| blob | e1f5e082b26bd82187ea00521dbe55aa4068981c |
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 CROSS_MEMORY_ATTACH
265 bool "Enable process_vm_readv/writev syscalls"
266 depends on MMU
267 default y
268 help
269 Enabling this option adds the system calls process_vm_readv and
270 process_vm_writev which allow a process with the correct privileges
271 to directly read from or write to to another process's address space.
272 See the man page for more details.
274 config FHANDLE
275 bool "open by fhandle syscalls"
276 select EXPORTFS
277 help
278 If you say Y here, a user level program will be able to map
279 file names to handle and then later use the handle for
280 different file system operations. This is useful in implementing
281 userspace file servers, which now track files using handles instead
282 of names. The handle would remain the same even if file names
283 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
284 syscalls.
286 config USELIB
287 bool "uselib syscall"
288 default y
289 help
290 This option enables the uselib syscall, a system call used in the
291 dynamic linker from libc5 and earlier. glibc does not use this
292 system call. If you intend to run programs built on libc5 or
293 earlier, you may need to enable this syscall. Current systems
294 running glibc can safely disable this.
296 config AUDIT
297 bool "Auditing support"
298 depends on NET
299 help
300 Enable auditing infrastructure that can be used with another
301 kernel subsystem, such as SELinux (which requires this for
302 logging of avc messages output). Does not do system-call
303 auditing without CONFIG_AUDITSYSCALL.
305 config HAVE_ARCH_AUDITSYSCALL
306 bool
308 config AUDITSYSCALL
309 bool "Enable system-call auditing support"
310 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
311 default y if SECURITY_SELINUX
312 help
313 Enable low-overhead system-call auditing infrastructure that
314 can be used independently or with another kernel subsystem,
315 such as SELinux.
317 config AUDIT_WATCH
318 def_bool y
319 depends on AUDITSYSCALL
320 select FSNOTIFY
322 config AUDIT_TREE
323 def_bool y
324 depends on AUDITSYSCALL
325 select FSNOTIFY
327 source "kernel/irq/Kconfig"
328 source "kernel/time/Kconfig"
330 menu "CPU/Task time and stats accounting"
332 config VIRT_CPU_ACCOUNTING
333 bool
335 choice
336 prompt "Cputime accounting"
337 default TICK_CPU_ACCOUNTING if !PPC64
338 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
340 # Kind of a stub config for the pure tick based cputime accounting
341 config TICK_CPU_ACCOUNTING
342 bool "Simple tick based cputime accounting"
343 depends on !S390 && !NO_HZ_FULL
344 help
345 This is the basic tick based cputime accounting that maintains
346 statistics about user, system and idle time spent on per jiffies
347 granularity.
349 If unsure, say Y.
351 config VIRT_CPU_ACCOUNTING_NATIVE
352 bool "Deterministic task and CPU time accounting"
353 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
354 select VIRT_CPU_ACCOUNTING
355 help
356 Select this option to enable more accurate task and CPU time
357 accounting. This is done by reading a CPU counter on each
358 kernel entry and exit and on transitions within the kernel
359 between system, softirq and hardirq state, so there is a
360 small performance impact. In the case of s390 or IBM POWER > 5,
361 this also enables accounting of stolen time on logically-partitioned
362 systems.
364 config VIRT_CPU_ACCOUNTING_GEN
365 bool "Full dynticks CPU time accounting"
366 depends on HAVE_CONTEXT_TRACKING
367 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
368 select VIRT_CPU_ACCOUNTING
369 select CONTEXT_TRACKING
370 help
371 Select this option to enable task and CPU time accounting on full
372 dynticks systems. This accounting is implemented by watching every
373 kernel-user boundaries using the context tracking subsystem.
374 The accounting is thus performed at the expense of some significant
375 overhead.
377 For now this is only useful if you are working on the full
378 dynticks subsystem development.
380 If unsure, say N.
382 config IRQ_TIME_ACCOUNTING
383 bool "Fine granularity task level IRQ time accounting"
384 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
385 help
386 Select this option to enable fine granularity task irq time
387 accounting. This is done by reading a timestamp on each
388 transitions between softirq and hardirq state, so there can be a
389 small performance impact.
391 If in doubt, say N here.
393 endchoice
395 config BSD_PROCESS_ACCT
396 bool "BSD Process Accounting"
397 help
398 If you say Y here, a user level program will be able to instruct the
399 kernel (via a special system call) to write process accounting
400 information to a file: whenever a process exits, information about
401 that process will be appended to the file by the kernel. The
402 information includes things such as creation time, owning user,
403 command name, memory usage, controlling terminal etc. (the complete
404 list is in the struct acct in <file:include/linux/acct.h>). It is
405 up to the user level program to do useful things with this
406 information. This is generally a good idea, so say Y.
408 config BSD_PROCESS_ACCT_V3
409 bool "BSD Process Accounting version 3 file format"
410 depends on BSD_PROCESS_ACCT
411 default n
412 help
413 If you say Y here, the process accounting information is written
414 in a new file format that also logs the process IDs of each
415 process and it's parent. Note that this file format is incompatible
416 with previous v0/v1/v2 file formats, so you will need updated tools
417 for processing it. A preliminary version of these tools is available
418 at <http://www.gnu.org/software/acct/>.
420 config TASKSTATS
421 bool "Export task/process statistics through netlink"
422 depends on NET
423 default n
424 help
425 Export selected statistics for tasks/processes through the
426 generic netlink interface. Unlike BSD process accounting, the
427 statistics are available during the lifetime of tasks/processes as
428 responses to commands. Like BSD accounting, they are sent to user
429 space on task exit.
431 Say N if unsure.
433 config TASK_DELAY_ACCT
434 bool "Enable per-task delay accounting"
435 depends on TASKSTATS
436 help
437 Collect information on time spent by a task waiting for system
438 resources like cpu, synchronous block I/O completion and swapping
439 in pages. Such statistics can help in setting a task's priorities
440 relative to other tasks for cpu, io, rss limits etc.
442 Say N if unsure.
444 config TASK_XACCT
445 bool "Enable extended accounting over taskstats"
446 depends on TASKSTATS
447 help
448 Collect extended task accounting data and send the data
449 to userland for processing over the taskstats interface.
451 Say N if unsure.
453 config TASK_IO_ACCOUNTING
454 bool "Enable per-task storage I/O accounting"
455 depends on TASK_XACCT
456 help
457 Collect information on the number of bytes of storage I/O which this
458 task has caused.
460 Say N if unsure.
462 endmenu # "CPU/Task time and stats accounting"
464 menu "RCU Subsystem"
466 choice
467 prompt "RCU Implementation"
468 default TREE_RCU
470 config TREE_RCU
471 bool "Tree-based hierarchical RCU"
472 depends on !PREEMPT && SMP
473 select IRQ_WORK
474 help
475 This option selects the RCU implementation that is
476 designed for very large SMP system with hundreds or
477 thousands of CPUs. It also scales down nicely to
478 smaller systems.
