_COMMON && SMP
619 default n
620 help
621 This option permits CPUs to enter dynticks-idle state even if
622 they have RCU callbacks queued, and prevents RCU from waking
623 these CPUs up more than roughly once every four jiffies (by
624 default, you can adjust this using the rcutree.rcu_idle_gp_delay
625 parameter), thus improving energy efficiency. On the other
626 hand, this option increases the duration of RCU grace periods,
627 for example, slowing down synchronize_rcu().
629 Say Y if energy efficiency is critically important, and you
630 don't care about increased grace-period durations.
632 Say N if you are unsure.
634 config TREE_RCU_TRACE
635 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
636 select DEBUG_FS
637 help
638 This option provides tracing for the TREE_RCU and
639 TREE_PREEMPT_RCU implementations, permitting Makefile to
640 trivially select kernel/rcutree_trace.c.
642 config RCU_BOOST
643 bool "Enable RCU priority boosting"
644 depends on RT_MUTEXES && PREEMPT_RCU
645 default n
646 help
647 This option boosts the priority of preempted RCU readers that
648 block the current preemptible RCU grace period for too long.
649 This option also prevents heavy loads from blocking RCU
650 callback invocation for all flavors of RCU.
652 Say Y here if you are working with real-time apps or heavy loads
653 Say N here if you are unsure.
655 config RCU_BOOST_PRIO
656 int "Real-time priority to boost RCU readers to"
657 range 1 99
658 depends on RCU_BOOST
659 default 1
660 help
661 This option specifies the real-time priority to which long-term
662 preempted RCU readers are to be boosted. If you are working
663 with a real-time application that has one or more CPU-bound
664 threads running at a real-time priority level, you should set
665 RCU_BOOST_PRIO to a priority higher then the highest-priority
666 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
667 of 1 is appropriate in the common case, which is real-time
668 applications that do not have any CPU-bound threads.
670 Some real-time applications might not have a single real-time
671 thread that saturates a given CPU, but instead might have
672 multiple real-time threads that, taken together, fully utilize
673 that CPU. In this case, you should set RCU_BOOST_PRIO to
674 a priority higher than the lowest-priority thread that is
675 conspiring to prevent the CPU from running any non-real-time
676 tasks. For example, if one thread at priority 10 and another
677 thread at priority 5 are between themselves fully consuming
678 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
679 set to priority 6 or higher.
681 Specify the real-time priority, or take the default if unsure.
683 config RCU_BOOST_DELAY
684 int "Milliseconds to delay boosting after RCU grace-period start"
685 range 0 3000
686 depends on RCU_BOOST
687 default 500
688 help
689 This option specifies the time to wait after the beginning of
690 a given grace period before priority-boosting preempted RCU
691 readers blocking that grace period. Note that any RCU reader
692 blocking an expedited RCU grace period is boosted immediately.
694 Accept the default if unsure.
696 config RCU_NOCB_CPU
697 bool "Offload RCU callback processing from boot-selected CPUs"
698 depends on TREE_RCU || TREE_PREEMPT_RCU
699 default n
700 help
701 Use this option to reduce OS jitter for aggressive HPC or
702 real-time workloads. It can also be used to offload RCU
703 callback invocation to energy-efficient CPUs in battery-powered
704 asymmetric multiprocessors.
706 This option offloads callback invocation from the set of
707 CPUs specified at boot time by the rcu_nocbs parameter.
708 For each such CPU, a kthread ("rcuox/N") will be created to
709 invoke callbacks, where the "N" is the CPU being offloaded,
710 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
711 "s" for RCU-sched. Nothing prevents this kthread from running
712 on the specified CPUs, but (1) the kthreads may be preempted
713 between each callback, and (2) affinity or cgroups can be used
714 to force the kthreads to run on whatever set of CPUs is desired.
716 Say Y here if you want to help to debug reduced OS jitter.
717 Say N here if you are unsure.
719 choice
720 prompt "Build-forced no-CBs CPUs"
721 default RCU_NOCB_CPU_NONE
722 help
723 This option allows no-CBs CPUs (whose RCU callbacks are invoked
724 from kthreads rather than from softirq context) to be specified
725 at build time. Additional no-CBs CPUs may be specified by
726 the rcu_nocbs= boot parameter.
728 config RCU_NOCB_CPU_NONE
729 bool "No build_forced no-CBs CPUs"
730 depends on RCU_NOCB_CPU && !NO_HZ_FULL
731 help
732 This option does not force any of the CPUs to be no-CBs CPUs.
733 Only CPUs designated by the rcu_nocbs= boot parameter will be
734 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
735 kthreads whose names begin with "rcuo". All other CPUs will
736 invoke their own RCU callbacks in softirq context.
738 Select this option if you want to choose no-CBs CPUs at
739 boot time, for example, to allow testing of different no-CBs
740 configurations without having to rebuild the kernel each time.
742 config RCU_NOCB_CPU_ZERO
743 bool "CPU 0 is a build_forced no-CBs CPU"
744 depends on RCU_NOCB_CPU && !NO_HZ_FULL
745 help
746 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
747 callbacks are invoked by a per-CPU kthread whose name begins
748 with "rcuo". Additional CPUs may be designated as no-CBs
749 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
750 All other CPUs will invoke their own RCU callbacks in softirq
751 context.
