| blob | 0a2f09a80e90aaf01803419540db7d98d379b3ad |
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 EVENTFD
937 help
938 Provides a memory resource controller that manages both anonymous
939 memory and page cache. (See Documentation/cgroups/memory.txt)
941 Note that setting this option increases fixed memory overhead
942 associated with each page of memory in the system. By this,
943 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
944 usage tracking struct at boot. Total amount of this is printed out
945 at boot.
947 Only enable when you're ok with these trade offs and really
948 sure you need the memory resource controller. Even when you enable
949 this, you can set "cgroup_disable=memory" at your boot option to
950 disable memory resource controller and you can avoid overheads.
951 (and lose benefits of memory resource controller)
953 config MEMCG_SWAP
954 bool "Memory Resource Controller Swap Extension"
955 depends on MEMCG && SWAP
956 help
957 Add swap management feature to memory resource controller. When you
958 enable this, you can limit mem+swap usage per cgroup. In other words,
959 when you disable this, memory resource controller has no cares to
960 usage of swap...a process can exhaust all of the swap. This extension
961 is useful when you want to avoid exhaustion swap but this itself
962 adds more overheads and consumes memory for remembering information.
963 Especially if you use 32bit system or small memory system, please
964 be careful about enabling this. When memory resource controller
965 is disabled by boot option, this will be automatically disabled and
966 there will be no overhead from this. Even when you set this config=y,
967 if boot option "swapaccount=0" is set, swap will not be accounted.
968 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
969 size is 4096bytes, 512k per 1Gbytes of swap.
970 config MEMCG_SWAP_ENABLED
971 bool "Memory Resource Controller Swap Extension enabled by default"
972 depends on MEMCG_SWAP
973 default y
974 help
975 Memory Resource Controller Swap Extension comes with its price in
976 a bigger memory consumption. General purpose distribution kernels
977 which want to enable the feature but keep it disabled by default
978 and let the user enable it by swapaccount=1 boot command line
979 parameter should have this option unselected.
980 For those who want to have the feature enabled by default should
981 select this option (if, for some reason, they need to disable it
982 then swapaccount=0 does the trick).
983 config MEMCG_KMEM
984 bool "Memory Resource Controller Kernel Memory accounting"
985 depends on MEMCG
986 depends on SLUB || SLAB
987 help
988 The Kernel Memory extension for Memory Resource Controller can limit
989 the amount of memory used by kernel objects in the system. Those are
990 fundamentally different from the entities handled by the standard
991 Memory Controller, which are page-based, and can be swapped. Users of
992 the kmem extension can use it to guarantee that no group of processes
993 will ever exhaust kernel resources alone.
995 WARNING: Current implementation lacks reclaim support. That means
996 allocation attempts will fail when close to the limit even if there
997 are plenty of kmem available for reclaim. That makes this option
998 unusable in real life so DO NOT SELECT IT unless for development
999 purposes.
1001 config CGROUP_HUGETLB
1002 bool "HugeTLB Resource Controller for Control Groups"
1003 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
1004 default n
1005 help
1006 Provides a cgroup Resource Controller for HugeTLB pages.
1007 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1008 The limit is enforced during page fault. Since HugeTLB doesn't
1009 support page reclaim, enforcing the limit at page fault time implies
1010 that, the application will get SIGBUS signal if it tries to access
1011 HugeTLB pages beyond its limit. This requires the application to know
1012 beforehand how much HugeTLB pages it would require for its use. The
1013 control group is tracked in the third page lru pointer. This means
1014 that we cannot use the controller with huge page less than 3 pages.
1016 config CGROUP_PERF
1017 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1018 depends on PERF_EVENTS && CGROUPS
1019 help
1020 This option extends the per-cpu mode to restrict monitoring to
1021 threads which belong to the cgroup specified and run on the
1022 designated cpu.
1024 Say N if unsure.
1026 menuconfig CGROUP_SCHED
1027 bool "Group CPU scheduler"
1028 default n
1029 help
1030 This feature lets CPU scheduler recognize task groups and control CPU
1031 bandwidth allocation to such task groups. It uses cgroups to group
1032 tasks.
