| blob | 9d3a7887a6d3e0b7a8323865b658e1d088dcea85 |
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 LOCALVERSION
57 string "Local version - append to kernel release"
58 help
59 Append an extra string to the end of your kernel version.
60 This will show up when you type uname, for example.
61 The string you set here will be appended after the contents of
62 any files with a filename matching localversion* in your
63 object and source tree, in that order. Your total string can
64 be a maximum of 64 characters.
66 config LOCALVERSION_AUTO
67 bool "Automatically append version information to the version string"
68 default y
69 help
70 This will try to automatically determine if the current tree is a
71 release tree by looking for git tags that belong to the current
72 top of tree revision.
74 A string of the format -gxxxxxxxx will be added to the localversion
75 if a git-based tree is found. The string generated by this will be
76 appended after any matching localversion* files, and after the value
77 set in CONFIG_LOCALVERSION.
79 (The actual string used here is the first eight characters produced
80 by running the command:
82 $ git rev-parse --verify HEAD
84 which is done within the script "scripts/setlocalversion".)
86 config HAVE_KERNEL_GZIP
87 bool
89 config HAVE_KERNEL_BZIP2
90 bool
92 config HAVE_KERNEL_LZMA
93 bool
95 config HAVE_KERNEL_XZ
96 bool
98 config HAVE_KERNEL_LZO
99 bool
101 choice
102 prompt "Kernel compression mode"
103 default KERNEL_GZIP
104 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
105 help
106 The linux kernel is a kind of self-extracting executable.
107 Several compression algorithms are available, which differ
108 in efficiency, compression and decompression speed.
109 Compression speed is only relevant when building a kernel.
110 Decompression speed is relevant at each boot.
112 If you have any problems with bzip2 or lzma compressed
113 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
114 version of this functionality (bzip2 only), for 2.4, was
115 supplied by Christian Ludwig)
117 High compression options are mostly useful for users, who
118 are low on disk space (embedded systems), but for whom ram
119 size matters less.
121 If in doubt, select 'gzip'
123 config KERNEL_GZIP
124 bool "Gzip"
125 depends on HAVE_KERNEL_GZIP
126 help
127 The old and tried gzip compression. It provides a good balance
128 between compression ratio and decompression speed.
130 config KERNEL_BZIP2
131 bool "Bzip2"
132 depends on HAVE_KERNEL_BZIP2
133 help
134 Its compression ratio and speed is intermediate.
135 Decompression speed is slowest among the choices. The kernel
136 size is about 10% smaller with bzip2, in comparison to gzip.
137 Bzip2 uses a large amount of memory. For modern kernels you
138 will need at least 8MB RAM or more for booting.
140 config KERNEL_LZMA
141 bool "LZMA"
142 depends on HAVE_KERNEL_LZMA
143 help
144 This compression algorithm's ratio is best. Decompression speed
145 is between gzip and bzip2. Compression is slowest.
146 The kernel size is about 33% smaller with LZMA in comparison to gzip.
148 config KERNEL_XZ
149 bool "XZ"
150 depends on HAVE_KERNEL_XZ
151 help
152 XZ uses the LZMA2 algorithm and instruction set specific
153 BCJ filters which can improve compression ratio of executable
154 code. The size of the kernel is about 30% smaller with XZ in
155 comparison to gzip. On architectures for which there is a BCJ
156 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
157 will create a few percent smaller kernel than plain LZMA.
159 The speed is about the same as with LZMA: The decompression
160 speed of XZ is better than that of bzip2 but worse than gzip
161 and LZO. Compression is slow.
163 config KERNEL_LZO
164 bool "LZO"
165 depends on HAVE_KERNEL_LZO
166 help
167 Its compression ratio is the poorest among the choices. The kernel
168 size is about 10% bigger than gzip; however its speed
169 (both compression and decompression) is the fastest.
171 endchoice
173 config DEFAULT_HOSTNAME
174 string "Default hostname"
175 default "(none)"
176 help
177 This option determines the default system hostname before userspace
178 calls sethostname(2). The kernel traditionally uses "(none)" here,
179 but you may wish to use a different default here to make a minimal
180 system more usable with less configuration.
182 config SWAP
183 bool "Support for paging of anonymous memory (swap)"
184 depends on MMU && BLOCK
185 default y
186 help
187 This option allows you to choose whether you want to have support
188 for so called swap devices or swap files in your kernel that are
189 used to provide more virtual memory than the actual RAM present
190 in your computer. If unsure say Y.
192 config SYSVIPC
193 bool "System V IPC"
194 ---help---
195 Inter Process Communication is a suite of library functions and
196 system calls which let processes (running programs) synchronize and
197 exchange information. It is generally considered to be a good thing,
198 and some programs won't run unless you say Y here. In particular, if
199 you want to run the DOS emulator dosemu under Linux (read the
200 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
201 you'll need to say Y here.
203 You can find documentation about IPC with "info ipc" and also in
204 section 6.4 of the Linux Programmer's Guide, available from
205 <http://www.tldp.org/guides.html>.
207 config SYSVIPC_SYSCTL
208 bool
209 depends on SYSVIPC
210 depends on SYSCTL
211 default y
213 config POSIX_MQUEUE
214 bool "POSIX Message Queues"
215 depends on NET
216 ---help---
217 POSIX variant of message queues is a part of IPC. In POSIX message
218 queues every message has a priority which decides about succession
219 of receiving it by a process. If you want to compile and run
220 programs written e.g. for Solaris with use of its POSIX message
221 queues (functions mq_*) say Y here.
223 POSIX message queues are visible as a filesystem called 'mqueue'
224 and can be mounted somewhere if you want to do filesystem
225 operations on message queues.
227 If unsure, say Y.
229 config POSIX_MQUEUE_SYSCTL
230 bool
231 depends on POSIX_MQUEUE
232 depends on SYSCTL
233 default y
235 config FHANDLE
236 bool "open by fhandle syscalls"
237 select EXPORTFS
238 help
239 If you say Y here, a user level program will be able to map
240 file names to handle and then later use the handle for
241 different file system operations. This is useful in implementing
242 userspace file servers, which now track files using handles instead
243 of names. The handle would remain the same even if file names
244 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
245 syscalls.
247 config AUDIT
248 bool "Auditing support"
249 depends on NET
250 help
251 Enable auditing infrastructure that can be used with another
252 kernel subsystem, such as SELinux (which requires this for
253 logging of avc messages output). Does not do system-call
254 auditing without CONFIG_AUDITSYSCALL.
256 config AUDITSYSCALL
257 bool "Enable system-call auditing support"
258 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
259 default y if SECURITY_SELINUX
260 help
261 Enable low-overhead system-call auditing infrastructure that
262 can be used independently or with another kernel subsystem,
263 such as SELinux.
265 config AUDIT_WATCH
266 def_bool y
267 depends on AUDITSYSCALL
268 select FSNOTIFY
270 config AUDIT_TREE
271 def_bool y
272 depends on AUDITSYSCALL
273 select FSNOTIFY
275 config AUDIT_LOGINUID_IMMUTABLE
276 bool "Make audit loginuid immutable"
277 depends on AUDIT
278 help
279 The config option toggles if a task setting its loginuid requires
280 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
281 but should instead only allow setting its loginuid if it was never
282 previously set. On systems which use systemd or a similar central
283 process to restart login services this should be set to true. On older
284 systems in which an admin would typically have to directly stop and
285 start processes this should be set to false. Setting this to true allows
286 one to drop potentially dangerous capabilites from the login tasks,
287 but may not be backwards compatible with older init systems.