753 Select this if CPU 0 needs to be a no-CBs CPU for real-time
754 or energy-efficiency reasons, but the real reason it exists
755 is to ensure that randconfig testing covers mixed systems.
757 config RCU_NOCB_CPU_ALL
758 bool "All CPUs are build_forced no-CBs CPUs"
759 depends on RCU_NOCB_CPU
760 help
761 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
762 boot parameter will be ignored. All CPUs' RCU callbacks will
763 be executed in the context of per-CPU rcuo kthreads created for
764 this purpose. Assuming that the kthreads whose names start with
765 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
766 on the remaining CPUs, but might decrease memory locality during
767 RCU-callback invocation, thus potentially degrading throughput.
769 Select this if all CPUs need to be no-CBs CPUs for real-time
770 or energy-efficiency reasons.
772 endchoice
774 endmenu # "RCU Subsystem"
776 config IKCONFIG
777 tristate "Kernel .config support"
778 ---help---
779 This option enables the complete Linux kernel ".config" file
780 contents to be saved in the kernel. It provides documentation
781 of which kernel options are used in a running kernel or in an
782 on-disk kernel. This information can be extracted from the kernel
783 image file with the script scripts/extract-ikconfig and used as
784 input to rebuild the current kernel or to build another kernel.
785 It can also be extracted from a running kernel by reading
786 /proc/config.gz if enabled (below).
788 config IKCONFIG_PROC
789 bool "Enable access to .config through /proc/config.gz"
790 depends on IKCONFIG && PROC_FS
791 ---help---
792 This option enables access to the kernel configuration file
793 through /proc/config.gz.
795 config LOG_BUF_SHIFT
796 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
797 range 12 21
798 default 17
799 help
800 Select kernel log buffer size as a power of 2.
801 Examples:
802 17 => 128 KB
803 16 => 64 KB
804 15 => 32 KB
805 14 => 16 KB
806 13 => 8 KB
807 12 => 4 KB
809 #
810 # Architectures with an unreliable sched_clock() should select this:
811 #
812 config HAVE_UNSTABLE_SCHED_CLOCK
813 bool
815 config GENERIC_SCHED_CLOCK
816 bool
818 #
819 # For architectures that want to enable the support for NUMA-affine scheduler
820 # balancing logic:
821 #
822 config ARCH_SUPPORTS_NUMA_BALANCING
823 bool
825 # For architectures that (ab)use NUMA to represent different memory regions
826 # all cpu-local but of different latencies, such as SuperH.
827 #
828 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
829 bool
831 #
832 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
833 config ARCH_WANTS_PROT_NUMA_PROT_NONE
834 bool
836 config ARCH_USES_NUMA_PROT_NONE
837 bool
838 default y
839 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
840 depends on NUMA_BALANCING
842 config NUMA_BALANCING_DEFAULT_ENABLED
843 bool "Automatically enable NUMA aware memory/task placement"
844 default y
845 depends on NUMA_BALANCING
846 help
847 If set, autonumic NUMA balancing will be enabled if running on a NUMA
848 machine.
850 config NUMA_BALANCING
851 bool "Memory placement aware NUMA scheduler"
852 depends on ARCH_SUPPORTS_NUMA_BALANCING
853 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
854 depends on SMP && NUMA && MIGRATION
855 help
856 This option adds support for automatic NUMA aware memory/task placement.
857 The mechanism is quite primitive and is based on migrating memory when
858 it is references to the node the task is running on.
860 This system will be inactive on UMA systems.
862 menuconfig CGROUPS
863 boolean "Control Group support"
864 depends on EVENTFD
865 help
866 This option adds support for grouping sets of processes together, for
867 use with process control subsystems such as Cpusets, CFS, memory
868 controls or device isolation.
869 See
870 - Documentation/scheduler/sched-design-CFS.txt (CFS)
871 - Documentation/cgroups/ (features for grouping, isolation
872 and resource control)
874 Say N if unsure.
876 if CGROUPS
878 config CGROUP_DEBUG
879 bool "Example debug cgroup subsystem"
880 default n
881 help
882 This option enables a simple cgroup subsystem that
883 exports useful debugging information about the cgroups
884 framework.
886 Say N if unsure.
888 config CGROUP_FREEZER
889 bool "Freezer cgroup subsystem"
890 help
891 Provides a way to freeze and unfreeze all tasks in a
892 cgroup.
894 config CGROUP_DEVICE
895 bool "Device controller for cgroups"
896 help
897 Provides a cgroup implementing whitelists for devices which
898 a process in the cgroup can mknod or open.
900 config CPUSETS
901 bool "Cpuset support"
902 help
903 This option will let you create and manage CPUSETs which
904 allow dynamically partitioning a system into sets of CPUs and
905 Memory Nodes and assigning tasks to run only within those sets.
906 This is primarily useful on large SMP or NUMA systems.
908 Say N if unsure.
910 config PROC_PID_CPUSET
911 bool "Include legacy /proc/<pid>/cpuset file"
912 depends on CPUSETS
913 default y
915 config CGROUP_CPUACCT
916 bool "Simple CPU accounting cgroup subsystem"
917 help
918 Provides a simple Resource Controller for monitoring the
919 total CPU consumed by the tasks in a cgroup.
921 config RESOURCE_COUNTERS
922 bool "Resource counters"
923 help
924 This option enables controller independent resource accounting
925 infrastructure that works with cgroups.
