Version:  2.0.40 2.2.26 2.4.37 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17


  1 config ARCH
  2         string
  3         option env="ARCH"
  6         string
  7         option env="KERNELVERSION"
 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"
 20         bool
 21         depends on !UML
 23 config IRQ_WORK
 24         bool
 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
 40         int
 41         default 32 if !UML
 42         default 128 if UML
 43         help
 44           Maximum of each of the number of arguments and environment
 45           variables passed to init from the kernel command line.
 48 config CROSS_COMPILE
 49         string "Cross-compiler tool prefix"
 50         help
 51           Same as running 'make CROSS_COMPILE=prefix-' but stored for
 52           default make runs in this kernel build directory.  You don't
 53           need to set this unless you want the configured kernel build
 54           directory to select the cross-compiler automatically.
 56 config COMPILE_TEST
 57         bool "Compile also drivers which will not load"
 58         default n
 59         help
 60           Some drivers can be compiled on a different platform than they are
 61           intended to be run on. Despite they cannot be loaded there (or even
 62           when they load they cannot be used due to missing HW support),
 63           developers still, opposing to distributors, might want to build such
 64           drivers to compile-test them.
 66           If you are a developer and want to build everything available, say Y
 67           here. If you are a user/distributor, say N here to exclude useless
 68           drivers to be distributed.
 71         string "Local version - append to kernel release"
 72         help
 73           Append an extra string to the end of your kernel version.
 74           This will show up when you type uname, for example.
 75           The string you set here will be appended after the contents of
 76           any files with a filename matching localversion* in your
 77           object and source tree, in that order.  Your total string can
 78           be a maximum of 64 characters.
 81         bool "Automatically append version information to the version string"
 82         default y
 83         help
 84           This will try to automatically determine if the current tree is a
 85           release tree by looking for git tags that belong to the current
 86           top of tree revision.
 88           A string of the format -gxxxxxxxx will be added to the localversion
 89           if a git-based tree is found.  The string generated by this will be
 90           appended after any matching localversion* files, and after the value
 91           set in CONFIG_LOCALVERSION.
 93           (The actual string used here is the first eight characters produced
 94           by running the command:
 96             $ git rev-parse --verify HEAD
 98           which is done within the script "scripts/setlocalversion".)
101         bool
103 config HAVE_KERNEL_BZIP2
104         bool
107         bool
109 config HAVE_KERNEL_XZ
110         bool
112 config HAVE_KERNEL_LZO
113         bool
115 config HAVE_KERNEL_LZ4
116         bool
118 choice
119         prompt "Kernel compression mode"
120         default KERNEL_GZIP
122         help
123           The linux kernel is a kind of self-extracting executable.
124           Several compression algorithms are available, which differ
125           in efficiency, compression and decompression speed.
126           Compression speed is only relevant when building a kernel.
127           Decompression speed is relevant at each boot.
129           If you have any problems with bzip2 or lzma compressed
130           kernels, mail me (Alain Knaff) <>. (An older
131           version of this functionality (bzip2 only), for 2.4, was
132           supplied by Christian Ludwig)
134           High compression options are mostly useful for users, who
135           are low on disk space (embedded systems), but for whom ram
136           size matters less.
138           If in doubt, select 'gzip'
140 config KERNEL_GZIP
141         bool "Gzip"
142         depends on HAVE_KERNEL_GZIP
143         help
144           The old and tried gzip compression. It provides a good balance
145           between compression ratio and decompression speed.
147 config KERNEL_BZIP2
148         bool "Bzip2"
149         depends on HAVE_KERNEL_BZIP2
150         help
151           Its compression ratio and speed is intermediate.
152           Decompression speed is slowest among the choices.  The kernel
153           size is about 10% smaller with bzip2, in comparison to gzip.
154           Bzip2 uses a large amount of memory. For modern kernels you
155           will need at least 8MB RAM or more for booting.
157 config KERNEL_LZMA
158         bool "LZMA"
159         depends on HAVE_KERNEL_LZMA
160         help
161           This compression algorithm's ratio is best.  Decompression speed
162           is between gzip and bzip2.  Compression is slowest.
163           The kernel size is about 33% smaller with LZMA in comparison to gzip.
165 config KERNEL_XZ
166         bool "XZ"
167         depends on HAVE_KERNEL_XZ
168         help
169           XZ uses the LZMA2 algorithm and instruction set specific
170           BCJ filters which can improve compression ratio of executable
171           code. The size of the kernel is about 30% smaller with XZ in
172           comparison to gzip. On architectures for which there is a BCJ
173           filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
174           will create a few percent smaller kernel than plain LZMA.
176           The speed is about the same as with LZMA: The decompression
177           speed of XZ is better than that of bzip2 but worse than gzip
178           and LZO. Compression is slow.
180 config KERNEL_LZO
181         bool "LZO"
182         depends on HAVE_KERNEL_LZO
183         help
184           Its compression ratio is the poorest among the choices. The kernel
185           size is about 10% bigger than gzip; however its speed
186           (both compression and decompression) is the fastest.
188 config KERNEL_LZ4
189         bool "LZ4"
190         depends on HAVE_KERNEL_LZ4
191         help
192           LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
193           A preliminary version of LZ4 de/compression tool is available at
194           <>.
196           Its compression ratio is worse than LZO. The size of the kernel
197           is about 8% bigger than LZO. But the decompression speed is
198           faster than LZO.
200 endchoice
203         string "Default hostname"
204         default "(none)"
205         help
206           This option determines the default system hostname before userspace
207           calls sethostname(2). The kernel traditionally uses "(none)" here,
208           but you may wish to use a different default here to make a minimal
209           system more usable with less configuration.
211 config SWAP
212         bool "Support for paging of anonymous memory (swap)"
213         depends on MMU && BLOCK
214         default y
215         help
216           This option allows you to choose whether you want to have support
217           for so called swap devices or swap files in your kernel that are
218           used to provide more virtual memory than the actual RAM present
219           in your computer.  If unsure say Y.
221 config SYSVIPC
222         bool "System V IPC"
223         ---help---
224           Inter Process Communication is a suite of library functions and
225           system calls which let processes (running programs) synchronize and
226           exchange information. It is generally considered to be a good thing,
227           and some programs won't run unless you say Y here. In particular, if
228           you want to run the DOS emulator dosemu under Linux (read the
229           DOSEMU-HOWTO, available from <>),
230           you'll need to say Y here.
232           You can find documentation about IPC with "info ipc" and also in
233           section 6.4 of the Linux Programmer's Guide, available from
234           <>.
237         bool
238         depends on SYSVIPC
239         depends on SYSCTL
240         default y
242 config POSIX_MQUEUE
243         bool "POSIX Message Queues"
244         depends on NET
245         ---help---
246           POSIX variant of message queues is a part of IPC. In POSIX message
247           queues every message has a priority which decides about succession
248           of receiving it by a process. If you want to compile and run
249           programs written e.g. for Solaris with use of its POSIX message
250           queues (functions mq_*) say Y here.
252           POSIX message queues are visible as a filesystem called 'mqueue'
253           and can be mounted somewhere if you want to do filesystem
254           operations on message queues.
256           If unsure, say Y.
259         bool
260         depends on POSIX_MQUEUE
261         depends on SYSCTL
262         default y
265         bool "Enable process_vm_readv/writev syscalls"
266         depends on MMU
267         default y
268         help
269           Enabling this option adds the system calls process_vm_readv and
270           process_vm_writev which allow a process with the correct privileges
271           to directly read from or write to another process' address space.
272           See the man page for more details.
274 config FHANDLE
275         bool "open by fhandle syscalls"
276         select EXPORTFS
277         help
278           If you say Y here, a user level program will be able to map
279           file names to handle and then later use the handle for
280           different file system operations. This is useful in implementing
281           userspace file servers, which now track files using handles instead
282           of names. The handle would remain the same even if file names
283           get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
284           syscalls.
