| blob | 2d9b83104dcf715197f1a84d34b892783ff79fe2 |
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 select IRQ_WORK
435 help
436 This option selects the RCU implementation that is
437 designed for very large SMP system with hundreds or
438 thousands of CPUs. It also scales down nicely to
439 smaller systems.
441 config TREE_PREEMPT_RCU
442 bool "Preemptible tree-based hierarchical RCU"
443 depends on PREEMPT
444 help
445 This option selects the RCU implementation that is
446 designed for very large SMP systems with hundreds or
447 thousands of CPUs, but for which real-time response
448 is also required. It also scales down nicely to
449 smaller systems.
451 Select this option if you are unsure.
453 config TINY_RCU
454 bool "UP-only small-memory-footprint RCU"
455 depends on !PREEMPT && !SMP
456 help
457 This option selects the RCU implementation that is
458 designed for UP systems from which real-time response
459 is not required. This option greatly reduces the
460 memory footprint of RCU.
462 config TINY_PREEMPT_RCU
463 bool "Preemptible UP-only small-memory-footprint RCU"
464 depends on PREEMPT && !SMP
465 help
466 This option selects the RCU implementation that is designed
467 for real-time UP systems. This option greatly reduces the
468 memory footprint of RCU.
470 endchoice
472 config PREEMPT_RCU
473 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
474 help
475 This option enables preemptible-RCU code that is common between
476 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
478 config RCU_STALL_COMMON
479 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
480 help
481 This option enables RCU CPU stall code that is common between
482 the TINY and TREE variants of RCU. The purpose is to allow
483 the tiny variants to disable RCU CPU stall warnings, while
484 making these warnings mandatory for the tree variants.
486 config CONTEXT_TRACKING
487 bool
489 config RCU_USER_QS
490 bool "Consider userspace as in RCU extended quiescent state"
491 depends on HAVE_CONTEXT_TRACKING && SMP
492 select CONTEXT_TRACKING
493 help
494 This option sets hooks on kernel / userspace boundaries and
495 puts RCU in extended quiescent state when the CPU runs in
496 userspace. It means that when a CPU runs in userspace, it is
497 excluded from the global RCU state machine and thus doesn't
498 try to keep the timer tick on for RCU.
500 Unless you want to hack and help the development of the full
501 dynticks mode, you shouldn't enable this option. It also
502 adds unnecessary overhead.
504 If unsure say N
506 config CONTEXT_TRACKING_FORCE
507 bool "Force context tracking"
508 depends on CONTEXT_TRACKING
509 default CONTEXT_TRACKING
510 help
511 Probe on user/kernel boundaries by default in order to
512 test the features that rely on it such as userspace RCU extended
513 quiescent states.
514 This test is there for debugging until we have a real user like the
515 full dynticks mode.
517 config RCU_FANOUT
518 int "Tree-based hierarchical RCU fanout value"
519 range 2 64 if 64BIT
520 range 2 32 if !64BIT
521 depends on TREE_RCU || TREE_PREEMPT_RCU
522 default 64 if 64BIT
523 default 32 if !64BIT
524 help
525 This option controls the fanout of hierarchical implementations
526 of RCU, allowing RCU to work efficiently on machines with
527 large numbers of CPUs. This value must be at least the fourth
528 root of NR_CPUS, which allows NR_CPUS to be insanely large.
529 The default value of RCU_FANOUT should be used for production
530 systems, but if you are stress-testing the RCU implementation
531 itself, small RCU_FANOUT values allow you to test large-system
532 code paths on small(er) systems.
534 Select a specific number if testing RCU itself.
535 Take the default if unsure.
537 config RCU_FANOUT_LEAF
538 int "Tree-based hierarchical RCU leaf-level fanout value"
539 range 2 RCU_FANOUT if 64BIT
540 range 2 RCU_FANOUT if !64BIT
541 depends on TREE_RCU || TREE_PREEMPT_RCU
542 default 16
543 help
544 This option controls the leaf-level fanout of hierarchical
545 implementations of RCU, and allows trading off cache misses
546 against lock contention. Systems that synchronize their
547 scheduling-clock interrupts for energy-efficiency reasons will
548 want the default because the smaller leaf-level fanout keeps
549 lock contention levels acceptably low. Very large systems
550 (hundreds or thousands of CPUs) will instead want to set this
551 value to the maximum value possible in order to reduce the
552 number of cache misses incurred during RCU's grace-period
553 initialization. These systems tend to run CPU-bound, and thus
554 are not helped by synchronized interrupts, and thus tend to
555 skew them, which reduces lock contention enough that large
556 leaf-level fanouts work well.
558 Select a specific number if testing RCU itself.
560 Select the maximum permissible value for large systems.
562 Take the default if unsure.
564 config RCU_FANOUT_EXACT
565 bool "Disable tree-based hierarchical RCU auto-balancing"
566 depends on TREE_RCU || TREE_PREEMPT_RCU
567 default n
568 help
569 This option forces use of the exact RCU_FANOUT value specified,
570 regardless of imbalances in the hierarchy. This is useful for
571 testing RCU itself, and might one day be useful on systems with
572 strong NUMA behavior.
574 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
576 Say N if unsure.
578 config RCU_FAST_NO_HZ
579 bool "Accelerate last non-dyntick-idle CPU's grace periods"
580 depends on NO_HZ_COMMON && SMP
581 default n
582 help
583 This option permits CPUs to enter dynticks-idle state even if
584 they have RCU callbacks queued, and prevents RCU from waking
585 these CPUs up more than roughly once every four jiffies (by
586 default, you can adjust this using the rcutree.rcu_idle_gp_delay
587 parameter), thus improving energy efficiency. On the other
588 hand, this option increases the duration of RCU grace periods,
589 for example, slowing down synchronize_rcu().
591 Say Y if energy efficiency is critically important, and you
592 don't care about increased grace-period durations.