927 config MEMCG
928 bool "Memory Resource Controller for Control Groups"
929 depends on RESOURCE_COUNTERS
930 select MM_OWNER
931 help
932 Provides a memory resource controller that manages both anonymous
933 memory and page cache. (See Documentation/cgroups/memory.txt)
935 Note that setting this option increases fixed memory overhead
936 associated with each page of memory in the system. By this,
937 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
938 usage tracking struct at boot. Total amount of this is printed out
939 at boot.
941 Only enable when you're ok with these trade offs and really
942 sure you need the memory resource controller. Even when you enable
943 this, you can set "cgroup_disable=memory" at your boot option to
944 disable memory resource controller and you can avoid overheads.
945 (and lose benefits of memory resource controller)
947 This config option also selects MM_OWNER config option, which
948 could in turn add some fork/exit overhead.
950 config MEMCG_SWAP
951 bool "Memory Resource Controller Swap Extension"
952 depends on MEMCG && SWAP
953 help
954 Add swap management feature to memory resource controller. When you
955 enable this, you can limit mem+swap usage per cgroup. In other words,
956 when you disable this, memory resource controller has no cares to
957 usage of swap...a process can exhaust all of the swap. This extension
958 is useful when you want to avoid exhaustion swap but this itself
959 adds more overheads and consumes memory for remembering information.
960 Especially if you use 32bit system or small memory system, please
961 be careful about enabling this. When memory resource controller
962 is disabled by boot option, this will be automatically disabled and
963 there will be no overhead from this. Even when you set this config=y,
964 if boot option "swapaccount=0" is set, swap will not be accounted.
965 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
966 size is 4096bytes, 512k per 1Gbytes of swap.
967 config MEMCG_SWAP_ENABLED
968 bool "Memory Resource Controller Swap Extension enabled by default"
969 depends on MEMCG_SWAP
970 default y
971 help
972 Memory Resource Controller Swap Extension comes with its price in
973 a bigger memory consumption. General purpose distribution kernels
974 which want to enable the feature but keep it disabled by default
975 and let the user enable it by swapaccount=1 boot command line
976 parameter should have this option unselected.
977 For those who want to have the feature enabled by default should
978 select this option (if, for some reason, they need to disable it
979 then swapaccount=0 does the trick).
980 config MEMCG_KMEM
981 bool "Memory Resource Controller Kernel Memory accounting"
982 depends on MEMCG
983 depends on SLUB || SLAB
984 help
985 The Kernel Memory extension for Memory Resource Controller can limit
986 the amount of memory used by kernel objects in the system. Those are
987 fundamentally different from the entities handled by the standard
988 Memory Controller, which are page-based, and can be swapped. Users of
989 the kmem extension can use it to guarantee that no group of processes
990 will ever exhaust kernel resources alone.
992 config CGROUP_HUGETLB
993 bool "HugeTLB Resource Controller for Control Groups"
994 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
995 default n
996 help
997 Provides a cgroup Resource Controller for HugeTLB pages.
998 When you enable this, you can put a per cgroup limit on HugeTLB usage.
999 The limit is enforced during page fault. Since HugeTLB doesn't
1000 support page reclaim, enforcing the limit at page fault time implies
1001 that, the application will get SIGBUS signal if it tries to access
1002 HugeTLB pages beyond its limit. This requires the application to know
1003 beforehand how much HugeTLB pages it would require for its use. The
1004 control group is tracked in the third page lru pointer. This means
1005 that we cannot use the controller with huge page less than 3 pages.
1007 config CGROUP_PERF
1008 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1009 depends on PERF_EVENTS && CGROUPS
1010 help
1011 This option extends the per-cpu mode to restrict monitoring to
1012 threads which belong to the cgroup specified and run on the
1013 designated cpu.
1015 Say N if unsure.
1017 menuconfig CGROUP_SCHED
1018 bool "Group CPU scheduler"
1019 default n
1020 help
1021 This feature lets CPU scheduler recognize task groups and control CPU
1022 bandwidth allocation to such task groups. It uses cgroups to group
1023 tasks.
1025 if CGROUP_SCHED
1026 config FAIR_GROUP_SCHED
1027 bool "Group scheduling for SCHED_OTHER"
1028 depends on CGROUP_SCHED
1029 default CGROUP_SCHED
1031 config CFS_BANDWIDTH
1032 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1033 depends on FAIR_GROUP_SCHED
1034 default n
1035 help
1036 This option allows users to define CPU bandwidth rates (limits) for
1037 tasks running within the fair group scheduler. Groups with no limit
1038 set are considered to be unconstrained and will run with no
1039 restriction.
1040 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1042 config RT_GROUP_SCHED
1043 bool "Group scheduling for SCHED_RR/FIFO"
1044 depends on CGROUP_SCHED
1045 default n
1046 help
1047 This feature lets you explicitly allocate real CPU bandwidth
1048 to task groups. If enabled, it will also make it impossible to
1049 schedule realtime tasks for non-root users until you allocate
1050 realtime bandwidth for them.
1051 See Documentation/scheduler/sched-rt-group.txt for more information.
1053 endif #CGROUP_SCHED
1055 config BLK_CGROUP
1056 bool "Block IO controller"
1057 depends on BLOCK
1058 default n
1059 ---help---
1060 Generic block IO controller cgroup interface. This is the common
1061 cgroup interface which should be used by various IO controlling
1062 policies.