286 config USELIB
287         bool "uselib syscall"
288         default y
289         help
290           This option enables the uselib syscall, a system call used in the
291           dynamic linker from libc5 and earlier.  glibc does not use this
292           system call.  If you intend to run programs built on libc5 or
293           earlier, you may need to enable this syscall.  Current systems
294           running glibc can safely disable this.
296 config AUDIT
297         bool "Auditing support"
298         depends on NET
299         help
300           Enable auditing infrastructure that can be used with another
301           kernel subsystem, such as SELinux (which requires this for
302           logging of avc messages output).  Does not do system-call
303           auditing without CONFIG_AUDITSYSCALL.
306         bool
309         bool "Enable system-call auditing support"
310         depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
311         default y if SECURITY_SELINUX
312         help
313           Enable low-overhead system-call auditing infrastructure that
314           can be used independently or with another kernel subsystem,
315           such as SELinux.
317 config AUDIT_WATCH
318         def_bool y
319         depends on AUDITSYSCALL
320         select FSNOTIFY
322 config AUDIT_TREE
323         def_bool y
324         depends on AUDITSYSCALL
325         select FSNOTIFY
327 source "kernel/irq/Kconfig"
328 source "kernel/time/Kconfig"
330 menu "CPU/Task time and stats accounting"
333         bool
335 choice
336         prompt "Cputime accounting"
337         default TICK_CPU_ACCOUNTING if !PPC64
338         default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
340 # Kind of a stub config for the pure tick based cputime accounting
342         bool "Simple tick based cputime accounting"
343         depends on !S390 && !NO_HZ_FULL
344         help
345           This is the basic tick based cputime accounting that maintains
346           statistics about user, system and idle time spent on per jiffies
347           granularity.
349           If unsure, say Y.
352         bool "Deterministic task and CPU time accounting"
353         depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
354         select VIRT_CPU_ACCOUNTING
355         help
356           Select this option to enable more accurate task and CPU time
357           accounting.  This is done by reading a CPU counter on each
358           kernel entry and exit and on transitions within the kernel
359           between system, softirq and hardirq state, so there is a
360           small performance impact.  In the case of s390 or IBM POWER > 5,
361           this also enables accounting of stolen time on logically-partitioned
362           systems.
365         bool "Full dynticks CPU time accounting"
366         depends on HAVE_CONTEXT_TRACKING
367         depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
368         select VIRT_CPU_ACCOUNTING
369         select CONTEXT_TRACKING
370         help
371           Select this option to enable task and CPU time accounting on full
372           dynticks systems. This accounting is implemented by watching every
373           kernel-user boundaries using the context tracking subsystem.
374           The accounting is thus performed at the expense of some significant
375           overhead.
377           For now this is only useful if you are working on the full
378           dynticks subsystem development.
380           If unsure, say N.
383         bool "Fine granularity task level IRQ time accounting"
384         depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
385         help
386           Select this option to enable fine granularity task irq time
387           accounting. This is done by reading a timestamp on each
388           transitions between softirq and hardirq state, so there can be a
389           small performance impact.
391           If in doubt, say N here.
393 endchoice
396         bool "BSD Process Accounting"
397         help
398           If you say Y here, a user level program will be able to instruct the
399           kernel (via a special system call) to write process accounting
400           information to a file: whenever a process exits, information about
401           that process will be appended to the file by the kernel.  The
402           information includes things such as creation time, owning user,
403           command name, memory usage, controlling terminal etc. (the complete
404           list is in the struct acct in <file:include/linux/acct.h>).  It is
405           up to the user level program to do useful things with this
406           information.  This is generally a good idea, so say Y.
408 config BSD_PROCESS_ACCT_V3
409         bool "BSD Process Accounting version 3 file format"
410         depends on BSD_PROCESS_ACCT
411         default n
412         help
413           If you say Y here, the process accounting information is written
414           in a new file format that also logs the process IDs of each
415           process and it's parent. Note that this file format is incompatible
416           with previous v0/v1/v2 file formats, so you will need updated tools
417           for processing it. A preliminary version of these tools is available
418           at <>.
420 config TASKSTATS
421         bool "Export task/process statistics through netlink"
422         depends on NET
423         default n
424         help
425           Export selected statistics for tasks/processes through the
426           generic netlink interface. Unlike BSD process accounting, the
427           statistics are available during the lifetime of tasks/processes as
428           responses to commands. Like BSD accounting, they are sent to user
429           space on task exit.
431           Say N if unsure.
433 config TASK_DELAY_ACCT
434         bool "Enable per-task delay accounting"
435         depends on TASKSTATS
436         help
437           Collect information on time spent by a task waiting for system
438           resources like cpu, synchronous block I/O completion and swapping
439           in pages. Such statistics can help in setting a task's priorities
440           relative to other tasks for cpu, io, rss limits etc.
442           Say N if unsure.
444 config TASK_XACCT
445         bool "Enable extended accounting over taskstats"
446         depends on TASKSTATS
447         help
448           Collect extended task accounting data and send the data
449           to userland for processing over the taskstats interface.
451           Say N if unsure.
454         bool "Enable per-task storage I/O accounting"
455         depends on TASK_XACCT
456         help
457           Collect information on the number of bytes of storage I/O which this
458           task has caused.
460           Say N if unsure.
462 endmenu # "CPU/Task time and stats accounting"
464 menu "RCU Subsystem"
466 choice
467         prompt "RCU Implementation"
468         default TREE_RCU
470 config TREE_RCU
471         bool "Tree-based hierarchical RCU"
472         depends on !PREEMPT && SMP
473         select IRQ_WORK
474         help
475           This option selects the RCU implementation that is
476           designed for very large SMP system with hundreds or
477           thousands of CPUs.  It also scales down nicely to
478           smaller systems.
481         bool "Preemptible tree-based hierarchical RCU"
482         depends on PREEMPT
483         select IRQ_WORK
484         help
485           This option selects the RCU implementation that is
486           designed for very large SMP systems with hundreds or
487           thousands of CPUs, but for which real-time response
488           is also required.  It also scales down nicely to
489           smaller systems.
491           Select this option if you are unsure.
493 config TINY_RCU
494         bool "UP-only small-memory-footprint RCU"
495         depends on !PREEMPT && !SMP
496         help
497           This option selects the RCU implementation that is
498           designed for UP systems from which real-time response
499           is not required.  This option greatly reduces the
500           memory footprint of RCU.
502 endchoice
504 config PREEMPT_RCU
505         def_bool TREE_PREEMPT_RCU
506         help
507           This option enables preemptible-RCU code that is common between
508           TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU.
511         def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
512         help
513           This option enables RCU CPU stall code that is common between
514           the TINY and TREE variants of RCU.  The purpose is to allow
515           the tiny variants to disable RCU CPU stall warnings, while
516           making these warnings mandatory for the tree variants.
519        bool
521 config RCU_USER_QS
522         bool "Consider userspace as in RCU extended quiescent state"
523         depends on HAVE_CONTEXT_TRACKING && SMP
524         select CONTEXT_TRACKING
525         help
526           This option sets hooks on kernel / userspace boundaries and
527           puts RCU in extended quiescent state when the CPU runs in
528           userspace. It means that when a CPU runs in userspace, it is
529           excluded from the global RCU state machine and thus doesn't
530           try to keep the timer tick on for RCU.
532           Unless you want to hack and help the development of the full
533           dynticks mode, you shouldn't enable this option.  It also
534           adds unnecessary overhead.
536           If unsure say N
539         bool "Force context tracking"
540         depends on CONTEXT_TRACKING
541         default y if !NO_HZ_FULL
542         help
543           The major pre-requirement for full dynticks to work is to
544           support the context tracking subsystem. But there are also
545           other dependencies to provide in order to make the full
546           dynticks working.