1034 if CGROUP_SCHED
1035 config FAIR_GROUP_SCHED
1036 bool "Group scheduling for SCHED_OTHER"
1037 depends on CGROUP_SCHED
1038 default CGROUP_SCHED
1040 config CFS_BANDWIDTH
1041 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1042 depends on FAIR_GROUP_SCHED
1043 default n
1044 help
1045 This option allows users to define CPU bandwidth rates (limits) for
1046 tasks running within the fair group scheduler. Groups with no limit
1047 set are considered to be unconstrained and will run with no
1048 restriction.
1049 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1051 config RT_GROUP_SCHED
1052 bool "Group scheduling for SCHED_RR/FIFO"
1053 depends on CGROUP_SCHED
1054 default n
1055 help
1056 This feature lets you explicitly allocate real CPU bandwidth
1057 to task groups. If enabled, it will also make it impossible to
1058 schedule realtime tasks for non-root users until you allocate
1059 realtime bandwidth for them.
1060 See Documentation/scheduler/sched-rt-group.txt for more information.
1062 endif #CGROUP_SCHED
1064 config BLK_CGROUP
1065 bool "Block IO controller"
1066 depends on BLOCK
1067 default n
1068 ---help---
1069 Generic block IO controller cgroup interface. This is the common
1070 cgroup interface which should be used by various IO controlling
1071 policies.
1073 Currently, CFQ IO scheduler uses it to recognize task groups and
1074 control disk bandwidth allocation (proportional time slice allocation)
1075 to such task groups. It is also used by bio throttling logic in
1076 block layer to implement upper limit in IO rates on a device.
1078 This option only enables generic Block IO controller infrastructure.
1079 One needs to also enable actual IO controlling logic/policy. For
1080 enabling proportional weight division of disk bandwidth in CFQ, set
1081 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1082 CONFIG_BLK_DEV_THROTTLING=y.
1084 See Documentation/cgroups/blkio-controller.txt for more information.
1086 config DEBUG_BLK_CGROUP
1087 bool "Enable Block IO controller debugging"
1088 depends on BLK_CGROUP
1089 default n
1090 ---help---
1091 Enable some debugging help. Currently it exports additional stat
1092 files in a cgroup which can be useful for debugging.
1094 endif # CGROUPS
1096 config CHECKPOINT_RESTORE
1097 bool "Checkpoint/restore support" if EXPERT
1098 default n
1099 help
1100 Enables additional kernel features in a sake of checkpoint/restore.
1101 In particular it adds auxiliary prctl codes to setup process text,
1102 data and heap segment sizes, and a few additional /proc filesystem
1103 entries.
1105 If unsure, say N here.
1107 menuconfig NAMESPACES
1108 bool "Namespaces support" if EXPERT
1109 default !EXPERT
1110 help
1111 Provides the way to make tasks work with different objects using
1112 the same id. For example same IPC id may refer to different objects
1113 or same user id or pid may refer to different tasks when used in
1114 different namespaces.
1116 if NAMESPACES
1118 config UTS_NS
1119 bool "UTS namespace"
1120 default y
1121 help
1122 In this namespace tasks see different info provided with the
1123 uname() system call
1125 config IPC_NS
1126 bool "IPC namespace"
1127 depends on (SYSVIPC || POSIX_MQUEUE)
1128 default y
1129 help
1130 In this namespace tasks work with IPC ids which correspond to
1131 different IPC objects in different namespaces.
1133 config USER_NS
1134 bool "User namespace"
1135 default n
1136 help
1137 This allows containers, i.e. vservers, to use user namespaces
1138 to provide different user info for different servers.
1140 When user namespaces are enabled in the kernel it is
1141 recommended that the MEMCG and MEMCG_KMEM options also be
1142 enabled and that user-space use the memory control groups to
1143 limit the amount of memory a memory unprivileged users can
1144 use.
1146 If unsure, say N.
1148 config PID_NS
1149 bool "PID Namespaces"
1150 default y
1151 help
1152 Support process id namespaces. This allows having multiple
1153 processes with the same pid as long as they are in different
1154 pid namespaces. This is a building block of containers.