1064 Currently, CFQ IO scheduler uses it to recognize task groups and
1065 control disk bandwidth allocation (proportional time slice allocation)
1066 to such task groups. It is also used by bio throttling logic in
1067 block layer to implement upper limit in IO rates on a device.
1069 This option only enables generic Block IO controller infrastructure.
1070 One needs to also enable actual IO controlling logic/policy. For
1071 enabling proportional weight division of disk bandwidth in CFQ, set
1072 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1073 CONFIG_BLK_DEV_THROTTLING=y.
1075 See Documentation/cgroups/blkio-controller.txt for more information.
1077 config DEBUG_BLK_CGROUP
1078 bool "Enable Block IO controller debugging"
1079 depends on BLK_CGROUP
1080 default n
1081 ---help---
1082 Enable some debugging help. Currently it exports additional stat
1083 files in a cgroup which can be useful for debugging.
1085 endif # CGROUPS
1087 config CHECKPOINT_RESTORE
1088 bool "Checkpoint/restore support" if EXPERT
1089 default n
1090 help
1091 Enables additional kernel features in a sake of checkpoint/restore.
1092 In particular it adds auxiliary prctl codes to setup process text,
1093 data and heap segment sizes, and a few additional /proc filesystem
1094 entries.
1096 If unsure, say N here.
1098 menuconfig NAMESPACES
1099 bool "Namespaces support" if EXPERT
1100 default !EXPERT
1101 help
1102 Provides the way to make tasks work with different objects using
1103 the same id. For example same IPC id may refer to different objects
1104 or same user id or pid may refer to different tasks when used in
1105 different namespaces.
1107 if NAMESPACES
1109 config UTS_NS
1110 bool "UTS namespace"
1111 default y
1112 help
1113 In this namespace tasks see different info provided with the
1114 uname() system call
1116 config IPC_NS
1117 bool "IPC namespace"
1118 depends on (SYSVIPC || POSIX_MQUEUE)
1119 default y
1120 help
1121 In this namespace tasks work with IPC ids which correspond to
1122 different IPC objects in different namespaces.
1124 config USER_NS
1125 bool "User namespace"
1126 select UIDGID_STRICT_TYPE_CHECKS
1128 default n
1129 help
1130 This allows containers, i.e. vservers, to use user namespaces
1131 to provide different user info for different servers.
1133 When user namespaces are enabled in the kernel it is
1134 recommended that the MEMCG and MEMCG_KMEM options also be
1135 enabled and that user-space use the memory control groups to
1136 limit the amount of memory a memory unprivileged users can
1137 use.
1139 If unsure, say N.
1141 config PID_NS
1142 bool "PID Namespaces"
1143 default y
1144 help
1145 Support process id namespaces. This allows having multiple
1146 processes with the same pid as long as they are in different
1147 pid namespaces. This is a building block of containers.
1149 config NET_NS
1150 bool "Network namespace"
1151 depends on NET
1152 default y
1153 help
1154 Allow user space to create what appear to be multiple instances
1155 of the network stack.
1157 endif # NAMESPACES
1159 config UIDGID_STRICT_TYPE_CHECKS
1160 bool "Require conversions between uid/gids and their internal representation"
1161 default n
1162 help
1163 While the nececessary conversions are being added to all subsystems this option allows
1164 the code to continue to build for unconverted subsystems.
1166 Say Y here if you want the strict type checking enabled
1168 config SCHED_AUTOGROUP
1169 bool "Automatic process group scheduling"
1170 select EVENTFD
1171 select CGROUPS
1172 select CGROUP_SCHED
1173 select FAIR_GROUP_SCHED
1174 help
1175 This option optimizes the scheduler for common desktop workloads by
1176 automatically creating and populating task groups. This separation
1177 of workloads isolates aggressive CPU burners (like build jobs) from
1178 desktop applications. Task group autogeneration is currently based
1179 upon task session.
1181 config MM_OWNER
1182 bool
1184 config SYSFS_DEPRECATED
1185 bool "Enable deprecated sysfs features to support old userspace tools"
1186 depends on SYSFS
1187 default n
1188 help
1189 This option adds code that switches the layout of the "block" class
1190 devices, to not show up in /sys/class/block/, but only in
1191 /sys/block/.
1193 This switch is only active when the sysfs.deprecated=1 boot option is
1194 passed or the SYSFS_DEPRECATED_V2 option is set.
1196 This option allows new kernels to run on old distributions and tools,
1197 which might get confused by /sys/class/block/. Since 2007/2008 all
1198 major distributions and tools handle this just fine.
1200 Recent distributions and userspace tools after 2009/2010 depend on
1201 the existence of /sys/class/block/, and will not work with this
1202 option enabled.
1204 Only if you are using a new kernel on an old distribution, you might
1205 need to say Y here.
1207 config SYSFS_DEPRECATED_V2
1208 bool "Enable deprecated sysfs features by default"
1209 default n
1210 depends on SYSFS
1211 depends on SYSFS_DEPRECATED
1212 help
1213 Enable deprecated sysfs by default.
1215 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1216 option.
1218 Only if you are using a new kernel on an old distribution, you might
1219 need to say Y here. Even then, odds are you would not need it
1220 enabled, you can always pass the boot option if absolutely necessary.
