| blob | 247084be059030162838199c953ebac6409f7e01 |
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 help
474 This option selects the RCU implementation that is
475 designed for very large SMP systems with hundreds or
476 thousands of CPUs, but for which real-time response
477 is also required. It also scales down nicely to
478 smaller systems.
480 Select this option if you are unsure.
482 config TINY_RCU
483 bool "UP-only small-memory-footprint RCU"
484 depends on !PREEMPT && !SMP
485 help
486 This option selects the RCU implementation that is
487 designed for UP systems from which real-time response
488 is not required. This option greatly reduces the
489 memory footprint of RCU.
491 endchoice
493 config PREEMPT_RCU
494 def_bool TREE_PREEMPT_RCU
495 help
496 This option enables preemptible-RCU code that is common between
497 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
499 config RCU_STALL_COMMON
500 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
501 help
502 This option enables RCU CPU stall code that is common between
503 the TINY and TREE variants of RCU. The purpose is to allow
504 the tiny variants to disable RCU CPU stall warnings, while
505 making these warnings mandatory for the tree variants.
507 config CONTEXT_TRACKING
508 bool
510 config RCU_USER_QS
511 bool "Consider userspace as in RCU extended quiescent state"
512 depends on HAVE_CONTEXT_TRACKING && SMP
513 select CONTEXT_TRACKING
514 help
515 This option sets hooks on kernel / userspace boundaries and
516 puts RCU in extended quiescent state when the CPU runs in
517 userspace. It means that when a CPU runs in userspace, it is
518 excluded from the global RCU state machine and thus doesn't
519 try to keep the timer tick on for RCU.
521 Unless you want to hack and help the development of the full
522 dynticks mode, you shouldn't enable this option. It also
523 adds unnecessary overhead.
525 If unsure say N
527 config CONTEXT_TRACKING_FORCE
528 bool "Force context tracking"
529 depends on CONTEXT_TRACKING
530 default CONTEXT_TRACKING
531 help
532 Probe on user/kernel boundaries by default in order to
533 test the features that rely on it such as userspace RCU extended
534 quiescent states.
535 This test is there for debugging until we have a real user like the
536 full dynticks mode.
538 config RCU_FANOUT
539 int "Tree-based hierarchical RCU fanout value"
540 range 2 64 if 64BIT
541 range 2 32 if !64BIT
542 depends on TREE_RCU || TREE_PREEMPT_RCU
543 default 64 if 64BIT
544 default 32 if !64BIT
545 help
546 This option controls the fanout of hierarchical implementations
547 of RCU, allowing RCU to work efficiently on machines with
548 large numbers of CPUs. This value must be at least the fourth
549 root of NR_CPUS, which allows NR_CPUS to be insanely large.
550 The default value of RCU_FANOUT should be used for production
551 systems, but if you are stress-testing the RCU implementation
552 itself, small RCU_FANOUT values allow you to test large-system
553 code paths on small(er) systems.
555 Select a specific number if testing RCU itself.
556 Take the default if unsure.
558 config RCU_FANOUT_LEAF
559 int "Tree-based hierarchical RCU leaf-level fanout value"
560 range 2 RCU_FANOUT if 64BIT
561 range 2 RCU_FANOUT if !64BIT
562 depends on TREE_RCU || TREE_PREEMPT_RCU
563 default 16
564 help
565 This option controls the leaf-level fanout of hierarchical
566 implementations of RCU, and allows trading off cache misses
567 against lock contention. Systems that synchronize their
568 scheduling-clock interrupts for energy-efficiency reasons will
569 want the default because the smaller leaf-level fanout keeps
570 lock contention levels acceptably low. Very large systems
571 (hundreds or thousands of CPUs) will instead want to set this
572 value to the maximum value possible in order to reduce the
573 number of cache misses incurred during RCU's grace-period
574 initialization. These systems tend to run CPU-bound, and thus
575 are not helped by synchronized interrupts, and thus tend to
576 skew them, which reduces lock contention enough that large
577 leaf-level fanouts work well.
579 Select a specific number if testing RCU itself.
581 Select the maximum permissible value for large systems.
583 Take the default if unsure.
585 config RCU_FANOUT_EXACT
586 bool "Disable tree-based hierarchical RCU auto-balancing"
587 depends on TREE_RCU || TREE_PREEMPT_RCU
588 default n
589 help
590 This option forces use of the exact RCU_FANOUT value specified,
591 regardless of imbalances in the hierarchy. This is useful for
592 testing RCU itself, and might one day be useful on systems with
593 strong NUMA behavior.
595 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
597 Say N if unsure.
599 config RCU_FAST_NO_HZ
600 bool "Accelerate last non-dyntick-idle CPU's grace periods"
601 depends on NO_HZ_COMMON && SMP
602 default n
603 help
604 This option permits CPUs to enter dynticks-idle state even if
605 they have RCU callbacks queued, and prevents RCU from waking
606 these CPUs up more than roughly once every four jiffies (by
607 default, you can adjust this using the rcutree.rcu_idle_gp_delay
608 parameter), thus improving energy efficiency. On the other
609 hand, this option increases the duration of RCU grace periods,
610 for example, slowing down synchronize_rcu().
612 Say Y if energy efficiency is critically important, and you
613 don't care about increased grace-period durations.
615 Say N if you are unsure.
617 config TREE_RCU_TRACE
618 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
619 select DEBUG_FS
620 help
621 This option provides tracing for the TREE_RCU and
622 TREE_PREEMPT_RCU implementations, permitting Makefile to
623 trivially select kernel/rcutree_trace.c.
625 config RCU_BOOST
626 bool "Enable RCU priority boosting"
627 depends on RT_MUTEXES && PREEMPT_RCU
628 default n
629 help
630 This option boosts the priority of preempted RCU readers that
631 block the current preemptible RCU grace period for too long.
632 This option also prevents heavy loads from blocking RCU
633 callback invocation for all flavors of RCU.