289 source "kernel/irq/Kconfig"
290 source "kernel/time/Kconfig"
292 menu "CPU/Task time and stats accounting"
294 config VIRT_CPU_ACCOUNTING
295 bool
297 choice
298 prompt "Cputime accounting"
299 default TICK_CPU_ACCOUNTING if !PPC64
300 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
302 # Kind of a stub config for the pure tick based cputime accounting
303 config TICK_CPU_ACCOUNTING
304 bool "Simple tick based cputime accounting"
305 depends on !S390 && !NO_HZ_FULL
306 help
307 This is the basic tick based cputime accounting that maintains
308 statistics about user, system and idle time spent on per jiffies
309 granularity.
311 If unsure, say Y.
313 config VIRT_CPU_ACCOUNTING_NATIVE
314 bool "Deterministic task and CPU time accounting"
315 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
316 select VIRT_CPU_ACCOUNTING
317 help
318 Select this option to enable more accurate task and CPU time
319 accounting. This is done by reading a CPU counter on each
320 kernel entry and exit and on transitions within the kernel
321 between system, softirq and hardirq state, so there is a
322 small performance impact. In the case of s390 or IBM POWER > 5,
323 this also enables accounting of stolen time on logically-partitioned
324 systems.
326 config VIRT_CPU_ACCOUNTING_GEN
327 bool "Full dynticks CPU time accounting"
328 depends on HAVE_CONTEXT_TRACKING && 64BIT
329 select VIRT_CPU_ACCOUNTING
330 select CONTEXT_TRACKING
331 help
332 Select this option to enable task and CPU time accounting on full
333 dynticks systems. This accounting is implemented by watching every
334 kernel-user boundaries using the context tracking subsystem.
335 The accounting is thus performed at the expense of some significant
336 overhead.
338 For now this is only useful if you are working on the full
339 dynticks subsystem development.
341 If unsure, say N.
343 config IRQ_TIME_ACCOUNTING
344 bool "Fine granularity task level IRQ time accounting"
345 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
346 help
347 Select this option to enable fine granularity task irq time
348 accounting. This is done by reading a timestamp on each
349 transitions between softirq and hardirq state, so there can be a
350 small performance impact.
352 If in doubt, say N here.
354 endchoice
356 config BSD_PROCESS_ACCT
357 bool "BSD Process Accounting"
358 help
359 If you say Y here, a user level program will be able to instruct the
360 kernel (via a special system call) to write process accounting
361 information to a file: whenever a process exits, information about
362 that process will be appended to the file by the kernel. The
363 information includes things such as creation time, owning user,
364 command name, memory usage, controlling terminal etc. (the complete
365 list is in the struct acct in <file:include/linux/acct.h>). It is
366 up to the user level program to do useful things with this
367 information. This is generally a good idea, so say Y.
369 config BSD_PROCESS_ACCT_V3
370 bool "BSD Process Accounting version 3 file format"
371 depends on BSD_PROCESS_ACCT
372 default n
373 help
374 If you say Y here, the process accounting information is written
375 in a new file format that also logs the process IDs of each
376 process and it's parent. Note that this file format is incompatible
377 with previous v0/v1/v2 file formats, so you will need updated tools
378 for processing it. A preliminary version of these tools is available
379 at <http://www.gnu.org/software/acct/>.
381 config TASKSTATS
382 bool "Export task/process statistics through netlink"
383 depends on NET
384 default n
385 help
386 Export selected statistics for tasks/processes through the
387 generic netlink interface. Unlike BSD process accounting, the
388 statistics are available during the lifetime of tasks/processes as
389 responses to commands. Like BSD accounting, they are sent to user
390 space on task exit.
392 Say N if unsure.
394 config TASK_DELAY_ACCT
395 bool "Enable per-task delay accounting"
396 depends on TASKSTATS
397 help
398 Collect information on time spent by a task waiting for system
399 resources like cpu, synchronous block I/O completion and swapping
400 in pages. Such statistics can help in setting a task's priorities
401 relative to other tasks for cpu, io, rss limits etc.
403 Say N if unsure.
405 config TASK_XACCT
406 bool "Enable extended accounting over taskstats"
407 depends on TASKSTATS
408 help
409 Collect extended task accounting data and send the data
410 to userland for processing over the taskstats interface.
412 Say N if unsure.
414 config TASK_IO_ACCOUNTING
415 bool "Enable per-task storage I/O accounting"
416 depends on TASK_XACCT
417 help
418 Collect information on the number of bytes of storage I/O which this
419 task has caused.
421 Say N if unsure.
423 endmenu # "CPU/Task time and stats accounting"
425 menu "RCU Subsystem"
427 choice
428 prompt "RCU Implementation"
429 default TREE_RCU
431 config TREE_RCU
432 bool "Tree-based hierarchical RCU"
433 depends on !PREEMPT && SMP
434 help
435 This option selects the RCU implementation that is
436 designed for very large SMP system with hundreds or
437 thousands of CPUs. It also scales down nicely to
438 smaller systems.
440 config TREE_PREEMPT_RCU
441 bool "Preemptible tree-based hierarchical RCU"
442 depends on PREEMPT
443 help
444 This option selects the RCU implementation that is
445 designed for very large SMP systems with hundreds or
446 thousands of CPUs, but for which real-time response
447 is also required. It also scales down nicely to
448 smaller systems.
450 Select this option if you are unsure.
452 config TINY_RCU
453 bool "UP-only small-memory-footprint RCU"
454 depends on !PREEMPT && !SMP
455 help
456 This option selects the RCU implementation that is
457 designed for UP systems from which real-time response
458 is not required. This option greatly reduces the
459 memory footprint of RCU.
461 config TINY_PREEMPT_RCU
462 bool "Preemptible UP-only small-memory-footprint RCU"
463 depends on PREEMPT && !SMP
464 help
465 This option selects the RCU implementation that is designed
466 for real-time UP systems. This option greatly reduces the
467 memory footprint of RCU.
469 endchoice
471 config PREEMPT_RCU
472 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
473 help
474 This option enables preemptible-RCU code that is common between
475 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
477 config RCU_STALL_COMMON
478 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
479 help
480 This option enables RCU CPU stall code that is common between
481 the TINY and TREE variants of RCU. The purpose is to allow
482 the tiny variants to disable RCU CPU stall warnings, while
483 making these warnings mandatory for the tree variants.
485 config CONTEXT_TRACKING
486 bool
488 config RCU_USER_QS
489 bool "Consider userspace as in RCU extended quiescent state"
490 depends on HAVE_CONTEXT_TRACKING && SMP
491 select CONTEXT_TRACKING
492 help
493 This option sets hooks on kernel / userspace boundaries and
494 puts RCU in extended quiescent state when the CPU runs in
495 userspace. It means that when a CPU runs in userspace, it is
496 excluded from the global RCU state machine and thus doesn't
497 try to keep the timer tick on for RCU.
499 Unless you want to hack and help the development of the full
500 dynticks mode, you shouldn't enable this option. It also
501 adds unnecessary overhead.