1156 config NET_NS
1157 bool "Network namespace"
1158 depends on NET
1159 default y
1160 help
1161 Allow user space to create what appear to be multiple instances
1162 of the network stack.
1164 endif # NAMESPACES
1166 config SCHED_AUTOGROUP
1167 bool "Automatic process group scheduling"
1168 select CGROUPS
1169 select CGROUP_SCHED
1170 select FAIR_GROUP_SCHED
1171 help
1172 This option optimizes the scheduler for common desktop workloads by
1173 automatically creating and populating task groups. This separation
1174 of workloads isolates aggressive CPU burners (like build jobs) from
1175 desktop applications. Task group autogeneration is currently based
1176 upon task session.
1178 config SYSFS_DEPRECATED
1179 bool "Enable deprecated sysfs features to support old userspace tools"
1180 depends on SYSFS
1181 default n
1182 help
1183 This option adds code that switches the layout of the "block" class
1184 devices, to not show up in /sys/class/block/, but only in
1185 /sys/block/.
1187 This switch is only active when the sysfs.deprecated=1 boot option is
1188 passed or the SYSFS_DEPRECATED_V2 option is set.
1190 This option allows new kernels to run on old distributions and tools,
1191 which might get confused by /sys/class/block/. Since 2007/2008 all
1192 major distributions and tools handle this just fine.
1194 Recent distributions and userspace tools after 2009/2010 depend on
1195 the existence of /sys/class/block/, and will not work with this
1196 option enabled.
1198 Only if you are using a new kernel on an old distribution, you might
1199 need to say Y here.
1201 config SYSFS_DEPRECATED_V2
1202 bool "Enable deprecated sysfs features by default"
1203 default n
1204 depends on SYSFS
1205 depends on SYSFS_DEPRECATED
1206 help
1207 Enable deprecated sysfs by default.
1209 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1210 option.
1212 Only if you are using a new kernel on an old distribution, you might
1213 need to say Y here. Even then, odds are you would not need it
1214 enabled, you can always pass the boot option if absolutely necessary.
1216 config RELAY
1217 bool "Kernel->user space relay support (formerly relayfs)"
1218 help
1219 This option enables support for relay interface support in
1220 certain file systems (such as debugfs).
1221 It is designed to provide an efficient mechanism for tools and
1222 facilities to relay large amounts of data from kernel space to
1223 user space.
1225 If unsure, say N.
1227 config BLK_DEV_INITRD
1228 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1229 depends on BROKEN || !FRV
1230 help
1231 The initial RAM filesystem is a ramfs which is loaded by the
1232 boot loader (loadlin or lilo) and that is mounted as root
1233 before the normal boot procedure. It is typically used to
1234 load modules needed to mount the "real" root file system,
1235 etc. See <file:Documentation/initrd.txt> for details.
1237 If RAM disk support (BLK_DEV_RAM) is also included, this
1238 also enables initial RAM disk (initrd) support and adds
1239 15 Kbytes (more on some other architectures) to the kernel size.
1241 If unsure say Y.
1243 if BLK_DEV_INITRD
1245 source "usr/Kconfig"
1247 endif
1249 config CC_OPTIMIZE_FOR_SIZE
1250 bool "Optimize for size"
1251 help
1252 Enabling this option will pass "-Os" instead of "-O2" to gcc
1253 resulting in a smaller kernel.
1255 If unsure, say N.
1257 config SYSCTL
1258 bool
1260 config ANON_INODES
1261 bool
1263 config HAVE_UID16
1264 bool
1266 config SYSCTL_EXCEPTION_TRACE
1267 bool
1268 help
1269 Enable support for /proc/sys/debug/exception-trace.
1271 config SYSCTL_ARCH_UNALIGN_NO_WARN
1272 bool
1273 help
1274 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1275 Allows arch to define/use @no_unaligned_warning to possibly warn
1276 about unaligned access emulation going on under the hood.
1278 config SYSCTL_ARCH_UNALIGN_ALLOW
1279 bool
1280 help
1281 Enable support for /proc/sys/kernel/unaligned-trap
1282 Allows arches to define/use @unaligned_enabled to runtime toggle
1283 the unaligned access emulation.