548           This option stands for testing when an arch implements the
549           context tracking backend but doesn't yet fullfill all the
550           requirements to make the full dynticks feature working.
551           Without the full dynticks, there is no way to test the support
552           for context tracking and the subsystems that rely on it: RCU
553           userspace extended quiescent state and tickless cputime
554           accounting. This option copes with the absence of the full
555           dynticks subsystem by forcing the context tracking on all
556           CPUs in the system.
558           Say Y only if you're working on the development of an
559           architecture backend for the context tracking.
561           Say N otherwise, this option brings an overhead that you
562           don't want in production.
565 config RCU_FANOUT
566         int "Tree-based hierarchical RCU fanout value"
567         range 2 64 if 64BIT
568         range 2 32 if !64BIT
569         depends on TREE_RCU || TREE_PREEMPT_RCU
570         default 64 if 64BIT
571         default 32 if !64BIT
572         help
573           This option controls the fanout of hierarchical implementations
574           of RCU, allowing RCU to work efficiently on machines with
575           large numbers of CPUs.  This value must be at least the fourth
576           root of NR_CPUS, which allows NR_CPUS to be insanely large.
577           The default value of RCU_FANOUT should be used for production
578           systems, but if you are stress-testing the RCU implementation
579           itself, small RCU_FANOUT values allow you to test large-system
580           code paths on small(er) systems.
582           Select a specific number if testing RCU itself.
583           Take the default if unsure.
585 config RCU_FANOUT_LEAF
586         int "Tree-based hierarchical RCU leaf-level fanout value"
587         range 2 RCU_FANOUT if 64BIT
588         range 2 RCU_FANOUT if !64BIT
589         depends on TREE_RCU || TREE_PREEMPT_RCU
590         default 16
591         help
592           This option controls the leaf-level fanout of hierarchical
593           implementations of RCU, and allows trading off cache misses
594           against lock contention.  Systems that synchronize their
595           scheduling-clock interrupts for energy-efficiency reasons will
596           want the default because the smaller leaf-level fanout keeps
597           lock contention levels acceptably low.  Very large systems
598           (hundreds or thousands of CPUs) will instead want to set this
599           value to the maximum value possible in order to reduce the
600           number of cache misses incurred during RCU's grace-period
601           initialization.  These systems tend to run CPU-bound, and thus
602           are not helped by synchronized interrupts, and thus tend to
603           skew them, which reduces lock contention enough that large
604           leaf-level fanouts work well.
606           Select a specific number if testing RCU itself.
608           Select the maximum permissible value for large systems.
610           Take the default if unsure.
613         bool "Disable tree-based hierarchical RCU auto-balancing"
614         depends on TREE_RCU || TREE_PREEMPT_RCU
615         default n
616         help
617           This option forces use of the exact RCU_FANOUT value specified,
618           regardless of imbalances in the hierarchy.  This is useful for
619           testing RCU itself, and might one day be useful on systems with
620           strong NUMA behavior.
622           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
624           Say N if unsure.
626 config RCU_FAST_NO_HZ
627         bool "Accelerate last non-dyntick-idle CPU's grace periods"
628         depends on NO_HZ_COMMON && SMP
629         default n
630         help
631           This option permits CPUs to enter dynticks-idle state even if
632           they have RCU callbacks queued, and prevents RCU from waking
633           these CPUs up more than roughly once every four jiffies (by
634           default, you can adjust this using the rcutree.rcu_idle_gp_delay
635           parameter), thus improving energy efficiency.  On the other
636           hand, this option increases the duration of RCU grace periods,
637           for example, slowing down synchronize_rcu().
639           Say Y if energy efficiency is critically important, and you
640                 don't care about increased grace-period durations.
642           Say N if you are unsure.
644 config TREE_RCU_TRACE
645         def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
646         select DEBUG_FS
647         help
648           This option provides tracing for the TREE_RCU and
649           TREE_PREEMPT_RCU implementations, permitting Makefile to
650           trivially select kernel/rcutree_trace.c.
652 config RCU_BOOST
653         bool "Enable RCU priority boosting"
654         depends on RT_MUTEXES && PREEMPT_RCU
655         default n
656         help
657           This option boosts the priority of preempted RCU readers that
658           block the current preemptible RCU grace period for too long.
659           This option also prevents heavy loads from blocking RCU
660           callback invocation for all flavors of RCU.
662           Say Y here if you are working with real-time apps or heavy loads
663           Say N here if you are unsure.
665 config RCU_BOOST_PRIO
666         int "Real-time priority to boost RCU readers to"
667         range 1 99
668         depends on RCU_BOOST
669         default 1
670         help
671           This option specifies the real-time priority to which long-term
672           preempted RCU readers are to be boosted.  If you are working
673           with a real-time application that has one or more CPU-bound
674           threads running at a real-time priority level, you should set
675           RCU_BOOST_PRIO to a priority higher then the highest-priority
676           real-time CPU-bound thread.  The default RCU_BOOST_PRIO value
677           of 1 is appropriate in the common case, which is real-time
678           applications that do not have any CPU-bound threads.
680           Some real-time applications might not have a single real-time
681           thread that saturates a given CPU, but instead might have
682           multiple real-time threads that, taken together, fully utilize
683           that CPU.  In this case, you should set RCU_BOOST_PRIO to
684           a priority higher than the lowest-priority thread that is
685           conspiring to prevent the CPU from running any non-real-time
686           tasks.  For example, if one thread at priority 10 and another
687           thread at priority 5 are between themselves fully consuming
688           the CPU time on a given CPU, then RCU_BOOST_PRIO should be
689           set to priority 6 or higher.
691           Specify the real-time priority, or take the default if unsure.
693 config RCU_BOOST_DELAY
694         int "Milliseconds to delay boosting after RCU grace-period start"
695         range 0 3000
696         depends on RCU_BOOST
697         default 500
698         help
699           This option specifies the time to wait after the beginning of
700           a given grace period before priority-boosting preempted RCU
701           readers blocking that grace period.  Note that any RCU reader
702           blocking an expedited RCU grace period is boosted immediately.
704           Accept the default if unsure.
706 config RCU_NOCB_CPU
707         bool "Offload RCU callback processing from boot-selected CPUs"
708         depends on TREE_RCU || TREE_PREEMPT_RCU
709         default n
710         help
711           Use this option to reduce OS jitter for aggressive HPC or
712           real-time workloads.  It can also be used to offload RCU
713           callback invocation to energy-efficient CPUs in battery-powered
714           asymmetric multiprocessors.
716           This option offloads callback invocation from the set of
717           CPUs specified at boot time by the rcu_nocbs parameter.
718           For each such CPU, a kthread ("rcuox/N") will be created to
719           invoke callbacks, where the "N" is the CPU being offloaded,
720           and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
721           "s" for RCU-sched.  Nothing prevents this kthread from running
722           on the specified CPUs, but (1) the kthreads may be preempted
723           between each callback, and (2) affinity or cgroups can be used
724           to force the kthreads to run on whatever set of CPUs is desired.
726           Say Y here if you want to help to debug reduced OS jitter.
727           Say N here if you are unsure.
729 choice
730         prompt "Build-forced no-CBs CPUs"
731         default RCU_NOCB_CPU_NONE
732         help
733           This option allows no-CBs CPUs (whose RCU callbacks are invoked
734           from kthreads rather than from softirq context) to be specified
735           at build time.  Additional no-CBs CPUs may be specified by
736           the rcu_nocbs= boot parameter.
738 config RCU_NOCB_CPU_NONE
739         bool "No build_forced no-CBs CPUs"
740         depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
741         help
742           This option does not force any of the CPUs to be no-CBs CPUs.
743           Only CPUs designated by the rcu_nocbs= boot parameter will be
744           no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
745           kthreads whose names begin with "rcuo".  All other CPUs will
746           invoke their own RCU callbacks in softirq context.