503 If unsure say N
505 config CONTEXT_TRACKING_FORCE
506 bool "Force context tracking"
507 depends on CONTEXT_TRACKING
508 default CONTEXT_TRACKING
509 help
510 Probe on user/kernel boundaries by default in order to
511 test the features that rely on it such as userspace RCU extended
512 quiescent states.
513 This test is there for debugging until we have a real user like the
514 full dynticks mode.
516 config RCU_FANOUT
517 int "Tree-based hierarchical RCU fanout value"
518 range 2 64 if 64BIT
519 range 2 32 if !64BIT
520 depends on TREE_RCU || TREE_PREEMPT_RCU
521 default 64 if 64BIT
522 default 32 if !64BIT
523 help
524 This option controls the fanout of hierarchical implementations
525 of RCU, allowing RCU to work efficiently on machines with
526 large numbers of CPUs. This value must be at least the fourth
527 root of NR_CPUS, which allows NR_CPUS to be insanely large.
528 The default value of RCU_FANOUT should be used for production
529 systems, but if you are stress-testing the RCU implementation
530 itself, small RCU_FANOUT values allow you to test large-system
531 code paths on small(er) systems.
533 Select a specific number if testing RCU itself.
534 Take the default if unsure.
536 config RCU_FANOUT_LEAF
537 int "Tree-based hierarchical RCU leaf-level fanout value"
538 range 2 RCU_FANOUT if 64BIT
539 range 2 RCU_FANOUT if !64BIT
540 depends on TREE_RCU || TREE_PREEMPT_RCU
541 default 16
542 help
543 This option controls the leaf-level fanout of hierarchical
544 implementations of RCU, and allows trading off cache misses
545 against lock contention. Systems that synchronize their
546 scheduling-clock interrupts for energy-efficiency reasons will
547 want the default because the smaller leaf-level fanout keeps
548 lock contention levels acceptably low. Very large systems
549 (hundreds or thousands of CPUs) will instead want to set this
550 value to the maximum value possible in order to reduce the
551 number of cache misses incurred during RCU's grace-period
552 initialization. These systems tend to run CPU-bound, and thus
553 are not helped by synchronized interrupts, and thus tend to
554 skew them, which reduces lock contention enough that large
555 leaf-level fanouts work well.
557 Select a specific number if testing RCU itself.
559 Select the maximum permissible value for large systems.
561 Take the default if unsure.
563 config RCU_FANOUT_EXACT
564 bool "Disable tree-based hierarchical RCU auto-balancing"
565 depends on TREE_RCU || TREE_PREEMPT_RCU
566 default n
567 help
568 This option forces use of the exact RCU_FANOUT value specified,
569 regardless of imbalances in the hierarchy. This is useful for
570 testing RCU itself, and might one day be useful on systems with
571 strong NUMA behavior.
573 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
575 Say N if unsure.
577 config RCU_FAST_NO_HZ
578 bool "Accelerate last non-dyntick-idle CPU's grace periods"
579 depends on NO_HZ_COMMON && SMP
580 default n
581 help
582 This option permits CPUs to enter dynticks-idle state even if
583 they have RCU callbacks queued, and prevents RCU from waking
584 these CPUs up more than roughly once every four jiffies (by
585 default, you can adjust this using the rcutree.rcu_idle_gp_delay
586 parameter), thus improving energy efficiency. On the other
587 hand, this option increases the duration of RCU grace periods,
588 for example, slowing down synchronize_rcu().
590 Say Y if energy efficiency is critically important, and you
591 don't care about increased grace-period durations.
593 Say N if you are unsure.
595 config TREE_RCU_TRACE
596 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
597 select DEBUG_FS
598 help
599 This option provides tracing for the TREE_RCU and
600 TREE_PREEMPT_RCU implementations, permitting Makefile to
601 trivially select kernel/rcutree_trace.c.
603 config RCU_BOOST
604 bool "Enable RCU priority boosting"
605 depends on RT_MUTEXES && PREEMPT_RCU
606 default n
607 help
608 This option boosts the priority of preempted RCU readers that
609 block the current preemptible RCU grace period for too long.
610 This option also prevents heavy loads from blocking RCU
611 callback invocation for all flavors of RCU.
613 Say Y here if you are working with real-time apps or heavy loads
614 Say N here if you are unsure.
616 config RCU_BOOST_PRIO
617 int "Real-time priority to boost RCU readers to"
618 range 1 99
619 depends on RCU_BOOST
620 default 1
621 help
622 This option specifies the real-time priority to which long-term
623 preempted RCU readers are to be boosted. If you are working
624 with a real-time application that has one or more CPU-bound
625 threads running at a real-time priority level, you should set
626 RCU_BOOST_PRIO to a priority higher then the highest-priority
627 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
628 of 1 is appropriate in the common case, which is real-time
629 applications that do not have any CPU-bound threads.
631 Some real-time applications might not have a single real-time
632 thread that saturates a given CPU, but instead might have
633 multiple real-time threads that, taken together, fully utilize
634 that CPU. In this case, you should set RCU_BOOST_PRIO to
635 a priority higher than the lowest-priority thread that is
636 conspiring to prevent the CPU from running any non-real-time
637 tasks. For example, if one thread at priority 10 and another
638 thread at priority 5 are between themselves fully consuming
639 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
640 set to priority 6 or higher.
642 Specify the real-time priority, or take the default if unsure.
644 config RCU_BOOST_DELAY
645 int "Milliseconds to delay boosting after RCU grace-period start"
646 range 0 3000
647 depends on RCU_BOOST
648 default 500
649 help
650 This option specifies the time to wait after the beginning of
651 a given grace period before priority-boosting preempted RCU
652 readers blocking that grace period. Note that any RCU reader
653 blocking an expedited RCU grace period is boosted immediately.
655 Accept the default if unsure.
657 config RCU_NOCB_CPU
658 bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
659 depends on TREE_RCU || TREE_PREEMPT_RCU
660 default n
661 help
662 Use this option to reduce OS jitter for aggressive HPC or
663 real-time workloads. It can also be used to offload RCU
664 callback invocation to energy-efficient CPUs in battery-powered
665 asymmetric multiprocessors.
667 This option offloads callback invocation from the set of
668 CPUs specified at boot time by the rcu_nocbs parameter.
669 For each such CPU, a kthread ("rcuox/N") will be created to
670 invoke callbacks, where the "N" is the CPU being offloaded,
671 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
672 "s" for RCU-sched. Nothing prevents this kthread from running
673 on the specified CPUs, but (1) the kthreads may be preempted
674 between each callback, and (2) affinity or cgroups can be used
675 to force the kthreads to run on whatever set of CPUs is desired.
677 Say Y here if you want to help to debug reduced OS jitter.
678 Say N here if you are unsure.
680 choice
681 prompt "Build-forced no-CBs CPUs"
682 default RCU_NOCB_CPU_NONE
683 help
684 This option allows no-CBs CPUs to be specified at build time.
685 Additional no-CBs CPUs may be specified by the rcu_nocbs=
686 boot parameter.
688 config RCU_NOCB_CPU_NONE
689 bool "No build_forced no-CBs CPUs"
690 depends on RCU_NOCB_CPU && !NO_HZ_FULL
691 help
692 This option does not force any of the CPUs to be no-CBs CPUs.
693 Only CPUs designated by the rcu_nocbs= boot parameter will be
694 no-CBs CPUs.