1284 see arch/parisc/kernel/unaligned.c for reference
1286 config HAVE_PCSPKR_PLATFORM
1287 bool
1289 menuconfig EXPERT
1290 bool "Configure standard kernel features (expert users)"
1291 # Unhide debug options, to make the on-by-default options visible
1292 select DEBUG_KERNEL
1293 help
1294 This option allows certain base kernel options and settings
1295 to be disabled or tweaked. This is for specialized
1296 environments which can tolerate a "non-standard" kernel.
1297 Only use this if you really know what you are doing.
1299 config UID16
1300 bool "Enable 16-bit UID system calls" if EXPERT
1301 depends on HAVE_UID16
1302 default y
1303 help
1304 This enables the legacy 16-bit UID syscall wrappers.
1306 config SYSFS_SYSCALL
1307 bool "Sysfs syscall support" if EXPERT
1308 default y
1309 ---help---
1310 sys_sysfs is an obsolete system call no longer supported in libc.
1311 Note that disabling this option is more secure but might break
1312 compatibility with some systems.
1314 If unsure say Y here.
1316 config SYSCTL_SYSCALL
1317 bool "Sysctl syscall support" if EXPERT
1318 depends on PROC_SYSCTL
1319 default n
1320 select SYSCTL
1321 ---help---
1322 sys_sysctl uses binary paths that have been found challenging
1323 to properly maintain and use. The interface in /proc/sys
1324 using paths with ascii names is now the primary path to this
1325 information.
1327 Almost nothing using the binary sysctl interface so if you are
1328 trying to save some space it is probably safe to disable this,
1329 making your kernel marginally smaller.
1331 If unsure say N here.
1333 config KALLSYMS
1334 bool "Load all symbols for debugging/ksymoops" if EXPERT
1335 default y
1336 help
1337 Say Y here to let the kernel print out symbolic crash information and
1338 symbolic stack backtraces. This increases the size of the kernel
1339 somewhat, as all symbols have to be loaded into the kernel image.
1341 config KALLSYMS_ALL
1342 bool "Include all symbols in kallsyms"
1343 depends on DEBUG_KERNEL && KALLSYMS
1344 help
1345 Normally kallsyms only contains the symbols of functions for nicer
1346 OOPS messages and backtraces (i.e., symbols from the text and inittext
1347 sections). This is sufficient for most cases. And only in very rare
1348 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1349 names of variables from the data sections, etc).
1351 This option makes sure that all symbols are loaded into the kernel
1352 image (i.e., symbols from all sections) in cost of increased kernel
1353 size (depending on the kernel configuration, it may be 300KiB or
1354 something like this).
1356 Say N unless you really need all symbols.
1358 config PRINTK
1359 default y
1360 bool "Enable support for printk" if EXPERT
1361 select IRQ_WORK
1362 help
1363 This option enables normal printk support. Removing it
1364 eliminates most of the message strings from the kernel image
1365 and makes the kernel more or less silent. As this makes it
1366 very difficult to diagnose system problems, saying N here is
1367 strongly discouraged.
1369 config BUG
1370 bool "BUG() support" if EXPERT
1371 default y
1372 help
1373 Disabling this option eliminates support for BUG and WARN, reducing
1374 the size of your kernel image and potentially quietly ignoring
1375 numerous fatal conditions. You should only consider disabling this
1376 option for embedded systems with no facilities for reporting errors.
1377 Just say Y.
1379 config ELF_CORE
1380 depends on COREDUMP
1381 default y
1382 bool "Enable ELF core dumps" if EXPERT
1383 help
1384 Enable support for generating core dumps. Disabling saves about 4k.
1387 config PCSPKR_PLATFORM
1388 bool "Enable PC-Speaker support" if EXPERT
1389 depends on HAVE_PCSPKR_PLATFORM
1390 select I8253_LOCK
1391 default y
1392 help
1393 This option allows to disable the internal PC-Speaker
1394 support, saving some memory.
