7 option env="KERNELVERSION"
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"
26 config BUILDTIME_EXTABLE_SORT
29 config THREAD_INFO_IN_TASK
32 Select this to move thread_info off the stack into task_struct. To
33 make this work, an arch will need to remove all thread_info fields
34 except flags and fix any runtime bugs.
36 One subtle change that will be needed is to use try_get_task_stack()
37 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
46 depends on BROKEN || !SMP
49 config INIT_ENV_ARG_LIMIT
54 Maximum of each of the number of arguments and environment
55 variables passed to init from the kernel command line.
59 string "Cross-compiler tool prefix"
61 Same as running 'make CROSS_COMPILE=prefix-' but stored for
62 default make runs in this kernel build directory. You don't
63 need to set this unless you want the configured kernel build
64 directory to select the cross-compiler automatically.
67 bool "Compile also drivers which will not load"
70 Some drivers can be compiled on a different platform than they are
71 intended to be run on. Despite they cannot be loaded there (or even
72 when they load they cannot be used due to missing HW support),
73 developers still, opposing to distributors, might want to build such
74 drivers to compile-test them.
76 If you are a developer and want to build everything available, say Y
77 here. If you are a user/distributor, say N here to exclude useless
78 drivers to be distributed.
81 string "Local version - append to kernel release"
83 Append an extra string to the end of your kernel version.
84 This will show up when you type uname, for example.
85 The string you set here will be appended after the contents of
86 any files with a filename matching localversion* in your
87 object and source tree, in that order. Your total string can
88 be a maximum of 64 characters.
90 config LOCALVERSION_AUTO
91 bool "Automatically append version information to the version string"
94 This will try to automatically determine if the current tree is a
95 release tree by looking for git tags that belong to the current
98 A string of the format -gxxxxxxxx will be added to the localversion
99 if a git-based tree is found. The string generated by this will be
100 appended after any matching localversion* files, and after the value
101 set in CONFIG_LOCALVERSION.
103 (The actual string used here is the first eight characters produced
104 by running the command:
106 $ git rev-parse --verify HEAD
108 which is done within the script "scripts/setlocalversion".)
110 config HAVE_KERNEL_GZIP
113 config HAVE_KERNEL_BZIP2
116 config HAVE_KERNEL_LZMA
119 config HAVE_KERNEL_XZ
122 config HAVE_KERNEL_LZO
125 config HAVE_KERNEL_LZ4
129 prompt "Kernel compression mode"
131 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
133 The linux kernel is a kind of self-extracting executable.
134 Several compression algorithms are available, which differ
135 in efficiency, compression and decompression speed.
136 Compression speed is only relevant when building a kernel.
137 Decompression speed is relevant at each boot.
139 If you have any problems with bzip2 or lzma compressed
140 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
141 version of this functionality (bzip2 only), for 2.4, was
142 supplied by Christian Ludwig)
144 High compression options are mostly useful for users, who
145 are low on disk space (embedded systems), but for whom ram
148 If in doubt, select 'gzip'
152 depends on HAVE_KERNEL_GZIP
154 The old and tried gzip compression. It provides a good balance
155 between compression ratio and decompression speed.
159 depends on HAVE_KERNEL_BZIP2
161 Its compression ratio and speed is intermediate.
162 Decompression speed is slowest among the choices. The kernel
163 size is about 10% smaller with bzip2, in comparison to gzip.
164 Bzip2 uses a large amount of memory. For modern kernels you
165 will need at least 8MB RAM or more for booting.
169 depends on HAVE_KERNEL_LZMA
171 This compression algorithm's ratio is best. Decompression speed
172 is between gzip and bzip2. Compression is slowest.
173 The kernel size is about 33% smaller with LZMA in comparison to gzip.
177 depends on HAVE_KERNEL_XZ
179 XZ uses the LZMA2 algorithm and instruction set specific
180 BCJ filters which can improve compression ratio of executable
181 code. The size of the kernel is about 30% smaller with XZ in
182 comparison to gzip. On architectures for which there is a BCJ
183 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
184 will create a few percent smaller kernel than plain LZMA.
186 The speed is about the same as with LZMA: The decompression
187 speed of XZ is better than that of bzip2 but worse than gzip
188 and LZO. Compression is slow.
192 depends on HAVE_KERNEL_LZO
194 Its compression ratio is the poorest among the choices. The kernel
195 size is about 10% bigger than gzip; however its speed
196 (both compression and decompression) is the fastest.
200 depends on HAVE_KERNEL_LZ4
202 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
203 A preliminary version of LZ4 de/compression tool is available at
204 <https://code.google.com/p/lz4/>.