1222 config RELAY
1223 bool "Kernel->user space relay support (formerly relayfs)"
1224 help
1225 This option enables support for relay interface support in
1226 certain file systems (such as debugfs).
1227 It is designed to provide an efficient mechanism for tools and
1228 facilities to relay large amounts of data from kernel space to
1229 user space.
1231 If unsure, say N.
1233 config BLK_DEV_INITRD
1234 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1235 depends on BROKEN || !FRV
1236 help
1237 The initial RAM filesystem is a ramfs which is loaded by the
1238 boot loader (loadlin or lilo) and that is mounted as root
1239 before the normal boot procedure. It is typically used to
1240 load modules needed to mount the "real" root file system,
1241 etc. See <file:Documentation/initrd.txt> for details.
1243 If RAM disk support (BLK_DEV_RAM) is also included, this
1244 also enables initial RAM disk (initrd) support and adds
1245 15 Kbytes (more on some other architectures) to the kernel size.
1247 If unsure say Y.
1249 if BLK_DEV_INITRD
1251 source "usr/Kconfig"
1253 endif
1255 config CC_OPTIMIZE_FOR_SIZE
1256 bool "Optimize for size"
1257 help
1258 Enabling this option will pass "-Os" instead of "-O2" to gcc
1259 resulting in a smaller kernel.
1261 If unsure, say N.
1263 config SYSCTL
1264 bool
1266 config ANON_INODES
1267 bool
1269 config HAVE_UID16
1270 bool
1272 config SYSCTL_EXCEPTION_TRACE
1273 bool
1274 help
1275 Enable support for /proc/sys/debug/exception-trace.
1277 config SYSCTL_ARCH_UNALIGN_NO_WARN
1278 bool
1279 help
1280 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1281 Allows arch to define/use @no_unaligned_warning to possibly warn
1282 about unaligned access emulation going on under the hood.
1284 config SYSCTL_ARCH_UNALIGN_ALLOW
1285 bool
1286 help
1287 Enable support for /proc/sys/kernel/unaligned-trap
1288 Allows arches to define/use @unaligned_enabled to runtime toggle
1289 the unaligned access emulation.
1290 see arch/parisc/kernel/unaligned.c for reference
1292 config HAVE_PCSPKR_PLATFORM
1293 bool
1295 menuconfig EXPERT
1296 bool "Configure standard kernel features (expert users)"
1297 # Unhide debug options, to make the on-by-default options visible
1298 select DEBUG_KERNEL
1299 help
1300 This option allows certain base kernel options and settings
1301 to be disabled or tweaked. This is for specialized
1302 environments which can tolerate a "non-standard" kernel.
1303 Only use this if you really know what you are doing.
1305 config UID16
1306 bool "Enable 16-bit UID system calls" if EXPERT
1307 depends on HAVE_UID16
1308 default y
1309 help
1310 This enables the legacy 16-bit UID syscall wrappers.
1312 config SYSCTL_SYSCALL
1313 bool "Sysctl syscall support" if EXPERT
1314 depends on PROC_SYSCTL
1315 default n
1316 select SYSCTL
1317 ---help---
1318 sys_sysctl uses binary paths that have been found challenging
1319 to properly maintain and use. The interface in /proc/sys
1320 using paths with ascii names is now the primary path to this
1321 information.
1323 Almost nothing using the binary sysctl interface so if you are
1324 trying to save some space it is probably safe to disable this,
1325 making your kernel marginally smaller.
1327 If unsure say N here.
1329 config KALLSYMS
1330 bool "Load all symbols for debugging/ksymoops" if EXPERT
1331 default y
1332 help
1333 Say Y here to let the kernel print out symbolic crash information and
1334 symbolic stack backtraces. This increases the size of the kernel
1335 somewhat, as all symbols have to be loaded into the kernel image.
1337 config KALLSYMS_ALL
1338 bool "Include all symbols in kallsyms"
1339 depends on DEBUG_KERNEL && KALLSYMS
1340 help
1341 Normally kallsyms only contains the symbols of functions for nicer
1342 OOPS messages and backtraces (i.e., symbols from the text and inittext
1343 sections). This is sufficient for most cases. And only in very rare
1344 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1345 names of variables from the data sections, etc).
1347 This option makes sure that all symbols are loaded into the kernel
1348 image (i.e., symbols from all sections) in cost of increased kernel
1349 size (depending on the kernel configuration, it may be 300KiB or
1350 something like this).
1352 Say N unless you really need all symbols.
1354 config PRINTK
1355 default y
1356 bool "Enable support for printk" if EXPERT
1357 select IRQ_WORK
1358 help
1359 This option enables normal printk support. Removing it
1360 eliminates most of the message strings from the kernel image
1361 and makes the kernel more or less silent. As this makes it
1362 very difficult to diagnose system problems, saying N here is
1363 strongly discouraged.
1365 config BUG
1366 bool "BUG() support" if EXPERT
1367 default y
1368 help
1369 Disabling this option eliminates support for BUG and WARN, reducing
1370 the size of your kernel image and potentially quietly ignoring
1371 numerous fatal conditions. You should only consider disabling this
1372 option for embedded systems with no facilities for reporting errors.