594 Say N if you are unsure.
596 config TREE_RCU_TRACE
597 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
598 select DEBUG_FS
599 help
600 This option provides tracing for the TREE_RCU and
601 TREE_PREEMPT_RCU implementations, permitting Makefile to
602 trivially select kernel/rcutree_trace.c.
604 config RCU_BOOST
605 bool "Enable RCU priority boosting"
606 depends on RT_MUTEXES && PREEMPT_RCU
607 default n
608 help
609 This option boosts the priority of preempted RCU readers that
610 block the current preemptible RCU grace period for too long.
611 This option also prevents heavy loads from blocking RCU
612 callback invocation for all flavors of RCU.
614 Say Y here if you are working with real-time apps or heavy loads
615 Say N here if you are unsure.
617 config RCU_BOOST_PRIO
618 int "Real-time priority to boost RCU readers to"
619 range 1 99
620 depends on RCU_BOOST
621 default 1
622 help
623 This option specifies the real-time priority to which long-term
624 preempted RCU readers are to be boosted. If you are working
625 with a real-time application that has one or more CPU-bound
626 threads running at a real-time priority level, you should set
627 RCU_BOOST_PRIO to a priority higher then the highest-priority
628 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
629 of 1 is appropriate in the common case, which is real-time
630 applications that do not have any CPU-bound threads.
632 Some real-time applications might not have a single real-time
633 thread that saturates a given CPU, but instead might have
634 multiple real-time threads that, taken together, fully utilize
635 that CPU. In this case, you should set RCU_BOOST_PRIO to
636 a priority higher than the lowest-priority thread that is
637 conspiring to prevent the CPU from running any non-real-time
638 tasks. For example, if one thread at priority 10 and another
639 thread at priority 5 are between themselves fully consuming
640 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
641 set to priority 6 or higher.
643 Specify the real-time priority, or take the default if unsure.
645 config RCU_BOOST_DELAY
646 int "Milliseconds to delay boosting after RCU grace-period start"
647 range 0 3000
648 depends on RCU_BOOST
649 default 500
650 help
651 This option specifies the time to wait after the beginning of
652 a given grace period before priority-boosting preempted RCU
653 readers blocking that grace period. Note that any RCU reader
654 blocking an expedited RCU grace period is boosted immediately.
656 Accept the default if unsure.
658 config RCU_NOCB_CPU
659 bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
660 depends on TREE_RCU || TREE_PREEMPT_RCU
661 default n
662 help
663 Use this option to reduce OS jitter for aggressive HPC or
664 real-time workloads. It can also be used to offload RCU
665 callback invocation to energy-efficient CPUs in battery-powered
666 asymmetric multiprocessors.
668 This option offloads callback invocation from the set of
669 CPUs specified at boot time by the rcu_nocbs parameter.
670 For each such CPU, a kthread ("rcuox/N") will be created to
671 invoke callbacks, where the "N" is the CPU being offloaded,
672 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
673 "s" for RCU-sched. Nothing prevents this kthread from running
674 on the specified CPUs, but (1) the kthreads may be preempted
675 between each callback, and (2) affinity or cgroups can be used
676 to force the kthreads to run on whatever set of CPUs is desired.
678 Say Y here if you want to help to debug reduced OS jitter.
679 Say N here if you are unsure.
681 choice
682 prompt "Build-forced no-CBs CPUs"
683 default RCU_NOCB_CPU_NONE
684 help
685 This option allows no-CBs CPUs to be specified at build time.
686 Additional no-CBs CPUs may be specified by the rcu_nocbs=
687 boot parameter.
689 config RCU_NOCB_CPU_NONE
690 bool "No build_forced no-CBs CPUs"
691 depends on RCU_NOCB_CPU && !NO_HZ_FULL
692 help
693 This option does not force any of the CPUs to be no-CBs CPUs.
694 Only CPUs designated by the rcu_nocbs= boot parameter will be
695 no-CBs CPUs.
697 config RCU_NOCB_CPU_ZERO
698 bool "CPU 0 is a build_forced no-CBs CPU"
699 depends on RCU_NOCB_CPU && !NO_HZ_FULL
700 help
701 This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
702 may be designated as no-CBs CPUs using the rcu_nocbs= boot
703 parameter will be no-CBs CPUs.
705 Select this if CPU 0 needs to be a no-CBs CPU for real-time
706 or energy-efficiency reasons.
708 config RCU_NOCB_CPU_ALL
709 bool "All CPUs are build_forced no-CBs CPUs"
710 depends on RCU_NOCB_CPU
711 help
712 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
713 boot parameter will be ignored.
715 Select this if all CPUs need to be no-CBs CPUs for real-time
716 or energy-efficiency reasons.
718 endchoice
720 endmenu # "RCU Subsystem"
722 config IKCONFIG
723 tristate "Kernel .config support"
724 ---help---
725 This option enables the complete Linux kernel ".config" file
726 contents to be saved in the kernel. It provides documentation
727 of which kernel options are used in a running kernel or in an
728 on-disk kernel. This information can be extracted from the kernel
729 image file with the script scripts/extract-ikconfig and used as
730 input to rebuild the current kernel or to build another kernel.
731 It can also be extracted from a running kernel by reading
732 /proc/config.gz if enabled (below).
734 config IKCONFIG_PROC
735 bool "Enable access to .config through /proc/config.gz"
736 depends on IKCONFIG && PROC_FS
737 ---help---
738 This option enables access to the kernel configuration file
739 through /proc/config.gz.