480 config TREE_PREEMPT_RCU
481 bool "Preemptible tree-based hierarchical RCU"
482 depends on PREEMPT
483 select IRQ_WORK
484 help
485 This option selects the RCU implementation that is
486 designed for very large SMP systems with hundreds or
487 thousands of CPUs, but for which real-time response
488 is also required. It also scales down nicely to
489 smaller systems.
491 Select this option if you are unsure.
493 config TINY_RCU
494 bool "UP-only small-memory-footprint RCU"
495 depends on !PREEMPT && !SMP
496 help
497 This option selects the RCU implementation that is
498 designed for UP systems from which real-time response
499 is not required. This option greatly reduces the
500 memory footprint of RCU.
502 endchoice
504 config PREEMPT_RCU
505 def_bool TREE_PREEMPT_RCU
506 help
507 This option enables preemptible-RCU code that is common between
508 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
510 config RCU_STALL_COMMON
511 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
512 help
513 This option enables RCU CPU stall code that is common between
514 the TINY and TREE variants of RCU. The purpose is to allow
515 the tiny variants to disable RCU CPU stall warnings, while
516 making these warnings mandatory for the tree variants.
518 config CONTEXT_TRACKING
519 bool
521 config RCU_USER_QS
522 bool "Consider userspace as in RCU extended quiescent state"
523 depends on HAVE_CONTEXT_TRACKING && SMP
524 select CONTEXT_TRACKING
525 help
526 This option sets hooks on kernel / userspace boundaries and
527 puts RCU in extended quiescent state when the CPU runs in
528 userspace. It means that when a CPU runs in userspace, it is
529 excluded from the global RCU state machine and thus doesn't
530 try to keep the timer tick on for RCU.
532 Unless you want to hack and help the development of the full
533 dynticks mode, you shouldn't enable this option. It also
534 adds unnecessary overhead.
536 If unsure say N
538 config CONTEXT_TRACKING_FORCE
539 bool "Force context tracking"
540 depends on CONTEXT_TRACKING
541 default y if !NO_HZ_FULL
542 help
543 The major pre-requirement for full dynticks to work is to
544 support the context tracking subsystem. But there are also
545 other dependencies to provide in order to make the full
546 dynticks working.
548 This option stands for testing when an arch implements the
549 context tracking backend but doesn't yet fullfill all the
550 requirements to make the full dynticks feature working.
551 Without the full dynticks, there is no way to test the support
552 for context tracking and the subsystems that rely on it: RCU
553 userspace extended quiescent state and tickless cputime
554 accounting. This option copes with the absence of the full
555 dynticks subsystem by forcing the context tracking on all
556 CPUs in the system.
558 Say Y only if you're working on the development of an
559 architecture backend for the context tracking.
561 Say N otherwise, this option brings an overhead that you
562 don't want in production.
565 config RCU_FANOUT
566 int "Tree-based hierarchical RCU fanout value"
567 range 2 64 if 64BIT
568 range 2 32 if !64BIT
569 depends on TREE_RCU || TREE_PREEMPT_RCU
570 default 64 if 64BIT
571 default 32 if !64BIT
572 help
573 This option controls the fanout of hierarchical implementations
574 of RCU, allowing RCU to work efficiently on machines with
575 large numbers of CPUs. This value must be at least the fourth
576 root of NR_CPUS, which allows NR_CPUS to be insanely large.
577 The default value of RCU_FANOUT should be used for production
578 systems, but if you are stress-testing the RCU implementation
579 itself, small RCU_FANOUT values allow you to test large-system
580 code paths on small(er) systems.
582 Select a specific number if testing RCU itself.
583 Take the default if unsure.
585 config RCU_FANOUT_LEAF
586 int "Tree-based hierarchical RCU leaf-level fanout value"
587 range 2 RCU_FANOUT if 64BIT
588 range 2 RCU_FANOUT if !64BIT
589 depends on TREE_RCU || TREE_PREEMPT_RCU
590 default 16
591 help
592 This option controls the leaf-level fanout of hierarchical
593 implementations of RCU, and allows trading off cache misses
594 against lock contention. Systems that synchronize their
595 scheduling-clock interrupts for energy-efficiency reasons will
596 want the default because the smaller leaf-level fanout keeps
597 lock contention levels acceptably low. Very large systems
598 (hundreds or thousands of CPUs) will instead want to set this
599 value to the maximum value possible in order to reduce the
600 number of cache misses incurred during RCU's grace-period
601 initialization. These systems tend to run CPU-bound, and thus
602 are not helped by synchronized interrupts, and thus tend to
603 skew them, which reduces lock contention enough that large
604 leaf-level fanouts work well.
606 Select a specific number if testing RCU itself.
608 Select the maximum permissible value for large systems.
610 Take the default if unsure.
612 config RCU_FANOUT_EXACT
613 bool "Disable tree-based hierarchical RCU auto-balancing"
614 depends on TREE_RCU || TREE_PREEMPT_RCU
615 default n
616 help
617 This option forces use of the exact RCU_FANOUT value specified,
618 regardless of imbalances in the hierarchy. This is useful for
619 testing RCU itself, and might one day be useful on systems with
620 strong NUMA behavior.
622 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
624 Say N if unsure.
626 config RCU_FAST_NO_HZ
627 bool "Accelerate last non-dyntick-idle CPU's grace periods"
628 depends on NO_HZ_COMMON && SMP
629 default n
630 help
631 This option permits CPUs to enter dynticks-idle state even if
632 they have RCU callbacks queued, and prevents RCU from waking
633 these CPUs up more than roughly once every four jiffies (by
634 default, you can adjust this using the rcutree.rcu_idle_gp_delay
635 parameter), thus improving energy efficiency. On the other
636 hand, this option increases the duration of RCU grace periods,
637 for example, slowing down synchronize_rcu().
639 Say Y if energy efficiency is critically important, and you
640 don't care about increased grace-period durations.
642 Say N if you are unsure.
644 config TREE_RCU_TRACE
645 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
646 select DEBUG_FS
647 help
648 This option provides tracing for the TREE_RCU and
649 TREE_PREEMPT_RCU implementations, permitting Makefile to
650 trivially select kernel/rcutree_trace.c.
652 config RCU_BOOST
653 bool "Enable RCU priority boosting"
654 depends on RT_MUTEXES && PREEMPT_RCU
655 default n
656 help
657 This option boosts the priority of preempted RCU readers that
658 block the current preemptible RCU grace period for too long.
659 This option also prevents heavy loads from blocking RCU
660 callback invocation for all flavors of RCU.
662 Say Y here if you are working with real-time apps or heavy loads
663 Say N here if you are unsure.
665 config RCU_BOOST_PRIO
666 int "Real-time priority to boost RCU readers to"
667 range 1 99
668 depends on RCU_BOOST
669 default 1
670 help
671 This option specifies the real-time priority to which long-term
672 preempted RCU readers are to be boosted. If you are working
673 with a real-time application that has one or more CPU-bound
674 threads running at a real-time priority level, you should set
675 RCU_BOOST_PRIO to a priority higher then the highest-priority
676 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
677 of 1 is appropriate in the common case, which is real-time
678 applications that do not have any CPU-bound threads.
