| blob | 9d3585bb2a7a3cbb58234d24761f597b0af95c7c |
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 USELIB
277 bool "uselib syscall"
278 default y
279 help
280 This option enables the uselib syscall, a system call used in the
281 dynamic linker from libc5 and earlier. glibc does not use this
282 system call. If you intend to run programs built on libc5 or
283 earlier, you may need to enable this syscall. Current systems
284 running glibc can safely disable this.
286 config AUDIT
287 bool "Auditing support"
288 depends on NET
289 help
290 Enable auditing infrastructure that can be used with another
291 kernel subsystem, such as SELinux (which requires this for
292 logging of avc messages output). Does not do system-call
293 auditing without CONFIG_AUDITSYSCALL.
295 config HAVE_ARCH_AUDITSYSCALL
296 bool
298 config AUDITSYSCALL
299 bool "Enable system-call auditing support"
300 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
301 default y if SECURITY_SELINUX
302 help
303 Enable low-overhead system-call auditing infrastructure that
304 can be used independently or with another kernel subsystem,
305 such as SELinux.
307 config AUDIT_WATCH
308 def_bool y
309 depends on AUDITSYSCALL
310 select FSNOTIFY
312 config AUDIT_TREE
313 def_bool y
314 depends on AUDITSYSCALL
315 select FSNOTIFY
317 source "kernel/irq/Kconfig"
318 source "kernel/time/Kconfig"
320 menu "CPU/Task time and stats accounting"
322 config VIRT_CPU_ACCOUNTING
323 bool
325 choice
326 prompt "Cputime accounting"
327 default TICK_CPU_ACCOUNTING if !PPC64
328 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
330 # Kind of a stub config for the pure tick based cputime accounting
331 config TICK_CPU_ACCOUNTING
332 bool "Simple tick based cputime accounting"
333 depends on !S390 && !NO_HZ_FULL
334 help
335 This is the basic tick based cputime accounting that maintains
336 statistics about user, system and idle time spent on per jiffies
337 granularity.
339 If unsure, say Y.
341 config VIRT_CPU_ACCOUNTING_NATIVE
342 bool "Deterministic task and CPU time accounting"
343 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
344 select VIRT_CPU_ACCOUNTING
345 help
346 Select this option to enable more accurate task and CPU time
347 accounting. This is done by reading a CPU counter on each
348 kernel entry and exit and on transitions within the kernel
349 between system, softirq and hardirq state, so there is a
350 small performance impact. In the case of s390 or IBM POWER > 5,
351 this also enables accounting of stolen time on logically-partitioned
352 systems.
354 config VIRT_CPU_ACCOUNTING_GEN
355 bool "Full dynticks CPU time accounting"
356 depends on HAVE_CONTEXT_TRACKING
357 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
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 development 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 #
826 # For architectures that know their GCC __int128 support is sound
827 #
828 config ARCH_SUPPORTS_INT128
829 bool
831 # For architectures that (ab)use NUMA to represent different memory regions
832 # all cpu-local but of different latencies, such as SuperH.
833 #
834 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
835 bool
837 #
838 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
839 config ARCH_WANTS_PROT_NUMA_PROT_NONE
840 bool
842 config ARCH_USES_NUMA_PROT_NONE
843 bool
844 default y
845 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
846 depends on NUMA_BALANCING
848 config NUMA_BALANCING_DEFAULT_ENABLED
849 bool "Automatically enable NUMA aware memory/task placement"
850 default y
851 depends on NUMA_BALANCING
852 help
853 If set, automatic NUMA balancing will be enabled if running on a NUMA
854 machine.
856 config NUMA_BALANCING
857 bool "Memory placement aware NUMA scheduler"
858 depends on ARCH_SUPPORTS_NUMA_BALANCING
859 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
860 depends on SMP && NUMA && MIGRATION
861 help
862 This option adds support for automatic NUMA aware memory/task placement.
863 The mechanism is quite primitive and is based on migrating memory when
864 it has references to the node the task is running on.
866 This system will be inactive on UMA systems.
868 menuconfig CGROUPS
869 boolean "Control Group support"
870 select KERNFS
871 help
872 This option adds support for grouping sets of processes together, for
873 use with process control subsystems such as Cpusets, CFS, memory
874 controls or device isolation.
875 See
876 - Documentation/scheduler/sched-design-CFS.txt (CFS)
877 - Documentation/cgroups/ (features for grouping, isolation
878 and resource control)
880 Say N if unsure.
882 if CGROUPS
884 config CGROUP_DEBUG
885 bool "Example debug cgroup subsystem"
886 default n
887 help
888 This option enables a simple cgroup subsystem that
889 exports useful debugging information about the cgroups
890 framework.
892 Say N if unsure.
894 config CGROUP_FREEZER
895 bool "Freezer cgroup subsystem"
896 help
897 Provides a way to freeze and unfreeze all tasks in a
898 cgroup.