748           Select this option if you want to choose no-CBs CPUs at
749           boot time, for example, to allow testing of different no-CBs
750           configurations without having to rebuild the kernel each time.
752 config RCU_NOCB_CPU_ZERO
753         bool "CPU 0 is a build_forced no-CBs CPU"
754         depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
755         help
756           This option forces CPU 0 to be a no-CBs CPU, so that its RCU
757           callbacks are invoked by a per-CPU kthread whose name begins
758           with "rcuo".  Additional CPUs may be designated as no-CBs
759           CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
760           All other CPUs will invoke their own RCU callbacks in softirq
761           context.
763           Select this if CPU 0 needs to be a no-CBs CPU for real-time
764           or energy-efficiency reasons, but the real reason it exists
765           is to ensure that randconfig testing covers mixed systems.
767 config RCU_NOCB_CPU_ALL
768         bool "All CPUs are build_forced no-CBs CPUs"
769         depends on RCU_NOCB_CPU
770         help
771           This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
772           boot parameter will be ignored.  All CPUs' RCU callbacks will
773           be executed in the context of per-CPU rcuo kthreads created for
774           this purpose.  Assuming that the kthreads whose names start with
775           "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
776           on the remaining CPUs, but might decrease memory locality during
777           RCU-callback invocation, thus potentially degrading throughput.
779           Select this if all CPUs need to be no-CBs CPUs for real-time
780           or energy-efficiency reasons.
782 endchoice
784 endmenu # "RCU Subsystem"
786 config BUILD_BIN2C
787         bool
788         default n
790 config IKCONFIG
791         tristate "Kernel .config support"
792         select BUILD_BIN2C
793         ---help---
794           This option enables the complete Linux kernel ".config" file
795           contents to be saved in the kernel. It provides documentation
796           of which kernel options are used in a running kernel or in an
797           on-disk kernel.  This information can be extracted from the kernel
798           image file with the script scripts/extract-ikconfig and used as
799           input to rebuild the current kernel or to build another kernel.
800           It can also be extracted from a running kernel by reading
801           /proc/config.gz if enabled (below).
803 config IKCONFIG_PROC
804         bool "Enable access to .config through /proc/config.gz"
805         depends on IKCONFIG && PROC_FS
806         ---help---
807           This option enables access to the kernel configuration file
808           through /proc/config.gz.
810 config LOG_BUF_SHIFT
811         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
812         range 12 21
813         default 17
814         depends on PRINTK
815         help
816           Select the minimal kernel log buffer size as a power of 2.
817           The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
818           parameter, see below. Any higher size also might be forced
819           by "log_buf_len" boot parameter.
821           Examples:
822                      17 => 128 KB
823                      16 => 64 KB
824                      15 => 32 KB
825                      14 => 16 KB
826                      13 =>  8 KB
827                      12 =>  4 KB
830         int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
831         range 0 21
832         default 12 if !BASE_SMALL
833         default 0 if BASE_SMALL
834         depends on PRINTK
835         help
836           This option allows to increase the default ring buffer size
837           according to the number of CPUs. The value defines the contribution
838           of each CPU as a power of 2. The used space is typically only few
839           lines however it might be much more when problems are reported,
840           e.g. backtraces.
842           The increased size means that a new buffer has to be allocated and
843           the original static one is unused. It makes sense only on systems
844           with more CPUs. Therefore this value is used only when the sum of
845           contributions is greater than the half of the default kernel ring
846           buffer as defined by LOG_BUF_SHIFT. The default values are set
847           so that more than 64 CPUs are needed to trigger the allocation.
849           Also this option is ignored when "log_buf_len" kernel parameter is
850           used as it forces an exact (power of two) size of the ring buffer.
852           The number of possible CPUs is used for this computation ignoring
853           hotplugging making the compuation optimal for the the worst case
854           scenerio while allowing a simple algorithm to be used from bootup.
856           Examples shift values and their meaning:
857                      17 => 128 KB for each CPU
858                      16 =>  64 KB for each CPU
859                      15 =>  32 KB for each CPU
860                      14 =>  16 KB for each CPU
861                      13 =>   8 KB for each CPU
862                      12 =>   4 KB for each CPU
864 #
865 # Architectures with an unreliable sched_clock() should select this:
866 #
868         bool
871         bool
873 #
874 # For architectures that want to enable the support for NUMA-affine scheduler
875 # balancing logic:
876 #
878         bool
880 #
881 # For architectures that know their GCC __int128 support is sound
882 #
883 config ARCH_SUPPORTS_INT128
884         bool
886 # For architectures that (ab)use NUMA to represent different memory regions
887 # all cpu-local but of different latencies, such as SuperH.
888 #
890         bool
892 #
893 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
895         bool
898         bool
899         default y
900         depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
901         depends on NUMA_BALANCING
904         bool "Automatically enable NUMA aware memory/task placement"
905         default y
906         depends on NUMA_BALANCING
907         help
908           If set, automatic NUMA balancing will be enabled if running on a NUMA
909           machine.
912         bool "Memory placement aware NUMA scheduler"
913         depends on ARCH_SUPPORTS_NUMA_BALANCING
914         depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
915         depends on SMP && NUMA && MIGRATION
916         help
917           This option adds support for automatic NUMA aware memory/task placement.
918           The mechanism is quite primitive and is based on migrating memory when
919           it has references to the node the task is running on.
921           This system will be inactive on UMA systems.
923 menuconfig CGROUPS
924         boolean "Control Group support"
925         select KERNFS
926         help
927           This option adds support for grouping sets of processes together, for
928           use with process control subsystems such as Cpusets, CFS, memory
929           controls or device isolation.
930           See
931                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
932                 - Documentation/cgroups/ (features for grouping, isolation
933                                           and resource control)
935           Say N if unsure.
937 if CGROUPS
939 config CGROUP_DEBUG
940         bool "Example debug cgroup subsystem"
941         default n
942         help
943           This option enables a simple cgroup subsystem that
944           exports useful debugging information about the cgroups
945           framework.
947           Say N if unsure.
950         bool "Freezer cgroup subsystem"
951         help
952           Provides a way to freeze and unfreeze all tasks in a
953           cgroup.
955 config CGROUP_DEVICE
956         bool "Device controller for cgroups"
957         help
958           Provides a cgroup implementing whitelists for devices which
959           a process in the cgroup can mknod or open.
961 config CPUSETS
962         bool "Cpuset support"
963         help
964           This option will let you create and manage CPUSETs which
965           allow dynamically partitioning a system into sets of CPUs and
966           Memory Nodes and assigning tasks to run only within those sets.
967           This is primarily useful on large SMP or NUMA systems.
969           Say N if unsure.
971 config PROC_PID_CPUSET
972         bool "Include legacy /proc/<pid>/cpuset file"
973         depends on CPUSETS
974         default y
977         bool "Simple CPU accounting cgroup subsystem"
978         help
979           Provides a simple Resource Controller for monitoring the
980           total CPU consumed by the tasks in a cgroup.
983         bool "Resource counters"
984         help
985           This option enables controller independent resource accounting
986           infrastructure that works with cgroups.
988 config MEMCG
989         bool "Memory Resource Controller for Control Groups"
990         depends on RESOURCE_COUNTERS
991         select EVENTFD
992         help
993           Provides a memory resource controller that manages both anonymous
994           memory and page cache. (See Documentation/cgroups/memory.txt)
996           Note that setting this option increases fixed memory overhead
997           associated with each page of memory in the system. By this,
998           8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
999           usage tracking struct at boot. Total amount of this is printed out
1000           at boot.
1002           Only enable when you're ok with these trade offs and really
1003           sure you need the memory resource controller. Even when you enable
1004           this, you can set "cgroup_disable=memory" at your boot option to
1005           disable memory resource controller and you can avoid overheads.