635 Say Y here if you are working with real-time apps or heavy loads
636 Say N here if you are unsure.
638 config RCU_BOOST_PRIO
639 int "Real-time priority to boost RCU readers to"
640 range 1 99
641 depends on RCU_BOOST
642 default 1
643 help
644 This option specifies the real-time priority to which long-term
645 preempted RCU readers are to be boosted. If you are working
646 with a real-time application that has one or more CPU-bound
647 threads running at a real-time priority level, you should set
648 RCU_BOOST_PRIO to a priority higher then the highest-priority
649 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
650 of 1 is appropriate in the common case, which is real-time
651 applications that do not have any CPU-bound threads.
653 Some real-time applications might not have a single real-time
654 thread that saturates a given CPU, but instead might have
655 multiple real-time threads that, taken together, fully utilize
656 that CPU. In this case, you should set RCU_BOOST_PRIO to
657 a priority higher than the lowest-priority thread that is
658 conspiring to prevent the CPU from running any non-real-time
659 tasks. For example, if one thread at priority 10 and another
660 thread at priority 5 are between themselves fully consuming
661 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
662 set to priority 6 or higher.
664 Specify the real-time priority, or take the default if unsure.
666 config RCU_BOOST_DELAY
667 int "Milliseconds to delay boosting after RCU grace-period start"
668 range 0 3000
669 depends on RCU_BOOST
670 default 500
671 help
672 This option specifies the time to wait after the beginning of
673 a given grace period before priority-boosting preempted RCU
674 readers blocking that grace period. Note that any RCU reader
675 blocking an expedited RCU grace period is boosted immediately.
677 Accept the default if unsure.
679 config RCU_NOCB_CPU
680 bool "Offload RCU callback processing from boot-selected CPUs"
681 depends on TREE_RCU || TREE_PREEMPT_RCU
682 default n
683 help
684 Use this option to reduce OS jitter for aggressive HPC or
685 real-time workloads. It can also be used to offload RCU
686 callback invocation to energy-efficient CPUs in battery-powered
687 asymmetric multiprocessors.
689 This option offloads callback invocation from the set of
690 CPUs specified at boot time by the rcu_nocbs parameter.
691 For each such CPU, a kthread ("rcuox/N") will be created to
692 invoke callbacks, where the "N" is the CPU being offloaded,
693 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
694 "s" for RCU-sched. Nothing prevents this kthread from running
695 on the specified CPUs, but (1) the kthreads may be preempted
696 between each callback, and (2) affinity or cgroups can be used
697 to force the kthreads to run on whatever set of CPUs is desired.
699 Say Y here if you want to help to debug reduced OS jitter.
700 Say N here if you are unsure.
702 choice
703 prompt "Build-forced no-CBs CPUs"
704 default RCU_NOCB_CPU_NONE
705 help
706 This option allows no-CBs CPUs (whose RCU callbacks are invoked
707 from kthreads rather than from softirq context) to be specified
708 at build time. Additional no-CBs CPUs may be specified by
709 the rcu_nocbs= boot parameter.
711 config RCU_NOCB_CPU_NONE
712 bool "No build_forced no-CBs CPUs"
713 depends on RCU_NOCB_CPU && !NO_HZ_FULL
714 help
715 This option does not force any of the CPUs to be no-CBs CPUs.
716 Only CPUs designated by the rcu_nocbs= boot parameter will be
717 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
718 kthreads whose names begin with "rcuo". All other CPUs will
719 invoke their own RCU callbacks in softirq context.
721 Select this option if you want to choose no-CBs CPUs at
722 boot time, for example, to allow testing of different no-CBs
723 configurations without having to rebuild the kernel each time.
725 config RCU_NOCB_CPU_ZERO
726 bool "CPU 0 is a build_forced no-CBs CPU"
727 depends on RCU_NOCB_CPU && !NO_HZ_FULL
728 help
729 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
730 callbacks are invoked by a per-CPU kthread whose name begins
731 with "rcuo". Additional CPUs may be designated as no-CBs
732 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
733 All other CPUs will invoke their own RCU callbacks in softirq
734 context.
736 Select this if CPU 0 needs to be a no-CBs CPU for real-time
737 or energy-efficiency reasons, but the real reason it exists
738 is to ensure that randconfig testing covers mixed systems.
740 config RCU_NOCB_CPU_ALL
741 bool "All CPUs are build_forced no-CBs CPUs"
742 depends on RCU_NOCB_CPU
743 help
744 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
745 boot parameter will be ignored. All CPUs' RCU callbacks will
746 be executed in the context of per-CPU rcuo kthreads created for
747 this purpose. Assuming that the kthreads whose names start with
748 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
749 on the remaining CPUs, but might decrease memory locality during
750 RCU-callback invocation, thus potentially degrading throughput.
752 Select this if all CPUs need to be no-CBs CPUs for real-time
753 or energy-efficiency reasons.
755 endchoice
757 endmenu # "RCU Subsystem"
759 config IKCONFIG
760 tristate "Kernel .config support"
761 ---help---
762 This option enables the complete Linux kernel ".config" file
763 contents to be saved in the kernel. It provides documentation
764 of which kernel options are used in a running kernel or in an
765 on-disk kernel. This information can be extracted from the kernel
766 image file with the script scripts/extract-ikconfig and used as
767 input to rebuild the current kernel or to build another kernel.
768 It can also be extracted from a running kernel by reading
769 /proc/config.gz if enabled (below).
771 config IKCONFIG_PROC
772 bool "Enable access to .config through /proc/config.gz"
773 depends on IKCONFIG && PROC_FS
774 ---help---
775 This option enables access to the kernel configuration file
776 through /proc/config.gz.