1396 config BASE_FULL
1397 default y
1398 bool "Enable full-sized data structures for core" if EXPERT
1399 help
1400 Disabling this option reduces the size of miscellaneous core
1401 kernel data structures. This saves memory on small machines,
1402 but may reduce performance.
1404 config FUTEX
1405 bool "Enable futex support" if EXPERT
1406 default y
1407 select RT_MUTEXES
1408 help
1409 Disabling this option will cause the kernel to be built without
1410 support for "fast userspace mutexes". The resulting kernel may not
1411 run glibc-based applications correctly.
1413 config HAVE_FUTEX_CMPXCHG
1414 bool
1415 help
1416 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1417 is implemented and always working. This removes a couple of runtime
1418 checks.
1420 config EPOLL
1421 bool "Enable eventpoll support" if EXPERT
1422 default y
1423 select ANON_INODES
1424 help
1425 Disabling this option will cause the kernel to be built without
1426 support for epoll family of system calls.
1428 config SIGNALFD
1429 bool "Enable signalfd() system call" if EXPERT
1430 select ANON_INODES
1431 default y
1432 help
1433 Enable the signalfd() system call that allows to receive signals
1434 on a file descriptor.
1436 If unsure, say Y.
1438 config TIMERFD
1439 bool "Enable timerfd() system call" if EXPERT
1440 select ANON_INODES
1441 default y
1442 help
1443 Enable the timerfd() system call that allows to receive timer
1444 events on a file descriptor.
1446 If unsure, say Y.
1448 config EVENTFD
1449 bool "Enable eventfd() system call" if EXPERT
1450 select ANON_INODES
1451 default y
1452 help
1453 Enable the eventfd() system call that allows to receive both
1454 kernel notification (ie. KAIO) or userspace notifications.
1456 If unsure, say Y.
1458 config SHMEM
1459 bool "Use full shmem filesystem" if EXPERT
1460 default y
1461 depends on MMU
1462 help
1463 The shmem is an internal filesystem used to manage shared memory.
1464 It is backed by swap and manages resource limits. It is also exported
1465 to userspace as tmpfs if TMPFS is enabled. Disabling this
1466 option replaces shmem and tmpfs with the much simpler ramfs code,
1467 which may be appropriate on small systems without swap.
1469 config AIO
1470 bool "Enable AIO support" if EXPERT
1471 default y
1472 help
1473 This option enables POSIX asynchronous I/O which may by used
1474 by some high performance threaded applications. Disabling
1475 this option saves about 7k.
1477 config PCI_QUIRKS
1478 default y
1479 bool "Enable PCI quirk workarounds" if EXPERT
1480 depends on PCI
1481 help
1482 This enables workarounds for various PCI chipset
1483 bugs/quirks. Disable this only if your target machine is
1484 unaffected by PCI quirks.
1486 config EMBEDDED
1487 bool "Embedded system"
1488 option allnoconfig_y
1489 select EXPERT
1490 help
1491 This option should be enabled if compiling the kernel for
1492 an embedded system so certain expert options are available
1493 for configuration.
1495 config HAVE_PERF_EVENTS
1496 bool
1497 help
1498 See tools/perf/design.txt for details.
1500 config PERF_USE_VMALLOC
1501 bool
1502 help
1503 See tools/perf/design.txt for details
1505 menu "Kernel Performance Events And Counters"
1507 config PERF_EVENTS
1508 bool "Kernel performance events and counters"
1509 default y if PROFILING
1510 depends on HAVE_PERF_EVENTS
1511 select ANON_INODES
1512 select IRQ_WORK
1513 help
1514 Enable kernel support for various performance events provided
1515 by software and hardware.
1517 Software events are supported either built-in or via the
1518 use of generic tracepoints.
1520 Most modern CPUs support performance events via performance
1521 counter registers. These registers count the number of certain
1522 types of hw events: such as instructions executed, cachemisses
1523 suffered, or branches mis-predicted - without slowing down the
1524 kernel or applications. These registers can also trigger interrupts
1525 when a threshold number of events have passed - and can thus be
1526 used to profile the code that runs on that CPU.