680 Some real-time applications might not have a single real-time
681 thread that saturates a given CPU, but instead might have
682 multiple real-time threads that, taken together, fully utilize
683 that CPU. In this case, you should set RCU_BOOST_PRIO to
684 a priority higher than the lowest-priority thread that is
685 conspiring to prevent the CPU from running any non-real-time
686 tasks. For example, if one thread at priority 10 and another
687 thread at priority 5 are between themselves fully consuming
688 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
689 set to priority 6 or higher.
691 Specify the real-time priority, or take the default if unsure.
693 config RCU_BOOST_DELAY
694 int "Milliseconds to delay boosting after RCU grace-period start"
695 range 0 3000
696 depends on RCU_BOOST
697 default 500
698 help
699 This option specifies the time to wait after the beginning of
700 a given grace period before priority-boosting preempted RCU
701 readers blocking that grace period. Note that any RCU reader
702 blocking an expedited RCU grace period is boosted immediately.
704 Accept the default if unsure.
706 config RCU_NOCB_CPU
707 bool "Offload RCU callback processing from boot-selected CPUs"
708 depends on TREE_RCU || TREE_PREEMPT_RCU
709 default n
710 help
711 Use this option to reduce OS jitter for aggressive HPC or
712 real-time workloads. It can also be used to offload RCU
713 callback invocation to energy-efficient CPUs in battery-powered
714 asymmetric multiprocessors.
716 This option offloads callback invocation from the set of
717 CPUs specified at boot time by the rcu_nocbs parameter.
718 For each such CPU, a kthread ("rcuox/N") will be created to
719 invoke callbacks, where the "N" is the CPU being offloaded,
720 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
721 "s" for RCU-sched. Nothing prevents this kthread from running
722 on the specified CPUs, but (1) the kthreads may be preempted
723 between each callback, and (2) affinity or cgroups can be used
724 to force the kthreads to run on whatever set of CPUs is desired.
726 Say Y here if you want to help to debug reduced OS jitter.
727 Say N here if you are unsure.
729 choice
730 prompt "Build-forced no-CBs CPUs"
731 default RCU_NOCB_CPU_NONE
732 help
733 This option allows no-CBs CPUs (whose RCU callbacks are invoked
734 from kthreads rather than from softirq context) to be specified
735 at build time. Additional no-CBs CPUs may be specified by
736 the rcu_nocbs= boot parameter.
738 config RCU_NOCB_CPU_NONE
739 bool "No build_forced no-CBs CPUs"
740 depends on RCU_NOCB_CPU && !NO_HZ_FULL
741 help
742 This option does not force any of the CPUs to be no-CBs CPUs.
743 Only CPUs designated by the rcu_nocbs= boot parameter will be
744 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
745 kthreads whose names begin with "rcuo". All other CPUs will
746 invoke their own RCU callbacks in softirq context.
748 Select this option if you want to choose no-CBs CPUs at
749 boot time, for example, to allow testing of different no-CBs
750 configurations without having to rebuild the kernel each time.
752 config RCU_NOCB_CPU_ZERO
753 bool "CPU 0 is a build_forced no-CBs CPU"
754 depends on RCU_NOCB_CPU && !NO_HZ_FULL
755 help
756 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
757 callbacks are invoked by a per-CPU kthread whose name begins
758 with "rcuo". Additional CPUs may be designated as no-CBs
759 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
760 All other CPUs will invoke their own RCU callbacks in softirq
761 context.
763 Select this if CPU 0 needs to be a no-CBs CPU for real-time
764 or energy-efficiency reasons, but the real reason it exists
765 is to ensure that randconfig testing covers mixed systems.
767 config RCU_NOCB_CPU_ALL
768 bool "All CPUs are build_forced no-CBs CPUs"
769 depends on RCU_NOCB_CPU
770 help
771 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
772 boot parameter will be ignored. All CPUs' RCU callbacks will
773 be executed in the context of per-CPU rcuo kthreads created for
774 this purpose. Assuming that the kthreads whose names start with
775 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
776 on the remaining CPUs, but might decrease memory locality during
777 RCU-callback invocation, thus potentially degrading throughput.
779 Select this if all CPUs need to be no-CBs CPUs for real-time
780 or energy-efficiency reasons.
782 endchoice
784 endmenu # "RCU Subsystem"
786 config IKCONFIG
787 tristate "Kernel .config support"
788 ---help---
789 This option enables the complete Linux kernel ".config" file
790 contents to be saved in the kernel. It provides documentation
791 of which kernel options are used in a running kernel or in an
792 on-disk kernel. This information can be extracted from the kernel
793 image file with the script scripts/extract-ikconfig and used as
794 input to rebuild the current kernel or to build another kernel.
795 It can also be extracted from a running kernel by reading
796 /proc/config.gz if enabled (below).
798 config IKCONFIG_PROC
799 bool "Enable access to .config through /proc/config.gz"
800 depends on IKCONFIG && PROC_FS
801 ---help---
802 This option enables access to the kernel configuration file
803 through /proc/config.gz.
805 config LOG_BUF_SHIFT
806 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
807 range 12 21
808 default 17
809 depends on PRINTK
810 help
811 Select kernel log buffer size as a power of 2.
812 Examples:
813 17 => 128 KB
814 16 => 64 KB
815 15 => 32 KB
816 14 => 16 KB
817 13 => 8 KB
818 12 => 4 KB
820 #
821 # Architectures with an unreliable sched_clock() should select this:
822 #
823 config HAVE_UNSTABLE_SCHED_CLOCK
824 bool
826 config GENERIC_SCHED_CLOCK
827 bool
829 #
830 # For architectures that want to enable the support for NUMA-affine scheduler
831 # balancing logic:
832 #
833 config ARCH_SUPPORTS_NUMA_BALANCING
834 bool
836 #
837 # For architectures that know their GCC __int128 support is sound
838 #
839 config ARCH_SUPPORTS_INT128
840 bool
842 # For architectures that (ab)use NUMA to represent different memory regions
843 # all cpu-local but of different latencies, such as SuperH.
844 #
845 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
846 bool
848 #
849 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
850 config ARCH_WANTS_PROT_NUMA_PROT_NONE
851 bool
853 config ARCH_USES_NUMA_PROT_NONE
854 bool
855 default y
856 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
857 depends on NUMA_BALANCING
859 config NUMA_BALANCING_DEFAULT_ENABLED
860 bool "Automatically enable NUMA aware memory/task placement"
861 default y
862 depends on NUMA_BALANCING
863 help
864 If set, automatic NUMA balancing will be enabled if running on a NUMA
865 machine.
867 config NUMA_BALANCING
868 bool "Memory placement aware NUMA scheduler"
869 depends on ARCH_SUPPORTS_NUMA_BALANCING
870 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
871 depends on SMP && NUMA && MIGRATION
872 help
873 This option adds support for automatic NUMA aware memory/task placement.
874 The mechanism is quite primitive and is based on migrating memory when
875 it has references to the node the task is running on.