1373 Just say Y.
1375 config ELF_CORE
1376 depends on COREDUMP
1377 default y
1378 bool "Enable ELF core dumps" if EXPERT
1379 help
1380 Enable support for generating core dumps. Disabling saves about 4k.
1383 config PCSPKR_PLATFORM
1384 bool "Enable PC-Speaker support" if EXPERT
1385 depends on HAVE_PCSPKR_PLATFORM
1386 select I8253_LOCK
1387 default y
1388 help
1389 This option allows to disable the internal PC-Speaker
1390 support, saving some memory.
1392 config BASE_FULL
1393 default y
1394 bool "Enable full-sized data structures for core" if EXPERT
1395 help
1396 Disabling this option reduces the size of miscellaneous core
1397 kernel data structures. This saves memory on small machines,
1398 but may reduce performance.
1400 config FUTEX
1401 bool "Enable futex support" if EXPERT
1402 default y
1403 select RT_MUTEXES
1404 help
1405 Disabling this option will cause the kernel to be built without
1406 support for "fast userspace mutexes". The resulting kernel may not
1407 run glibc-based applications correctly.
1409 config HAVE_FUTEX_CMPXCHG
1410 bool
1411 help
1412 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1413 is implemented and always working. This removes a couple of runtime
1414 checks.
1416 config EPOLL
1417 bool "Enable eventpoll support" if EXPERT
1418 default y
1419 select ANON_INODES
1420 help
1421 Disabling this option will cause the kernel to be built without
1422 support for epoll family of system calls.
1424 config SIGNALFD
1425 bool "Enable signalfd() system call" if EXPERT
1426 select ANON_INODES
1427 default y
1428 help
1429 Enable the signalfd() system call that allows to receive signals
1430 on a file descriptor.
1432 If unsure, say Y.
1434 config TIMERFD
1435 bool "Enable timerfd() system call" if EXPERT
1436 select ANON_INODES
1437 default y
1438 help
1439 Enable the timerfd() system call that allows to receive timer
1440 events on a file descriptor.
1442 If unsure, say Y.
1444 config EVENTFD
1445 bool "Enable eventfd() system call" if EXPERT
1446 select ANON_INODES
1447 default y
1448 help
1449 Enable the eventfd() system call that allows to receive both
1450 kernel notification (ie. KAIO) or userspace notifications.
1452 If unsure, say Y.
1454 config SHMEM
1455 bool "Use full shmem filesystem" if EXPERT
1456 default y
1457 depends on MMU
1458 help
1459 The shmem is an internal filesystem used to manage shared memory.
1460 It is backed by swap and manages resource limits. It is also exported
1461 to userspace as tmpfs if TMPFS is enabled. Disabling this
1462 option replaces shmem and tmpfs with the much simpler ramfs code,
1463 which may be appropriate on small systems without swap.
1465 config AIO
1466 bool "Enable AIO support" if EXPERT
1467 default y
1468 help
1469 This option enables POSIX asynchronous I/O which may by used
1470 by some high performance threaded applications. Disabling
1471 this option saves about 7k.
1473 config PCI_QUIRKS
1474 default y
1475 bool "Enable PCI quirk workarounds" if EXPERT
1476 depends on PCI
1477 help
1478 This enables workarounds for various PCI chipset
1479 bugs/quirks. Disable this only if your target machine is
1480 unaffected by PCI quirks.
1482 config EMBEDDED
1483 bool "Embedded system"
1484 select EXPERT
1485 help
1486 This option should be enabled if compiling the kernel for
1487 an embedded system so certain expert options are available
1488 for configuration.
1490 config HAVE_PERF_EVENTS
1491 bool
1492 help
1493 See tools/perf/design.txt for details.
1495 config PERF_USE_VMALLOC
1496 bool
1497 help
1498 See tools/perf/design.txt for details
1500 menu "Kernel Performance Events And Counters"
1502 config PERF_EVENTS
1503 bool "Kernel performance events and counters"
1504 default y if PROFILING
1505 depends on HAVE_PERF_EVENTS
1506 select ANON_INODES
1507 select IRQ_WORK
1508 help
1509 Enable kernel support for various performance events provided
1510 by software and hardware.
1512 Software events are supported either built-in or via the
1513 use of generic tracepoints.
1515 Most modern CPUs support performance events via performance
1516 counter registers. These registers count the number of certain
1517 types of hw events: such as instructions executed, cachemisses
1518 suffered, or branches mis-predicted - without slowing down the
1519 kernel or applications. These registers can also trigger interrupts
1520 when a threshold number of events have passed - and can thus be
1521 used to profile the code that runs on that CPU.
1523 The Linux Performance Event subsystem provides an abstraction of
1524 these software and hardware event capabilities, available via a
1525 system call and used by the "perf" utility in tools/perf/. It
1526 provides per task and per CPU counters, and it provides event
1527 capabilities on top of those.
1529 Say Y if unsure.
1531 config DEBUG_PERF_USE_VMALLOC
1532 default n
1533 bool "Debug: use vmalloc to back perf mmap() buffers"
1534 depends on PERF_EVENTS && DEBUG_KERNEL
1535 select PERF_USE_VMALLOC
1536 help
1537 Use vmalloc memory to back perf mmap() buffers.
1539 Mostly useful for debugging the vmalloc code on platforms
1540 that don't require it.
1542 Say N if unsure.
1544 endmenu
1546 config VM_EVENT_COUNTERS
1547 default y
1548 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1549 help
1550 VM event counters are needed for event counts to be shown.
1551 This option allows the disabling of the VM event counters
1552 on EXPERT systems. /proc/vmstat will only show page counts
1553 if VM event counters are disabled.