1528 The Linux Performance Event subsystem provides an abstraction of
1529 these software and hardware event capabilities, available via a
1530 system call and used by the "perf" utility in tools/perf/. It
1531 provides per task and per CPU counters, and it provides event
1532 capabilities on top of those.
1534 Say Y if unsure.
1536 config DEBUG_PERF_USE_VMALLOC
1537 default n
1538 bool "Debug: use vmalloc to back perf mmap() buffers"
1539 depends on PERF_EVENTS && DEBUG_KERNEL
1540 select PERF_USE_VMALLOC
1541 help
1542 Use vmalloc memory to back perf mmap() buffers.
1544 Mostly useful for debugging the vmalloc code on platforms
1545 that don't require it.
1547 Say N if unsure.
1549 endmenu
1551 config VM_EVENT_COUNTERS
1552 default y
1553 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1554 help
1555 VM event counters are needed for event counts to be shown.
1556 This option allows the disabling of the VM event counters
1557 on EXPERT systems. /proc/vmstat will only show page counts
1558 if VM event counters are disabled.
1560 config SLUB_DEBUG
1561 default y
1562 bool "Enable SLUB debugging support" if EXPERT
1563 depends on SLUB && SYSFS
1564 help
1565 SLUB has extensive debug support features. Disabling these can
1566 result in significant savings in code size. This also disables
1567 SLUB sysfs support. /sys/slab will not exist and there will be
1568 no support for cache validation etc.
1570 config COMPAT_BRK
1571 bool "Disable heap randomization"
1572 default y
1573 help
1574 Randomizing heap placement makes heap exploits harder, but it
1575 also breaks ancient binaries (including anything libc5 based).
1576 This option changes the bootup default to heap randomization
1577 disabled, and can be overridden at runtime by setting
1578 /proc/sys/kernel/randomize_va_space to 2.
1580 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1582 choice
1583 prompt "Choose SLAB allocator"
1584 default SLUB
1585 help
1586 This option allows to select a slab allocator.
1588 config SLAB
1589 bool "SLAB"
1590 help
1591 The regular slab allocator that is established and known to work
1592 well in all environments. It organizes cache hot objects in
1593 per cpu and per node queues.
1595 config SLUB
1596 bool "SLUB (Unqueued Allocator)"
1597 help
1598 SLUB is a slab allocator that minimizes cache line usage
1599 instead of managing queues of cached objects (SLAB approach).
1600 Per cpu caching is realized using slabs of objects instead
1601 of queues of objects. SLUB can use memory efficiently
1602 and has enhanced diagnostics. SLUB is the default choice for
1603 a slab allocator.
1605 config SLOB
1606 depends on EXPERT
1607 bool "SLOB (Simple Allocator)"
1608 help
1609 SLOB replaces the stock allocator with a drastically simpler
1610 allocator. SLOB is generally more space efficient but
1611 does not perform as well on large systems.
1613 endchoice
1615 config SLUB_CPU_PARTIAL
1616 default y
1617 depends on SLUB && SMP
1618 bool "SLUB per cpu partial cache"
1619 help
1620 Per cpu partial caches accellerate objects allocation and freeing
1621 that is local to a processor at the price of more indeterminism
1622 in the latency of the free. On overflow these caches will be cleared
1623 which requires the taking of locks that may cause latency spikes.
1624 Typically one would choose no for a realtime system.
1626 config MMAP_ALLOW_UNINITIALIZED
1627 bool "Allow mmapped anonymous memory to be uninitialized"
1628 depends on EXPERT && !MMU
1629 default n
1630 help
1631 Normally, and according to the Linux spec, anonymous memory obtained
1632 from mmap() has it's contents cleared before it is passed to
1633 userspace. Enabling this config option allows you to request that
1634 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1635 providing a huge performance boost. If this option is not enabled,
1636 then the flag will be ignored.
1638 This is taken advantage of by uClibc's malloc(), and also by
1639 ELF-FDPIC binfmt's brk and stack allocator.
1641 Because of the obvious security issues, this option should only be
1642 enabled on embedded devices where you control what is run in
1643 userspace. Since that isn't generally a problem on no-MMU systems,
1644 it is normally safe to say Y here.