741 config LOG_BUF_SHIFT
742 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
743 range 12 21
744 default 17
745 help
746 Select kernel log buffer size as a power of 2.
747 Examples:
748 17 => 128 KB
749 16 => 64 KB
750 15 => 32 KB
751 14 => 16 KB
752 13 => 8 KB
753 12 => 4 KB
755 #
756 # Architectures with an unreliable sched_clock() should select this:
757 #
758 config HAVE_UNSTABLE_SCHED_CLOCK
759 bool
761 #
762 # For architectures that want to enable the support for NUMA-affine scheduler
763 # balancing logic:
764 #
765 config ARCH_SUPPORTS_NUMA_BALANCING
766 bool
768 # For architectures that (ab)use NUMA to represent different memory regions
769 # all cpu-local but of different latencies, such as SuperH.
770 #
771 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
772 bool
774 #
775 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
776 config ARCH_WANTS_PROT_NUMA_PROT_NONE
777 bool
779 config ARCH_USES_NUMA_PROT_NONE
780 bool
781 default y
782 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
783 depends on NUMA_BALANCING
785 config NUMA_BALANCING_DEFAULT_ENABLED
786 bool "Automatically enable NUMA aware memory/task placement"
787 default y
788 depends on NUMA_BALANCING
789 help
790 If set, autonumic NUMA balancing will be enabled if running on a NUMA
791 machine.
793 config NUMA_BALANCING
794 bool "Memory placement aware NUMA scheduler"
795 depends on ARCH_SUPPORTS_NUMA_BALANCING
796 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
797 depends on SMP && NUMA && MIGRATION
798 help
799 This option adds support for automatic NUMA aware memory/task placement.
800 The mechanism is quite primitive and is based on migrating memory when
801 it is references to the node the task is running on.
803 This system will be inactive on UMA systems.
805 menuconfig CGROUPS
806 boolean "Control Group support"
807 depends on EVENTFD
808 help
809 This option adds support for grouping sets of processes together, for
810 use with process control subsystems such as Cpusets, CFS, memory
811 controls or device isolation.
812 See
813 - Documentation/scheduler/sched-design-CFS.txt (CFS)
814 - Documentation/cgroups/ (features for grouping, isolation
815 and resource control)
817 Say N if unsure.
819 if CGROUPS
821 config CGROUP_DEBUG
822 bool "Example debug cgroup subsystem"
823 default n
824 help
825 This option enables a simple cgroup subsystem that
826 exports useful debugging information about the cgroups
827 framework.
829 Say N if unsure.
831 config CGROUP_FREEZER
832 bool "Freezer cgroup subsystem"
833 help
834 Provides a way to freeze and unfreeze all tasks in a
835 cgroup.
837 config CGROUP_DEVICE
838 bool "Device controller for cgroups"
839 help
840 Provides a cgroup implementing whitelists for devices which
841 a process in the cgroup can mknod or open.
843 config CPUSETS
844 bool "Cpuset support"
845 help
846 This option will let you create and manage CPUSETs which
847 allow dynamically partitioning a system into sets of CPUs and
848 Memory Nodes and assigning tasks to run only within those sets.
849 This is primarily useful on large SMP or NUMA systems.
851 Say N if unsure.
853 config PROC_PID_CPUSET
854 bool "Include legacy /proc/<pid>/cpuset file"
855 depends on CPUSETS
856 default y
858 config CGROUP_CPUACCT
859 bool "Simple CPU accounting cgroup subsystem"
860 help
861 Provides a simple Resource Controller for monitoring the
862 total CPU consumed by the tasks in a cgroup.
864 config RESOURCE_COUNTERS
865 bool "Resource counters"
866 help
867 This option enables controller independent resource accounting
868 infrastructure that works with cgroups.
870 config MEMCG
871 bool "Memory Resource Controller for Control Groups"
872 depends on RESOURCE_COUNTERS
873 select MM_OWNER
874 help
875 Provides a memory resource controller that manages both anonymous
876 memory and page cache. (See Documentation/cgroups/memory.txt)
878 Note that setting this option increases fixed memory overhead
879 associated with each page of memory in the system. By this,
880 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
881 usage tracking struct at boot. Total amount of this is printed out
882 at boot.
884 Only enable when you're ok with these trade offs and really
885 sure you need the memory resource controller. Even when you enable
886 this, you can set "cgroup_disable=memory" at your boot option to
887 disable memory resource controller and you can avoid overheads.
888 (and lose benefits of memory resource controller)
890 This config option also selects MM_OWNER config option, which
891 could in turn add some fork/exit overhead.
893 config MEMCG_SWAP
894 bool "Memory Resource Controller Swap Extension"
895 depends on MEMCG && SWAP
896 help
897 Add swap management feature to memory resource controller. When you
898 enable this, you can limit mem+swap usage per cgroup. In other words,
899 when you disable this, memory resource controller has no cares to
900 usage of swap...a process can exhaust all of the swap. This extension
901 is useful when you want to avoid exhaustion swap but this itself
902 adds more overheads and consumes memory for remembering information.
903 Especially if you use 32bit system or small memory system, please
904 be careful about enabling this. When memory resource controller
905 is disabled by boot option, this will be automatically disabled and
906 there will be no overhead from this. Even when you set this config=y,
907 if boot option "swapaccount=0" is set, swap will not be accounted.
908 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
909 size is 4096bytes, 512k per 1Gbytes of swap.
910 config MEMCG_SWAP_ENABLED
911 bool "Memory Resource Controller Swap Extension enabled by default"
912 depends on MEMCG_SWAP
913 default y
914 help
915 Memory Resource Controller Swap Extension comes with its price in
916 a bigger memory consumption. General purpose distribution kernels
917 which want to enable the feature but keep it disabled by default
918 and let the user enable it by swapaccount boot command line
919 parameter should have this option unselected.
920 For those who want to have the feature enabled by default should
921 select this option (if, for some reason, they need to disable it
922 then swapaccount=0 does the trick).
923 config MEMCG_KMEM
924 bool "Memory Resource Controller Kernel Memory accounting"
925 depends on MEMCG
926 depends on SLUB || SLAB
927 help
928 The Kernel Memory extension for Memory Resource Controller can limit
929 the amount of memory used by kernel objects in the system. Those are
930 fundamentally different from the entities handled by the standard
931 Memory Controller, which are page-based, and can be swapped. Users of
932 the kmem extension can use it to guarantee that no group of processes
933 will ever exhaust kernel resources alone.