696 config RCU_NOCB_CPU_ZERO
697 bool "CPU 0 is a build_forced no-CBs CPU"
698 depends on RCU_NOCB_CPU && !NO_HZ_FULL
699 help
700 This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
701 may be designated as no-CBs CPUs using the rcu_nocbs= boot
702 parameter will be no-CBs CPUs.
704 Select this if CPU 0 needs to be a no-CBs CPU for real-time
705 or energy-efficiency reasons.
707 config RCU_NOCB_CPU_ALL
708 bool "All CPUs are build_forced no-CBs CPUs"
709 depends on RCU_NOCB_CPU
710 help
711 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
712 boot parameter will be ignored.
714 Select this if all CPUs need to be no-CBs CPUs for real-time
715 or energy-efficiency reasons.
717 endchoice
719 endmenu # "RCU Subsystem"
721 config IKCONFIG
722 tristate "Kernel .config support"
723 ---help---
724 This option enables the complete Linux kernel ".config" file
725 contents to be saved in the kernel. It provides documentation
726 of which kernel options are used in a running kernel or in an
727 on-disk kernel. This information can be extracted from the kernel
728 image file with the script scripts/extract-ikconfig and used as
729 input to rebuild the current kernel or to build another kernel.
730 It can also be extracted from a running kernel by reading
731 /proc/config.gz if enabled (below).
733 config IKCONFIG_PROC
734 bool "Enable access to .config through /proc/config.gz"
735 depends on IKCONFIG && PROC_FS
736 ---help---
737 This option enables access to the kernel configuration file
738 through /proc/config.gz.
740 config LOG_BUF_SHIFT
741 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
742 range 12 21
743 default 17
744 help
745 Select kernel log buffer size as a power of 2.
746 Examples:
747 17 => 128 KB
748 16 => 64 KB
749 15 => 32 KB
750 14 => 16 KB
751 13 => 8 KB
752 12 => 4 KB
754 #
755 # Architectures with an unreliable sched_clock() should select this:
756 #
757 config HAVE_UNSTABLE_SCHED_CLOCK
758 bool
760 #
761 # For architectures that want to enable the support for NUMA-affine scheduler
762 # balancing logic:
763 #
764 config ARCH_SUPPORTS_NUMA_BALANCING
765 bool
767 # For architectures that (ab)use NUMA to represent different memory regions
768 # all cpu-local but of different latencies, such as SuperH.
769 #
770 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
771 bool
773 #
774 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
775 config ARCH_WANTS_PROT_NUMA_PROT_NONE
776 bool
778 config ARCH_USES_NUMA_PROT_NONE
779 bool
780 default y
781 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
782 depends on NUMA_BALANCING
784 config NUMA_BALANCING_DEFAULT_ENABLED
785 bool "Automatically enable NUMA aware memory/task placement"
786 default y
787 depends on NUMA_BALANCING
788 help
789 If set, autonumic NUMA balancing will be enabled if running on a NUMA
790 machine.
792 config NUMA_BALANCING
793 bool "Memory placement aware NUMA scheduler"
794 depends on ARCH_SUPPORTS_NUMA_BALANCING
795 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
796 depends on SMP && NUMA && MIGRATION
797 help
798 This option adds support for automatic NUMA aware memory/task placement.
799 The mechanism is quite primitive and is based on migrating memory when
800 it is references to the node the task is running on.
802 This system will be inactive on UMA systems.
804 menuconfig CGROUPS
805 boolean "Control Group support"
806 depends on EVENTFD
807 help
808 This option adds support for grouping sets of processes together, for
809 use with process control subsystems such as Cpusets, CFS, memory
810 controls or device isolation.
811 See
812 - Documentation/scheduler/sched-design-CFS.txt (CFS)
813 - Documentation/cgroups/ (features for grouping, isolation
814 and resource control)
816 Say N if unsure.
818 if CGROUPS
820 config CGROUP_DEBUG
821 bool "Example debug cgroup subsystem"
822 default n
823 help
824 This option enables a simple cgroup subsystem that
825 exports useful debugging information about the cgroups
826 framework.
828 Say N if unsure.
830 config CGROUP_FREEZER
831 bool "Freezer cgroup subsystem"
832 help
833 Provides a way to freeze and unfreeze all tasks in a
834 cgroup.
836 config CGROUP_DEVICE
837 bool "Device controller for cgroups"
838 help
839 Provides a cgroup implementing whitelists for devices which
840 a process in the cgroup can mknod or open.
842 config CPUSETS
843 bool "Cpuset support"
844 help
845 This option will let you create and manage CPUSETs which
846 allow dynamically partitioning a system into sets of CPUs and
847 Memory Nodes and assigning tasks to run only within those sets.
848 This is primarily useful on large SMP or NUMA systems.
850 Say N if unsure.
852 config PROC_PID_CPUSET
853 bool "Include legacy /proc/<pid>/cpuset file"
854 depends on CPUSETS
855 default y
857 config CGROUP_CPUACCT
858 bool "Simple CPU accounting cgroup subsystem"
859 help
860 Provides a simple Resource Controller for monitoring the
861 total CPU consumed by the tasks in a cgroup.
863 config RESOURCE_COUNTERS
864 bool "Resource counters"
865 help
866 This option enables controller independent resource accounting
867 infrastructure that works with cgroups.
869 config MEMCG
870 bool "Memory Resource Controller for Control Groups"
871 depends on RESOURCE_COUNTERS
872 select MM_OWNER
873 help
874 Provides a memory resource controller that manages both anonymous
875 memory and page cache. (See Documentation/cgroups/memory.txt)
877 Note that setting this option increases fixed memory overhead
878 associated with each page of memory in the system. By this,
879 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
880 usage tracking struct at boot. Total amount of this is printed out
881 at boot.
883 Only enable when you're ok with these trade offs and really
884 sure you need the memory resource controller. Even when you enable
885 this, you can set "cgroup_disable=memory" at your boot option to
886 disable memory resource controller and you can avoid overheads.
887 (and lose benefits of memory resource controller)
889 This config option also selects MM_OWNER config option, which
890 could in turn add some fork/exit overhead.
892 config MEMCG_SWAP
893 bool "Memory Resource Controller Swap Extension"
894 depends on MEMCG && SWAP
895 help
896 Add swap management feature to memory resource controller. When you
897 enable this, you can limit mem+swap usage per cgroup. In other words,
898 when you disable this, memory resource controller has no cares to
899 usage of swap...a process can exhaust all of the swap. This extension
900 is useful when you want to avoid exhaustion swap but this itself
901 adds more overheads and consumes memory for remembering information.
902 Especially if you use 32bit system or small memory system, please
903 be careful about enabling this. When memory resource controller
904 is disabled by boot option, this will be automatically disabled and
905 there will be no overhead from this. Even when you set this config=y,
906 if boot option "swapaccount=0" is set, swap will not be accounted.
907 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
908 size is 4096bytes, 512k per 1Gbytes of swap.
909 config MEMCG_SWAP_ENABLED
910 bool "Memory Resource Controller Swap Extension enabled by default"
911 depends on MEMCG_SWAP
912 default y
913 help
914 Memory Resource Controller Swap Extension comes with its price in
915 a bigger memory consumption. General purpose distribution kernels
916 which want to enable the feature but keep it disabled by default
917 and let the user enable it by swapaccount boot command line
918 parameter should have this option unselected.
919 For those who want to have the feature enabled by default should
920 select this option (if, for some reason, they need to disable it
921 then swapaccount=0 does the trick).