1646 See Documentation/nommu-mmap.txt for more information.
1648 config SYSTEM_TRUSTED_KEYRING
1649 bool "Provide system-wide ring of trusted keys"
1650 depends on KEYS
1651 help
1652 Provide a system keyring to which trusted keys can be added. Keys in
1653 the keyring are considered to be trusted. Keys may be added at will
1654 by the kernel from compiled-in data and from hardware key stores, but
1655 userspace may only add extra keys if those keys can be verified by
1656 keys already in the keyring.
1658 Keys in this keyring are used by module signature checking.
1660 config PROFILING
1661 bool "Profiling support"
1662 help
1663 Say Y here to enable the extended profiling support mechanisms used
1664 by profilers such as OProfile.
1666 #
1667 # Place an empty function call at each tracepoint site. Can be
1668 # dynamically changed for a probe function.
1669 #
1670 config TRACEPOINTS
1671 bool
1673 source "arch/Kconfig"
1675 endmenu # General setup
1677 config HAVE_GENERIC_DMA_COHERENT
1678 bool
1679 default n
1681 config SLABINFO
1682 bool
1683 depends on PROC_FS
1684 depends on SLAB || SLUB_DEBUG
1685 default y
1687 config RT_MUTEXES
1688 boolean
1690 config BASE_SMALL
1691 int
1692 default 0 if BASE_FULL
1693 default 1 if !BASE_FULL
1695 menuconfig MODULES
1696 bool "Enable loadable module support"
1697 option modules
1698 help
1699 Kernel modules are small pieces of compiled code which can
1700 be inserted in the running kernel, rather than being
1701 permanently built into the kernel. You use the "modprobe"
1702 tool to add (and sometimes remove) them. If you say Y here,
1703 many parts of the kernel can be built as modules (by
1704 answering M instead of Y where indicated): this is most
1705 useful for infrequently used options which are not required
1706 for booting. For more information, see the man pages for
1707 modprobe, lsmod, modinfo, insmod and rmmod.
1709 If you say Y here, you will need to run "make
1710 modules_install" to put the modules under /lib/modules/
1711 where modprobe can find them (you may need to be root to do
1712 this).
1714 If unsure, say Y.
1716 if MODULES
1718 config MODULE_FORCE_LOAD
1719 bool "Forced module loading"
1720 default n
1721 help
1722 Allow loading of modules without version information (ie. modprobe
1723 --force). Forced module loading sets the 'F' (forced) taint flag and
1724 is usually a really bad idea.
1726 config MODULE_UNLOAD
1727 bool "Module unloading"
1728 help
1729 Without this option you will not be able to unload any
1730 modules (note that some modules may not be unloadable
1731 anyway), which makes your kernel smaller, faster
1732 and simpler. If unsure, say Y.
1734 config MODULE_FORCE_UNLOAD
1735 bool "Forced module unloading"
1736 depends on MODULE_UNLOAD
1737 help
1738 This option allows you to force a module to unload, even if the
1739 kernel believes it is unsafe: the kernel will remove the module
1740 without waiting for anyone to stop using it (using the -f option to
1741 rmmod). This is mainly for kernel developers and desperate users.
1742 If unsure, say N.
1744 config MODVERSIONS
1745 bool "Module versioning support"
1746 help
1747 Usually, you have to use modules compiled with your kernel.
1748 Saying Y here makes it sometimes possible to use modules
1749 compiled for different kernels, by adding enough information
1750 to the modules to (hopefully) spot any changes which would
1751 make them incompatible with the kernel you are running. If
1752 unsure, say N.
1754 config MODULE_SRCVERSION_ALL
1755 bool "Source checksum for all modules"
1756 help
1757 Modules which contain a MODULE_VERSION get an extra "srcversion"
1758 field inserted into their modinfo section, which contains a
1759 sum of the source files which made it. This helps maintainers
1760 see exactly which source was used to build a module (since
1761 others sometimes change the module source without updating
1762 the version). With this option, such a "srcversion" field
1763 will be created for all modules. If unsure, say N.