877 This system will be inactive on UMA systems.
879 menuconfig CGROUPS
880 boolean "Control Group support"
881 select KERNFS
882 help
883 This option adds support for grouping sets of processes together, for
884 use with process control subsystems such as Cpusets, CFS, memory
885 controls or device isolation.
886 See
887 - Documentation/scheduler/sched-design-CFS.txt (CFS)
888 - Documentation/cgroups/ (features for grouping, isolation
889 and resource control)
891 Say N if unsure.
893 if CGROUPS
895 config CGROUP_DEBUG
896 bool "Example debug cgroup subsystem"
897 default n
898 help
899 This option enables a simple cgroup subsystem that
900 exports useful debugging information about the cgroups
901 framework.
903 Say N if unsure.
905 config CGROUP_FREEZER
906 bool "Freezer cgroup subsystem"
907 help
908 Provides a way to freeze and unfreeze all tasks in a
909 cgroup.
911 config CGROUP_DEVICE
912 bool "Device controller for cgroups"
913 help
914 Provides a cgroup implementing whitelists for devices which
915 a process in the cgroup can mknod or open.
917 config CPUSETS
918 bool "Cpuset support"
919 help
920 This option will let you create and manage CPUSETs which
921 allow dynamically partitioning a system into sets of CPUs and
922 Memory Nodes and assigning tasks to run only within those sets.
923 This is primarily useful on large SMP or NUMA systems.
925 Say N if unsure.
927 config PROC_PID_CPUSET
928 bool "Include legacy /proc/<pid>/cpuset file"
929 depends on CPUSETS
930 default y
932 config CGROUP_CPUACCT
933 bool "Simple CPU accounting cgroup subsystem"
934 help
935 Provides a simple Resource Controller for monitoring the
936 total CPU consumed by the tasks in a cgroup.
938 config RESOURCE_COUNTERS
939 bool "Resource counters"
940 help
941 This option enables controller independent resource accounting
942 infrastructure that works with cgroups.
944 config MEMCG
945 bool "Memory Resource Controller for Control Groups"
946 depends on RESOURCE_COUNTERS
947 select EVENTFD
948 help
949 Provides a memory resource controller that manages both anonymous
950 memory and page cache. (See Documentation/cgroups/memory.txt)
952 Note that setting this option increases fixed memory overhead
953 associated with each page of memory in the system. By this,
954 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
955 usage tracking struct at boot. Total amount of this is printed out
956 at boot.
958 Only enable when you're ok with these trade offs and really
959 sure you need the memory resource controller. Even when you enable
960 this, you can set "cgroup_disable=memory" at your boot option to
961 disable memory resource controller and you can avoid overheads.
962 (and lose benefits of memory resource controller)
964 config MEMCG_SWAP
965 bool "Memory Resource Controller Swap Extension"
966 depends on MEMCG && SWAP
967 help
968 Add swap management feature to memory resource controller. When you
969 enable this, you can limit mem+swap usage per cgroup. In other words,
970 when you disable this, memory resource controller has no cares to
971 usage of swap...a process can exhaust all of the swap. This extension
972 is useful when you want to avoid exhaustion swap but this itself
973 adds more overheads and consumes memory for remembering information.
974 Especially if you use 32bit system or small memory system, please
975 be careful about enabling this. When memory resource controller
976 is disabled by boot option, this will be automatically disabled and
977 there will be no overhead from this. Even when you set this config=y,
978 if boot option "swapaccount=0" is set, swap will not be accounted.
979 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
980 size is 4096bytes, 512k per 1Gbytes of swap.
981 config MEMCG_SWAP_ENABLED
982 bool "Memory Resource Controller Swap Extension enabled by default"
983 depends on MEMCG_SWAP
984 default y
985 help
986 Memory Resource Controller Swap Extension comes with its price in
987 a bigger memory consumption. General purpose distribution kernels
988 which want to enable the feature but keep it disabled by default
989 and let the user enable it by swapaccount=1 boot command line
990 parameter should have this option unselected.
991 For those who want to have the feature enabled by default should
992 select this option (if, for some reason, they need to disable it
993 then swapaccount=0 does the trick).
994 config MEMCG_KMEM
995 bool "Memory Resource Controller Kernel Memory accounting"
996 depends on MEMCG
997 depends on SLUB || SLAB
998 help
999 The Kernel Memory extension for Memory Resource Controller can limit
1000 the amount of memory used by kernel objects in the system. Those are
1001 fundamentally different from the entities handled by the standard
1002 Memory Controller, which are page-based, and can be swapped. Users of
1003 the kmem extension can use it to guarantee that no group of processes
1004 will ever exhaust kernel resources alone.
1006 WARNING: Current implementation lacks reclaim support. That means
1007 allocation attempts will fail when close to the limit even if there
1008 are plenty of kmem available for reclaim. That makes this option
1009 unusable in real life so DO NOT SELECT IT unless for development
1010 purposes.
1012 config CGROUP_HUGETLB
1013 bool "HugeTLB Resource Controller for Control Groups"
1014 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
1015 default n
1016 help
1017 Provides a cgroup Resource Controller for HugeTLB pages.
1018 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1019 The limit is enforced during page fault. Since HugeTLB doesn't
1020 support page reclaim, enforcing the limit at page fault time implies
1021 that, the application will get SIGBUS signal if it tries to access
1022 HugeTLB pages beyond its limit. This requires the application to know
1023 beforehand how much HugeTLB pages it would require for its use. The
1024 control group is tracked in the third page lru pointer. This means
1025 that we cannot use the controller with huge page less than 3 pages.
1027 config CGROUP_PERF
1028 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1029 depends on PERF_EVENTS && CGROUPS
1030 help
1031 This option extends the per-cpu mode to restrict monitoring to
1032 threads which belong to the cgroup specified and run on the
1033 designated cpu.
1035 Say N if unsure.
1037 menuconfig CGROUP_SCHED
1038 bool "Group CPU scheduler"
1039 default n
1040 help
1041 This feature lets CPU scheduler recognize task groups and control CPU
1042 bandwidth allocation to such task groups. It uses cgroups to group
1043 tasks.
1045 if CGROUP_SCHED
1046 config FAIR_GROUP_SCHED
1047 bool "Group scheduling for SCHED_OTHER"
1048 depends on CGROUP_SCHED
1049 default CGROUP_SCHED
1051 config CFS_BANDWIDTH
1052 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1053 depends on FAIR_GROUP_SCHED
1054 default n
1055 help
1056 This option allows users to define CPU bandwidth rates (limits) for
1057 tasks running within the fair group scheduler. Groups with no limit
1058 set are considered to be unconstrained and will run with no
1059 restriction.