206 Its compression ratio is worse than LZO. The size of the kernel
207 is about 8% bigger than LZO. But the decompression speed is
212 config DEFAULT_HOSTNAME
213 string "Default hostname"
216 This option determines the default system hostname before userspace
217 calls sethostname(2). The kernel traditionally uses "(none)" here,
218 but you may wish to use a different default here to make a minimal
219 system more usable with less configuration.
222 bool "Support for paging of anonymous memory (swap)"
223 depends on MMU && BLOCK
226 This option allows you to choose whether you want to have support
227 for so called swap devices or swap files in your kernel that are
228 used to provide more virtual memory than the actual RAM present
229 in your computer. If unsure say Y.
234 Inter Process Communication is a suite of library functions and
235 system calls which let processes (running programs) synchronize and
236 exchange information. It is generally considered to be a good thing,
237 and some programs won't run unless you say Y here. In particular, if
238 you want to run the DOS emulator dosemu under Linux (read the
239 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
240 you'll need to say Y here.
242 You can find documentation about IPC with "info ipc" and also in
243 section 6.4 of the Linux Programmer's Guide, available from
244 <http://www.tldp.org/guides.html>.
246 config SYSVIPC_SYSCTL
253 bool "POSIX Message Queues"
256 POSIX variant of message queues is a part of IPC. In POSIX message
257 queues every message has a priority which decides about succession
258 of receiving it by a process. If you want to compile and run
259 programs written e.g. for Solaris with use of its POSIX message
260 queues (functions mq_*) say Y here.
262 POSIX message queues are visible as a filesystem called 'mqueue'
263 and can be mounted somewhere if you want to do filesystem
264 operations on message queues.
268 config POSIX_MQUEUE_SYSCTL
270 depends on POSIX_MQUEUE
274 config CROSS_MEMORY_ATTACH
275 bool "Enable process_vm_readv/writev syscalls"
279 Enabling this option adds the system calls process_vm_readv and
280 process_vm_writev which allow a process with the correct privileges
281 to directly read from or write to another process' address space.
282 See the man page for more details.
285 bool "open by fhandle syscalls"
288 If you say Y here, a user level program will be able to map
289 file names to handle and then later use the handle for
290 different file system operations. This is useful in implementing
291 userspace file servers, which now track files using handles instead
292 of names. The handle would remain the same even if file names
293 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
297 bool "uselib syscall"
300 This option enables the uselib syscall, a system call used in the
301 dynamic linker from libc5 and earlier. glibc does not use this
302 system call. If you intend to run programs built on libc5 or
303 earlier, you may need to enable this syscall. Current systems
304 running glibc can safely disable this.
307 bool "Auditing support"
310 Enable auditing infrastructure that can be used with another
311 kernel subsystem, such as SELinux (which requires this for
312 logging of avc messages output). Does not do system-call
313 auditing without CONFIG_AUDITSYSCALL.
315 config HAVE_ARCH_AUDITSYSCALL
319 bool "Enable system-call auditing support"
320 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
321 default y if SECURITY_SELINUX
323 Enable low-overhead system-call auditing infrastructure that
324 can be used independently or with another kernel subsystem,
329 depends on AUDITSYSCALL
334 depends on AUDITSYSCALL
337 source "kernel/irq/Kconfig"
338 source "kernel/time/Kconfig"
340 menu "CPU/Task time and stats accounting"
342 config VIRT_CPU_ACCOUNTING
346 prompt "Cputime accounting"
347 default TICK_CPU_ACCOUNTING if !PPC64
348 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
350 # Kind of a stub config for the pure tick based cputime accounting
351 config TICK_CPU_ACCOUNTING
352 bool "Simple tick based cputime accounting"
353 depends on !S390 && !NO_HZ_FULL
355 This is the basic tick based cputime accounting that maintains
356 statistics about user, system and idle time spent on per jiffies
361 config VIRT_CPU_ACCOUNTING_NATIVE
362 bool "Deterministic task and CPU time accounting"
363 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
364 select VIRT_CPU_ACCOUNTING
366 Select this option to enable more accurate task and CPU time
367 accounting. This is done by reading a CPU counter on each
368 kernel entry and exit and on transitions within the kernel
369 between system, softirq and hardirq state, so there is a
370 small performance impact. In the case of s390 or IBM POWER > 5,
371 this also enables accounting of stolen time on logically-partitioned
374 config VIRT_CPU_ACCOUNTING_GEN
375 bool "Full dynticks CPU time accounting"
376 depends on HAVE_CONTEXT_TRACKING
377 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
378 select VIRT_CPU_ACCOUNTING
379 select CONTEXT_TRACKING
381 Select this option to enable task and CPU time accounting on full
382 dynticks systems. This accounting is implemented by watching every
383 kernel-user boundaries using the context tracking subsystem.