1006           (and lose benefits of memory resource controller)
1008 config MEMCG_SWAP
1009         bool "Memory Resource Controller Swap Extension"
1010         depends on MEMCG && SWAP
1011         help
1012           Add swap management feature to memory resource controller. When you
1013           enable this, you can limit mem+swap usage per cgroup. In other words,
1014           when you disable this, memory resource controller has no cares to
1015           usage of swap...a process can exhaust all of the swap. This extension
1016           is useful when you want to avoid exhaustion swap but this itself
1017           adds more overheads and consumes memory for remembering information.
1018           Especially if you use 32bit system or small memory system, please
1019           be careful about enabling this. When memory resource controller
1020           is disabled by boot option, this will be automatically disabled and
1021           there will be no overhead from this. Even when you set this config=y,
1022           if boot option "swapaccount=0" is set, swap will not be accounted.
1023           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1024           size is 4096bytes, 512k per 1Gbytes of swap.
1026         bool "Memory Resource Controller Swap Extension enabled by default"
1027         depends on MEMCG_SWAP
1028         default y
1029         help
1030           Memory Resource Controller Swap Extension comes with its price in
1031           a bigger memory consumption. General purpose distribution kernels
1032           which want to enable the feature but keep it disabled by default
1033           and let the user enable it by swapaccount=1 boot command line
1034           parameter should have this option unselected.
1035           For those who want to have the feature enabled by default should
1036           select this option (if, for some reason, they need to disable it
1037           then swapaccount=0 does the trick).
1038 config MEMCG_KMEM
1039         bool "Memory Resource Controller Kernel Memory accounting"
1040         depends on MEMCG
1041         depends on SLUB || SLAB
1042         help
1043           The Kernel Memory extension for Memory Resource Controller can limit
1044           the amount of memory used by kernel objects in the system. Those are
1045           fundamentally different from the entities handled by the standard
1046           Memory Controller, which are page-based, and can be swapped. Users of
1047           the kmem extension can use it to guarantee that no group of processes
1048           will ever exhaust kernel resources alone.
1050           WARNING: Current implementation lacks reclaim support. That means
1051           allocation attempts will fail when close to the limit even if there
1052           are plenty of kmem available for reclaim. That makes this option
1053           unusable in real life so DO NOT SELECT IT unless for development
1054           purposes.
1056 config CGROUP_HUGETLB
1057         bool "HugeTLB Resource Controller for Control Groups"
1058         depends on RESOURCE_COUNTERS && HUGETLB_PAGE
1059         default n
1060         help
1061           Provides a cgroup Resource Controller for HugeTLB pages.
1062           When you enable this, you can put a per cgroup limit on HugeTLB usage.
1063           The limit is enforced during page fault. Since HugeTLB doesn't
1064           support page reclaim, enforcing the limit at page fault time implies
1065           that, the application will get SIGBUS signal if it tries to access
1066           HugeTLB pages beyond its limit. This requires the application to know
1067           beforehand how much HugeTLB pages it would require for its use. The
1068           control group is tracked in the third page lru pointer. This means
1069           that we cannot use the controller with huge page less than 3 pages.
1071 config CGROUP_PERF
1072         bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1073         depends on PERF_EVENTS && CGROUPS
1074         help
1075           This option extends the per-cpu mode to restrict monitoring to
1076           threads which belong to the cgroup specified and run on the
1077           designated cpu.
1079           Say N if unsure.
1081 menuconfig CGROUP_SCHED
1082         bool "Group CPU scheduler"
1083         default n
1084         help
1085           This feature lets CPU scheduler recognize task groups and control CPU
1086           bandwidth allocation to such task groups. It uses cgroups to group
1087           tasks.
1090 config FAIR_GROUP_SCHED
1091         bool "Group scheduling for SCHED_OTHER"
1092         depends on CGROUP_SCHED
1093         default CGROUP_SCHED
1095 config CFS_BANDWIDTH
1096         bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1097         depends on FAIR_GROUP_SCHED
1098         default n
1099         help
1100           This option allows users to define CPU bandwidth rates (limits) for
1101           tasks running within the fair group scheduler.  Groups with no limit
1102           set are considered to be unconstrained and will run with no
1103           restriction.
1104           See tip/Documentation/scheduler/sched-bwc.txt for more information.
1106 config RT_GROUP_SCHED
1107         bool "Group scheduling for SCHED_RR/FIFO"
1108         depends on CGROUP_SCHED
1109         default n
1110         help
1111           This feature lets you explicitly allocate real CPU bandwidth
1112           to task groups. If enabled, it will also make it impossible to
1113           schedule realtime tasks for non-root users until you allocate
1114           realtime bandwidth for them.
1115           See Documentation/scheduler/sched-rt-group.txt for more information.
1117 endif #CGROUP_SCHED
1119 config BLK_CGROUP
1120         bool "Block IO controller"
1121         depends on BLOCK
1122         default n
1123         ---help---
1124         Generic block IO controller cgroup interface. This is the common
1125         cgroup interface which should be used by various IO controlling
1126         policies.
1128         Currently, CFQ IO scheduler uses it to recognize task groups and
1129         control disk bandwidth allocation (proportional time slice allocation)
1130         to such task groups. It is also used by bio throttling logic in
1131         block layer to implement upper limit in IO rates on a device.
1133         This option only enables generic Block IO controller infrastructure.
1134         One needs to also enable actual IO controlling logic/policy. For
1135         enabling proportional weight division of disk bandwidth in CFQ, set
1136         CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1139         See Documentation/cgroups/blkio-controller.txt for more information.
1141 config DEBUG_BLK_CGROUP
1142         bool "Enable Block IO controller debugging"
1143         depends on BLK_CGROUP
1144         default n
1145         ---help---
1146         Enable some debugging help. Currently it exports additional stat
1147         files in a cgroup which can be useful for debugging.
1149 endif # CGROUPS
1152         bool "Checkpoint/restore support" if EXPERT
1153         default n
1154         help
1155           Enables additional kernel features in a sake of checkpoint/restore.
1156           In particular it adds auxiliary prctl codes to setup process text,
1157           data and heap segment sizes, and a few additional /proc filesystem
1158           entries.
1160           If unsure, say N here.
1162 menuconfig NAMESPACES
1163         bool "Namespaces support" if EXPERT
1164         default !EXPERT
1165         help
1166           Provides the way to make tasks work with different objects using
1167           the same id. For example same IPC id may refer to different objects
1168           or same user id or pid may refer to different tasks when used in
1169           different namespaces.
1173 config UTS_NS
1174         bool "UTS namespace"
1175         default y
1176         help
1177           In this namespace tasks see different info provided with the
1178           uname() system call
1180 config IPC_NS
1181         bool "IPC namespace"
1182         depends on (SYSVIPC || POSIX_MQUEUE)
1183         default y
1184         help
1185           In this namespace tasks work with IPC ids which correspond to
1186           different IPC objects in different namespaces.
1188 config USER_NS
1189         bool "User namespace"
1190         default n
1191         help
1192           This allows containers, i.e. vservers, to use user namespaces
1193           to provide different user info for different servers.
1195           When user namespaces are enabled in the kernel it is
1196           recommended that the MEMCG and MEMCG_KMEM options also be
1197           enabled and that user-space use the memory control groups to
1198           limit the amount of memory a memory unprivileged users can
1199           use.
1201           If unsure, say N.
1203 config PID_NS
1204         bool "PID Namespaces"
1205         default y
1206         help
1207           Support process id namespaces.  This allows having multiple
1208           processes with the same pid as long as they are in different
1209           pid namespaces.  This is a building block of containers.
1211 config NET_NS
1212         bool "Network namespace"
1213         depends on NET
1214         default y
1215         help
1216           Allow user space to create what appear to be multiple instances
1217           of the network stack.