922 config MEMCG_KMEM
923 bool "Memory Resource Controller Kernel Memory accounting"
924 depends on MEMCG
925 depends on SLUB || SLAB
926 help
927 The Kernel Memory extension for Memory Resource Controller can limit
928 the amount of memory used by kernel objects in the system. Those are
929 fundamentally different from the entities handled by the standard
930 Memory Controller, which are page-based, and can be swapped. Users of
931 the kmem extension can use it to guarantee that no group of processes
932 will ever exhaust kernel resources alone.
934 config CGROUP_HUGETLB
935 bool "HugeTLB Resource Controller for Control Groups"
936 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
937 default n
938 help
939 Provides a cgroup Resource Controller for HugeTLB pages.
940 When you enable this, you can put a per cgroup limit on HugeTLB usage.
941 The limit is enforced during page fault. Since HugeTLB doesn't
942 support page reclaim, enforcing the limit at page fault time implies
943 that, the application will get SIGBUS signal if it tries to access
944 HugeTLB pages beyond its limit. This requires the application to know
945 beforehand how much HugeTLB pages it would require for its use. The
946 control group is tracked in the third page lru pointer. This means
947 that we cannot use the controller with huge page less than 3 pages.
949 config CGROUP_PERF
950 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
951 depends on PERF_EVENTS && CGROUPS
952 help
953 This option extends the per-cpu mode to restrict monitoring to
954 threads which belong to the cgroup specified and run on the
955 designated cpu.
957 Say N if unsure.
959 menuconfig CGROUP_SCHED
960 bool "Group CPU scheduler"
961 default n
962 help
963 This feature lets CPU scheduler recognize task groups and control CPU
964 bandwidth allocation to such task groups. It uses cgroups to group
965 tasks.
967 if CGROUP_SCHED
968 config FAIR_GROUP_SCHED
969 bool "Group scheduling for SCHED_OTHER"
970 depends on CGROUP_SCHED
971 default CGROUP_SCHED
973 config CFS_BANDWIDTH
974 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
975 depends on FAIR_GROUP_SCHED
976 default n
977 help
978 This option allows users to define CPU bandwidth rates (limits) for
979 tasks running within the fair group scheduler. Groups with no limit
980 set are considered to be unconstrained and will run with no
981 restriction.
982 See tip/Documentation/scheduler/sched-bwc.txt for more information.
984 config RT_GROUP_SCHED
985 bool "Group scheduling for SCHED_RR/FIFO"
986 depends on CGROUP_SCHED
987 default n
988 help
989 This feature lets you explicitly allocate real CPU bandwidth
990 to task groups. If enabled, it will also make it impossible to
991 schedule realtime tasks for non-root users until you allocate
992 realtime bandwidth for them.
993 See Documentation/scheduler/sched-rt-group.txt for more information.
995 endif #CGROUP_SCHED
997 config BLK_CGROUP
998 bool "Block IO controller"
999 depends on BLOCK
1000 default n
1001 ---help---
1002 Generic block IO controller cgroup interface. This is the common
1003 cgroup interface which should be used by various IO controlling
1004 policies.
1006 Currently, CFQ IO scheduler uses it to recognize task groups and
1007 control disk bandwidth allocation (proportional time slice allocation)
1008 to such task groups. It is also used by bio throttling logic in
1009 block layer to implement upper limit in IO rates on a device.
1011 This option only enables generic Block IO controller infrastructure.
1012 One needs to also enable actual IO controlling logic/policy. For
1013 enabling proportional weight division of disk bandwidth in CFQ, set
1014 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1015 CONFIG_BLK_DEV_THROTTLING=y.
1017 See Documentation/cgroups/blkio-controller.txt for more information.
1019 config DEBUG_BLK_CGROUP
1020 bool "Enable Block IO controller debugging"
1021 depends on BLK_CGROUP
1022 default n
1023 ---help---
1024 Enable some debugging help. Currently it exports additional stat
1025 files in a cgroup which can be useful for debugging.
1027 endif # CGROUPS
1029 config CHECKPOINT_RESTORE
1030 bool "Checkpoint/restore support" if EXPERT
1031 default n
1032 help
1033 Enables additional kernel features in a sake of checkpoint/restore.
1034 In particular it adds auxiliary prctl codes to setup process text,
1035 data and heap segment sizes, and a few additional /proc filesystem
1036 entries.
1038 If unsure, say N here.
1040 menuconfig NAMESPACES
1041 bool "Namespaces support" if EXPERT
1042 default !EXPERT
1043 help
1044 Provides the way to make tasks work with different objects using
1045 the same id. For example same IPC id may refer to different objects
1046 or same user id or pid may refer to different tasks when used in
1047 different namespaces.
1049 if NAMESPACES
1051 config UTS_NS
1052 bool "UTS namespace"
1053 default y
1054 help
1055 In this namespace tasks see different info provided with the
1056 uname() system call
1058 config IPC_NS
1059 bool "IPC namespace"
1060 depends on (SYSVIPC || POSIX_MQUEUE)
1061 default y
1062 help
1063 In this namespace tasks work with IPC ids which correspond to
1064 different IPC objects in different namespaces.
1066 config USER_NS
1067 bool "User namespace"
1068 depends on UIDGID_CONVERTED
1069 select UIDGID_STRICT_TYPE_CHECKS
1071 default n
1072 help
1073 This allows containers, i.e. vservers, to use user namespaces
1074 to provide different user info for different servers.
1076 When user namespaces are enabled in the kernel it is
1077 recommended that the MEMCG and MEMCG_KMEM options also be
1078 enabled and that user-space use the memory control groups to
1079 limit the amount of memory a memory unprivileged users can
1080 use.
1082 If unsure, say N.
1084 config PID_NS
1085 bool "PID Namespaces"
1086 default y
1087 help
1088 Support process id namespaces. This allows having multiple
1089 processes with the same pid as long as they are in different
1090 pid namespaces. This is a building block of containers.
1092 config NET_NS
1093 bool "Network namespace"
1094 depends on NET
1095 default y
1096 help
1097 Allow user space to create what appear to be multiple instances
1098 of the network stack.
1100 endif # NAMESPACES
1102 config UIDGID_CONVERTED
1103 # True if all of the selected software conmponents are known
1104 # to have uid_t and gid_t converted to kuid_t and kgid_t
1105 # where appropriate and are otherwise safe to use with
1106 # the user namespace.
1107 bool
1108 default y
1110 # Filesystems
1111 depends on XFS_FS = n
1113 config UIDGID_STRICT_TYPE_CHECKS
1114 bool "Require conversions between uid/gids and their internal representation"
1115 depends on UIDGID_CONVERTED
1116 default n
1117 help
1118 While the nececessary conversions are being added to all subsystems this option allows
1119 the code to continue to build for unconverted subsystems.
1121 Say Y here if you want the strict type checking enabled
1123 config SCHED_AUTOGROUP
1124 bool "Automatic process group scheduling"
1125 select EVENTFD
1126 select CGROUPS
1127 select CGROUP_SCHED
1128 select FAIR_GROUP_SCHED
1129 help
1130 This option optimizes the scheduler for common desktop workloads by
1131 automatically creating and populating task groups. This separation
1132 of workloads isolates aggressive CPU burners (like build jobs) from
1133 desktop applications. Task group autogeneration is currently based
1134 upon task session.