935 config CGROUP_HUGETLB
936 bool "HugeTLB Resource Controller for Control Groups"
937 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
938 default n
939 help
940 Provides a cgroup Resource Controller for HugeTLB pages.
941 When you enable this, you can put a per cgroup limit on HugeTLB usage.
942 The limit is enforced during page fault. Since HugeTLB doesn't
943 support page reclaim, enforcing the limit at page fault time implies
944 that, the application will get SIGBUS signal if it tries to access
945 HugeTLB pages beyond its limit. This requires the application to know
946 beforehand how much HugeTLB pages it would require for its use. The
947 control group is tracked in the third page lru pointer. This means
948 that we cannot use the controller with huge page less than 3 pages.
950 config CGROUP_PERF
951 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
952 depends on PERF_EVENTS && CGROUPS
953 help
954 This option extends the per-cpu mode to restrict monitoring to
955 threads which belong to the cgroup specified and run on the
956 designated cpu.
958 Say N if unsure.
960 menuconfig CGROUP_SCHED
961 bool "Group CPU scheduler"
962 default n
963 help
964 This feature lets CPU scheduler recognize task groups and control CPU
965 bandwidth allocation to such task groups. It uses cgroups to group
966 tasks.
968 if CGROUP_SCHED
969 config FAIR_GROUP_SCHED
970 bool "Group scheduling for SCHED_OTHER"
971 depends on CGROUP_SCHED
972 default CGROUP_SCHED
974 config CFS_BANDWIDTH
975 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
976 depends on FAIR_GROUP_SCHED
977 default n
978 help
979 This option allows users to define CPU bandwidth rates (limits) for
980 tasks running within the fair group scheduler. Groups with no limit
981 set are considered to be unconstrained and will run with no
982 restriction.
983 See tip/Documentation/scheduler/sched-bwc.txt for more information.
985 config RT_GROUP_SCHED
986 bool "Group scheduling for SCHED_RR/FIFO"
987 depends on CGROUP_SCHED
988 default n
989 help
990 This feature lets you explicitly allocate real CPU bandwidth
991 to task groups. If enabled, it will also make it impossible to
992 schedule realtime tasks for non-root users until you allocate
993 realtime bandwidth for them.
994 See Documentation/scheduler/sched-rt-group.txt for more information.
996 endif #CGROUP_SCHED
998 config BLK_CGROUP
999 bool "Block IO controller"
1000 depends on BLOCK
1001 default n
1002 ---help---
1003 Generic block IO controller cgroup interface. This is the common
1004 cgroup interface which should be used by various IO controlling
1005 policies.
1007 Currently, CFQ IO scheduler uses it to recognize task groups and
1008 control disk bandwidth allocation (proportional time slice allocation)
1009 to such task groups. It is also used by bio throttling logic in
1010 block layer to implement upper limit in IO rates on a device.
1012 This option only enables generic Block IO controller infrastructure.
1013 One needs to also enable actual IO controlling logic/policy. For
1014 enabling proportional weight division of disk bandwidth in CFQ, set
1015 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1016 CONFIG_BLK_DEV_THROTTLING=y.
1018 See Documentation/cgroups/blkio-controller.txt for more information.
1020 config DEBUG_BLK_CGROUP
1021 bool "Enable Block IO controller debugging"
1022 depends on BLK_CGROUP
1023 default n
1024 ---help---
1025 Enable some debugging help. Currently it exports additional stat
1026 files in a cgroup which can be useful for debugging.
1028 endif # CGROUPS
1030 config CHECKPOINT_RESTORE
1031 bool "Checkpoint/restore support" if EXPERT
1032 default n
1033 help
1034 Enables additional kernel features in a sake of checkpoint/restore.
1035 In particular it adds auxiliary prctl codes to setup process text,
1036 data and heap segment sizes, and a few additional /proc filesystem
1037 entries.
1039 If unsure, say N here.
1041 menuconfig NAMESPACES
1042 bool "Namespaces support" if EXPERT
1043 default !EXPERT
1044 help
1045 Provides the way to make tasks work with different objects using
1046 the same id. For example same IPC id may refer to different objects
1047 or same user id or pid may refer to different tasks when used in
1048 different namespaces.
1050 if NAMESPACES
1052 config UTS_NS
1053 bool "UTS namespace"
1054 default y
1055 help
1056 In this namespace tasks see different info provided with the
1057 uname() system call
1059 config IPC_NS
1060 bool "IPC namespace"
1061 depends on (SYSVIPC || POSIX_MQUEUE)
1062 default y
1063 help
1064 In this namespace tasks work with IPC ids which correspond to
1065 different IPC objects in different namespaces.
1067 config USER_NS
1068 bool "User namespace"
1069 depends on UIDGID_CONVERTED
1070 select UIDGID_STRICT_TYPE_CHECKS
1072 default n
1073 help
1074 This allows containers, i.e. vservers, to use user namespaces
1075 to provide different user info for different servers.
1077 When user namespaces are enabled in the kernel it is
1078 recommended that the MEMCG and MEMCG_KMEM options also be
1079 enabled and that user-space use the memory control groups to
1080 limit the amount of memory a memory unprivileged users can
1081 use.
1083 If unsure, say N.
1085 config PID_NS
1086 bool "PID Namespaces"
1087 default y
1088 help
1089 Support process id namespaces. This allows having multiple
1090 processes with the same pid as long as they are in different
1091 pid namespaces. This is a building block of containers.
1093 config NET_NS
1094 bool "Network namespace"
1095 depends on NET
1096 default y
1097 help
1098 Allow user space to create what appear to be multiple instances
1099 of the network stack.