900 config CGROUP_DEVICE
901 bool "Device controller for cgroups"
902 help
903 Provides a cgroup implementing whitelists for devices which
904 a process in the cgroup can mknod or open.
906 config CPUSETS
907 bool "Cpuset support"
908 help
909 This option will let you create and manage CPUSETs which
910 allow dynamically partitioning a system into sets of CPUs and
911 Memory Nodes and assigning tasks to run only within those sets.
912 This is primarily useful on large SMP or NUMA systems.
914 Say N if unsure.
916 config PROC_PID_CPUSET
917 bool "Include legacy /proc/<pid>/cpuset file"
918 depends on CPUSETS
919 default y
921 config CGROUP_CPUACCT
922 bool "Simple CPU accounting cgroup subsystem"
923 help
924 Provides a simple Resource Controller for monitoring the
925 total CPU consumed by the tasks in a cgroup.
927 config RESOURCE_COUNTERS
928 bool "Resource counters"
929 help
930 This option enables controller independent resource accounting
931 infrastructure that works with cgroups.
933 config MEMCG
934 bool "Memory Resource Controller for Control Groups"
935 depends on RESOURCE_COUNTERS
936 select MM_OWNER
937 select EVENTFD
938 help
939 Provides a memory resource controller that manages both anonymous
940 memory and page cache. (See Documentation/cgroups/memory.txt)
942 Note that setting this option increases fixed memory overhead
943 associated with each page of memory in the system. By this,
944 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
945 usage tracking struct at boot. Total amount of this is printed out
946 at boot.
948 Only enable when you're ok with these trade offs and really
949 sure you need the memory resource controller. Even when you enable
950 this, you can set "cgroup_disable=memory" at your boot option to
951 disable memory resource controller and you can avoid overheads.
952 (and lose benefits of memory resource controller)
954 This config option also selects MM_OWNER config option, which
955 could in turn add some fork/exit overhead.
957 config MEMCG_SWAP
958 bool "Memory Resource Controller Swap Extension"
959 depends on MEMCG && SWAP
960 help
961 Add swap management feature to memory resource controller. When you
962 enable this, you can limit mem+swap usage per cgroup. In other words,
963 when you disable this, memory resource controller has no cares to
964 usage of swap...a process can exhaust all of the swap. This extension
965 is useful when you want to avoid exhaustion swap but this itself
966 adds more overheads and consumes memory for remembering information.
967 Especially if you use 32bit system or small memory system, please
968 be careful about enabling this. When memory resource controller
969 is disabled by boot option, this will be automatically disabled and
970 there will be no overhead from this. Even when you set this config=y,
971 if boot option "swapaccount=0" is set, swap will not be accounted.
972 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
973 size is 4096bytes, 512k per 1Gbytes of swap.
974 config MEMCG_SWAP_ENABLED
975 bool "Memory Resource Controller Swap Extension enabled by default"
976 depends on MEMCG_SWAP
977 default y
978 help
979 Memory Resource Controller Swap Extension comes with its price in
980 a bigger memory consumption. General purpose distribution kernels
981 which want to enable the feature but keep it disabled by default
982 and let the user enable it by swapaccount=1 boot command line
983 parameter should have this option unselected.
984 For those who want to have the feature enabled by default should
985 select this option (if, for some reason, they need to disable it
986 then swapaccount=0 does the trick).
987 config MEMCG_KMEM
988 bool "Memory Resource Controller Kernel Memory accounting"
989 depends on MEMCG
990 depends on SLUB || SLAB
991 help
992 The Kernel Memory extension for Memory Resource Controller can limit
993 the amount of memory used by kernel objects in the system. Those are
994 fundamentally different from the entities handled by the standard
995 Memory Controller, which are page-based, and can be swapped. Users of
996 the kmem extension can use it to guarantee that no group of processes
997 will ever exhaust kernel resources alone.
999 config CGROUP_HUGETLB
1000 bool "HugeTLB Resource Controller for Control Groups"
1001 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
1002 default n
1003 help
1004 Provides a cgroup Resource Controller for HugeTLB pages.
1005 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1006 The limit is enforced during page fault. Since HugeTLB doesn't
1007 support page reclaim, enforcing the limit at page fault time implies
1008 that, the application will get SIGBUS signal if it tries to access
1009 HugeTLB pages beyond its limit. This requires the application to know
1010 beforehand how much HugeTLB pages it would require for its use. The
1011 control group is tracked in the third page lru pointer. This means
1012 that we cannot use the controller with huge page less than 3 pages.
1014 config CGROUP_PERF
1015 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1016 depends on PERF_EVENTS && CGROUPS
1017 help
1018 This option extends the per-cpu mode to restrict monitoring to
1019 threads which belong to the cgroup specified and run on the
1020 designated cpu.