1136 config MM_OWNER
1137 bool
1139 config SYSFS_DEPRECATED
1140 bool "Enable deprecated sysfs features to support old userspace tools"
1141 depends on SYSFS
1142 default n
1143 help
1144 This option adds code that switches the layout of the "block" class
1145 devices, to not show up in /sys/class/block/, but only in
1146 /sys/block/.
1148 This switch is only active when the sysfs.deprecated=1 boot option is
1149 passed or the SYSFS_DEPRECATED_V2 option is set.
1151 This option allows new kernels to run on old distributions and tools,
1152 which might get confused by /sys/class/block/. Since 2007/2008 all
1153 major distributions and tools handle this just fine.
1155 Recent distributions and userspace tools after 2009/2010 depend on
1156 the existence of /sys/class/block/, and will not work with this
1157 option enabled.
1159 Only if you are using a new kernel on an old distribution, you might
1160 need to say Y here.
1162 config SYSFS_DEPRECATED_V2
1163 bool "Enable deprecated sysfs features by default"
1164 default n
1165 depends on SYSFS
1166 depends on SYSFS_DEPRECATED
1167 help
1168 Enable deprecated sysfs by default.
1170 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1171 option.
1173 Only if you are using a new kernel on an old distribution, you might
1174 need to say Y here. Even then, odds are you would not need it
1175 enabled, you can always pass the boot option if absolutely necessary.
1177 config RELAY
1178 bool "Kernel->user space relay support (formerly relayfs)"
1179 help
1180 This option enables support for relay interface support in
1181 certain file systems (such as debugfs).
1182 It is designed to provide an efficient mechanism for tools and
1183 facilities to relay large amounts of data from kernel space to
1184 user space.
1186 If unsure, say N.
1188 config BLK_DEV_INITRD
1189 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1190 depends on BROKEN || !FRV
1191 help
1192 The initial RAM filesystem is a ramfs which is loaded by the
1193 boot loader (loadlin or lilo) and that is mounted as root
1194 before the normal boot procedure. It is typically used to
1195 load modules needed to mount the "real" root file system,
1196 etc. See <file:Documentation/initrd.txt> for details.
1198 If RAM disk support (BLK_DEV_RAM) is also included, this
1199 also enables initial RAM disk (initrd) support and adds
1200 15 Kbytes (more on some other architectures) to the kernel size.
1202 If unsure say Y.
1204 if BLK_DEV_INITRD
1206 source "usr/Kconfig"
1208 endif
1210 config CC_OPTIMIZE_FOR_SIZE
1211 bool "Optimize for size"
1212 help
1213 Enabling this option will pass "-Os" instead of "-O2" to gcc
1214 resulting in a smaller kernel.
1216 If unsure, say N.
1218 config SYSCTL
1219 bool
1221 config ANON_INODES
1222 bool
1224 config HAVE_UID16
1225 bool
1227 config SYSCTL_EXCEPTION_TRACE
1228 bool
1229 help
1230 Enable support for /proc/sys/debug/exception-trace.
1232 config SYSCTL_ARCH_UNALIGN_NO_WARN
1233 bool
1234 help
1235 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1236 Allows arch to define/use @no_unaligned_warning to possibly warn
1237 about unaligned access emulation going on under the hood.
1239 config SYSCTL_ARCH_UNALIGN_ALLOW
1240 bool
1241 help
1242 Enable support for /proc/sys/kernel/unaligned-trap
1243 Allows arches to define/use @unaligned_enabled to runtime toggle
1244 the unaligned access emulation.
1245 see arch/parisc/kernel/unaligned.c for reference
1247 config HOTPLUG
1248 def_bool y
1250 config HAVE_PCSPKR_PLATFORM
1251 bool
1253 menuconfig EXPERT
1254 bool "Configure standard kernel features (expert users)"
1255 # Unhide debug options, to make the on-by-default options visible
1256 select DEBUG_KERNEL
1257 help
1258 This option allows certain base kernel options and settings
1259 to be disabled or tweaked. This is for specialized
1260 environments which can tolerate a "non-standard" kernel.
1261 Only use this if you really know what you are doing.
1263 config UID16
1264 bool "Enable 16-bit UID system calls" if EXPERT
1265 depends on HAVE_UID16
1266 default y
1267 help
1268 This enables the legacy 16-bit UID syscall wrappers.
1270 config SYSCTL_SYSCALL
1271 bool "Sysctl syscall support" if EXPERT
1272 depends on PROC_SYSCTL
1273 default n
1274 select SYSCTL
1275 ---help---
1276 sys_sysctl uses binary paths that have been found challenging
1277 to properly maintain and use. The interface in /proc/sys
1278 using paths with ascii names is now the primary path to this
1279 information.
1281 Almost nothing using the binary sysctl interface so if you are
1282 trying to save some space it is probably safe to disable this,
1283 making your kernel marginally smaller.
1285 If unsure say N here.
1287 config KALLSYMS
1288 bool "Load all symbols for debugging/ksymoops" if EXPERT
1289 default y
1290 help
1291 Say Y here to let the kernel print out symbolic crash information and
1292 symbolic stack backtraces. This increases the size of the kernel
1293 somewhat, as all symbols have to be loaded into the kernel image.
1295 config KALLSYMS_ALL
1296 bool "Include all symbols in kallsyms"
1297 depends on DEBUG_KERNEL && KALLSYMS
1298 help
1299 Normally kallsyms only contains the symbols of functions for nicer
1300 OOPS messages and backtraces (i.e., symbols from the text and inittext
1301 sections). This is sufficient for most cases. And only in very rare
1302 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1303 names of variables from the data sections, etc).
1305 This option makes sure that all symbols are loaded into the kernel
1306 image (i.e., symbols from all sections) in cost of increased kernel
1307 size (depending on the kernel configuration, it may be 300KiB or
1308 something like this).
1310 Say N unless you really need all symbols.
1312 config PRINTK
1313 default y
1314 bool "Enable support for printk" if EXPERT
1315 select IRQ_WORK
1316 help
1317 This option enables normal printk support. Removing it
1318 eliminates most of the message strings from the kernel image
1319 and makes the kernel more or less silent. As this makes it
1320 very difficult to diagnose system problems, saying N here is
1321 strongly discouraged.
1323 config BUG
1324 bool "BUG() support" if EXPERT
1325 default y
1326 help
1327 Disabling this option eliminates support for BUG and WARN, reducing
1328 the size of your kernel image and potentially quietly ignoring
1329 numerous fatal conditions. You should only consider disabling this
1330 option for embedded systems with no facilities for reporting errors.
1331 Just say Y.
1333 config ELF_CORE
1334 depends on COREDUMP
1335 default y
1336 bool "Enable ELF core dumps" if EXPERT
1337 help
1338 Enable support for generating core dumps. Disabling saves about 4k.
1341 config PCSPKR_PLATFORM
1342 bool "Enable PC-Speaker support" if EXPERT
1343 depends on HAVE_PCSPKR_PLATFORM
1344 select I8253_LOCK
1345 default y
1346 help
1347 This option allows to disable the internal PC-Speaker
1348 support, saving some memory.
1350 config BASE_FULL
1351 default y
1352 bool "Enable full-sized data structures for core" if EXPERT
1353 help
1354 Disabling this option reduces the size of miscellaneous core
1355 kernel data structures. This saves memory on small machines,
1356 but may reduce performance.