1219 endif # NAMESPACES
1222         bool "Automatic process group scheduling"
1223         select CGROUPS
1224         select CGROUP_SCHED
1225         select FAIR_GROUP_SCHED
1226         help
1227           This option optimizes the scheduler for common desktop workloads by
1228           automatically creating and populating task groups.  This separation
1229           of workloads isolates aggressive CPU burners (like build jobs) from
1230           desktop applications.  Task group autogeneration is currently based
1231           upon task session.
1234         bool "Enable deprecated sysfs features to support old userspace tools"
1235         depends on SYSFS
1236         default n
1237         help
1238           This option adds code that switches the layout of the "block" class
1239           devices, to not show up in /sys/class/block/, but only in
1240           /sys/block/.
1242           This switch is only active when the sysfs.deprecated=1 boot option is
1243           passed or the SYSFS_DEPRECATED_V2 option is set.
1245           This option allows new kernels to run on old distributions and tools,
1246           which might get confused by /sys/class/block/. Since 2007/2008 all
1247           major distributions and tools handle this just fine.
1249           Recent distributions and userspace tools after 2009/2010 depend on
1250           the existence of /sys/class/block/, and will not work with this
1251           option enabled.
1253           Only if you are using a new kernel on an old distribution, you might
1254           need to say Y here.
1257         bool "Enable deprecated sysfs features by default"
1258         default n
1259         depends on SYSFS
1260         depends on SYSFS_DEPRECATED
1261         help
1262           Enable deprecated sysfs by default.
1264           See the CONFIG_SYSFS_DEPRECATED option for more details about this
1265           option.
1267           Only if you are using a new kernel on an old distribution, you might
1268           need to say Y here. Even then, odds are you would not need it
1269           enabled, you can always pass the boot option if absolutely necessary.
1271 config RELAY
1272         bool "Kernel->user space relay support (formerly relayfs)"
1273         help
1274           This option enables support for relay interface support in
1275           certain file systems (such as debugfs).
1276           It is designed to provide an efficient mechanism for tools and
1277           facilities to relay large amounts of data from kernel space to
1278           user space.
1280           If unsure, say N.
1282 config BLK_DEV_INITRD
1283         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1284         depends on BROKEN || !FRV
1285         help
1286           The initial RAM filesystem is a ramfs which is loaded by the
1287           boot loader (loadlin or lilo) and that is mounted as root
1288           before the normal boot procedure. It is typically used to
1289           load modules needed to mount the "real" root file system,
1290           etc. See <file:Documentation/initrd.txt> for details.
1292           If RAM disk support (BLK_DEV_RAM) is also included, this
1293           also enables initial RAM disk (initrd) support and adds
1294           15 Kbytes (more on some other architectures) to the kernel size.
1296           If unsure say Y.
1300 source "usr/Kconfig"
1302 endif
1305         bool "Optimize for size"
1306         help
1307           Enabling this option will pass "-Os" instead of "-O2" to gcc
1308           resulting in a smaller kernel.
1310           If unsure, say N.
1312 config SYSCTL
1313         bool
1315 config ANON_INODES
1316         bool
1318 config HAVE_UID16
1319         bool
1322         bool
1323         help
1324           Enable support for /proc/sys/debug/exception-trace.
1327         bool
1328         help
1329           Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1330           Allows arch to define/use @no_unaligned_warning to possibly warn
1331           about unaligned access emulation going on under the hood.
1334         bool
1335         help
1336           Enable support for /proc/sys/kernel/unaligned-trap
1337           Allows arches to define/use @unaligned_enabled to runtime toggle
1338           the unaligned access emulation.
1339           see arch/parisc/kernel/unaligned.c for reference
1342         bool
1344 menuconfig EXPERT
1345         bool "Configure standard kernel features (expert users)"
1346         # Unhide debug options, to make the on-by-default options visible
1347         select DEBUG_KERNEL
1348         help
1349           This option allows certain base kernel options and settings
1350           to be disabled or tweaked. This is for specialized
1351           environments which can tolerate a "non-standard" kernel.
1352           Only use this if you really know what you are doing.
1354 config UID16
1355         bool "Enable 16-bit UID system calls" if EXPERT
1356         depends on HAVE_UID16
1357         default y
1358         help
1359           This enables the legacy 16-bit UID syscall wrappers.
1362         bool "sgetmask/ssetmask syscalls support" if EXPERT
1363         def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1364         ---help---
1365           sys_sgetmask and sys_ssetmask are obsolete system calls
1366           no longer supported in libc but still enabled by default in some
1367           architectures.
1369           If unsure, leave the default option here.
1371 config SYSFS_SYSCALL
1372         bool "Sysfs syscall support" if EXPERT
1373         default y
1374         ---help---
1375           sys_sysfs is an obsolete system call no longer supported in libc.
1376           Note that disabling this option is more secure but might break
1377           compatibility with some systems.
1379           If unsure say Y here.
1381 config SYSCTL_SYSCALL
1382         bool "Sysctl syscall support" if EXPERT
1383         depends on PROC_SYSCTL
1384         default n
1385         select SYSCTL
1386         ---help---
1387           sys_sysctl uses binary paths that have been found challenging
1388           to properly maintain and use.  The interface in /proc/sys
1389           using paths with ascii names is now the primary path to this
1390           information.
1392           Almost nothing using the binary sysctl interface so if you are
1393           trying to save some space it is probably safe to disable this,
1394           making your kernel marginally smaller.
1396           If unsure say N here.
1398 config KALLSYMS
1399          bool "Load all symbols for debugging/ksymoops" if EXPERT
1400          default y
1401          help
1402            Say Y here to let the kernel print out symbolic crash information and
1403            symbolic stack backtraces. This increases the size of the kernel
1404            somewhat, as all symbols have to be loaded into the kernel image.
1406 config KALLSYMS_ALL
1407         bool "Include all symbols in kallsyms"
1408         depends on DEBUG_KERNEL && KALLSYMS
1409         help
1410            Normally kallsyms only contains the symbols of functions for nicer
1411            OOPS messages and backtraces (i.e., symbols from the text and inittext
1412            sections). This is sufficient for most cases. And only in very rare
1413            cases (e.g., when a debugger is used) all symbols are required (e.g.,
1414            names of variables from the data sections, etc).
1416            This option makes sure that all symbols are loaded into the kernel
1417            image (i.e., symbols from all sections) in cost of increased kernel
1418            size (depending on the kernel configuration, it may be 300KiB or
1419            something like this).
1421            Say N unless you really need all symbols.
1423 config PRINTK
1424         default y
1425         bool "Enable support for printk" if EXPERT
1426         select IRQ_WORK
1427         help
1428           This option enables normal printk support. Removing it
1429           eliminates most of the message strings from the kernel image
1430           and makes the kernel more or less silent. As this makes it
1431           very difficult to diagnose system problems, saying N here is
1432           strongly discouraged.
1434 config BUG
1435         bool "BUG() support" if EXPERT
1436         default y
1437         help
1438           Disabling this option eliminates support for BUG and WARN, reducing
1439           the size of your kernel image and potentially quietly ignoring
1440           numerous fatal conditions. You should only consider disabling this
1441           option for embedded systems with no facilities for reporting errors.
1442           Just say Y.
1444 config ELF_CORE
1445         depends on COREDUMP
1446         default y
1447         bool "Enable ELF core dumps" if EXPERT
1448         help
1449           Enable support for generating core dumps. Disabling saves about 4k.
1453         bool "Enable PC-Speaker support" if EXPERT
1454         depends on HAVE_PCSPKR_PLATFORM
1455         select I8253_LOCK
1456         default y
1457         help
1458           This option allows to disable the internal PC-Speaker
1459           support, saving some memory.