1555 config SLUB_DEBUG
1556 default y
1557 bool "Enable SLUB debugging support" if EXPERT
1558 depends on SLUB && SYSFS
1559 help
1560 SLUB has extensive debug support features. Disabling these can
1561 result in significant savings in code size. This also disables
1562 SLUB sysfs support. /sys/slab will not exist and there will be
1563 no support for cache validation etc.
1565 config COMPAT_BRK
1566 bool "Disable heap randomization"
1567 default y
1568 help
1569 Randomizing heap placement makes heap exploits harder, but it
1570 also breaks ancient binaries (including anything libc5 based).
1571 This option changes the bootup default to heap randomization
1572 disabled, and can be overridden at runtime by setting
1573 /proc/sys/kernel/randomize_va_space to 2.
1575 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1577 choice
1578 prompt "Choose SLAB allocator"
1579 default SLUB
1580 help
1581 This option allows to select a slab allocator.
1583 config SLAB
1584 bool "SLAB"
1585 help
1586 The regular slab allocator that is established and known to work
1587 well in all environments. It organizes cache hot objects in
1588 per cpu and per node queues.
1590 config SLUB
1591 bool "SLUB (Unqueued Allocator)"
1592 help
1593 SLUB is a slab allocator that minimizes cache line usage
1594 instead of managing queues of cached objects (SLAB approach).
1595 Per cpu caching is realized using slabs of objects instead
1596 of queues of objects. SLUB can use memory efficiently
1597 and has enhanced diagnostics. SLUB is the default choice for
1598 a slab allocator.
1600 config SLOB
1601 depends on EXPERT
1602 bool "SLOB (Simple Allocator)"
1603 help
1604 SLOB replaces the stock allocator with a drastically simpler
1605 allocator. SLOB is generally more space efficient but
1606 does not perform as well on large systems.
1608 endchoice
1610 config SLUB_CPU_PARTIAL
1611 default y
1612 depends on SLUB && SMP
1613 bool "SLUB per cpu partial cache"
1614 help
1615 Per cpu partial caches accellerate objects allocation and freeing
1616 that is local to a processor at the price of more indeterminism
1617 in the latency of the free. On overflow these caches will be cleared
1618 which requires the taking of locks that may cause latency spikes.
1619 Typically one would choose no for a realtime system.
1621 config MMAP_ALLOW_UNINITIALIZED
1622 bool "Allow mmapped anonymous memory to be uninitialized"
1623 depends on EXPERT && !MMU
1624 default n
1625 help
1626 Normally, and according to the Linux spec, anonymous memory obtained
1627 from mmap() has it's contents cleared before it is passed to
1628 userspace. Enabling this config option allows you to request that
1629 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1630 providing a huge performance boost. If this option is not enabled,
1631 then the flag will be ignored.
1633 This is taken advantage of by uClibc's malloc(), and also by
1634 ELF-FDPIC binfmt's brk and stack allocator.
1636 Because of the obvious security issues, this option should only be
1637 enabled on embedded devices where you control what is run in
1638 userspace. Since that isn't generally a problem on no-MMU systems,
1639 it is normally safe to say Y here.
1641 See Documentation/nommu-mmap.txt for more information.
1643 config PROFILING
1644 bool "Profiling support"
1645 help
1646 Say Y here to enable the extended profiling support mechanisms used
1647 by profilers such as OProfile.
1649 #
1650 # Place an empty function call at each tracepoint site. Can be
1651 # dynamically changed for a probe function.
1652 #
1653 config TRACEPOINTS
1654 bool
1656 source "arch/Kconfig"
1658 endmenu # General setup
1660 config HAVE_GENERIC_DMA_COHERENT
1661 bool
1662 default n
1664 config SLABINFO
1665 bool
1666 depends on PROC_FS
1667 depends on SLAB || SLUB_DEBUG
1668 default y
1670 config RT_MUTEXES
1671 boolean
1673 config BASE_SMALL
1674 int
1675 default 0 if BASE_FULL
1676 default 1 if !BASE_FULL
1678 menuconfig MODULES
1679 bool "Enable loadable module support"
1680 option modules
1681 help
1682 Kernel modules are small pieces of compiled code which can
1683 be inserted in the running kernel, rather than being
1684 permanently built into the kernel. You use the "modprobe"
1685 tool to add (and sometimes remove) them. If you say Y here,
1686 many parts of the kernel can be built as modules (by
1687 answering M instead of Y where indicated): this is most
1688 useful for infrequently used options which are not required
1689 for booting. For more information, see the man pages for
1690 modprobe, lsmod, modinfo, insmod and rmmod.
1692 If you say Y here, you will need to run "make
1693 modules_install" to put the modules under /lib/modules/
1694 where modprobe can find them (you may need to be root to do
1695 this).
1697 If unsure, say Y.
1699 if MODULES
1701 config MODULE_FORCE_LOAD
1702 bool "Forced module loading"
1703 default n
1704 help
1705 Allow loading of modules without version information (ie. modprobe
1706 --force). Forced module loading sets the 'F' (forced) taint flag and
1707 is usually a really bad idea.
1709 config MODULE_UNLOAD
1710 bool "Module unloading"
1711 help
1712 Without this option you will not be able to unload any
1713 modules (note that some modules may not be unloadable
1714 anyway), which makes your kernel smaller, faster
1715 and simpler. If unsure, say Y.