1101 endif # NAMESPACES
1103 config UIDGID_CONVERTED
1104 # True if all of the selected software conmponents are known
1105 # to have uid_t and gid_t converted to kuid_t and kgid_t
1106 # where appropriate and are otherwise safe to use with
1107 # the user namespace.
1108 bool
1109 default y
1111 # Filesystems
1112 depends on XFS_FS = n
1114 config UIDGID_STRICT_TYPE_CHECKS
1115 bool "Require conversions between uid/gids and their internal representation"
1116 depends on UIDGID_CONVERTED
1117 default n
1118 help
1119 While the nececessary conversions are being added to all subsystems this option allows
1120 the code to continue to build for unconverted subsystems.
1122 Say Y here if you want the strict type checking enabled
1124 config SCHED_AUTOGROUP
1125 bool "Automatic process group scheduling"
1126 select EVENTFD
1127 select CGROUPS
1128 select CGROUP_SCHED
1129 select FAIR_GROUP_SCHED
1130 help
1131 This option optimizes the scheduler for common desktop workloads by
1132 automatically creating and populating task groups. This separation
1133 of workloads isolates aggressive CPU burners (like build jobs) from
1134 desktop applications. Task group autogeneration is currently based
1135 upon task session.
1137 config MM_OWNER
1138 bool
1140 config SYSFS_DEPRECATED
1141 bool "Enable deprecated sysfs features to support old userspace tools"
1142 depends on SYSFS
1143 default n
1144 help
1145 This option adds code that switches the layout of the "block" class
1146 devices, to not show up in /sys/class/block/, but only in
1147 /sys/block/.
1149 This switch is only active when the sysfs.deprecated=1 boot option is
1150 passed or the SYSFS_DEPRECATED_V2 option is set.
1152 This option allows new kernels to run on old distributions and tools,
1153 which might get confused by /sys/class/block/. Since 2007/2008 all
1154 major distributions and tools handle this just fine.
1156 Recent distributions and userspace tools after 2009/2010 depend on
1157 the existence of /sys/class/block/, and will not work with this
1158 option enabled.
1160 Only if you are using a new kernel on an old distribution, you might
1161 need to say Y here.
1163 config SYSFS_DEPRECATED_V2
1164 bool "Enable deprecated sysfs features by default"
1165 default n
1166 depends on SYSFS
1167 depends on SYSFS_DEPRECATED
1168 help
1169 Enable deprecated sysfs by default.
1171 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1172 option.
1174 Only if you are using a new kernel on an old distribution, you might
1175 need to say Y here. Even then, odds are you would not need it
1176 enabled, you can always pass the boot option if absolutely necessary.
1178 config RELAY
1179 bool "Kernel->user space relay support (formerly relayfs)"
1180 help
1181 This option enables support for relay interface support in
1182 certain file systems (such as debugfs).
1183 It is designed to provide an efficient mechanism for tools and
1184 facilities to relay large amounts of data from kernel space to
1185 user space.
1187 If unsure, say N.
1189 config BLK_DEV_INITRD
1190 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1191 depends on BROKEN || !FRV
1192 help
1193 The initial RAM filesystem is a ramfs which is loaded by the
1194 boot loader (loadlin or lilo) and that is mounted as root
1195 before the normal boot procedure. It is typically used to
1196 load modules needed to mount the "real" root file system,
1197 etc. See <file:Documentation/initrd.txt> for details.
1199 If RAM disk support (BLK_DEV_RAM) is also included, this
1200 also enables initial RAM disk (initrd) support and adds
1201 15 Kbytes (more on some other architectures) to the kernel size.
1203 If unsure say Y.
1205 if BLK_DEV_INITRD
1207 source "usr/Kconfig"
1209 endif
1211 config CC_OPTIMIZE_FOR_SIZE
1212 bool "Optimize for size"
1213 help
1214 Enabling this option will pass "-Os" instead of "-O2" to gcc
1215 resulting in a smaller kernel.
1217 If unsure, say N.
1219 config SYSCTL
1220 bool
1222 config ANON_INODES
1223 bool
1225 config HAVE_UID16
1226 bool
1228 config SYSCTL_EXCEPTION_TRACE
1229 bool
1230 help
1231 Enable support for /proc/sys/debug/exception-trace.
1233 config SYSCTL_ARCH_UNALIGN_NO_WARN
1234 bool
1235 help
1236 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1237 Allows arch to define/use @no_unaligned_warning to possibly warn
1238 about unaligned access emulation going on under the hood.
1240 config SYSCTL_ARCH_UNALIGN_ALLOW
1241 bool
1242 help
1243 Enable support for /proc/sys/kernel/unaligned-trap
1244 Allows arches to define/use @unaligned_enabled to runtime toggle
1245 the unaligned access emulation.
1246 see arch/parisc/kernel/unaligned.c for reference
1248 config HOTPLUG
1249 def_bool y
1251 config HAVE_PCSPKR_PLATFORM
1252 bool
1254 menuconfig EXPERT
1255 bool "Configure standard kernel features (expert users)"
1256 # Unhide debug options, to make the on-by-default options visible
1257 select DEBUG_KERNEL
1258 help
1259 This option allows certain base kernel options and settings
1260 to be disabled or tweaked. This is for specialized
1261 environments which can tolerate a "non-standard" kernel.
1262 Only use this if you really know what you are doing.
1264 config UID16
1265 bool "Enable 16-bit UID system calls" if EXPERT
1266 depends on HAVE_UID16
1267 default y
1268 help
1269 This enables the legacy 16-bit UID syscall wrappers.
1271 config SYSCTL_SYSCALL
1272 bool "Sysctl syscall support" if EXPERT
1273 depends on PROC_SYSCTL
1274 default n
1275 select SYSCTL
1276 ---help---
1277 sys_sysctl uses binary paths that have been found challenging
1278 to properly maintain and use. The interface in /proc/sys
1279 using paths with ascii names is now the primary path to this
1280 information.