1461 config BASE_FULL
1462         default y
1463         bool "Enable full-sized data structures for core" if EXPERT
1464         help
1465           Disabling this option reduces the size of miscellaneous core
1466           kernel data structures. This saves memory on small machines,
1467           but may reduce performance.
1469 config FUTEX
1470         bool "Enable futex support" if EXPERT
1471         default y
1472         select RT_MUTEXES
1473         help
1474           Disabling this option will cause the kernel to be built without
1475           support for "fast userspace mutexes".  The resulting kernel may not
1476           run glibc-based applications correctly.
1479         bool
1480         depends on FUTEX
1481         help
1482           Architectures should select this if futex_atomic_cmpxchg_inatomic()
1483           is implemented and always working. This removes a couple of runtime
1484           checks.
1486 config EPOLL
1487         bool "Enable eventpoll support" if EXPERT
1488         default y
1489         select ANON_INODES
1490         help
1491           Disabling this option will cause the kernel to be built without
1492           support for epoll family of system calls.
1494 config SIGNALFD
1495         bool "Enable signalfd() system call" if EXPERT
1496         select ANON_INODES
1497         default y
1498         help
1499           Enable the signalfd() system call that allows to receive signals
1500           on a file descriptor.
1502           If unsure, say Y.
1504 config TIMERFD
1505         bool "Enable timerfd() system call" if EXPERT
1506         select ANON_INODES
1507         default y
1508         help
1509           Enable the timerfd() system call that allows to receive timer
1510           events on a file descriptor.
1512           If unsure, say Y.
1514 config EVENTFD
1515         bool "Enable eventfd() system call" if EXPERT
1516         select ANON_INODES
1517         default y
1518         help
1519           Enable the eventfd() system call that allows to receive both
1520           kernel notification (ie. KAIO) or userspace notifications.
1522           If unsure, say Y.
1524 config SHMEM
1525         bool "Use full shmem filesystem" if EXPERT
1526         default y
1527         depends on MMU
1528         help
1529           The shmem is an internal filesystem used to manage shared memory.
1530           It is backed by swap and manages resource limits. It is also exported
1531           to userspace as tmpfs if TMPFS is enabled. Disabling this
1532           option replaces shmem and tmpfs with the much simpler ramfs code,
1533           which may be appropriate on small systems without swap.
1535 config AIO
1536         bool "Enable AIO support" if EXPERT
1537         default y
1538         help
1539           This option enables POSIX asynchronous I/O which may by used
1540           by some high performance threaded applications. Disabling
1541           this option saves about 7k.
1543 config PCI_QUIRKS
1544         default y
1545         bool "Enable PCI quirk workarounds" if EXPERT
1546         depends on PCI
1547         help
1548           This enables workarounds for various PCI chipset
1549           bugs/quirks. Disable this only if your target machine is
1550           unaffected by PCI quirks.
1552 config EMBEDDED
1553         bool "Embedded system"
1554         option allnoconfig_y
1555         select EXPERT
1556         help
1557           This option should be enabled if compiling the kernel for
1558           an embedded system so certain expert options are available
1559           for configuration.
1561 config HAVE_PERF_EVENTS
1562         bool
1563         help
1564           See tools/perf/design.txt for details.
1566 config PERF_USE_VMALLOC
1567         bool
1568         help
1569           See tools/perf/design.txt for details
1571 menu "Kernel Performance Events And Counters"
1573 config PERF_EVENTS
1574         bool "Kernel performance events and counters"
1575         default y if PROFILING
1576         depends on HAVE_PERF_EVENTS
1577         select ANON_INODES
1578         select IRQ_WORK
1579         help
1580           Enable kernel support for various performance events provided
1581           by software and hardware.
1583           Software events are supported either built-in or via the
1584           use of generic tracepoints.
1586           Most modern CPUs support performance events via performance
1587           counter registers. These registers count the number of certain
1588           types of hw events: such as instructions executed, cachemisses
1589           suffered, or branches mis-predicted - without slowing down the
1590           kernel or applications. These registers can also trigger interrupts
1591           when a threshold number of events have passed - and can thus be
1592           used to profile the code that runs on that CPU.
1594           The Linux Performance Event subsystem provides an abstraction of
1595           these software and hardware event capabilities, available via a
1596           system call and used by the "perf" utility in tools/perf/. It
1597           provides per task and per CPU counters, and it provides event
1598           capabilities on top of those.
1600           Say Y if unsure.
1603         default n
1604         bool "Debug: use vmalloc to back perf mmap() buffers"
1605         depends on PERF_EVENTS && DEBUG_KERNEL
1606         select PERF_USE_VMALLOC
1607         help
1608          Use vmalloc memory to back perf mmap() buffers.
1610          Mostly useful for debugging the vmalloc code on platforms
1611          that don't require it.
1613          Say N if unsure.
1615 endmenu
1618         default y
1619         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1620         help
1621           VM event counters are needed for event counts to be shown.
1622           This option allows the disabling of the VM event counters
1623           on EXPERT systems.  /proc/vmstat will only show page counts
1624           if VM event counters are disabled.
1626 config SLUB_DEBUG
1627         default y
1628         bool "Enable SLUB debugging support" if EXPERT
1629         depends on SLUB && SYSFS
1630         help
1631           SLUB has extensive debug support features. Disabling these can
1632           result in significant savings in code size. This also disables
1633           SLUB sysfs support. /sys/slab will not exist and there will be
1634           no support for cache validation etc.
1636 config COMPAT_BRK
1637         bool "Disable heap randomization"
1638         default y
1639         help
1640           Randomizing heap placement makes heap exploits harder, but it
1641           also breaks ancient binaries (including anything libc5 based).
1642           This option changes the bootup default to heap randomization
1643           disabled, and can be overridden at runtime by setting
1644           /proc/sys/kernel/randomize_va_space to 2.
1646           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1648 choice
1649         prompt "Choose SLAB allocator"
1650         default SLUB
1651         help
1652            This option allows to select a slab allocator.
1654 config SLAB
1655         bool "SLAB"
1656         help
1657           The regular slab allocator that is established and known to work
1658           well in all environments. It organizes cache hot objects in
1659           per cpu and per node queues.
1661 config SLUB
1662         bool "SLUB (Unqueued Allocator)"
1663         help
1664            SLUB is a slab allocator that minimizes cache line usage
1665            instead of managing queues of cached objects (SLAB approach).
1666            Per cpu caching is realized using slabs of objects instead
1667            of queues of objects. SLUB can use memory efficiently
1668            and has enhanced diagnostics. SLUB is the default choice for
1669            a slab allocator.
1671 config SLOB
1672         depends on EXPERT
1673         bool "SLOB (Simple Allocator)"
1674         help
1675            SLOB replaces the stock allocator with a drastically simpler
1676            allocator. SLOB is generally more space efficient but
1677            does not perform as well on large systems.
1679 endchoice
1681 config SLUB_CPU_PARTIAL
1682         default y
1683         depends on SLUB && SMP
1684         bool "SLUB per cpu partial cache"
1685         help
1686           Per cpu partial caches accellerate objects allocation and freeing
1687           that is local to a processor at the price of more indeterminism
1688           in the latency of the free. On overflow these caches will be cleared
1689           which requires the taking of locks that may cause latency spikes.
1690           Typically one would choose no for a realtime system.
1693         bool "Allow mmapped anonymous memory to be uninitialized"
1694         depends on EXPERT && !MMU
1695         default n
1696         help
1697           Normally, and according to the Linux spec, anonymous memory obtained
1698           from mmap() has it's contents cleared before it is passed to
1699           userspace.  Enabling this config option allows you to request that
1700           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1701           providing a huge performance boost.  If this option is not enabled,
1702           then the flag will be ignored.
1704           This is taken advantage of by uClibc's malloc(), and also by
1705           ELF-FDPIC binfmt's brk and stack allocator.
1707           Because of the obvious security issues, this option should only be
1708           enabled on embedded devices where you control what is run in
1709           userspace.  Since that isn't generally a problem on no-MMU systems,
1710           it is normally safe to say Y here.