1022 Say N if unsure.
1024 menuconfig CGROUP_SCHED
1025 bool "Group CPU scheduler"
1026 default n
1027 help
1028 This feature lets CPU scheduler recognize task groups and control CPU
1029 bandwidth allocation to such task groups. It uses cgroups to group
1030 tasks.
1032 if CGROUP_SCHED
1033 config FAIR_GROUP_SCHED
1034 bool "Group scheduling for SCHED_OTHER"
1035 depends on CGROUP_SCHED
1036 default CGROUP_SCHED
1038 config CFS_BANDWIDTH
1039 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1040 depends on FAIR_GROUP_SCHED
1041 default n
1042 help
1043 This option allows users to define CPU bandwidth rates (limits) for
1044 tasks running within the fair group scheduler. Groups with no limit
1045 set are considered to be unconstrained and will run with no
1046 restriction.
1047 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1049 config RT_GROUP_SCHED
1050 bool "Group scheduling for SCHED_RR/FIFO"
1051 depends on CGROUP_SCHED
1052 default n
1053 help
1054 This feature lets you explicitly allocate real CPU bandwidth
1055 to task groups. If enabled, it will also make it impossible to
1056 schedule realtime tasks for non-root users until you allocate
1057 realtime bandwidth for them.
1058 See Documentation/scheduler/sched-rt-group.txt for more information.
1060 endif #CGROUP_SCHED
1062 config BLK_CGROUP
1063 bool "Block IO controller"
1064 depends on BLOCK
1065 default n
1066 ---help---
1067 Generic block IO controller cgroup interface. This is the common
1068 cgroup interface which should be used by various IO controlling
1069 policies.
1071 Currently, CFQ IO scheduler uses it to recognize task groups and
1072 control disk bandwidth allocation (proportional time slice allocation)
1073 to such task groups. It is also used by bio throttling logic in
1074 block layer to implement upper limit in IO rates on a device.
1076 This option only enables generic Block IO controller infrastructure.
1077 One needs to also enable actual IO controlling logic/policy. For
1078 enabling proportional weight division of disk bandwidth in CFQ, set
1079 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1080 CONFIG_BLK_DEV_THROTTLING=y.
1082 See Documentation/cgroups/blkio-controller.txt for more information.
1084 config DEBUG_BLK_CGROUP
1085 bool "Enable Block IO controller debugging"
1086 depends on BLK_CGROUP
1087 default n
1088 ---help---
1089 Enable some debugging help. Currently it exports additional stat
1090 files in a cgroup which can be useful for debugging.
1092 endif # CGROUPS
1094 config CHECKPOINT_RESTORE
1095 bool "Checkpoint/restore support" if EXPERT
1096 default n
1097 help
1098 Enables additional kernel features in a sake of checkpoint/restore.
1099 In particular it adds auxiliary prctl codes to setup process text,
1100 data and heap segment sizes, and a few additional /proc filesystem
1101 entries.
1103 If unsure, say N here.
1105 menuconfig NAMESPACES
1106 bool "Namespaces support" if EXPERT
1107 default !EXPERT
1108 help
1109 Provides the way to make tasks work with different objects using
1110 the same id. For example same IPC id may refer to different objects
1111 or same user id or pid may refer to different tasks when used in
1112 different namespaces.
1114 if NAMESPACES
1116 config UTS_NS
1117 bool "UTS namespace"
1118 default y
1119 help
1120 In this namespace tasks see different info provided with the
1121 uname() system call
1123 config IPC_NS
1124 bool "IPC namespace"
1125 depends on (SYSVIPC || POSIX_MQUEUE)
1126 default y
1127 help
1128 In this namespace tasks work with IPC ids which correspond to
1129 different IPC objects in different namespaces.
1131 config USER_NS
1132 bool "User namespace"
1133 default n
1134 help
1135 This allows containers, i.e. vservers, to use user namespaces
1136 to provide different user info for different servers.
1138 When user namespaces are enabled in the kernel it is
1139 recommended that the MEMCG and MEMCG_KMEM options also be
1140 enabled and that user-space use the memory control groups to
1141 limit the amount of memory a memory unprivileged users can
1142 use.
1144 If unsure, say N.
1146 config PID_NS
1147 bool "PID Namespaces"
1148 default y
1149 help
1150 Support process id namespaces. This allows having multiple
1151 processes with the same pid as long as they are in different
1152 pid namespaces. This is a building block of containers.
1154 config NET_NS
1155 bool "Network namespace"
1156 depends on NET
1157 default y
1158 help
1159 Allow user space to create what appear to be multiple instances
1160 of the network stack.