1060 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1062 config RT_GROUP_SCHED
1063 bool "Group scheduling for SCHED_RR/FIFO"
1064 depends on CGROUP_SCHED
1065 default n
1066 help
1067 This feature lets you explicitly allocate real CPU bandwidth
1068 to task groups. If enabled, it will also make it impossible to
1069 schedule realtime tasks for non-root users until you allocate
1070 realtime bandwidth for them.
1071 See Documentation/scheduler/sched-rt-group.txt for more information.
1073 endif #CGROUP_SCHED
1075 config BLK_CGROUP
1076 bool "Block IO controller"
1077 depends on BLOCK
1078 default n
1079 ---help---
1080 Generic block IO controller cgroup interface. This is the common
1081 cgroup interface which should be used by various IO controlling
1082 policies.
1084 Currently, CFQ IO scheduler uses it to recognize task groups and
1085 control disk bandwidth allocation (proportional time slice allocation)
1086 to such task groups. It is also used by bio throttling logic in
1087 block layer to implement upper limit in IO rates on a device.
1089 This option only enables generic Block IO controller infrastructure.
1090 One needs to also enable actual IO controlling logic/policy. For
1091 enabling proportional weight division of disk bandwidth in CFQ, set
1092 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1093 CONFIG_BLK_DEV_THROTTLING=y.
1095 See Documentation/cgroups/blkio-controller.txt for more information.
1097 config DEBUG_BLK_CGROUP
1098 bool "Enable Block IO controller debugging"
1099 depends on BLK_CGROUP
1100 default n
1101 ---help---
1102 Enable some debugging help. Currently it exports additional stat
1103 files in a cgroup which can be useful for debugging.
1105 endif # CGROUPS
1107 config CHECKPOINT_RESTORE
1108 bool "Checkpoint/restore support" if EXPERT
1109 default n
1110 help
1111 Enables additional kernel features in a sake of checkpoint/restore.
1112 In particular it adds auxiliary prctl codes to setup process text,
1113 data and heap segment sizes, and a few additional /proc filesystem
1114 entries.
1116 If unsure, say N here.
1118 menuconfig NAMESPACES
1119 bool "Namespaces support" if EXPERT
1120 default !EXPERT
1121 help
1122 Provides the way to make tasks work with different objects using
1123 the same id. For example same IPC id may refer to different objects
1124 or same user id or pid may refer to different tasks when used in
1125 different namespaces.
1127 if NAMESPACES
1129 config UTS_NS
1130 bool "UTS namespace"
1131 default y
1132 help
1133 In this namespace tasks see different info provided with the
1134 uname() system call
1136 config IPC_NS
1137 bool "IPC namespace"
1138 depends on (SYSVIPC || POSIX_MQUEUE)
1139 default y
1140 help
1141 In this namespace tasks work with IPC ids which correspond to
1142 different IPC objects in different namespaces.
1144 config USER_NS
1145 bool "User namespace"
1146 default n
1147 help
1148 This allows containers, i.e. vservers, to use user namespaces
1149 to provide different user info for different servers.
1151 When user namespaces are enabled in the kernel it is
1152 recommended that the MEMCG and MEMCG_KMEM options also be
1153 enabled and that user-space use the memory control groups to
1154 limit the amount of memory a memory unprivileged users can
1155 use.
1157 If unsure, say N.
1159 config PID_NS
1160 bool "PID Namespaces"
1161 default y
1162 help
1163 Support process id namespaces. This allows having multiple
1164 processes with the same pid as long as they are in different
1165 pid namespaces. This is a building block of containers.
1167 config NET_NS
1168 bool "Network namespace"
1169 depends on NET
1170 default y
1171 help
1172 Allow user space to create what appear to be multiple instances
1173 of the network stack.
1175 endif # NAMESPACES
1177 config SCHED_AUTOGROUP
1178 bool "Automatic process group scheduling"
1179 select CGROUPS
1180 select CGROUP_SCHED
1181 select FAIR_GROUP_SCHED
1182 help
1183 This option optimizes the scheduler for common desktop workloads by
1184 automatically creating and populating task groups. This separation
1185 of workloads isolates aggressive CPU burners (like build jobs) from
1186 desktop applications. Task group autogeneration is currently based
1187 upon task session.
1189 config SYSFS_DEPRECATED
1190 bool "Enable deprecated sysfs features to support old userspace tools"
1191 depends on SYSFS
1192 default n
1193 help
1194 This option adds code that switches the layout of the "block" class
1195 devices, to not show up in /sys/class/block/, but only in
1196 /sys/block/.
1198 This switch is only active when the sysfs.deprecated=1 boot option is
1199 passed or the SYSFS_DEPRECATED_V2 option is set.
1201 This option allows new kernels to run on old distributions and tools,
1202 which might get confused by /sys/class/block/. Since 2007/2008 all
1203 major distributions and tools handle this just fine.
1205 Recent distributions and userspace tools after 2009/2010 depend on
1206 the existence of /sys/class/block/, and will not work with this
1207 option enabled.
1209 Only if you are using a new kernel on an old distribution, you might
1210 need to say Y here.
1212 config SYSFS_DEPRECATED_V2
1213 bool "Enable deprecated sysfs features by default"
1214 default n
1215 depends on SYSFS
1216 depends on SYSFS_DEPRECATED
1217 help
1218 Enable deprecated sysfs by default.
1220 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1221 option.
1223 Only if you are using a new kernel on an old distribution, you might
1224 need to say Y here. Even then, odds are you would not need it
1225 enabled, you can always pass the boot option if absolutely necessary.
1227 config RELAY
1228 bool "Kernel->user space relay support (formerly relayfs)"
1229 help
1230 This option enables support for relay interface support in
1231 certain file systems (such as debugfs).
1232 It is designed to provide an efficient mechanism for tools and
1233 facilities to relay large amounts of data from kernel space to
1234 user space.
1236 If unsure, say N.
1238 config BLK_DEV_INITRD
1239 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1240 depends on BROKEN || !FRV
1241 help
1242 The initial RAM filesystem is a ramfs which is loaded by the
1243 boot loader (loadlin or lilo) and that is mounted as root
1244 before the normal boot procedure. It is typically used to
1245 load modules needed to mount the "real" root file system,
1246 etc. See <file:Documentation/initrd.txt> for details.
1248 If RAM disk support (BLK_DEV_RAM) is also included, this
1249 also enables initial RAM disk (initrd) support and adds
1250 15 Kbytes (more on some other architectures) to the kernel size.
1252 If unsure say Y.
1254 if BLK_DEV_INITRD
1256 source "usr/Kconfig"
1258 endif
1260 config CC_OPTIMIZE_FOR_SIZE
1261 bool "Optimize for size"
1262 help
1263 Enabling this option will pass "-Os" instead of "-O2" to gcc
1264 resulting in a smaller kernel.
1266 If unsure, say N.
1268 config SYSCTL
1269 bool
1271 config ANON_INODES
1272 bool
1274 config HAVE_UID16
1275 bool
1277 config SYSCTL_EXCEPTION_TRACE
1278 bool
1279 help
1280 Enable support for /proc/sys/debug/exception-trace.
1282 config SYSCTL_ARCH_UNALIGN_NO_WARN
1283 bool
1284 help
1285 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1286 Allows arch to define/use @no_unaligned_warning to possibly warn
1287 about unaligned access emulation going on under the hood.