1712           See Documentation/nommu-mmap.txt for more information.
1715         bool "Provide system-wide ring of trusted keys"
1716         depends on KEYS
1717         help
1718           Provide a system keyring to which trusted keys can be added.  Keys in
1719           the keyring are considered to be trusted.  Keys may be added at will
1720           by the kernel from compiled-in data and from hardware key stores, but
1721           userspace may only add extra keys if those keys can be verified by
1722           keys already in the keyring.
1724           Keys in this keyring are used by module signature checking.
1726 config PROFILING
1727         bool "Profiling support"
1728         help
1729           Say Y here to enable the extended profiling support mechanisms used
1730           by profilers such as OProfile.
1732 #
1733 # Place an empty function call at each tracepoint site. Can be
1734 # dynamically changed for a probe function.
1735 #
1736 config TRACEPOINTS
1737         bool
1739 source "arch/Kconfig"
1741 endmenu         # General setup
1744         bool
1745         default n
1747 config SLABINFO
1748         bool
1749         depends on PROC_FS
1750         depends on SLAB || SLUB_DEBUG
1751         default y
1753 config RT_MUTEXES
1754         boolean
1756 config BASE_SMALL
1757         int
1758         default 0 if BASE_FULL
1759         default 1 if !BASE_FULL
1761 menuconfig MODULES
1762         bool "Enable loadable module support"
1763         option modules
1764         help
1765           Kernel modules are small pieces of compiled code which can
1766           be inserted in the running kernel, rather than being
1767           permanently built into the kernel.  You use the "modprobe"
1768           tool to add (and sometimes remove) them.  If you say Y here,
1769           many parts of the kernel can be built as modules (by
1770           answering M instead of Y where indicated): this is most
1771           useful for infrequently used options which are not required
1772           for booting.  For more information, see the man pages for
1773           modprobe, lsmod, modinfo, insmod and rmmod.
1775           If you say Y here, you will need to run "make
1776           modules_install" to put the modules under /lib/modules/
1777           where modprobe can find them (you may need to be root to do
1778           this).
1780           If unsure, say Y.
1782 if MODULES
1785         bool "Forced module loading"
1786         default n
1787         help
1788           Allow loading of modules without version information (ie. modprobe
1789           --force).  Forced module loading sets the 'F' (forced) taint flag and
1790           is usually a really bad idea.
1792 config MODULE_UNLOAD
1793         bool "Module unloading"
1794         help
1795           Without this option you will not be able to unload any
1796           modules (note that some modules may not be unloadable
1797           anyway), which makes your kernel smaller, faster
1798           and simpler.  If unsure, say Y.
1801         bool "Forced module unloading"
1802         depends on MODULE_UNLOAD
1803         help
1804           This option allows you to force a module to unload, even if the
1805           kernel believes it is unsafe: the kernel will remove the module
1806           without waiting for anyone to stop using it (using the -f option to
1807           rmmod).  This is mainly for kernel developers and desperate users.
1808           If unsure, say N.
1810 config MODVERSIONS
1811         bool "Module versioning support"
1812         help
1813           Usually, you have to use modules compiled with your kernel.
1814           Saying Y here makes it sometimes possible to use modules
1815           compiled for different kernels, by adding enough information
1816           to the modules to (hopefully) spot any changes which would
1817           make them incompatible with the kernel you are running.  If
1818           unsure, say N.
1821         bool "Source checksum for all modules"
1822         help
1823           Modules which contain a MODULE_VERSION get an extra "srcversion"
1824           field inserted into their modinfo section, which contains a
1825           sum of the source files which made it.  This helps maintainers
1826           see exactly which source was used to build a module (since
1827           others sometimes change the module source without updating
1828           the version).  With this option, such a "srcversion" field
1829           will be created for all modules.  If unsure, say N.
1831 config MODULE_SIG
1832         bool "Module signature verification"
1833         depends on MODULES
1834         select SYSTEM_TRUSTED_KEYRING
1835         select KEYS
1836         select CRYPTO
1837         select ASYMMETRIC_KEY_TYPE
1839         select PUBLIC_KEY_ALGO_RSA
1840         select ASN1
1841         select OID_REGISTRY
1842         select X509_CERTIFICATE_PARSER
1843         help
1844           Check modules for valid signatures upon load: the signature
1845           is simply appended to the module. For more information see
1846           Documentation/module-signing.txt.
1848           !!!WARNING!!!  If you enable this option, you MUST make sure that the
1849           module DOES NOT get stripped after being signed.  This includes the
1850           debuginfo strip done by some packagers (such as rpmbuild) and
1851           inclusion into an initramfs that wants the module size reduced.
1853 config MODULE_SIG_FORCE
1854         bool "Require modules to be validly signed"
1855         depends on MODULE_SIG
1856         help
1857           Reject unsigned modules or signed modules for which we don't have a
1858           key.  Without this, such modules will simply taint the kernel.
1860 config MODULE_SIG_ALL
1861         bool "Automatically sign all modules"
1862         default y
1863         depends on MODULE_SIG
1864         help
1865           Sign all modules during make modules_install. Without this option,
1866           modules must be signed manually, using the scripts/sign-file tool.
1868 comment "Do not forget to sign required modules with scripts/sign-file"
1869         depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1871 choice
1872         prompt "Which hash algorithm should modules be signed with?"
1873         depends on MODULE_SIG
1874         help
1875           This determines which sort of hashing algorithm will be used during
1876           signature generation.  This algorithm _must_ be built into the kernel
1877           directly so that signature verification can take place.  It is not
1878           possible to load a signed module containing the algorithm to check
1879           the signature on that module.
1881 config MODULE_SIG_SHA1
1882         bool "Sign modules with SHA-1"
1883         select CRYPTO_SHA1
1885 config MODULE_SIG_SHA224
1886         bool "Sign modules with SHA-224"
1887         select CRYPTO_SHA256
1889 config MODULE_SIG_SHA256
1890         bool "Sign modules with SHA-256"
1891         select CRYPTO_SHA256
1893 config MODULE_SIG_SHA384
1894         bool "Sign modules with SHA-384"
1895         select CRYPTO_SHA512
1897 config MODULE_SIG_SHA512
1898         bool "Sign modules with SHA-512"
1899         select CRYPTO_SHA512
1901 endchoice
1903 config MODULE_SIG_HASH
1904         string
1905         depends on MODULE_SIG
1906         default "sha1" if MODULE_SIG_SHA1
1907         default "sha224" if MODULE_SIG_SHA224
1908         default "sha256" if MODULE_SIG_SHA256
1909         default "sha384" if MODULE_SIG_SHA384
1910         default "sha512" if MODULE_SIG_SHA512
1912 endif # MODULES
1915         bool
1916         help
1917           Back when each arch used to define their own cpu_online_mask and
1918           cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1919           with all 1s, and others with all 0s.  When they were centralised,
1920           it was better to provide this option than to break all the archs
1921           and have several arch maintainers pursuing me down dark alleys.
1923 config STOP_MACHINE
1924         bool
1925         default y
1926         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1927         help
1928           Need stop_machine() primitive.
1930 source "block/Kconfig"
1933         bool
1935 config PADATA
1936         depends on SMP
1937         bool
1939 # Can be selected by architectures with broken toolchains
1940 # that get confused by correct const<->read_only section
1941 # mappings
1942 config BROKEN_RODATA
1943         bool
1945 config ASN1
1946         tristate
1947         help
1948           Build a simple ASN.1 grammar compiler that produces a bytecode output
1949           that can be interpreted by the ASN.1 stream decoder and used to
1950           inform it as to what tags are to be expected in a stream and what
1951           functions to call on what tags.
1953 source "kernel/Kconfig.locks"

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