778 config LOG_BUF_SHIFT
779 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
780 range 12 21
781 default 17
782 help
783 Select kernel log buffer size as a power of 2.
784 Examples:
785 17 => 128 KB
786 16 => 64 KB
787 15 => 32 KB
788 14 => 16 KB
789 13 => 8 KB
790 12 => 4 KB
792 #
793 # Architectures with an unreliable sched_clock() should select this:
794 #
795 config HAVE_UNSTABLE_SCHED_CLOCK
796 bool
798 config GENERIC_SCHED_CLOCK
799 bool
801 #
802 # For architectures that want to enable the support for NUMA-affine scheduler
803 # balancing logic:
804 #
805 config ARCH_SUPPORTS_NUMA_BALANCING
806 bool
808 # For architectures that (ab)use NUMA to represent different memory regions
809 # all cpu-local but of different latencies, such as SuperH.
810 #
811 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
812 bool
814 #
815 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
816 config ARCH_WANTS_PROT_NUMA_PROT_NONE
817 bool
819 config ARCH_USES_NUMA_PROT_NONE
820 bool
821 default y
822 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
823 depends on NUMA_BALANCING
825 config NUMA_BALANCING_DEFAULT_ENABLED
826 bool "Automatically enable NUMA aware memory/task placement"
827 default y
828 depends on NUMA_BALANCING
829 help
830 If set, autonumic NUMA balancing will be enabled if running on a NUMA
831 machine.
833 config NUMA_BALANCING
834 bool "Memory placement aware NUMA scheduler"
835 depends on ARCH_SUPPORTS_NUMA_BALANCING
836 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
837 depends on SMP && NUMA && MIGRATION
838 help
839 This option adds support for automatic NUMA aware memory/task placement.
840 The mechanism is quite primitive and is based on migrating memory when
841 it is references to the node the task is running on.
843 This system will be inactive on UMA systems.
845 menuconfig CGROUPS
846 boolean "Control Group support"
847 depends on EVENTFD
848 help
849 This option adds support for grouping sets of processes together, for
850 use with process control subsystems such as Cpusets, CFS, memory
851 controls or device isolation.
852 See
853 - Documentation/scheduler/sched-design-CFS.txt (CFS)
854 - Documentation/cgroups/ (features for grouping, isolation
855 and resource control)
857 Say N if unsure.
859 if CGROUPS
861 config CGROUP_DEBUG
862 bool "Example debug cgroup subsystem"
863 default n
864 help
865 This option enables a simple cgroup subsystem that
866 exports useful debugging information about the cgroups
867 framework.
869 Say N if unsure.
871 config CGROUP_FREEZER
872 bool "Freezer cgroup subsystem"
873 help
874 Provides a way to freeze and unfreeze all tasks in a
875 cgroup.
877 config CGROUP_DEVICE
878 bool "Device controller for cgroups"
879 help
880 Provides a cgroup implementing whitelists for devices which
881 a process in the cgroup can mknod or open.
883 config CPUSETS
884 bool "Cpuset support"
885 help
886 This option will let you create and manage CPUSETs which
887 allow dynamically partitioning a system into sets of CPUs and
888 Memory Nodes and assigning tasks to run only within those sets.
889 This is primarily useful on large SMP or NUMA systems.
891 Say N if unsure.
893 config PROC_PID_CPUSET
894 bool "Include legacy /proc/<pid>/cpuset file"
895 depends on CPUSETS
896 default y
898 config CGROUP_CPUACCT
899 bool "Simple CPU accounting cgroup subsystem"
900 help
901 Provides a simple Resource Controller for monitoring the
902 total CPU consumed by the tasks in a cgroup.
904 config RESOURCE_COUNTERS
905 bool "Resource counters"
906 help
907 This option enables controller independent resource accounting
908 infrastructure that works with cgroups.
910 config MEMCG
911 bool "Memory Resource Controller for Control Groups"
912 depends on RESOURCE_COUNTERS
913 select MM_OWNER
914 help
915 Provides a memory resource controller that manages both anonymous
916 memory and page cache. (See Documentation/cgroups/memory.txt)
918 Note that setting this option increases fixed memory overhead
919 associated with each page of memory in the system. By this,
920 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
921 usage tracking struct at boot. Total amount of this is printed out
922 at boot.
924 Only enable when you're ok with these trade offs and really
925 sure you need the memory resource controller. Even when you enable
926 this, you can set "cgroup_disable=memory" at your boot option to
927 disable memory resource controller and you can avoid overheads.
928 (and lose benefits of memory resource controller)
930 This config option also selects MM_OWNER config option, which
931 could in turn add some fork/exit overhead.
933 config MEMCG_SWAP
934 bool "Memory Resource Controller Swap Extension"
935 depends on MEMCG && SWAP
936 help
937 Add swap management feature to memory resource controller. When you
938 enable this, you can limit mem+swap usage per cgroup. In other words,
939 when you disable this, memory resource controller has no cares to
940 usage of swap...a process can exhaust all of the swap. This extension
941 is useful when you want to avoid exhaustion swap but this itself
942 adds more overheads and consumes memory for remembering information.
943 Especially if you use 32bit system or small memory system, please
944 be careful about enabling this. When memory resource controller
945 is disabled by boot option, this will be automatically disabled and
946 there will be no overhead from this. Even when you set this config=y,
947 if boot option "swapaccount=0" is set, swap will not be accounted.
948 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
949 size is 4096bytes, 512k per 1Gbytes of swap.
950 config MEMCG_SWAP_ENABLED
951 bool "Memory Resource Controller Swap Extension enabled by default"
952 depends on MEMCG_SWAP
953 default y
954 help
955 Memory Resource Controller Swap Extension comes with its price in
956 a bigger memory consumption. General purpose distribution kernels
957 which want to enable the feature but keep it disabled by default
958 and let the user enable it by swapaccount boot command line
959 parameter should have this option unselected.
960 For those who want to have the feature enabled by default should
961 select this option (if, for some reason, they need to disable it
962 then swapaccount=0 does the trick).