384 The accounting is thus performed at the expense of some significant
387 For now this is only useful if you are working on the full
388 dynticks subsystem development.
392 config IRQ_TIME_ACCOUNTING
393 bool "Fine granularity task level IRQ time accounting"
394 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
396 Select this option to enable fine granularity task irq time
397 accounting. This is done by reading a timestamp on each
398 transitions between softirq and hardirq state, so there can be a
399 small performance impact.
401 If in doubt, say N here.
406 bool "Support window based load tracking"
408 depends on FAIR_GROUP_SCHED
410 This feature will allow the scheduler to maintain a tunable window
411 based set of metrics for tasks and runqueues. These metrics can be
412 used to guide task placement as well as task frequency requirements
413 for cpufreq governors.
415 config BSD_PROCESS_ACCT
416 bool "BSD Process Accounting"
419 If you say Y here, a user level program will be able to instruct the
420 kernel (via a special system call) to write process accounting
421 information to a file: whenever a process exits, information about
422 that process will be appended to the file by the kernel. The
423 information includes things such as creation time, owning user,
424 command name, memory usage, controlling terminal etc. (the complete
425 list is in the struct acct in <file:include/linux/acct.h>). It is
426 up to the user level program to do useful things with this
427 information. This is generally a good idea, so say Y.
429 config BSD_PROCESS_ACCT_V3
430 bool "BSD Process Accounting version 3 file format"
431 depends on BSD_PROCESS_ACCT
434 If you say Y here, the process accounting information is written
435 in a new file format that also logs the process IDs of each
436 process and it's parent. Note that this file format is incompatible
437 with previous v0/v1/v2 file formats, so you will need updated tools
438 for processing it. A preliminary version of these tools is available
439 at <http://www.gnu.org/software/acct/>.
442 bool "Export task/process statistics through netlink"
447 Export selected statistics for tasks/processes through the
448 generic netlink interface. Unlike BSD process accounting, the
449 statistics are available during the lifetime of tasks/processes as
450 responses to commands. Like BSD accounting, they are sent to user
455 config TASK_DELAY_ACCT
456 bool "Enable per-task delay accounting"
460 Collect information on time spent by a task waiting for system
461 resources like cpu, synchronous block I/O completion and swapping
462 in pages. Such statistics can help in setting a task's priorities
463 relative to other tasks for cpu, io, rss limits etc.
468 bool "Enable extended accounting over taskstats"
471 Collect extended task accounting data and send the data
472 to userland for processing over the taskstats interface.
476 config TASK_IO_ACCOUNTING
477 bool "Enable per-task storage I/O accounting"
478 depends on TASK_XACCT
480 Collect information on the number of bytes of storage I/O which this
485 endmenu # "CPU/Task time and stats accounting"
491 default y if !PREEMPT && SMP
493 This option selects the RCU implementation that is
494 designed for very large SMP system with hundreds or
495 thousands of CPUs. It also scales down nicely to
502 This option selects the RCU implementation that is
503 designed for very large SMP systems with hundreds or
504 thousands of CPUs, but for which real-time response
505 is also required. It also scales down nicely to
508 Select this option if you are unsure.
512 default y if !PREEMPT && !SMP
514 This option selects the RCU implementation that is
515 designed for UP systems from which real-time response
516 is not required. This option greatly reduces the
517 memory footprint of RCU.
520 bool "Make expert-level adjustments to RCU configuration"
523 This option needs to be enabled if you wish to make
524 expert-level adjustments to RCU configuration. By default,
525 no such adjustments can be made, which has the often-beneficial
526 side-effect of preventing "make oldconfig" from asking you all
527 sorts of detailed questions about how you would like numerous
528 obscure RCU options to be set up.
530 Say Y if you need to make expert-level adjustments to RCU.
532 Say N if you are unsure.
537 This option selects the sleepable version of RCU. This version
538 permits arbitrary sleeping or blocking within RCU read-side critical
546 This option enables a task-based RCU implementation that uses
547 only voluntary context switch (not preemption!), idle, and
548 user-mode execution as quiescent states.
550 config RCU_STALL_COMMON
551 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
553 This option enables RCU CPU stall code that is common between
554 the TINY and TREE variants of RCU. The purpose is to allow
555 the tiny variants to disable RCU CPU stall warnings, while
556 making these warnings mandatory for the tree variants.
558 config CONTEXT_TRACKING
561 config CONTEXT_TRACKING_FORCE
562 bool "Force context tracking"
563 depends on CONTEXT_TRACKING
564 default y if !NO_HZ_FULL
566 The major pre-requirement for full dynticks to work is to
567 support the context tracking subsystem. But there are also
568 other dependencies to provide in order to make the full
571 This option stands for testing when an arch implements the
572 context tracking backend but doesn't yet fullfill all the
573 requirements to make the full dynticks feature working.