1717 config MODULE_FORCE_UNLOAD
1718 bool "Forced module unloading"
1719 depends on MODULE_UNLOAD
1720 help
1721 This option allows you to force a module to unload, even if the
1722 kernel believes it is unsafe: the kernel will remove the module
1723 without waiting for anyone to stop using it (using the -f option to
1724 rmmod). This is mainly for kernel developers and desperate users.
1725 If unsure, say N.
1727 config MODVERSIONS
1728 bool "Module versioning support"
1729 help
1730 Usually, you have to use modules compiled with your kernel.
1731 Saying Y here makes it sometimes possible to use modules
1732 compiled for different kernels, by adding enough information
1733 to the modules to (hopefully) spot any changes which would
1734 make them incompatible with the kernel you are running. If
1735 unsure, say N.
1737 config MODULE_SRCVERSION_ALL
1738 bool "Source checksum for all modules"
1739 help
1740 Modules which contain a MODULE_VERSION get an extra "srcversion"
1741 field inserted into their modinfo section, which contains a
1742 sum of the source files which made it. This helps maintainers
1743 see exactly which source was used to build a module (since
1744 others sometimes change the module source without updating
1745 the version). With this option, such a "srcversion" field
1746 will be created for all modules. If unsure, say N.
1748 config MODULE_SIG
1749 bool "Module signature verification"
1750 depends on MODULES
1751 select KEYS
1752 select CRYPTO
1753 select ASYMMETRIC_KEY_TYPE
1754 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1755 select PUBLIC_KEY_ALGO_RSA
1756 select ASN1
1757 select OID_REGISTRY
1758 select X509_CERTIFICATE_PARSER
1759 help
1760 Check modules for valid signatures upon load: the signature
1761 is simply appended to the module. For more information see
1762 Documentation/module-signing.txt.
1764 !!!WARNING!!! If you enable this option, you MUST make sure that the
1765 module DOES NOT get stripped after being signed. This includes the
1766 debuginfo strip done by some packagers (such as rpmbuild) and
1767 inclusion into an initramfs that wants the module size reduced.
1769 config MODULE_SIG_FORCE
1770 bool "Require modules to be validly signed"
1771 depends on MODULE_SIG
1772 help
1773 Reject unsigned modules or signed modules for which we don't have a
1774 key. Without this, such modules will simply taint the kernel.
1776 config MODULE_SIG_ALL
1777 bool "Automatically sign all modules"
1778 default y
1779 depends on MODULE_SIG
1780 help
1781 Sign all modules during make modules_install. Without this option,
1782 modules must be signed manually, using the scripts/sign-file tool.
1784 comment "Do not forget to sign required modules with scripts/sign-file"
1785 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1787 choice
1788 prompt "Which hash algorithm should modules be signed with?"
1789 depends on MODULE_SIG
1790 help
1791 This determines which sort of hashing algorithm will be used during
1792 signature generation. This algorithm _must_ be built into the kernel
1793 directly so that signature verification can take place. It is not
1794 possible to load a signed module containing the algorithm to check
1795 the signature on that module.
1797 config MODULE_SIG_SHA1
1798 bool "Sign modules with SHA-1"
1799 select CRYPTO_SHA1
1801 config MODULE_SIG_SHA224
1802 bool "Sign modules with SHA-224"
1803 select CRYPTO_SHA256
1805 config MODULE_SIG_SHA256
1806 bool "Sign modules with SHA-256"
1807 select CRYPTO_SHA256
1809 config MODULE_SIG_SHA384
1810 bool "Sign modules with SHA-384"
1811 select CRYPTO_SHA512
1813 config MODULE_SIG_SHA512
1814 bool "Sign modules with SHA-512"
1815 select CRYPTO_SHA512
1817 endchoice
1819 config MODULE_SIG_HASH
1820 string
1821 depends on MODULE_SIG
1822 default "sha1" if MODULE_SIG_SHA1
1823 default "sha224" if MODULE_SIG_SHA224
1824 default "sha256" if MODULE_SIG_SHA256
1825 default "sha384" if MODULE_SIG_SHA384
1826 default "sha512" if MODULE_SIG_SHA512
1828 endif # MODULES
1830 config INIT_ALL_POSSIBLE
1831 bool
1832 help
1833 Back when each arch used to define their own cpu_online_mask and
1834 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1835 with all 1s, and others with all 0s. When they were centralised,
1836 it was better to provide this option than to break all the archs
1837 and have several arch maintainers pursuing me down dark alleys.
1839 config STOP_MACHINE
1840 bool
1841 default y
1842 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1843 help
1844 Need stop_machine() primitive.
1846 source "block/Kconfig"
1848 config PREEMPT_NOTIFIERS
1849 bool
1851 config PADATA
1852 depends on SMP
1853 bool
1855 # Can be selected by architectures with broken toolchains
1856 # that get confused by correct const<->read_only section
1857 # mappings
1858 config BROKEN_RODATA
1859 bool
1861 config ASN1
1862 tristate
1863 help
1864 Build a simple ASN.1 grammar compiler that produces a bytecode output
1865 that can be interpreted by the ASN.1 stream decoder and used to
1866 inform it as to what tags are to be expected in a stream and what
1867 functions to call on what tags.
1869 source "kernel/Kconfig.locks"