1282 Almost nothing using the binary sysctl interface so if you are
1283 trying to save some space it is probably safe to disable this,
1284 making your kernel marginally smaller.
1286 If unsure say N here.
1288 config KALLSYMS
1289 bool "Load all symbols for debugging/ksymoops" if EXPERT
1290 default y
1291 help
1292 Say Y here to let the kernel print out symbolic crash information and
1293 symbolic stack backtraces. This increases the size of the kernel
1294 somewhat, as all symbols have to be loaded into the kernel image.
1296 config KALLSYMS_ALL
1297 bool "Include all symbols in kallsyms"
1298 depends on DEBUG_KERNEL && KALLSYMS
1299 help
1300 Normally kallsyms only contains the symbols of functions for nicer
1301 OOPS messages and backtraces (i.e., symbols from the text and inittext
1302 sections). This is sufficient for most cases. And only in very rare
1303 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1304 names of variables from the data sections, etc).
1306 This option makes sure that all symbols are loaded into the kernel
1307 image (i.e., symbols from all sections) in cost of increased kernel
1308 size (depending on the kernel configuration, it may be 300KiB or
1309 something like this).
1311 Say N unless you really need all symbols.
1313 config PRINTK
1314 default y
1315 bool "Enable support for printk" if EXPERT
1316 select IRQ_WORK
1317 help
1318 This option enables normal printk support. Removing it
1319 eliminates most of the message strings from the kernel image
1320 and makes the kernel more or less silent. As this makes it
1321 very difficult to diagnose system problems, saying N here is
1322 strongly discouraged.
1324 config BUG
1325 bool "BUG() support" if EXPERT
1326 default y
1327 help
1328 Disabling this option eliminates support for BUG and WARN, reducing
1329 the size of your kernel image and potentially quietly ignoring
1330 numerous fatal conditions. You should only consider disabling this
1331 option for embedded systems with no facilities for reporting errors.
1332 Just say Y.
1334 config ELF_CORE
1335 depends on COREDUMP
1336 default y
1337 bool "Enable ELF core dumps" if EXPERT
1338 help
1339 Enable support for generating core dumps. Disabling saves about 4k.
1342 config PCSPKR_PLATFORM
1343 bool "Enable PC-Speaker support" if EXPERT
1344 depends on HAVE_PCSPKR_PLATFORM
1345 select I8253_LOCK
1346 default y
1347 help
1348 This option allows to disable the internal PC-Speaker
1349 support, saving some memory.
1351 config BASE_FULL
1352 default y
1353 bool "Enable full-sized data structures for core" if EXPERT
1354 help
1355 Disabling this option reduces the size of miscellaneous core
1356 kernel data structures. This saves memory on small machines,
1357 but may reduce performance.
1359 config FUTEX
1360 bool "Enable futex support" if EXPERT
1361 default y
1362 select RT_MUTEXES
1363 help
1364 Disabling this option will cause the kernel to be built without
1365 support for "fast userspace mutexes". The resulting kernel may not
1366 run glibc-based applications correctly.
1368 config EPOLL
1369 bool "Enable eventpoll support" if EXPERT
1370 default y
1371 select ANON_INODES
1372 help
1373 Disabling this option will cause the kernel to be built without
1374 support for epoll family of system calls.
1376 config SIGNALFD
1377 bool "Enable signalfd() system call" if EXPERT
1378 select ANON_INODES
1379 default y
1380 help
1381 Enable the signalfd() system call that allows to receive signals
1382 on a file descriptor.
1384 If unsure, say Y.
1386 config TIMERFD
1387 bool "Enable timerfd() system call" if EXPERT
1388 select ANON_INODES
1389 default y
1390 help
1391 Enable the timerfd() system call that allows to receive timer
1392 events on a file descriptor.
1394 If unsure, say Y.
1396 config EVENTFD
1397 bool "Enable eventfd() system call" if EXPERT
1398 select ANON_INODES
1399 default y
1400 help
1401 Enable the eventfd() system call that allows to receive both
1402 kernel notification (ie. KAIO) or userspace notifications.
1404 If unsure, say Y.
1406 config SHMEM
1407 bool "Use full shmem filesystem" if EXPERT
1408 default y
1409 depends on MMU
1410 help
1411 The shmem is an internal filesystem used to manage shared memory.
1412 It is backed by swap and manages resource limits. It is also exported
1413 to userspace as tmpfs if TMPFS is enabled. Disabling this
1414 option replaces shmem and tmpfs with the much simpler ramfs code,
1415 which may be appropriate on small systems without swap.
1417 config AIO
1418 bool "Enable AIO support" if EXPERT
1419 default y
1420 help
1421 This option enables POSIX asynchronous I/O which may by used
1422 by some high performance threaded applications. Disabling
1423 this option saves about 7k.
1425 config PCI_QUIRKS
1426 default y
1427 bool "Enable PCI quirk workarounds" if EXPERT
1428 depends on PCI
1429 help
1430 This enables workarounds for various PCI chipset
1431 bugs/quirks. Disable this only if your target machine is
1432 unaffected by PCI quirks.
1434 config EMBEDDED
1435 bool "Embedded system"
1436 select EXPERT
1437 help
1438 This option should be enabled if compiling the kernel for
1439 an embedded system so certain expert options are available
1440 for configuration.
1442 config HAVE_PERF_EVENTS
1443 bool
1444 help
1445 See tools/perf/design.txt for details.
1447 config PERF_USE_VMALLOC
1448 bool
1449 help
1450 See tools/perf/design.txt for details
1452 menu "Kernel Performance Events And Counters"
1454 config PERF_EVENTS
1455 bool "Kernel performance events and counters"
1456 default y if PROFILING
1457 depends on HAVE_PERF_EVENTS
1458 select ANON_INODES
1459 select IRQ_WORK
1460 help
1461 Enable kernel support for various performance events provided
1462 by software and hardware.