963 config MEMCG_KMEM
964 bool "Memory Resource Controller Kernel Memory accounting"
965 depends on MEMCG
966 depends on SLUB || SLAB
967 help
968 The Kernel Memory extension for Memory Resource Controller can limit
969 the amount of memory used by kernel objects in the system. Those are
970 fundamentally different from the entities handled by the standard
971 Memory Controller, which are page-based, and can be swapped. Users of
972 the kmem extension can use it to guarantee that no group of processes
973 will ever exhaust kernel resources alone.
975 config CGROUP_HUGETLB
976 bool "HugeTLB Resource Controller for Control Groups"
977 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
978 default n
979 help
980 Provides a cgroup Resource Controller for HugeTLB pages.
981 When you enable this, you can put a per cgroup limit on HugeTLB usage.
982 The limit is enforced during page fault. Since HugeTLB doesn't
983 support page reclaim, enforcing the limit at page fault time implies
984 that, the application will get SIGBUS signal if it tries to access
985 HugeTLB pages beyond its limit. This requires the application to know
986 beforehand how much HugeTLB pages it would require for its use. The
987 control group is tracked in the third page lru pointer. This means
988 that we cannot use the controller with huge page less than 3 pages.
990 config CGROUP_PERF
991 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
992 depends on PERF_EVENTS && CGROUPS
993 help
994 This option extends the per-cpu mode to restrict monitoring to
995 threads which belong to the cgroup specified and run on the
996 designated cpu.
998 Say N if unsure.
1000 menuconfig CGROUP_SCHED
1001 bool "Group CPU scheduler"
1002 default n
1003 help
1004 This feature lets CPU scheduler recognize task groups and control CPU
1005 bandwidth allocation to such task groups. It uses cgroups to group
1006 tasks.
1008 if CGROUP_SCHED
1009 config FAIR_GROUP_SCHED
1010 bool "Group scheduling for SCHED_OTHER"
1011 depends on CGROUP_SCHED
1012 default CGROUP_SCHED
1014 config CFS_BANDWIDTH
1015 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1016 depends on FAIR_GROUP_SCHED
1017 default n
1018 help
1019 This option allows users to define CPU bandwidth rates (limits) for
1020 tasks running within the fair group scheduler. Groups with no limit
1021 set are considered to be unconstrained and will run with no
1022 restriction.
1023 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1025 config RT_GROUP_SCHED
1026 bool "Group scheduling for SCHED_RR/FIFO"
1027 depends on CGROUP_SCHED
1028 default n
1029 help
1030 This feature lets you explicitly allocate real CPU bandwidth
1031 to task groups. If enabled, it will also make it impossible to
1032 schedule realtime tasks for non-root users until you allocate
1033 realtime bandwidth for them.
1034 See Documentation/scheduler/sched-rt-group.txt for more information.
1036 endif #CGROUP_SCHED
1038 config BLK_CGROUP
1039 bool "Block IO controller"
1040 depends on BLOCK
1041 default n
1042 ---help---
1043 Generic block IO controller cgroup interface. This is the common
1044 cgroup interface which should be used by various IO controlling
1045 policies.
1047 Currently, CFQ IO scheduler uses it to recognize task groups and
1048 control disk bandwidth allocation (proportional time slice allocation)
1049 to such task groups. It is also used by bio throttling logic in
1050 block layer to implement upper limit in IO rates on a device.
1052 This option only enables generic Block IO controller infrastructure.
1053 One needs to also enable actual IO controlling logic/policy. For
1054 enabling proportional weight division of disk bandwidth in CFQ, set
1055 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1056 CONFIG_BLK_DEV_THROTTLING=y.
1058 See Documentation/cgroups/blkio-controller.txt for more information.
1060 config DEBUG_BLK_CGROUP
1061 bool "Enable Block IO controller debugging"
1062 depends on BLK_CGROUP
1063 default n
1064 ---help---
1065 Enable some debugging help. Currently it exports additional stat
1066 files in a cgroup which can be useful for debugging.
1068 endif # CGROUPS
1070 config CHECKPOINT_RESTORE
1071 bool "Checkpoint/restore support" if EXPERT
1072 default n
1073 help
1074 Enables additional kernel features in a sake of checkpoint/restore.
1075 In particular it adds auxiliary prctl codes to setup process text,
1076 data and heap segment sizes, and a few additional /proc filesystem
1077 entries.
1079 If unsure, say N here.
1081 menuconfig NAMESPACES
1082 bool "Namespaces support" if EXPERT
1083 default !EXPERT
1084 help
1085 Provides the way to make tasks work with different objects using
1086 the same id. For example same IPC id may refer to different objects
1087 or same user id or pid may refer to different tasks when used in
1088 different namespaces.
1090 if NAMESPACES
1092 config UTS_NS
1093 bool "UTS namespace"
1094 default y
1095 help
1096 In this namespace tasks see different info provided with the
1097 uname() system call
1099 config IPC_NS
1100 bool "IPC namespace"
1101 depends on (SYSVIPC || POSIX_MQUEUE)
1102 default y
1103 help
1104 In this namespace tasks work with IPC ids which correspond to
1105 different IPC objects in different namespaces.
1107 config USER_NS
1108 bool "User namespace"
1109 depends on UIDGID_CONVERTED
1110 select UIDGID_STRICT_TYPE_CHECKS
1112 default n
1113 help
1114 This allows containers, i.e. vservers, to use user namespaces
1115 to provide different user info for different servers.
1117 When user namespaces are enabled in the kernel it is
1118 recommended that the MEMCG and MEMCG_KMEM options also be
1119 enabled and that user-space use the memory control groups to
1120 limit the amount of memory a memory unprivileged users can
1121 use.
1123 If unsure, say N.
1125 config PID_NS
1126 bool "PID Namespaces"
1127 default y
1128 help
1129 Support process id namespaces. This allows having multiple
1130 processes with the same pid as long as they are in different
1131 pid namespaces. This is a building block of containers.
1133 config NET_NS
1134 bool "Network namespace"
1135 depends on NET
1136 default y
1137 help
1138 Allow user space to create what appear to be multiple instances
1139 of the network stack.