1289 config SYSCTL_ARCH_UNALIGN_ALLOW
1290 bool
1291 help
1292 Enable support for /proc/sys/kernel/unaligned-trap
1293 Allows arches to define/use @unaligned_enabled to runtime toggle
1294 the unaligned access emulation.
1295 see arch/parisc/kernel/unaligned.c for reference
1297 config HAVE_PCSPKR_PLATFORM
1298 bool
1300 menuconfig EXPERT
1301 bool "Configure standard kernel features (expert users)"
1302 # Unhide debug options, to make the on-by-default options visible
1303 select DEBUG_KERNEL
1304 help
1305 This option allows certain base kernel options and settings
1306 to be disabled or tweaked. This is for specialized
1307 environments which can tolerate a "non-standard" kernel.
1308 Only use this if you really know what you are doing.
1310 config UID16
1311 bool "Enable 16-bit UID system calls" if EXPERT
1312 depends on HAVE_UID16
1313 default y
1314 help
1315 This enables the legacy 16-bit UID syscall wrappers.
1317 config SGETMASK_SYSCALL
1318 bool "sgetmask/ssetmask syscalls support" if EXPERT
1319 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1320 ---help---
1321 sys_sgetmask and sys_ssetmask are obsolete system calls
1322 no longer supported in libc but still enabled by default in some
1323 architectures.
1325 If unsure, leave the default option here.
1327 config SYSFS_SYSCALL
1328 bool "Sysfs syscall support" if EXPERT
1329 default y
1330 ---help---
1331 sys_sysfs is an obsolete system call no longer supported in libc.
1332 Note that disabling this option is more secure but might break
1333 compatibility with some systems.
1335 If unsure say Y here.
1337 config SYSCTL_SYSCALL
1338 bool "Sysctl syscall support" if EXPERT
1339 depends on PROC_SYSCTL
1340 default n
1341 select SYSCTL
1342 ---help---
1343 sys_sysctl uses binary paths that have been found challenging
1344 to properly maintain and use. The interface in /proc/sys
1345 using paths with ascii names is now the primary path to this
1346 information.
1348 Almost nothing using the binary sysctl interface so if you are
1349 trying to save some space it is probably safe to disable this,
1350 making your kernel marginally smaller.
1352 If unsure say N here.
1354 config KALLSYMS
1355 bool "Load all symbols for debugging/ksymoops" if EXPERT
1356 default y
1357 help
1358 Say Y here to let the kernel print out symbolic crash information and
1359 symbolic stack backtraces. This increases the size of the kernel
1360 somewhat, as all symbols have to be loaded into the kernel image.
1362 config KALLSYMS_ALL
1363 bool "Include all symbols in kallsyms"
1364 depends on DEBUG_KERNEL && KALLSYMS
1365 help
1366 Normally kallsyms only contains the symbols of functions for nicer
1367 OOPS messages and backtraces (i.e., symbols from the text and inittext
1368 sections). This is sufficient for most cases. And only in very rare
1369 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1370 names of variables from the data sections, etc).
1372 This option makes sure that all symbols are loaded into the kernel
1373 image (i.e., symbols from all sections) in cost of increased kernel
1374 size (depending on the kernel configuration, it may be 300KiB or
1375 something like this).
1377 Say N unless you really need all symbols.
1379 config PRINTK
1380 default y
1381 bool "Enable support for printk" if EXPERT
1382 select IRQ_WORK
1383 help
1384 This option enables normal printk support. Removing it
1385 eliminates most of the message strings from the kernel image
1386 and makes the kernel more or less silent. As this makes it
1387 very difficult to diagnose system problems, saying N here is
1388 strongly discouraged.
1390 config BUG
1391 bool "BUG() support" if EXPERT
1392 default y
1393 help
1394 Disabling this option eliminates support for BUG and WARN, reducing
1395 the size of your kernel image and potentially quietly ignoring
1396 numerous fatal conditions. You should only consider disabling this
1397 option for embedded systems with no facilities for reporting errors.
1398 Just say Y.
1400 config ELF_CORE
1401 depends on COREDUMP
1402 default y
1403 bool "Enable ELF core dumps" if EXPERT
1404 help
1405 Enable support for generating core dumps. Disabling saves about 4k.
1408 config PCSPKR_PLATFORM
1409 bool "Enable PC-Speaker support" if EXPERT
1410 depends on HAVE_PCSPKR_PLATFORM
1411 select I8253_LOCK
1412 default y
1413 help
1414 This option allows to disable the internal PC-Speaker
1415 support, saving some memory.
1417 config BASE_FULL
1418 default y
1419 bool "Enable full-sized data structures for core" if EXPERT
1420 help
1421 Disabling this option reduces the size of miscellaneous core
1422 kernel data structures. This saves memory on small machines,
1423 but may reduce performance.
1425 config FUTEX
1426 bool "Enable futex support" if EXPERT
1427 default y
1428 select RT_MUTEXES
1429 help
1430 Disabling this option will cause the kernel to be built without
1431 support for "fast userspace mutexes". The resulting kernel may not
1432 run glibc-based applications correctly.
1434 config HAVE_FUTEX_CMPXCHG
1435 bool
1436 depends on FUTEX
1437 help
1438 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1439 is implemented and always working. This removes a couple of runtime
1440 checks.
1442 config EPOLL
1443 bool "Enable eventpoll support" if EXPERT
1444 default y
1445 select ANON_INODES
1446 help
1447 Disabling this option will cause the kernel to be built without
1448 support for epoll family of system calls.
1450 config SIGNALFD
1451 bool "Enable signalfd() system call" if EXPERT
1452 select ANON_INODES
1453 default y
1454 help
1455 Enable the signalfd() system call that allows to receive signals
1456 on a file descriptor.
1458 If unsure, say Y.
1460 config TIMERFD
1461 bool "Enable timerfd() system call" if EXPERT
1462 select ANON_INODES
1463 default y
1464 help
1465 Enable the timerfd() system call that allows to receive timer
1466 events on a file descriptor.
1468 If unsure, say Y.
1470 config EVENTFD
1471 bool "Enable eventfd() system call" if EXPERT
1472 select ANON_INODES
1473 default y
1474 help
1475 Enable the eventfd() system call that allows to receive both
1476 kernel notification (ie. KAIO) or userspace notifications.
1478 If unsure, say Y.
1480 config SHMEM
1481 bool "Use full shmem filesystem" if EXPERT
1482 default y
1483 depends on MMU
1484 help
1485 The shmem is an internal filesystem used to manage shared memory.
1486 It is backed by swap and manages resource limits. It is also exported
1487 to userspace as tmpfs if TMPFS is enabled. Disabling this
1488 option replaces shmem and tmpfs with the much simpler ramfs code,
1489 which may be appropriate on small systems without swap.