1464 Software events are supported either built-in or via the
1465 use of generic tracepoints.
1467 Most modern CPUs support performance events via performance
1468 counter registers. These registers count the number of certain
1469 types of hw events: such as instructions executed, cachemisses
1470 suffered, or branches mis-predicted - without slowing down the
1471 kernel or applications. These registers can also trigger interrupts
1472 when a threshold number of events have passed - and can thus be
1473 used to profile the code that runs on that CPU.
1475 The Linux Performance Event subsystem provides an abstraction of
1476 these software and hardware event capabilities, available via a
1477 system call and used by the "perf" utility in tools/perf/. It
1478 provides per task and per CPU counters, and it provides event
1479 capabilities on top of those.
1481 Say Y if unsure.
1483 config DEBUG_PERF_USE_VMALLOC
1484 default n
1485 bool "Debug: use vmalloc to back perf mmap() buffers"
1486 depends on PERF_EVENTS && DEBUG_KERNEL
1487 select PERF_USE_VMALLOC
1488 help
1489 Use vmalloc memory to back perf mmap() buffers.
1491 Mostly useful for debugging the vmalloc code on platforms
1492 that don't require it.
1494 Say N if unsure.
1496 endmenu
1498 config VM_EVENT_COUNTERS
1499 default y
1500 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1501 help
1502 VM event counters are needed for event counts to be shown.
1503 This option allows the disabling of the VM event counters
1504 on EXPERT systems. /proc/vmstat will only show page counts
1505 if VM event counters are disabled.
1507 config SLUB_DEBUG
1508 default y
1509 bool "Enable SLUB debugging support" if EXPERT
1510 depends on SLUB && SYSFS
1511 help
1512 SLUB has extensive debug support features. Disabling these can
1513 result in significant savings in code size. This also disables
1514 SLUB sysfs support. /sys/slab will not exist and there will be
1515 no support for cache validation etc.
1517 config COMPAT_BRK
1518 bool "Disable heap randomization"
1519 default y
1520 help
1521 Randomizing heap placement makes heap exploits harder, but it
1522 also breaks ancient binaries (including anything libc5 based).
1523 This option changes the bootup default to heap randomization
1524 disabled, and can be overridden at runtime by setting
1525 /proc/sys/kernel/randomize_va_space to 2.
1527 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1529 choice
1530 prompt "Choose SLAB allocator"
1531 default SLUB
1532 help
1533 This option allows to select a slab allocator.
1535 config SLAB
1536 bool "SLAB"
1537 help
1538 The regular slab allocator that is established and known to work
1539 well in all environments. It organizes cache hot objects in
1540 per cpu and per node queues.
1542 config SLUB
1543 bool "SLUB (Unqueued Allocator)"
1544 help
1545 SLUB is a slab allocator that minimizes cache line usage
1546 instead of managing queues of cached objects (SLAB approach).
1547 Per cpu caching is realized using slabs of objects instead
1548 of queues of objects. SLUB can use memory efficiently
1549 and has enhanced diagnostics. SLUB is the default choice for
1550 a slab allocator.
1552 config SLOB
1553 depends on EXPERT
1554 bool "SLOB (Simple Allocator)"
1555 help
1556 SLOB replaces the stock allocator with a drastically simpler
1557 allocator. SLOB is generally more space efficient but
1558 does not perform as well on large systems.
1560 endchoice
1562 config MMAP_ALLOW_UNINITIALIZED
1563 bool "Allow mmapped anonymous memory to be uninitialized"
1564 depends on EXPERT && !MMU
1565 default n
1566 help
1567 Normally, and according to the Linux spec, anonymous memory obtained
1568 from mmap() has it's contents cleared before it is passed to
1569 userspace. Enabling this config option allows you to request that
1570 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1571 providing a huge performance boost. If this option is not enabled,
1572 then the flag will be ignored.
1574 This is taken advantage of by uClibc's malloc(), and also by
1575 ELF-FDPIC binfmt's brk and stack allocator.
1577 Because of the obvious security issues, this option should only be
1578 enabled on embedded devices where you control what is run in
1579 userspace. Since that isn't generally a problem on no-MMU systems,
1580 it is normally safe to say Y here.
1582 See Documentation/nommu-mmap.txt for more information.
1584 config PROFILING
1585 bool "Profiling support"
1586 help
1587 Say Y here to enable the extended profiling support mechanisms used
1588 by profilers such as OProfile.
1590 #
1591 # Place an empty function call at each tracepoint site. Can be
1592 # dynamically changed for a probe function.
1593 #
1594 config TRACEPOINTS
1595 bool
1597 source "arch/Kconfig"
1599 endmenu # General setup
1601 config HAVE_GENERIC_DMA_COHERENT
1602 bool
1603 default n
1605 config SLABINFO
1606 bool
1607 depends on PROC_FS
1608 depends on SLAB || SLUB_DEBUG
1609 default y
1611 config RT_MUTEXES
1612 boolean
1614 config BASE_SMALL
1615 int
1616 default 0 if BASE_FULL
1617 default 1 if !BASE_FULL
1619 menuconfig MODULES
1620 bool "Enable loadable module support"
1621 help
1622 Kernel modules are small pieces of compiled code which can
1623 be inserted in the running kernel, rather than being
1624 permanently built into the kernel. You use the "modprobe"
1625 tool to add (and sometimes remove) them. If you say Y here,
1626 many parts of the kernel can be built as modules (by
1627 answering M instead of Y where indicated): this is most
1628 useful for infrequently used options which are not required
1629 for booting. For more information, see the man pages for
1630 modprobe, lsmod, modinfo, insmod and rmmod.
1632 If you say Y here, you will need to run "make
1633 modules_install" to put the modules under /lib/modules/
1634 where modprobe can find them (you may need to be root to do
1635 this).