1162 endif # NAMESPACES
1164 config SCHED_AUTOGROUP
1165 bool "Automatic process group scheduling"
1166 select CGROUPS
1167 select CGROUP_SCHED
1168 select FAIR_GROUP_SCHED
1169 help
1170 This option optimizes the scheduler for common desktop workloads by
1171 automatically creating and populating task groups. This separation
1172 of workloads isolates aggressive CPU burners (like build jobs) from
1173 desktop applications. Task group autogeneration is currently based
1174 upon task session.
1176 config MM_OWNER
1177 bool
1179 config SYSFS_DEPRECATED
1180 bool "Enable deprecated sysfs features to support old userspace tools"
1181 depends on SYSFS
1182 default n
1183 help
1184 This option adds code that switches the layout of the "block" class
1185 devices, to not show up in /sys/class/block/, but only in
1186 /sys/block/.
1188 This switch is only active when the sysfs.deprecated=1 boot option is
1189 passed or the SYSFS_DEPRECATED_V2 option is set.
1191 This option allows new kernels to run on old distributions and tools,
1192 which might get confused by /sys/class/block/. Since 2007/2008 all
1193 major distributions and tools handle this just fine.
1195 Recent distributions and userspace tools after 2009/2010 depend on
1196 the existence of /sys/class/block/, and will not work with this
1197 option enabled.
1199 Only if you are using a new kernel on an old distribution, you might
1200 need to say Y here.
1202 config SYSFS_DEPRECATED_V2
1203 bool "Enable deprecated sysfs features by default"
1204 default n
1205 depends on SYSFS
1206 depends on SYSFS_DEPRECATED
1207 help
1208 Enable deprecated sysfs by default.
1210 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1211 option.
1213 Only if you are using a new kernel on an old distribution, you might
1214 need to say Y here. Even then, odds are you would not need it
1215 enabled, you can always pass the boot option if absolutely necessary.
1217 config RELAY
1218 bool "Kernel->user space relay support (formerly relayfs)"
1219 help
1220 This option enables support for relay interface support in
1221 certain file systems (such as debugfs).
1222 It is designed to provide an efficient mechanism for tools and
1223 facilities to relay large amounts of data from kernel space to
1224 user space.
1226 If unsure, say N.
1228 config BLK_DEV_INITRD
1229 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1230 depends on BROKEN || !FRV
1231 help
1232 The initial RAM filesystem is a ramfs which is loaded by the
1233 boot loader (loadlin or lilo) and that is mounted as root
1234 before the normal boot procedure. It is typically used to
1235 load modules needed to mount the "real" root file system,
1236 etc. See <file:Documentation/initrd.txt> for details.
1238 If RAM disk support (BLK_DEV_RAM) is also included, this
1239 also enables initial RAM disk (initrd) support and adds
1240 15 Kbytes (more on some other architectures) to the kernel size.
1242 If unsure say Y.
1244 if BLK_DEV_INITRD
1246 source "usr/Kconfig"
1248 endif
1250 config CC_OPTIMIZE_FOR_SIZE
1251 bool "Optimize for size"
1252 help
1253 Enabling this option will pass "-Os" instead of "-O2" to gcc
1254 resulting in a smaller kernel.
1256 If unsure, say N.
1258 config SYSCTL
1259 bool
1261 config ANON_INODES
1262 bool
1264 config HAVE_UID16
1265 bool
1267 config SYSCTL_EXCEPTION_TRACE
1268 bool
1269 help
1270 Enable support for /proc/sys/debug/exception-trace.
1272 config SYSCTL_ARCH_UNALIGN_NO_WARN
1273 bool
1274 help
1275 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1276 Allows arch to define/use @no_unaligned_warning to possibly warn
1277 about unaligned access emulation going on under the hood.
1279 config SYSCTL_ARCH_UNALIGN_ALLOW
1280 bool
1281 help
1282 Enable support for /proc/sys/kernel/unaligned-trap
1283 Allows arches to define/use @unaligned_enabled to runtime toggle
1284 the unaligned access emulation.
1285 see arch/parisc/kernel/unaligned.c for reference
1287 config HAVE_PCSPKR_PLATFORM
1288 bool
1290 menuconfig EXPERT
1291 bool "Configure standard kernel features (expert users)"
1292 # Unhide debug options, to make the on-by-default options visible
1293 select DEBUG_KERNEL
1294 help
1295 This option allows certain base kernel options and settings
1296 to be disabled or tweaked. This is for specialized
1297 environments which can tolerate a "non-standard" kernel.
1298 Only use this if you really know what you are doing.
1300 config UID16
1301 bool "Enable 16-bit UID system calls" if EXPERT
1302 depends on HAVE_UID16
1303 default y
1304 help
1305 This enables the legacy 16-bit UID syscall wrappers.
1307 config SYSFS_SYSCALL
1308 bool "Sysfs syscall support" if EXPERT
1309 default y
1310 ---help---
1311 sys_sysfs is an obsolete system call no longer supported in libc.