1358 config FUTEX
1359 bool "Enable futex support" if EXPERT
1360 default y
1361 select RT_MUTEXES
1362 help
1363 Disabling this option will cause the kernel to be built without
1364 support for "fast userspace mutexes". The resulting kernel may not
1365 run glibc-based applications correctly.
1367 config EPOLL
1368 bool "Enable eventpoll support" if EXPERT
1369 default y
1370 select ANON_INODES
1371 help
1372 Disabling this option will cause the kernel to be built without
1373 support for epoll family of system calls.
1375 config SIGNALFD
1376 bool "Enable signalfd() system call" if EXPERT
1377 select ANON_INODES
1378 default y
1379 help
1380 Enable the signalfd() system call that allows to receive signals
1381 on a file descriptor.
1383 If unsure, say Y.
1385 config TIMERFD
1386 bool "Enable timerfd() system call" if EXPERT
1387 select ANON_INODES
1388 default y
1389 help
1390 Enable the timerfd() system call that allows to receive timer
1391 events on a file descriptor.
1393 If unsure, say Y.
1395 config EVENTFD
1396 bool "Enable eventfd() system call" if EXPERT
1397 select ANON_INODES
1398 default y
1399 help
1400 Enable the eventfd() system call that allows to receive both
1401 kernel notification (ie. KAIO) or userspace notifications.
1403 If unsure, say Y.
1405 config SHMEM
1406 bool "Use full shmem filesystem" if EXPERT
1407 default y
1408 depends on MMU
1409 help
1410 The shmem is an internal filesystem used to manage shared memory.
1411 It is backed by swap and manages resource limits. It is also exported
1412 to userspace as tmpfs if TMPFS is enabled. Disabling this
1413 option replaces shmem and tmpfs with the much simpler ramfs code,
1414 which may be appropriate on small systems without swap.
1416 config AIO
1417 bool "Enable AIO support" if EXPERT
1418 default y
1419 help
1420 This option enables POSIX asynchronous I/O which may by used
1421 by some high performance threaded applications. Disabling
1422 this option saves about 7k.
1424 config PCI_QUIRKS
1425 default y
1426 bool "Enable PCI quirk workarounds" if EXPERT
1427 depends on PCI
1428 help
1429 This enables workarounds for various PCI chipset
1430 bugs/quirks. Disable this only if your target machine is
1431 unaffected by PCI quirks.
1433 config EMBEDDED
1434 bool "Embedded system"
1435 select EXPERT
1436 help
1437 This option should be enabled if compiling the kernel for
1438 an embedded system so certain expert options are available
1439 for configuration.
1441 config HAVE_PERF_EVENTS
1442 bool
1443 help
1444 See tools/perf/design.txt for details.
1446 config PERF_USE_VMALLOC
1447 bool
1448 help
1449 See tools/perf/design.txt for details
1451 menu "Kernel Performance Events And Counters"
1453 config PERF_EVENTS
1454 bool "Kernel performance events and counters"
1455 default y if PROFILING
1456 depends on HAVE_PERF_EVENTS
1457 select ANON_INODES
1458 select IRQ_WORK
1459 help
1460 Enable kernel support for various performance events provided
1461 by software and hardware.
1463 Software events are supported either built-in or via the
1464 use of generic tracepoints.
1466 Most modern CPUs support performance events via performance
1467 counter registers. These registers count the number of certain
1468 types of hw events: such as instructions executed, cachemisses
1469 suffered, or branches mis-predicted - without slowing down the
1470 kernel or applications. These registers can also trigger interrupts
1471 when a threshold number of events have passed - and can thus be
1472 used to profile the code that runs on that CPU.
1474 The Linux Performance Event subsystem provides an abstraction of
1475 these software and hardware event capabilities, available via a
1476 system call and used by the "perf" utility in tools/perf/. It
1477 provides per task and per CPU counters, and it provides event
1478 capabilities on top of those.
1480 Say Y if unsure.
1482 config DEBUG_PERF_USE_VMALLOC
1483 default n
1484 bool "Debug: use vmalloc to back perf mmap() buffers"
1485 depends on PERF_EVENTS && DEBUG_KERNEL
1486 select PERF_USE_VMALLOC
1487 help
1488 Use vmalloc memory to back perf mmap() buffers.
1490 Mostly useful for debugging the vmalloc code on platforms
1491 that don't require it.
1493 Say N if unsure.
1495 endmenu
1497 config VM_EVENT_COUNTERS
1498 default y
1499 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1500 help
1501 VM event counters are needed for event counts to be shown.
1502 This option allows the disabling of the VM event counters
1503 on EXPERT systems. /proc/vmstat will only show page counts
1504 if VM event counters are disabled.
1506 config SLUB_DEBUG
1507 default y
1508 bool "Enable SLUB debugging support" if EXPERT
1509 depends on SLUB && SYSFS
1510 help
1511 SLUB has extensive debug support features. Disabling these can
1512 result in significant savings in code size. This also disables
1513 SLUB sysfs support. /sys/slab will not exist and there will be
1514 no support for cache validation etc.
1516 config COMPAT_BRK
1517 bool "Disable heap randomization"
1518 default y
1519 help
1520 Randomizing heap placement makes heap exploits harder, but it
1521 also breaks ancient binaries (including anything libc5 based).
1522 This option changes the bootup default to heap randomization
1523 disabled, and can be overridden at runtime by setting
1524 /proc/sys/kernel/randomize_va_space to 2.
1526 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1528 choice
1529 prompt "Choose SLAB allocator"
1530 default SLUB
1531 help
1532 This option allows to select a slab allocator.
1534 config SLAB
1535 bool "SLAB"
1536 help
1537 The regular slab allocator that is established and known to work
1538 well in all environments. It organizes cache hot objects in
1539 per cpu and per node queues.
1541 config SLUB
1542 bool "SLUB (Unqueued Allocator)"
1543 help
1544 SLUB is a slab allocator that minimizes cache line usage
1545 instead of managing queues of cached objects (SLAB approach).
1546 Per cpu caching is realized using slabs of objects instead
1547 of queues of objects. SLUB can use memory efficiently
1548 and has enhanced diagnostics. SLUB is the default choice for
1549 a slab allocator.
1551 config SLOB
1552 depends on EXPERT
1553 bool "SLOB (Simple Allocator)"
1554 help
1555 SLOB replaces the stock allocator with a drastically simpler
1556 allocator. SLOB is generally more space efficient but
1557 does not perform as well on large systems.
1559 endchoice
1561 config MMAP_ALLOW_UNINITIALIZED
1562 bool "Allow mmapped anonymous memory to be uninitialized"
1563 depends on EXPERT && !MMU
1564 default n
1565 help
1566 Normally, and according to the Linux spec, anonymous memory obtained
1567 from mmap() has it's contents cleared before it is passed to
1568 userspace. Enabling this config option allows you to request that
1569 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1570 providing a huge performance boost. If this option is not enabled,
1571 then the flag will be ignored.
1573 This is taken advantage of by uClibc's malloc(), and also by
1574 ELF-FDPIC binfmt's brk and stack allocator.
1576 Because of the obvious security issues, this option should only be
1577 enabled on embedded devices where you control what is run in
1578 userspace. Since that isn't generally a problem on no-MMU systems,
1579 it is normally safe to say Y here.