1637 If unsure, say Y.
1639 if MODULES
1641 config MODULE_FORCE_LOAD
1642 bool "Forced module loading"
1643 default n
1644 help
1645 Allow loading of modules without version information (ie. modprobe
1646 --force). Forced module loading sets the 'F' (forced) taint flag and
1647 is usually a really bad idea.
1649 config MODULE_UNLOAD
1650 bool "Module unloading"
1651 help
1652 Without this option you will not be able to unload any
1653 modules (note that some modules may not be unloadable
1654 anyway), which makes your kernel smaller, faster
1655 and simpler. If unsure, say Y.
1657 config MODULE_FORCE_UNLOAD
1658 bool "Forced module unloading"
1659 depends on MODULE_UNLOAD
1660 help
1661 This option allows you to force a module to unload, even if the
1662 kernel believes it is unsafe: the kernel will remove the module
1663 without waiting for anyone to stop using it (using the -f option to
1664 rmmod). This is mainly for kernel developers and desperate users.
1665 If unsure, say N.
1667 config MODVERSIONS
1668 bool "Module versioning support"
1669 help
1670 Usually, you have to use modules compiled with your kernel.
1671 Saying Y here makes it sometimes possible to use modules
1672 compiled for different kernels, by adding enough information
1673 to the modules to (hopefully) spot any changes which would
1674 make them incompatible with the kernel you are running. If
1675 unsure, say N.
1677 config MODULE_SRCVERSION_ALL
1678 bool "Source checksum for all modules"
1679 help
1680 Modules which contain a MODULE_VERSION get an extra "srcversion"
1681 field inserted into their modinfo section, which contains a
1682 sum of the source files which made it. This helps maintainers
1683 see exactly which source was used to build a module (since
1684 others sometimes change the module source without updating
1685 the version). With this option, such a "srcversion" field
1686 will be created for all modules. If unsure, say N.
1688 config MODULE_SIG
1689 bool "Module signature verification"
1690 depends on MODULES
1691 select KEYS
1692 select CRYPTO
1693 select ASYMMETRIC_KEY_TYPE
1694 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1695 select PUBLIC_KEY_ALGO_RSA
1696 select ASN1
1697 select OID_REGISTRY
1698 select X509_CERTIFICATE_PARSER
1699 help
1700 Check modules for valid signatures upon load: the signature
1701 is simply appended to the module. For more information see
1702 Documentation/module-signing.txt.
1704 !!!WARNING!!! If you enable this option, you MUST make sure that the
1705 module DOES NOT get stripped after being signed. This includes the
1706 debuginfo strip done by some packagers (such as rpmbuild) and
1707 inclusion into an initramfs that wants the module size reduced.
1709 config MODULE_SIG_FORCE
1710 bool "Require modules to be validly signed"
1711 depends on MODULE_SIG
1712 help
1713 Reject unsigned modules or signed modules for which we don't have a
1714 key. Without this, such modules will simply taint the kernel.
1716 config MODULE_SIG_ALL
1717 bool "Automatically sign all modules"
1718 default y
1719 depends on MODULE_SIG
1720 help
1721 Sign all modules during make modules_install. Without this option,
1722 modules must be signed manually, using the scripts/sign-file tool.
1724 comment "Do not forget to sign required modules with scripts/sign-file"
1725 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1727 choice
1728 prompt "Which hash algorithm should modules be signed with?"
1729 depends on MODULE_SIG
1730 help
1731 This determines which sort of hashing algorithm will be used during
1732 signature generation. This algorithm _must_ be built into the kernel
1733 directly so that signature verification can take place. It is not
1734 possible to load a signed module containing the algorithm to check
1735 the signature on that module.
1737 config MODULE_SIG_SHA1
1738 bool "Sign modules with SHA-1"
1739 select CRYPTO_SHA1
1741 config MODULE_SIG_SHA224
1742 bool "Sign modules with SHA-224"
1743 select CRYPTO_SHA256
1745 config MODULE_SIG_SHA256
1746 bool "Sign modules with SHA-256"
1747 select CRYPTO_SHA256
1749 config MODULE_SIG_SHA384
1750 bool "Sign modules with SHA-384"
1751 select CRYPTO_SHA512
1753 config MODULE_SIG_SHA512
1754 bool "Sign modules with SHA-512"
1755 select CRYPTO_SHA512
1757 endchoice
1759 config MODULE_SIG_HASH
1760 string
1761 depends on MODULE_SIG
1762 default "sha1" if MODULE_SIG_SHA1
1763 default "sha224" if MODULE_SIG_SHA224
1764 default "sha256" if MODULE_SIG_SHA256
1765 default "sha384" if MODULE_SIG_SHA384
1766 default "sha512" if MODULE_SIG_SHA512
1768 endif # MODULES
1770 config INIT_ALL_POSSIBLE
1771 bool
1772 help
1773 Back when each arch used to define their own cpu_online_mask and
1774 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1775 with all 1s, and others with all 0s. When they were centralised,
1776 it was better to provide this option than to break all the archs
1777 and have several arch maintainers pursuing me down dark alleys.
1779 config STOP_MACHINE
1780 bool
1781 default y
1782 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1783 help
1784 Need stop_machine() primitive.
1786 source "block/Kconfig"
1788 config PREEMPT_NOTIFIERS
1789 bool
1791 config PADATA
1792 depends on SMP
1793 bool
1795 # Can be selected by architectures with broken toolchains
1796 # that get confused by correct const<->read_only section
1797 # mappings
1798 config BROKEN_RODATA
1799 bool
1801 config ASN1
1802 tristate
1803 help
1804 Build a simple ASN.1 grammar compiler that produces a bytecode output
1805 that can be interpreted by the ASN.1 stream decoder and used to
1806 inform it as to what tags are to be expected in a stream and what
1807 functions to call on what tags.
1809 source "kernel/Kconfig.locks"