1491 config AIO
1492 bool "Enable AIO support" if EXPERT
1493 default y
1494 help
1495 This option enables POSIX asynchronous I/O which may by used
1496 by some high performance threaded applications. Disabling
1497 this option saves about 7k.
1499 config PCI_QUIRKS
1500 default y
1501 bool "Enable PCI quirk workarounds" if EXPERT
1502 depends on PCI
1503 help
1504 This enables workarounds for various PCI chipset
1505 bugs/quirks. Disable this only if your target machine is
1506 unaffected by PCI quirks.
1508 config EMBEDDED
1509 bool "Embedded system"
1510 option allnoconfig_y
1511 select EXPERT
1512 help
1513 This option should be enabled if compiling the kernel for
1514 an embedded system so certain expert options are available
1515 for configuration.
1517 config HAVE_PERF_EVENTS
1518 bool
1519 help
1520 See tools/perf/design.txt for details.
1522 config PERF_USE_VMALLOC
1523 bool
1524 help
1525 See tools/perf/design.txt for details
1527 menu "Kernel Performance Events And Counters"
1529 config PERF_EVENTS
1530 bool "Kernel performance events and counters"
1531 default y if PROFILING
1532 depends on HAVE_PERF_EVENTS
1533 select ANON_INODES
1534 select IRQ_WORK
1535 help
1536 Enable kernel support for various performance events provided
1537 by software and hardware.
1539 Software events are supported either built-in or via the
1540 use of generic tracepoints.
1542 Most modern CPUs support performance events via performance
1543 counter registers. These registers count the number of certain
1544 types of hw events: such as instructions executed, cachemisses
1545 suffered, or branches mis-predicted - without slowing down the
1546 kernel or applications. These registers can also trigger interrupts
1547 when a threshold number of events have passed - and can thus be
1548 used to profile the code that runs on that CPU.
1550 The Linux Performance Event subsystem provides an abstraction of
1551 these software and hardware event capabilities, available via a
1552 system call and used by the "perf" utility in tools/perf/. It
1553 provides per task and per CPU counters, and it provides event
1554 capabilities on top of those.
1556 Say Y if unsure.
1558 config DEBUG_PERF_USE_VMALLOC
1559 default n
1560 bool "Debug: use vmalloc to back perf mmap() buffers"
1561 depends on PERF_EVENTS && DEBUG_KERNEL
1562 select PERF_USE_VMALLOC
1563 help
1564 Use vmalloc memory to back perf mmap() buffers.
1566 Mostly useful for debugging the vmalloc code on platforms
1567 that don't require it.
1569 Say N if unsure.
1571 endmenu
1573 config VM_EVENT_COUNTERS
1574 default y
1575 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1576 help
1577 VM event counters are needed for event counts to be shown.
1578 This option allows the disabling of the VM event counters
1579 on EXPERT systems. /proc/vmstat will only show page counts
1580 if VM event counters are disabled.
1582 config SLUB_DEBUG
1583 default y
1584 bool "Enable SLUB debugging support" if EXPERT
1585 depends on SLUB && SYSFS
1586 help
1587 SLUB has extensive debug support features. Disabling these can
1588 result in significant savings in code size. This also disables
1589 SLUB sysfs support. /sys/slab will not exist and there will be
1590 no support for cache validation etc.
1592 config COMPAT_BRK
1593 bool "Disable heap randomization"
1594 default y
1595 help
1596 Randomizing heap placement makes heap exploits harder, but it
1597 also breaks ancient binaries (including anything libc5 based).
1598 This option changes the bootup default to heap randomization
1599 disabled, and can be overridden at runtime by setting
1600 /proc/sys/kernel/randomize_va_space to 2.
1602 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1604 choice
1605 prompt "Choose SLAB allocator"
1606 default SLUB
1607 help
1608 This option allows to select a slab allocator.
1610 config SLAB
1611 bool "SLAB"
1612 help
1613 The regular slab allocator that is established and known to work
1614 well in all environments. It organizes cache hot objects in
1615 per cpu and per node queues.
1617 config SLUB
1618 bool "SLUB (Unqueued Allocator)"
1619 help
1620 SLUB is a slab allocator that minimizes cache line usage
1621 instead of managing queues of cached objects (SLAB approach).
1622 Per cpu caching is realized using slabs of objects instead
1623 of queues of objects. SLUB can use memory efficiently
1624 and has enhanced diagnostics. SLUB is the default choice for
1625 a slab allocator.
1627 config SLOB
1628 depends on EXPERT
1629 bool "SLOB (Simple Allocator)"
1630 help
1631 SLOB replaces the stock allocator with a drastically simpler
1632 allocator. SLOB is generally more space efficient but
1633 does not perform as well on large systems.
1635 endchoice
1637 config SLUB_CPU_PARTIAL
1638 default y
1639 depends on SLUB && SMP
1640 bool "SLUB per cpu partial cache"
1641 help
1642 Per cpu partial caches accellerate objects allocation and freeing
1643 that is local to a processor at the price of more indeterminism
1644 in the latency of the free. On overflow these caches will be cleared
1645 which requires the taking of locks that may cause latency spikes.
1646 Typically one would choose no for a realtime system.
1648 config MMAP_ALLOW_UNINITIALIZED
1649 bool "Allow mmapped anonymous memory to be uninitialized"
1650 depends on EXPERT && !MMU
1651 default n
1652 help
1653 Normally, and according to the Linux spec, anonymous memory obtained
1654 from mmap() has it's contents cleared before it is passed to
1655 userspace. Enabling this config option allows you to request that
1656 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1657 providing a huge performance boost. If this option is not enabled,
1658 then the flag will be ignored.
1660 This is taken advantage of by uClibc's malloc(), and also by
1661 ELF-FDPIC binfmt's brk and stack allocator.
1663 Because of the obvious security issues, this option should only be
1664 enabled on embedded devices where you control what is run in
1665 userspace. Since that isn't generally a problem on no-MMU systems,
1666 it is normally safe to say Y here.
1668 See Documentation/nommu-mmap.txt for more information.
1670 config SYSTEM_TRUSTED_KEYRING
1671 bool "Provide system-wide ring of trusted keys"
1672 depends on KEYS
1673 help
1674 Provide a system keyring to which trusted keys can be added. Keys in
1675 the keyring are considered to be trusted. Keys may be added at will
1676 by the kernel from compiled-in data and from hardware key stores, but
1677 userspace may only add extra keys if those keys can be verified by
1678 keys already in the keyring.
1680 Keys in this keyring are used by module signature checking.
1682 config PROFILING
1683 bool "Profiling support"
1684 help
1685 Say Y here to enable the extended profiling support mechanisms used
1686 by profilers such as OProfile.
1688 #
1689 # Place an empty function call at each tracepoint site. Can be
1690 # dynamically changed for a probe function.