1141 endif # NAMESPACES
1143 config UIDGID_CONVERTED
1144 # True if all of the selected software conmponents are known
1145 # to have uid_t and gid_t converted to kuid_t and kgid_t
1146 # where appropriate and are otherwise safe to use with
1147 # the user namespace.
1148 bool
1149 default y
1151 # Filesystems
1152 depends on XFS_FS = n
1154 config UIDGID_STRICT_TYPE_CHECKS
1155 bool "Require conversions between uid/gids and their internal representation"
1156 depends on UIDGID_CONVERTED
1157 default n
1158 help
1159 While the nececessary conversions are being added to all subsystems this option allows
1160 the code to continue to build for unconverted subsystems.
1162 Say Y here if you want the strict type checking enabled
1164 config SCHED_AUTOGROUP
1165 bool "Automatic process group scheduling"
1166 select EVENTFD
1167 select CGROUPS
1168 select CGROUP_SCHED
1169 select FAIR_GROUP_SCHED
1170 help
1171 This option optimizes the scheduler for common desktop workloads by
1172 automatically creating and populating task groups. This separation
1173 of workloads isolates aggressive CPU burners (like build jobs) from
1174 desktop applications. Task group autogeneration is currently based
1175 upon task session.
1177 config MM_OWNER
1178 bool
1180 config SYSFS_DEPRECATED
1181 bool "Enable deprecated sysfs features to support old userspace tools"
1182 depends on SYSFS
1183 default n
1184 help
1185 This option adds code that switches the layout of the "block" class
1186 devices, to not show up in /sys/class/block/, but only in
1187 /sys/block/.
1189 This switch is only active when the sysfs.deprecated=1 boot option is
1190 passed or the SYSFS_DEPRECATED_V2 option is set.
1192 This option allows new kernels to run on old distributions and tools,
1193 which might get confused by /sys/class/block/. Since 2007/2008 all
1194 major distributions and tools handle this just fine.
1196 Recent distributions and userspace tools after 2009/2010 depend on
1197 the existence of /sys/class/block/, and will not work with this
1198 option enabled.
1200 Only if you are using a new kernel on an old distribution, you might
1201 need to say Y here.
1203 config SYSFS_DEPRECATED_V2
1204 bool "Enable deprecated sysfs features by default"
1205 default n
1206 depends on SYSFS
1207 depends on SYSFS_DEPRECATED
1208 help
1209 Enable deprecated sysfs by default.
1211 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1212 option.
1214 Only if you are using a new kernel on an old distribution, you might
1215 need to say Y here. Even then, odds are you would not need it
1216 enabled, you can always pass the boot option if absolutely necessary.
1218 config RELAY
1219 bool "Kernel->user space relay support (formerly relayfs)"
1220 help
1221 This option enables support for relay interface support in
1222 certain file systems (such as debugfs).
1223 It is designed to provide an efficient mechanism for tools and
1224 facilities to relay large amounts of data from kernel space to
1225 user space.
1227 If unsure, say N.
1229 config BLK_DEV_INITRD
1230 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1231 depends on BROKEN || !FRV
1232 help
1233 The initial RAM filesystem is a ramfs which is loaded by the
1234 boot loader (loadlin or lilo) and that is mounted as root
1235 before the normal boot procedure. It is typically used to
1236 load modules needed to mount the "real" root file system,
1237 etc. See <file:Documentation/initrd.txt> for details.
1239 If RAM disk support (BLK_DEV_RAM) is also included, this
1240 also enables initial RAM disk (initrd) support and adds
1241 15 Kbytes (more on some other architectures) to the kernel size.
1243 If unsure say Y.
1245 if BLK_DEV_INITRD
1247 source "usr/Kconfig"
1249 endif
1251 config CC_OPTIMIZE_FOR_SIZE
1252 bool "Optimize for size"
1253 help
1254 Enabling this option will pass "-Os" instead of "-O2" to gcc
1255 resulting in a smaller kernel.
1257 If unsure, say N.
1259 config SYSCTL
1260 bool
1262 config ANON_INODES
1263 bool
1265 config HAVE_UID16
1266 bool
1268 config SYSCTL_EXCEPTION_TRACE
1269 bool
1270 help
1271 Enable support for /proc/sys/debug/exception-trace.
1273 config SYSCTL_ARCH_UNALIGN_NO_WARN
1274 bool
1275 help
1276 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1277 Allows arch to define/use @no_unaligned_warning to possibly warn
1278 about unaligned access emulation going on under the hood.
1280 config SYSCTL_ARCH_UNALIGN_ALLOW
1281 bool
1282 help
1283 Enable support for /proc/sys/kernel/unaligned-trap
1284 Allows arches to define/use @unaligned_enabled to runtime toggle
1285 the unaligned access emulation.
1286 see arch/parisc/kernel/unaligned.c for reference
1288 config HAVE_PCSPKR_PLATFORM
1289 bool
1291 menuconfig EXPERT
1292 bool "Configure standard kernel features (expert users)"
1293 # Unhide debug options, to make the on-by-default options visible
1294 select DEBUG_KERNEL
1295 help
1296 This option allows certain base kernel options and settings
1297 to be disabled or tweaked. This is for specialized
1298 environments which can tolerate a "non-standard" kernel.
1299 Only use this if you really know what you are doing.
1301 config UID16
1302 bool "Enable 16-bit UID system calls" if EXPERT
1303 depends on HAVE_UID16
1304 default y
1305 help
1306 This enables the legacy 16-bit UID syscall wrappers.
1308 config SYSCTL_SYSCALL
1309 bool "Sysctl syscall support" if EXPERT
1310 depends on PROC_SYSCTL
1311 default n
1312 select SYSCTL
1313 ---help---
1314 sys_sysctl uses binary paths that have been found challenging
1315 to properly maintain and use. The interface in /proc/sys
1316 using paths with ascii names is now the primary path to this
1317 information.
1319 Almost nothing using the binary sysctl interface so if you are
1320 trying to save some space it is probably safe to disable this,
1321 making your kernel marginally smaller.