1312 Note that disabling this option is more secure but might break
1313 compatibility with some systems.
1315 If unsure say Y here.
1317 config SYSCTL_SYSCALL
1318 bool "Sysctl syscall support" if EXPERT
1319 depends on PROC_SYSCTL
1320 default n
1321 select SYSCTL
1322 ---help---
1323 sys_sysctl uses binary paths that have been found challenging
1324 to properly maintain and use. The interface in /proc/sys
1325 using paths with ascii names is now the primary path to this
1326 information.
1328 Almost nothing using the binary sysctl interface so if you are
1329 trying to save some space it is probably safe to disable this,
1330 making your kernel marginally smaller.
1332 If unsure say N here.
1334 config KALLSYMS
1335 bool "Load all symbols for debugging/ksymoops" if EXPERT
1336 default y
1337 help
1338 Say Y here to let the kernel print out symbolic crash information and
1339 symbolic stack backtraces. This increases the size of the kernel
1340 somewhat, as all symbols have to be loaded into the kernel image.
1342 config KALLSYMS_ALL
1343 bool "Include all symbols in kallsyms"
1344 depends on DEBUG_KERNEL && KALLSYMS
1345 help
1346 Normally kallsyms only contains the symbols of functions for nicer
1347 OOPS messages and backtraces (i.e., symbols from the text and inittext
1348 sections). This is sufficient for most cases. And only in very rare
1349 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1350 names of variables from the data sections, etc).
1352 This option makes sure that all symbols are loaded into the kernel
1353 image (i.e., symbols from all sections) in cost of increased kernel
1354 size (depending on the kernel configuration, it may be 300KiB or
1355 something like this).
1357 Say N unless you really need all symbols.
1359 config PRINTK
1360 default y
1361 bool "Enable support for printk" if EXPERT
1362 select IRQ_WORK
1363 help
1364 This option enables normal printk support. Removing it
1365 eliminates most of the message strings from the kernel image
1366 and makes the kernel more or less silent. As this makes it
1367 very difficult to diagnose system problems, saying N here is
1368 strongly discouraged.
1370 config BUG
1371 bool "BUG() support" if EXPERT
1372 default y
1373 help
1374 Disabling this option eliminates support for BUG and WARN, reducing
1375 the size of your kernel image and potentially quietly ignoring
1376 numerous fatal conditions. You should only consider disabling this
1377 option for embedded systems with no facilities for reporting errors.
1378 Just say Y.
1380 config ELF_CORE
1381 depends on COREDUMP
1382 default y
1383 bool "Enable ELF core dumps" if EXPERT
1384 help
1385 Enable support for generating core dumps. Disabling saves about 4k.
1388 config PCSPKR_PLATFORM
1389 bool "Enable PC-Speaker support" if EXPERT
1390 depends on HAVE_PCSPKR_PLATFORM
1391 select I8253_LOCK
1392 default y
1393 help
1394 This option allows to disable the internal PC-Speaker
1395 support, saving some memory.
1397 config BASE_FULL
1398 default y
1399 bool "Enable full-sized data structures for core" if EXPERT
1400 help
1401 Disabling this option reduces the size of miscellaneous core
1402 kernel data structures. This saves memory on small machines,
1403 but may reduce performance.
1405 config FUTEX
1406 bool "Enable futex support" if EXPERT
1407 default y
1408 select RT_MUTEXES
1409 help
1410 Disabling this option will cause the kernel to be built without
1411 support for "fast userspace mutexes". The resulting kernel may not
1412 run glibc-based applications correctly.
1414 config HAVE_FUTEX_CMPXCHG
1415 bool
1416 help
1417 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1418 is implemented and always working. This removes a couple of runtime
1419 checks.
1421 config EPOLL
1422 bool "Enable eventpoll support" if EXPERT
1423 default y
1424 select ANON_INODES
1425 help
1426 Disabling this option will cause the kernel to be built without
1427 support for epoll family of system calls.
1429 config SIGNALFD
1430 bool "Enable signalfd() system call" if EXPERT
1431 select ANON_INODES
1432 default y
1433 help
1434 Enable the signalfd() system call that allows to receive signals
1435 on a file descriptor.
1437 If unsure, say Y.
1439 config TIMERFD
1440 bool "Enable timerfd() system call" if EXPERT
1441 select ANON_INODES
1442 default y
1443 help
1444 Enable the timerfd() system call that allows to receive timer
1445 events on a file descriptor.
1447 If unsure, say Y.
1449 config EVENTFD
1450 bool "Enable eventfd() system call" if EXPERT
1451 select ANON_INODES
1452 default y
1453 help
1454 Enable the eventfd() system call that allows to receive both
1455 kernel notification (ie. KAIO) or userspace notifications.