1581 See Documentation/nommu-mmap.txt for more information.
1583 config PROFILING
1584 bool "Profiling support"
1585 help
1586 Say Y here to enable the extended profiling support mechanisms used
1587 by profilers such as OProfile.
1589 #
1590 # Place an empty function call at each tracepoint site. Can be
1591 # dynamically changed for a probe function.
1592 #
1593 config TRACEPOINTS
1594 bool
1596 source "arch/Kconfig"
1598 endmenu # General setup
1600 config HAVE_GENERIC_DMA_COHERENT
1601 bool
1602 default n
1604 config SLABINFO
1605 bool
1606 depends on PROC_FS
1607 depends on SLAB || SLUB_DEBUG
1608 default y
1610 config RT_MUTEXES
1611 boolean
1613 config BASE_SMALL
1614 int
1615 default 0 if BASE_FULL
1616 default 1 if !BASE_FULL
1618 menuconfig MODULES
1619 bool "Enable loadable module support"
1620 help
1621 Kernel modules are small pieces of compiled code which can
1622 be inserted in the running kernel, rather than being
1623 permanently built into the kernel. You use the "modprobe"
1624 tool to add (and sometimes remove) them. If you say Y here,
1625 many parts of the kernel can be built as modules (by
1626 answering M instead of Y where indicated): this is most
1627 useful for infrequently used options which are not required
1628 for booting. For more information, see the man pages for
1629 modprobe, lsmod, modinfo, insmod and rmmod.
1631 If you say Y here, you will need to run "make
1632 modules_install" to put the modules under /lib/modules/
1633 where modprobe can find them (you may need to be root to do
1634 this).
1636 If unsure, say Y.
1638 if MODULES
1640 config MODULE_FORCE_LOAD
1641 bool "Forced module loading"
1642 default n
1643 help
1644 Allow loading of modules without version information (ie. modprobe
1645 --force). Forced module loading sets the 'F' (forced) taint flag and
1646 is usually a really bad idea.
1648 config MODULE_UNLOAD
1649 bool "Module unloading"
1650 help
1651 Without this option you will not be able to unload any
1652 modules (note that some modules may not be unloadable
1653 anyway), which makes your kernel smaller, faster
1654 and simpler. If unsure, say Y.
1656 config MODULE_FORCE_UNLOAD
1657 bool "Forced module unloading"
1658 depends on MODULE_UNLOAD
1659 help
1660 This option allows you to force a module to unload, even if the
1661 kernel believes it is unsafe: the kernel will remove the module
1662 without waiting for anyone to stop using it (using the -f option to
1663 rmmod). This is mainly for kernel developers and desperate users.
1664 If unsure, say N.
1666 config MODVERSIONS
1667 bool "Module versioning support"
1668 help
1669 Usually, you have to use modules compiled with your kernel.
1670 Saying Y here makes it sometimes possible to use modules
1671 compiled for different kernels, by adding enough information
1672 to the modules to (hopefully) spot any changes which would
1673 make them incompatible with the kernel you are running. If
1674 unsure, say N.
1676 config MODULE_SRCVERSION_ALL
1677 bool "Source checksum for all modules"
1678 help
1679 Modules which contain a MODULE_VERSION get an extra "srcversion"
1680 field inserted into their modinfo section, which contains a
1681 sum of the source files which made it. This helps maintainers
1682 see exactly which source was used to build a module (since
1683 others sometimes change the module source without updating
1684 the version). With this option, such a "srcversion" field
1685 will be created for all modules. If unsure, say N.
1687 config MODULE_SIG
1688 bool "Module signature verification"
1689 depends on MODULES
1690 select KEYS
1691 select CRYPTO
1692 select ASYMMETRIC_KEY_TYPE
1693 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1694 select PUBLIC_KEY_ALGO_RSA
1695 select ASN1
1696 select OID_REGISTRY
1697 select X509_CERTIFICATE_PARSER
1698 help
1699 Check modules for valid signatures upon load: the signature
1700 is simply appended to the module. For more information see
1701 Documentation/module-signing.txt.
1703 !!!WARNING!!! If you enable this option, you MUST make sure that the
1704 module DOES NOT get stripped after being signed. This includes the
1705 debuginfo strip done by some packagers (such as rpmbuild) and
1706 inclusion into an initramfs that wants the module size reduced.
1708 config MODULE_SIG_FORCE
1709 bool "Require modules to be validly signed"
1710 depends on MODULE_SIG
1711 help
1712 Reject unsigned modules or signed modules for which we don't have a
1713 key. Without this, such modules will simply taint the kernel.
1715 config MODULE_SIG_ALL
1716 bool "Automatically sign all modules"
1717 default y
1718 depends on MODULE_SIG
1719 help
1720 Sign all modules during make modules_install. Without this option,
1721 modules must be signed manually, using the scripts/sign-file tool.
1723 comment "Do not forget to sign required modules with scripts/sign-file"
1724 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1726 choice
1727 prompt "Which hash algorithm should modules be signed with?"
1728 depends on MODULE_SIG
1729 help
1730 This determines which sort of hashing algorithm will be used during
1731 signature generation. This algorithm _must_ be built into the kernel
1732 directly so that signature verification can take place. It is not
1733 possible to load a signed module containing the algorithm to check
1734 the signature on that module.
1736 config MODULE_SIG_SHA1
1737 bool "Sign modules with SHA-1"
1738 select CRYPTO_SHA1
1740 config MODULE_SIG_SHA224
1741 bool "Sign modules with SHA-224"
1742 select CRYPTO_SHA256
1744 config MODULE_SIG_SHA256
1745 bool "Sign modules with SHA-256"
1746 select CRYPTO_SHA256
1748 config MODULE_SIG_SHA384
1749 bool "Sign modules with SHA-384"
1750 select CRYPTO_SHA512
1752 config MODULE_SIG_SHA512
1753 bool "Sign modules with SHA-512"
1754 select CRYPTO_SHA512
1756 endchoice
1758 config MODULE_SIG_HASH
1759 string
1760 depends on MODULE_SIG
1761 default "sha1" if MODULE_SIG_SHA1
1762 default "sha224" if MODULE_SIG_SHA224
1763 default "sha256" if MODULE_SIG_SHA256
1764 default "sha384" if MODULE_SIG_SHA384
1765 default "sha512" if MODULE_SIG_SHA512
1767 endif # MODULES
1769 config INIT_ALL_POSSIBLE
1770 bool
1771 help
1772 Back when each arch used to define their own cpu_online_mask and
1773 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1774 with all 1s, and others with all 0s. When they were centralised,
1775 it was better to provide this option than to break all the archs
1776 and have several arch maintainers pursuing me down dark alleys.
1778 config STOP_MACHINE
1779 bool
1780 default y
1781 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1782 help
1783 Need stop_machine() primitive.
1785 source "block/Kconfig"
1787 config PREEMPT_NOTIFIERS
1788 bool
1790 config PADATA
1791 depends on SMP
1792 bool
1794 # Can be selected by architectures with broken toolchains
1795 # that get confused by correct const<->read_only section
1796 # mappings
1797 config BROKEN_RODATA
1798 bool
1800 config ASN1
1801 tristate
1802 help
1803 Build a simple ASN.1 grammar compiler that produces a bytecode output
1804 that can be interpreted by the ASN.1 stream decoder and used to
1805 inform it as to what tags are to be expected in a stream and what
1806 functions to call on what tags.
1808 source "kernel/Kconfig.locks"