1323 If unsure say N here.
1325 config KALLSYMS
1326 bool "Load all symbols for debugging/ksymoops" if EXPERT
1327 default y
1328 help
1329 Say Y here to let the kernel print out symbolic crash information and
1330 symbolic stack backtraces. This increases the size of the kernel
1331 somewhat, as all symbols have to be loaded into the kernel image.
1333 config KALLSYMS_ALL
1334 bool "Include all symbols in kallsyms"
1335 depends on DEBUG_KERNEL && KALLSYMS
1336 help
1337 Normally kallsyms only contains the symbols of functions for nicer
1338 OOPS messages and backtraces (i.e., symbols from the text and inittext
1339 sections). This is sufficient for most cases. And only in very rare
1340 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1341 names of variables from the data sections, etc).
1343 This option makes sure that all symbols are loaded into the kernel
1344 image (i.e., symbols from all sections) in cost of increased kernel
1345 size (depending on the kernel configuration, it may be 300KiB or
1346 something like this).
1348 Say N unless you really need all symbols.
1350 config PRINTK
1351 default y
1352 bool "Enable support for printk" if EXPERT
1353 select IRQ_WORK
1354 help
1355 This option enables normal printk support. Removing it
1356 eliminates most of the message strings from the kernel image
1357 and makes the kernel more or less silent. As this makes it
1358 very difficult to diagnose system problems, saying N here is
1359 strongly discouraged.
1361 config BUG
1362 bool "BUG() support" if EXPERT
1363 default y
1364 help
1365 Disabling this option eliminates support for BUG and WARN, reducing
1366 the size of your kernel image and potentially quietly ignoring
1367 numerous fatal conditions. You should only consider disabling this
1368 option for embedded systems with no facilities for reporting errors.
1369 Just say Y.
1371 config ELF_CORE
1372 depends on COREDUMP
1373 default y
1374 bool "Enable ELF core dumps" if EXPERT
1375 help
1376 Enable support for generating core dumps. Disabling saves about 4k.
1379 config PCSPKR_PLATFORM
1380 bool "Enable PC-Speaker support" if EXPERT
1381 depends on HAVE_PCSPKR_PLATFORM
1382 select I8253_LOCK
1383 default y
1384 help
1385 This option allows to disable the internal PC-Speaker
1386 support, saving some memory.
1388 config BASE_FULL
1389 default y
1390 bool "Enable full-sized data structures for core" if EXPERT
1391 help
1392 Disabling this option reduces the size of miscellaneous core
1393 kernel data structures. This saves memory on small machines,
1394 but may reduce performance.
1396 config FUTEX
1397 bool "Enable futex support" if EXPERT
1398 default y
1399 select RT_MUTEXES
1400 help
1401 Disabling this option will cause the kernel to be built without
1402 support for "fast userspace mutexes". The resulting kernel may not
1403 run glibc-based applications correctly.
1405 config EPOLL
1406 bool "Enable eventpoll support" if EXPERT
1407 default y
1408 select ANON_INODES
1409 help
1410 Disabling this option will cause the kernel to be built without
1411 support for epoll family of system calls.
1413 config SIGNALFD
1414 bool "Enable signalfd() system call" if EXPERT
1415 select ANON_INODES
1416 default y
1417 help
1418 Enable the signalfd() system call that allows to receive signals
1419 on a file descriptor.
1421 If unsure, say Y.
1423 config TIMERFD
1424 bool "Enable timerfd() system call" if EXPERT
1425 select ANON_INODES
1426 default y
1427 help
1428 Enable the timerfd() system call that allows to receive timer
1429 events on a file descriptor.
1431 If unsure, say Y.
1433 config EVENTFD
1434 bool "Enable eventfd() system call" if EXPERT
1435 select ANON_INODES
1436 default y
1437 help
1438 Enable the eventfd() system call that allows to receive both
1439 kernel notification (ie. KAIO) or userspace notifications.
1441 If unsure, say Y.
1443 config SHMEM
1444 bool "Use full shmem filesystem" if EXPERT
1445 default y
1446 depends on MMU
1447 help
1448 The shmem is an internal filesystem used to manage shared memory.
1449 It is backed by swap and manages resource limits. It is also exported
1450 to userspace as tmpfs if TMPFS is enabled. Disabling this
1451 option replaces shmem and tmpfs with the much simpler ramfs code,
1452 which may be appropriate on small systems without swap.
1454 config AIO
1455 bool "Enable AIO support" if EXPERT
1456 default y
1457 help
1458 This option enables POSIX asynchronous I/O which may by used
1459 by some high performance threaded applications. Disabling
1460 this option saves about 7k.
1462 config PCI_QUIRKS
1463 default y
1464 bool "Enable PCI quirk workarounds" if EXPERT
1465 depends on PCI
1466 help
1467 This enables workarounds for various PCI chipset
1468 bugs/quirks. Disable this only if your target machine is
1469 unaffected by PCI quirks.
1471 config EMBEDDED
1472 bool "Embedded system"
1473 select EXPERT
1474 help
1475 This option should be enabled if compiling the kernel for
1476 an embedded system so certain expert options are available
1477 for configuration.
1479 config HAVE_PERF_EVENTS
1480 bool
1481 help
1482 See tools/perf/design.txt for details.
1484 config PERF_USE_VMALLOC
1485 bool
1486 help
1487 See tools/perf/design.txt for details
1489 menu "Kernel Performance Events And Counters"
1491 config PERF_EVENTS
1492 bool "Kernel performance events and counters"
1493 default y if PROFILING
1494 depends on HAVE_PERF_EVENTS
1495 select ANON_INODES
1496 select IRQ_WORK
1497 help
1498 Enable kernel support for various performance events provided
1499 by software and hardware.
1501 Software events are supported either built-in or via the
1502 use of generic tracepoints.