1457 If unsure, say Y.
1459 config SHMEM
1460 bool "Use full shmem filesystem" if EXPERT
1461 default y
1462 depends on MMU
1463 help
1464 The shmem is an internal filesystem used to manage shared memory.
1465 It is backed by swap and manages resource limits. It is also exported
1466 to userspace as tmpfs if TMPFS is enabled. Disabling this
1467 option replaces shmem and tmpfs with the much simpler ramfs code,
1468 which may be appropriate on small systems without swap.
1470 config AIO
1471 bool "Enable AIO support" if EXPERT
1472 default y
1473 help
1474 This option enables POSIX asynchronous I/O which may by used
1475 by some high performance threaded applications. Disabling
1476 this option saves about 7k.
1478 config PCI_QUIRKS
1479 default y
1480 bool "Enable PCI quirk workarounds" if EXPERT
1481 depends on PCI
1482 help
1483 This enables workarounds for various PCI chipset
1484 bugs/quirks. Disable this only if your target machine is
1485 unaffected by PCI quirks.
1487 config EMBEDDED
1488 bool "Embedded system"
1489 option allnoconfig_y
1490 select EXPERT
1491 help
1492 This option should be enabled if compiling the kernel for
1493 an embedded system so certain expert options are available
1494 for configuration.
1496 config HAVE_PERF_EVENTS
1497 bool
1498 help
1499 See tools/perf/design.txt for details.
1501 config PERF_USE_VMALLOC
1502 bool
1503 help
1504 See tools/perf/design.txt for details
1506 menu "Kernel Performance Events And Counters"
1508 config PERF_EVENTS
1509 bool "Kernel performance events and counters"
1510 default y if PROFILING
1511 depends on HAVE_PERF_EVENTS
1512 select ANON_INODES
1513 select IRQ_WORK
1514 help
1515 Enable kernel support for various performance events provided
1516 by software and hardware.
1518 Software events are supported either built-in or via the
1519 use of generic tracepoints.
1521 Most modern CPUs support performance events via performance
1522 counter registers. These registers count the number of certain
1523 types of hw events: such as instructions executed, cachemisses
1524 suffered, or branches mis-predicted - without slowing down the
1525 kernel or applications. These registers can also trigger interrupts
1526 when a threshold number of events have passed - and can thus be
1527 used to profile the code that runs on that CPU.
1529 The Linux Performance Event subsystem provides an abstraction of
1530 these software and hardware event capabilities, available via a
1531 system call and used by the "perf" utility in tools/perf/. It
1532 provides per task and per CPU counters, and it provides event
1533 capabilities on top of those.
1535 Say Y if unsure.
1537 config DEBUG_PERF_USE_VMALLOC
1538 default n
1539 bool "Debug: use vmalloc to back perf mmap() buffers"
1540 depends on PERF_EVENTS && DEBUG_KERNEL
1541 select PERF_USE_VMALLOC
1542 help
1543 Use vmalloc memory to back perf mmap() buffers.
1545 Mostly useful for debugging the vmalloc code on platforms
1546 that don't require it.
1548 Say N if unsure.
1550 endmenu
1552 config VM_EVENT_COUNTERS
1553 default y
1554 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1555 help
1556 VM event counters are needed for event counts to be shown.
1557 This option allows the disabling of the VM event counters
1558 on EXPERT systems. /proc/vmstat will only show page counts
1559 if VM event counters are disabled.
1561 config SLUB_DEBUG
1562 default y
1563 bool "Enable SLUB debugging support" if EXPERT
1564 depends on SLUB && SYSFS
1565 help
1566 SLUB has extensive debug support features. Disabling these can
1567 result in significant savings in code size. This also disables
1568 SLUB sysfs support. /sys/slab will not exist and there will be
1569 no support for cache validation etc.
1571 config COMPAT_BRK
1572 bool "Disable heap randomization"
1573 default y
1574 help
1575 Randomizing heap placement makes heap exploits harder, but it
1576 also breaks ancient binaries (including anything libc5 based).
1577 This option changes the bootup default to heap randomization
1578 disabled, and can be overridden at runtime by setting
1579 /proc/sys/kernel/randomize_va_space to 2.
1581 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1583 choice
1584 prompt "Choose SLAB allocator"
1585 default SLUB
1586 help
1587 This option allows to select a slab allocator.
1589 config SLAB
1590 bool "SLAB"
1591 help
1592 The regular slab allocator that is established and known to work
1593 well in all environments. It organizes cache hot objects in
1594 per cpu and per node queues.
1596 config SLUB
1597 bool "SLUB (Unqueued Allocator)"
1598 help
1599 SLUB is a slab allocator that minimizes cache line usage
1600 instead of managing queues of cached objects (SLAB approach).
1601 Per cpu caching is realized using slabs of objects instead
1602 of queues of objects. SLUB can use memory efficiently
1603 and has enhanced diagnostics. SLUB is the default choice for
1604 a slab allocator.