1691 #
1692 config TRACEPOINTS
1693 bool
1695 source "arch/Kconfig"
1697 endmenu # General setup
1699 config HAVE_GENERIC_DMA_COHERENT
1700 bool
1701 default n
1703 config SLABINFO
1704 bool
1705 depends on PROC_FS
1706 depends on SLAB || SLUB_DEBUG
1707 default y
1709 config RT_MUTEXES
1710 boolean
1712 config BASE_SMALL
1713 int
1714 default 0 if BASE_FULL
1715 default 1 if !BASE_FULL
1717 menuconfig MODULES
1718 bool "Enable loadable module support"
1719 option modules
1720 help
1721 Kernel modules are small pieces of compiled code which can
1722 be inserted in the running kernel, rather than being
1723 permanently built into the kernel. You use the "modprobe"
1724 tool to add (and sometimes remove) them. If you say Y here,
1725 many parts of the kernel can be built as modules (by
1726 answering M instead of Y where indicated): this is most
1727 useful for infrequently used options which are not required
1728 for booting. For more information, see the man pages for
1729 modprobe, lsmod, modinfo, insmod and rmmod.
1731 If you say Y here, you will need to run "make
1732 modules_install" to put the modules under /lib/modules/
1733 where modprobe can find them (you may need to be root to do
1734 this).
1736 If unsure, say Y.
1738 if MODULES
1740 config MODULE_FORCE_LOAD
1741 bool "Forced module loading"
1742 default n
1743 help
1744 Allow loading of modules without version information (ie. modprobe
1745 --force). Forced module loading sets the 'F' (forced) taint flag and
1746 is usually a really bad idea.
1748 config MODULE_UNLOAD
1749 bool "Module unloading"
1750 help
1751 Without this option you will not be able to unload any
1752 modules (note that some modules may not be unloadable
1753 anyway), which makes your kernel smaller, faster
1754 and simpler. If unsure, say Y.
1756 config MODULE_FORCE_UNLOAD
1757 bool "Forced module unloading"
1758 depends on MODULE_UNLOAD
1759 help
1760 This option allows you to force a module to unload, even if the
1761 kernel believes it is unsafe: the kernel will remove the module
1762 without waiting for anyone to stop using it (using the -f option to
1763 rmmod). This is mainly for kernel developers and desperate users.
1764 If unsure, say N.
1766 config MODVERSIONS
1767 bool "Module versioning support"
1768 help
1769 Usually, you have to use modules compiled with your kernel.
1770 Saying Y here makes it sometimes possible to use modules
1771 compiled for different kernels, by adding enough information
1772 to the modules to (hopefully) spot any changes which would
1773 make them incompatible with the kernel you are running. If
1774 unsure, say N.
1776 config MODULE_SRCVERSION_ALL
1777 bool "Source checksum for all modules"
1778 help
1779 Modules which contain a MODULE_VERSION get an extra "srcversion"
1780 field inserted into their modinfo section, which contains a
1781 sum of the source files which made it. This helps maintainers
1782 see exactly which source was used to build a module (since
1783 others sometimes change the module source without updating
1784 the version). With this option, such a "srcversion" field
1785 will be created for all modules. If unsure, say N.
1787 config MODULE_SIG
1788 bool "Module signature verification"
1789 depends on MODULES
1790 select SYSTEM_TRUSTED_KEYRING
1791 select KEYS
1792 select CRYPTO
1793 select ASYMMETRIC_KEY_TYPE
1794 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1795 select PUBLIC_KEY_ALGO_RSA
1796 select ASN1
1797 select OID_REGISTRY
1798 select X509_CERTIFICATE_PARSER
1799 help
1800 Check modules for valid signatures upon load: the signature
1801 is simply appended to the module. For more information see
1802 Documentation/module-signing.txt.
1804 !!!WARNING!!! If you enable this option, you MUST make sure that the
1805 module DOES NOT get stripped after being signed. This includes the
1806 debuginfo strip done by some packagers (such as rpmbuild) and
1807 inclusion into an initramfs that wants the module size reduced.
1809 config MODULE_SIG_FORCE
1810 bool "Require modules to be validly signed"
1811 depends on MODULE_SIG
1812 help
1813 Reject unsigned modules or signed modules for which we don't have a
1814 key. Without this, such modules will simply taint the kernel.
1816 config MODULE_SIG_ALL
1817 bool "Automatically sign all modules"
1818 default y
1819 depends on MODULE_SIG
1820 help
1821 Sign all modules during make modules_install. Without this option,
1822 modules must be signed manually, using the scripts/sign-file tool.
1824 comment "Do not forget to sign required modules with scripts/sign-file"
1825 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1827 choice
1828 prompt "Which hash algorithm should modules be signed with?"
1829 depends on MODULE_SIG
1830 help
1831 This determines which sort of hashing algorithm will be used during
1832 signature generation. This algorithm _must_ be built into the kernel
1833 directly so that signature verification can take place. It is not
1834 possible to load a signed module containing the algorithm to check
1835 the signature on that module.
1837 config MODULE_SIG_SHA1
1838 bool "Sign modules with SHA-1"
1839 select CRYPTO_SHA1
1841 config MODULE_SIG_SHA224
1842 bool "Sign modules with SHA-224"
1843 select CRYPTO_SHA256
1845 config MODULE_SIG_SHA256
1846 bool "Sign modules with SHA-256"
1847 select CRYPTO_SHA256
1849 config MODULE_SIG_SHA384
1850 bool "Sign modules with SHA-384"
1851 select CRYPTO_SHA512
1853 config MODULE_SIG_SHA512
1854 bool "Sign modules with SHA-512"
1855 select CRYPTO_SHA512
1857 endchoice
1859 config MODULE_SIG_HASH
1860 string
1861 depends on MODULE_SIG
1862 default "sha1" if MODULE_SIG_SHA1
1863 default "sha224" if MODULE_SIG_SHA224
1864 default "sha256" if MODULE_SIG_SHA256
1865 default "sha384" if MODULE_SIG_SHA384
1866 default "sha512" if MODULE_SIG_SHA512
1868 endif # MODULES
1870 config INIT_ALL_POSSIBLE
1871 bool
1872 help
1873 Back when each arch used to define their own cpu_online_mask and
1874 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1875 with all 1s, and others with all 0s. When they were centralised,
1876 it was better to provide this option than to break all the archs
1877 and have several arch maintainers pursuing me down dark alleys.
1879 config STOP_MACHINE
1880 bool
1881 default y
1882 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1883 help
1884 Need stop_machine() primitive.
1886 source "block/Kconfig"
1888 config PREEMPT_NOTIFIERS
1889 bool
1891 config PADATA
1892 depends on SMP
1893 bool
1895 # Can be selected by architectures with broken toolchains
1896 # that get confused by correct const<->read_only section
1897 # mappings
1898 config BROKEN_RODATA
1899 bool
1901 config ASN1
1902 tristate
1903 help
1904 Build a simple ASN.1 grammar compiler that produces a bytecode output
1905 that can be interpreted by the ASN.1 stream decoder and used to
1906 inform it as to what tags are to be expected in a stream and what
1907 functions to call on what tags.
1909 source "kernel/Kconfig.locks"