1504 Most modern CPUs support performance events via performance
1505 counter registers. These registers count the number of certain
1506 types of hw events: such as instructions executed, cachemisses
1507 suffered, or branches mis-predicted - without slowing down the
1508 kernel or applications. These registers can also trigger interrupts
1509 when a threshold number of events have passed - and can thus be
1510 used to profile the code that runs on that CPU.
1512 The Linux Performance Event subsystem provides an abstraction of
1513 these software and hardware event capabilities, available via a
1514 system call and used by the "perf" utility in tools/perf/. It
1515 provides per task and per CPU counters, and it provides event
1516 capabilities on top of those.
1518 Say Y if unsure.
1520 config DEBUG_PERF_USE_VMALLOC
1521 default n
1522 bool "Debug: use vmalloc to back perf mmap() buffers"
1523 depends on PERF_EVENTS && DEBUG_KERNEL
1524 select PERF_USE_VMALLOC
1525 help
1526 Use vmalloc memory to back perf mmap() buffers.
1528 Mostly useful for debugging the vmalloc code on platforms
1529 that don't require it.
1531 Say N if unsure.
1533 endmenu
1535 config VM_EVENT_COUNTERS
1536 default y
1537 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1538 help
1539 VM event counters are needed for event counts to be shown.
1540 This option allows the disabling of the VM event counters
1541 on EXPERT systems. /proc/vmstat will only show page counts
1542 if VM event counters are disabled.
1544 config SLUB_DEBUG
1545 default y
1546 bool "Enable SLUB debugging support" if EXPERT
1547 depends on SLUB && SYSFS
1548 help
1549 SLUB has extensive debug support features. Disabling these can
1550 result in significant savings in code size. This also disables
1551 SLUB sysfs support. /sys/slab will not exist and there will be
1552 no support for cache validation etc.
1554 config COMPAT_BRK
1555 bool "Disable heap randomization"
1556 default y
1557 help
1558 Randomizing heap placement makes heap exploits harder, but it
1559 also breaks ancient binaries (including anything libc5 based).
1560 This option changes the bootup default to heap randomization
1561 disabled, and can be overridden at runtime by setting
1562 /proc/sys/kernel/randomize_va_space to 2.
1564 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1566 choice
1567 prompt "Choose SLAB allocator"
1568 default SLUB
1569 help
1570 This option allows to select a slab allocator.
1572 config SLAB
1573 bool "SLAB"
1574 help
1575 The regular slab allocator that is established and known to work
1576 well in all environments. It organizes cache hot objects in
1577 per cpu and per node queues.
1579 config SLUB
1580 bool "SLUB (Unqueued Allocator)"
1581 help
1582 SLUB is a slab allocator that minimizes cache line usage
1583 instead of managing queues of cached objects (SLAB approach).
1584 Per cpu caching is realized using slabs of objects instead
1585 of queues of objects. SLUB can use memory efficiently
1586 and has enhanced diagnostics. SLUB is the default choice for
1587 a slab allocator.
1589 config SLOB
1590 depends on EXPERT
1591 bool "SLOB (Simple Allocator)"
1592 help
1593 SLOB replaces the stock allocator with a drastically simpler
1594 allocator. SLOB is generally more space efficient but
1595 does not perform as well on large systems.
1597 endchoice
1599 config SLUB_CPU_PARTIAL
1600 default y
1601 depends on SLUB
1602 bool "SLUB per cpu partial cache"
1603 help
1604 Per cpu partial caches accellerate objects allocation and freeing
1605 that is local to a processor at the price of more indeterminism
1606 in the latency of the free. On overflow these caches will be cleared
1607 which requires the taking of locks that may cause latency spikes.
1608 Typically one would choose no for a realtime system.
1610 config MMAP_ALLOW_UNINITIALIZED
1611 bool "Allow mmapped anonymous memory to be uninitialized"
1612 depends on EXPERT && !MMU
1613 default n
1614 help
1615 Normally, and according to the Linux spec, anonymous memory obtained
1616 from mmap() has it's contents cleared before it is passed to
1617 userspace. Enabling this config option allows you to request that
1618 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1619 providing a huge performance boost. If this option is not enabled,
1620 then the flag will be ignored.
1622 This is taken advantage of by uClibc's malloc(), and also by
1623 ELF-FDPIC binfmt's brk and stack allocator.
1625 Because of the obvious security issues, this option should only be
1626 enabled on embedded devices where you control what is run in
1627 userspace. Since that isn't generally a problem on no-MMU systems,
1628 it is normally safe to say Y here.
1630 See Documentation/nommu-mmap.txt for more information.
1632 config PROFILING
1633 bool "Profiling support"
1634 help
1635 Say Y here to enable the extended profiling support mechanisms used
1636 by profilers such as OProfile.
1638 #
1639 # Place an empty function call at each tracepoint site. Can be
1640 # dynamically changed for a probe function.
1641 #
1642 config TRACEPOINTS
1643 bool
1645 source "arch/Kconfig"
1647 endmenu # General setup
1649 config HAVE_GENERIC_DMA_COHERENT
1650 bool
1651 default n
1653 config SLABINFO
1654 bool
1655 depends on PROC_FS
1656 depends on SLAB || SLUB_DEBUG
1657 default y
1659 config RT_MUTEXES
1660 boolean
1662 config BASE_SMALL
1663 int
1664 default 0 if BASE_FULL
1665 default 1 if !BASE_FULL
1667 menuconfig MODULES
1668 bool "Enable loadable module support"
1669 help
1670 Kernel modules are small pieces of compiled code which can
1671 be inserted in the running kernel, rather than being
1672 permanently built into the kernel. You use the "modprobe"
1673 tool to add (and sometimes remove) them. If you say Y here,
1674 many parts of the kernel can be built as modules (by
1675 answering M instead of Y where indicated): this is most
1676 useful for infrequently used options which are not required
1677 for booting. For more information, see the man pages for
1678 modprobe, lsmod, modinfo, insmod and rmmod.