1606 config SLOB
1607 depends on EXPERT
1608 bool "SLOB (Simple Allocator)"
1609 help
1610 SLOB replaces the stock allocator with a drastically simpler
1611 allocator. SLOB is generally more space efficient but
1612 does not perform as well on large systems.
1614 endchoice
1616 config SLUB_CPU_PARTIAL
1617 default y
1618 depends on SLUB && SMP
1619 bool "SLUB per cpu partial cache"
1620 help
1621 Per cpu partial caches accellerate objects allocation and freeing
1622 that is local to a processor at the price of more indeterminism
1623 in the latency of the free. On overflow these caches will be cleared
1624 which requires the taking of locks that may cause latency spikes.
1625 Typically one would choose no for a realtime system.
1627 config MMAP_ALLOW_UNINITIALIZED
1628 bool "Allow mmapped anonymous memory to be uninitialized"
1629 depends on EXPERT && !MMU
1630 default n
1631 help
1632 Normally, and according to the Linux spec, anonymous memory obtained
1633 from mmap() has it's contents cleared before it is passed to
1634 userspace. Enabling this config option allows you to request that
1635 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1636 providing a huge performance boost. If this option is not enabled,
1637 then the flag will be ignored.
1639 This is taken advantage of by uClibc's malloc(), and also by
1640 ELF-FDPIC binfmt's brk and stack allocator.
1642 Because of the obvious security issues, this option should only be
1643 enabled on embedded devices where you control what is run in
1644 userspace. Since that isn't generally a problem on no-MMU systems,
1645 it is normally safe to say Y here.
1647 See Documentation/nommu-mmap.txt for more information.
1649 config SYSTEM_TRUSTED_KEYRING
1650 bool "Provide system-wide ring of trusted keys"
1651 depends on KEYS
1652 help
1653 Provide a system keyring to which trusted keys can be added. Keys in
1654 the keyring are considered to be trusted. Keys may be added at will
1655 by the kernel from compiled-in data and from hardware key stores, but
1656 userspace may only add extra keys if those keys can be verified by
1657 keys already in the keyring.
1659 Keys in this keyring are used by module signature checking.
1661 config PROFILING
1662 bool "Profiling support"
1663 help
1664 Say Y here to enable the extended profiling support mechanisms used
1665 by profilers such as OProfile.
1667 #
1668 # Place an empty function call at each tracepoint site. Can be
1669 # dynamically changed for a probe function.
1670 #
1671 config TRACEPOINTS
1672 bool
1674 source "arch/Kconfig"
1676 endmenu # General setup
1678 config HAVE_GENERIC_DMA_COHERENT
1679 bool
1680 default n
1682 config SLABINFO
1683 bool
1684 depends on PROC_FS
1685 depends on SLAB || SLUB_DEBUG
1686 default y
1688 config RT_MUTEXES
1689 boolean
1691 config BASE_SMALL
1692 int
1693 default 0 if BASE_FULL
1694 default 1 if !BASE_FULL
1696 menuconfig MODULES
1697 bool "Enable loadable module support"
1698 option modules
1699 help
1700 Kernel modules are small pieces of compiled code which can
1701 be inserted in the running kernel, rather than being
1702 permanently built into the kernel. You use the "modprobe"
1703 tool to add (and sometimes remove) them. If you say Y here,
1704 many parts of the kernel can be built as modules (by
1705 answering M instead of Y where indicated): this is most
1706 useful for infrequently used options which are not required
1707 for booting. For more information, see the man pages for
1708 modprobe, lsmod, modinfo, insmod and rmmod.
1710 If you say Y here, you will need to run "make
1711 modules_install" to put the modules under /lib/modules/
1712 where modprobe can find them (you may need to be root to do
1713 this).
1715 If unsure, say Y.
1717 if MODULES
1719 config MODULE_FORCE_LOAD
1720 bool "Forced module loading"
1721 default n
1722 help
1723 Allow loading of modules without version information (ie. modprobe
1724 --force). Forced module loading sets the 'F' (forced) taint flag and
1725 is usually a really bad idea.
1727 config MODULE_UNLOAD
1728 bool "Module unloading"
1729 help
1730 Without this option you will not be able to unload any
1731 modules (note that some modules may not be unloadable
1732 anyway), which makes your kernel smaller, faster
1733 and simpler. If unsure, say Y.
1735 config MODULE_FORCE_UNLOAD
1736 bool "Forced module unloading"
1737 depends on MODULE_UNLOAD
1738 help
1739 This option allows you to force a module to unload, even if the
1740 kernel believes it is unsafe: the kernel will remove the module
1741 without waiting for anyone to stop using it (using the -f option to
1742 rmmod). This is mainly for kernel developers and desperate users.