1765 config MODULE_SIG
1766 bool "Module signature verification"
1767 depends on MODULES
1768 select SYSTEM_TRUSTED_KEYRING
1769 select KEYS
1770 select CRYPTO
1771 select ASYMMETRIC_KEY_TYPE
1772 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1773 select PUBLIC_KEY_ALGO_RSA
1774 select ASN1
1775 select OID_REGISTRY
1776 select X509_CERTIFICATE_PARSER
1777 help
1778 Check modules for valid signatures upon load: the signature
1779 is simply appended to the module. For more information see
1780 Documentation/module-signing.txt.
1782 !!!WARNING!!! If you enable this option, you MUST make sure that the
1783 module DOES NOT get stripped after being signed. This includes the
1784 debuginfo strip done by some packagers (such as rpmbuild) and
1785 inclusion into an initramfs that wants the module size reduced.
1787 config MODULE_SIG_FORCE
1788 bool "Require modules to be validly signed"
1789 depends on MODULE_SIG
1790 help
1791 Reject unsigned modules or signed modules for which we don't have a
1792 key. Without this, such modules will simply taint the kernel.
1794 config MODULE_SIG_ALL
1795 bool "Automatically sign all modules"
1796 default y
1797 depends on MODULE_SIG
1798 help
1799 Sign all modules during make modules_install. Without this option,
1800 modules must be signed manually, using the scripts/sign-file tool.
1802 comment "Do not forget to sign required modules with scripts/sign-file"
1803 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1805 choice
1806 prompt "Which hash algorithm should modules be signed with?"
1807 depends on MODULE_SIG
1808 help
1809 This determines which sort of hashing algorithm will be used during
1810 signature generation. This algorithm _must_ be built into the kernel
1811 directly so that signature verification can take place. It is not
1812 possible to load a signed module containing the algorithm to check
1813 the signature on that module.
1815 config MODULE_SIG_SHA1
1816 bool "Sign modules with SHA-1"
1817 select CRYPTO_SHA1
1819 config MODULE_SIG_SHA224
1820 bool "Sign modules with SHA-224"
1821 select CRYPTO_SHA256
1823 config MODULE_SIG_SHA256
1824 bool "Sign modules with SHA-256"
1825 select CRYPTO_SHA256
1827 config MODULE_SIG_SHA384
1828 bool "Sign modules with SHA-384"
1829 select CRYPTO_SHA512
1831 config MODULE_SIG_SHA512
1832 bool "Sign modules with SHA-512"
1833 select CRYPTO_SHA512
1835 endchoice
1837 config MODULE_SIG_HASH
1838 string
1839 depends on MODULE_SIG
1840 default "sha1" if MODULE_SIG_SHA1
1841 default "sha224" if MODULE_SIG_SHA224
1842 default "sha256" if MODULE_SIG_SHA256
1843 default "sha384" if MODULE_SIG_SHA384
1844 default "sha512" if MODULE_SIG_SHA512
1846 endif # MODULES
1848 config INIT_ALL_POSSIBLE
1849 bool
1850 help
1851 Back when each arch used to define their own cpu_online_mask and
1852 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1853 with all 1s, and others with all 0s. When they were centralised,
1854 it was better to provide this option than to break all the archs
1855 and have several arch maintainers pursuing me down dark alleys.
1857 config STOP_MACHINE
1858 bool
1859 default y
1860 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1861 help
1862 Need stop_machine() primitive.
1864 source "block/Kconfig"
1866 config PREEMPT_NOTIFIERS
1867 bool
1869 config PADATA
1870 depends on SMP
1871 bool
1873 # Can be selected by architectures with broken toolchains
1874 # that get confused by correct const<->read_only section
1875 # mappings
1876 config BROKEN_RODATA
1877 bool
1879 config ASN1
1880 tristate
1881 help
1882 Build a simple ASN.1 grammar compiler that produces a bytecode output
1883 that can be interpreted by the ASN.1 stream decoder and used to
1884 inform it as to what tags are to be expected in a stream and what
1885 functions to call on what tags.
1887 source "kernel/Kconfig.locks"