1680 If you say Y here, you will need to run "make
1681 modules_install" to put the modules under /lib/modules/
1682 where modprobe can find them (you may need to be root to do
1683 this).
1685 If unsure, say Y.
1687 if MODULES
1689 config MODULE_FORCE_LOAD
1690 bool "Forced module loading"
1691 default n
1692 help
1693 Allow loading of modules without version information (ie. modprobe
1694 --force). Forced module loading sets the 'F' (forced) taint flag and
1695 is usually a really bad idea.
1697 config MODULE_UNLOAD
1698 bool "Module unloading"
1699 help
1700 Without this option you will not be able to unload any
1701 modules (note that some modules may not be unloadable
1702 anyway), which makes your kernel smaller, faster
1703 and simpler. If unsure, say Y.
1705 config MODULE_FORCE_UNLOAD
1706 bool "Forced module unloading"
1707 depends on MODULE_UNLOAD
1708 help
1709 This option allows you to force a module to unload, even if the
1710 kernel believes it is unsafe: the kernel will remove the module
1711 without waiting for anyone to stop using it (using the -f option to
1712 rmmod). This is mainly for kernel developers and desperate users.
1713 If unsure, say N.
1715 config MODVERSIONS
1716 bool "Module versioning support"
1717 help
1718 Usually, you have to use modules compiled with your kernel.
1719 Saying Y here makes it sometimes possible to use modules
1720 compiled for different kernels, by adding enough information
1721 to the modules to (hopefully) spot any changes which would
1722 make them incompatible with the kernel you are running. If
1723 unsure, say N.
1725 config MODULE_SRCVERSION_ALL
1726 bool "Source checksum for all modules"
1727 help
1728 Modules which contain a MODULE_VERSION get an extra "srcversion"
1729 field inserted into their modinfo section, which contains a
1730 sum of the source files which made it. This helps maintainers
1731 see exactly which source was used to build a module (since
1732 others sometimes change the module source without updating
1733 the version). With this option, such a "srcversion" field
1734 will be created for all modules. If unsure, say N.
1736 config MODULE_SIG
1737 bool "Module signature verification"
1738 depends on MODULES
1739 select KEYS
1740 select CRYPTO
1741 select ASYMMETRIC_KEY_TYPE
1742 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1743 select PUBLIC_KEY_ALGO_RSA
1744 select ASN1
1745 select OID_REGISTRY
1746 select X509_CERTIFICATE_PARSER
1747 help
1748 Check modules for valid signatures upon load: the signature
1749 is simply appended to the module. For more information see
1750 Documentation/module-signing.txt.
1752 !!!WARNING!!! If you enable this option, you MUST make sure that the
1753 module DOES NOT get stripped after being signed. This includes the
1754 debuginfo strip done by some packagers (such as rpmbuild) and
1755 inclusion into an initramfs that wants the module size reduced.
1757 config MODULE_SIG_FORCE
1758 bool "Require modules to be validly signed"
1759 depends on MODULE_SIG
1760 help
1761 Reject unsigned modules or signed modules for which we don't have a
1762 key. Without this, such modules will simply taint the kernel.
1764 config MODULE_SIG_ALL
1765 bool "Automatically sign all modules"
1766 default y
1767 depends on MODULE_SIG
1768 help
1769 Sign all modules during make modules_install. Without this option,
1770 modules must be signed manually, using the scripts/sign-file tool.
1772 comment "Do not forget to sign required modules with scripts/sign-file"
1773 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1775 choice
1776 prompt "Which hash algorithm should modules be signed with?"
1777 depends on MODULE_SIG
1778 help
1779 This determines which sort of hashing algorithm will be used during
1780 signature generation. This algorithm _must_ be built into the kernel
1781 directly so that signature verification can take place. It is not
1782 possible to load a signed module containing the algorithm to check
1783 the signature on that module.
1785 config MODULE_SIG_SHA1
1786 bool "Sign modules with SHA-1"
1787 select CRYPTO_SHA1
1789 config MODULE_SIG_SHA224
1790 bool "Sign modules with SHA-224"
1791 select CRYPTO_SHA256
1793 config MODULE_SIG_SHA256
1794 bool "Sign modules with SHA-256"
1795 select CRYPTO_SHA256
1797 config MODULE_SIG_SHA384
1798 bool "Sign modules with SHA-384"
1799 select CRYPTO_SHA512
1801 config MODULE_SIG_SHA512
1802 bool "Sign modules with SHA-512"
1803 select CRYPTO_SHA512
1805 endchoice
1807 config MODULE_SIG_HASH
1808 string
1809 depends on MODULE_SIG
1810 default "sha1" if MODULE_SIG_SHA1
1811 default "sha224" if MODULE_SIG_SHA224
1812 default "sha256" if MODULE_SIG_SHA256
1813 default "sha384" if MODULE_SIG_SHA384
1814 default "sha512" if MODULE_SIG_SHA512
1816 endif # MODULES
1818 config INIT_ALL_POSSIBLE
1819 bool
1820 help
1821 Back when each arch used to define their own cpu_online_mask and
1822 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1823 with all 1s, and others with all 0s. When they were centralised,
1824 it was better to provide this option than to break all the archs
1825 and have several arch maintainers pursuing me down dark alleys.
1827 config STOP_MACHINE
1828 bool
1829 default y
1830 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1831 help
1832 Need stop_machine() primitive.
1834 source "block/Kconfig"
1836 config PREEMPT_NOTIFIERS
1837 bool
1839 config PADATA
1840 depends on SMP
1841 bool
1843 # Can be selected by architectures with broken toolchains
1844 # that get confused by correct const<->read_only section
1845 # mappings
1846 config BROKEN_RODATA
1847 bool
1849 config ASN1
1850 tristate
1851 help
1852 Build a simple ASN.1 grammar compiler that produces a bytecode output
1853 that can be interpreted by the ASN.1 stream decoder and used to
1854 inform it as to what tags are to be expected in a stream and what
1855 functions to call on what tags.
1857 source "kernel/Kconfig.locks"