1743 If unsure, say N.
1745 config MODVERSIONS
1746 bool "Module versioning support"
1747 help
1748 Usually, you have to use modules compiled with your kernel.
1749 Saying Y here makes it sometimes possible to use modules
1750 compiled for different kernels, by adding enough information
1751 to the modules to (hopefully) spot any changes which would
1752 make them incompatible with the kernel you are running. If
1753 unsure, say N.
1755 config MODULE_SRCVERSION_ALL
1756 bool "Source checksum for all modules"
1757 help
1758 Modules which contain a MODULE_VERSION get an extra "srcversion"
1759 field inserted into their modinfo section, which contains a
1760 sum of the source files which made it. This helps maintainers
1761 see exactly which source was used to build a module (since
1762 others sometimes change the module source without updating
1763 the version). With this option, such a "srcversion" field
1764 will be created for all modules. If unsure, say N.
1766 config MODULE_SIG
1767 bool "Module signature verification"
1768 depends on MODULES
1769 select SYSTEM_TRUSTED_KEYRING
1770 select KEYS
1771 select CRYPTO
1772 select ASYMMETRIC_KEY_TYPE
1773 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1774 select PUBLIC_KEY_ALGO_RSA
1775 select ASN1
1776 select OID_REGISTRY
1777 select X509_CERTIFICATE_PARSER
1778 help
1779 Check modules for valid signatures upon load: the signature
1780 is simply appended to the module. For more information see
1781 Documentation/module-signing.txt.
1783 !!!WARNING!!! If you enable this option, you MUST make sure that the
1784 module DOES NOT get stripped after being signed. This includes the
1785 debuginfo strip done by some packagers (such as rpmbuild) and
1786 inclusion into an initramfs that wants the module size reduced.
1788 config MODULE_SIG_FORCE
1789 bool "Require modules to be validly signed"
1790 depends on MODULE_SIG
1791 help
1792 Reject unsigned modules or signed modules for which we don't have a
1793 key. Without this, such modules will simply taint the kernel.
1795 config MODULE_SIG_ALL
1796 bool "Automatically sign all modules"
1797 default y
1798 depends on MODULE_SIG
1799 help
1800 Sign all modules during make modules_install. Without this option,
1801 modules must be signed manually, using the scripts/sign-file tool.
1803 comment "Do not forget to sign required modules with scripts/sign-file"
1804 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1806 choice
1807 prompt "Which hash algorithm should modules be signed with?"
1808 depends on MODULE_SIG
1809 help
1810 This determines which sort of hashing algorithm will be used during
1811 signature generation. This algorithm _must_ be built into the kernel
1812 directly so that signature verification can take place. It is not
1813 possible to load a signed module containing the algorithm to check
1814 the signature on that module.
1816 config MODULE_SIG_SHA1
1817 bool "Sign modules with SHA-1"
1818 select CRYPTO_SHA1
1820 config MODULE_SIG_SHA224
1821 bool "Sign modules with SHA-224"
1822 select CRYPTO_SHA256
1824 config MODULE_SIG_SHA256
1825 bool "Sign modules with SHA-256"
1826 select CRYPTO_SHA256
1828 config MODULE_SIG_SHA384
1829 bool "Sign modules with SHA-384"
1830 select CRYPTO_SHA512
1832 config MODULE_SIG_SHA512
1833 bool "Sign modules with SHA-512"
1834 select CRYPTO_SHA512
1836 endchoice
1838 config MODULE_SIG_HASH
1839 string
1840 depends on MODULE_SIG
1841 default "sha1" if MODULE_SIG_SHA1
1842 default "sha224" if MODULE_SIG_SHA224
1843 default "sha256" if MODULE_SIG_SHA256
1844 default "sha384" if MODULE_SIG_SHA384
1845 default "sha512" if MODULE_SIG_SHA512
1847 endif # MODULES
1849 config INIT_ALL_POSSIBLE
1850 bool
1851 help
1852 Back when each arch used to define their own cpu_online_mask and
1853 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1854 with all 1s, and others with all 0s. When they were centralised,
1855 it was better to provide this option than to break all the archs
1856 and have several arch maintainers pursuing me down dark alleys.
1858 config STOP_MACHINE
1859 bool
1860 default y
1861 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1862 help
1863 Need stop_machine() primitive.
1865 source "block/Kconfig"
1867 config PREEMPT_NOTIFIERS
1868 bool
1870 config PADATA
1871 depends on SMP
1872 bool
1874 # Can be selected by architectures with broken toolchains
1875 # that get confused by correct const<->read_only section
1876 # mappings
1877 config BROKEN_RODATA
1878 bool
1880 config ASN1
1881 tristate
1882 help
1883 Build a simple ASN.1 grammar compiler that produces a bytecode output
1884 that can be interpreted by the ASN.1 stream decoder and used to
1885 inform it as to what tags are to be expected in a stream and what
1886 functions to call on what tags.
1888 source "kernel/Kconfig.locks"