574 Without the full dynticks, there is no way to test the support
575 for context tracking and the subsystems that rely on it: RCU
576 userspace extended quiescent state and tickless cputime
577 accounting. This option copes with the absence of the full
578 dynticks subsystem by forcing the context tracking on all
581 Say Y only if you're working on the development of an
582 architecture backend for the context tracking.
584 Say N otherwise, this option brings an overhead that you
585 don't want in production.
589 int "Tree-based hierarchical RCU fanout value"
592 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
596 This option controls the fanout of hierarchical implementations
597 of RCU, allowing RCU to work efficiently on machines with
598 large numbers of CPUs. This value must be at least the fourth
599 root of NR_CPUS, which allows NR_CPUS to be insanely large.
600 The default value of RCU_FANOUT should be used for production
601 systems, but if you are stress-testing the RCU implementation
602 itself, small RCU_FANOUT values allow you to test large-system
603 code paths on small(er) systems.
605 Select a specific number if testing RCU itself.
606 Take the default if unsure.
608 config RCU_FANOUT_LEAF
609 int "Tree-based hierarchical RCU leaf-level fanout value"
612 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
615 This option controls the leaf-level fanout of hierarchical
616 implementations of RCU, and allows trading off cache misses
617 against lock contention. Systems that synchronize their
618 scheduling-clock interrupts for energy-efficiency reasons will
619 want the default because the smaller leaf-level fanout keeps
620 lock contention levels acceptably low. Very large systems
621 (hundreds or thousands of CPUs) will instead want to set this
622 value to the maximum value possible in order to reduce the
623 number of cache misses incurred during RCU's grace-period
624 initialization. These systems tend to run CPU-bound, and thus
625 are not helped by synchronized interrupts, and thus tend to
626 skew them, which reduces lock contention enough that large
627 leaf-level fanouts work well.
629 Select a specific number if testing RCU itself.
631 Select the maximum permissible value for large systems.
633 Take the default if unsure.
635 config RCU_FAST_NO_HZ
636 bool "Accelerate last non-dyntick-idle CPU's grace periods"
637 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
640 This option permits CPUs to enter dynticks-idle state even if
641 they have RCU callbacks queued, and prevents RCU from waking
642 these CPUs up more than roughly once every four jiffies (by
643 default, you can adjust this using the rcutree.rcu_idle_gp_delay
644 parameter), thus improving energy efficiency. On the other
645 hand, this option increases the duration of RCU grace periods,
646 for example, slowing down synchronize_rcu().
648 Say Y if energy efficiency is critically important, and you
649 don't care about increased grace-period durations.
651 Say N if you are unsure.
653 config TREE_RCU_TRACE
654 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
657 This option provides tracing for the TREE_RCU and
658 PREEMPT_RCU implementations, permitting Makefile to
659 trivially select kernel/rcutree_trace.c.
662 bool "Enable RCU priority boosting"
663 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
666 This option boosts the priority of preempted RCU readers that
667 block the current preemptible RCU grace period for too long.
668 This option also prevents heavy loads from blocking RCU
669 callback invocation for all flavors of RCU.
671 Say Y here if you are working with real-time apps or heavy loads
672 Say N here if you are unsure.
674 config RCU_KTHREAD_PRIO
675 int "Real-time priority to use for RCU worker threads"
676 range 1 99 if RCU_BOOST
677 range 0 99 if !RCU_BOOST
678 default 1 if RCU_BOOST
679 default 0 if !RCU_BOOST
680 depends on RCU_EXPERT
682 This option specifies the SCHED_FIFO priority value that will be
683 assigned to the rcuc/n and rcub/n threads and is also the value
684 used for RCU_BOOST (if enabled). If you are working with a
685 real-time application that has one or more CPU-bound threads
686 running at a real-time priority level, you should set
687 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
688 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
689 value of 1 is appropriate in the common case, which is real-time
690 applications that do not have any CPU-bound threads.
692 Some real-time applications might not have a single real-time
693 thread that saturates a given CPU, but instead might have
694 multiple real-time threads that, taken together, fully utilize
695 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
696 a priority higher than the lowest-priority thread that is
697 conspiring to prevent the CPU from running any non-real-time
698 tasks. For example, if one thread at priority 10 and another
699 thread at priority 5 are between themselves fully consuming
700 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
701 set to priority 6 or higher.
703 Specify the real-time priority, or take the default if unsure.
705 config RCU_BOOST_DELAY
706 int "Milliseconds to delay boosting after RCU grace-period start"
711 This option specifies the time to wait after the beginning of
712 a given grace period before priority-boosting preempted RCU
713 readers blocking that grace period. Note that any RCU reader
714 blocking an expedited RCU grace period is boosted immediately.
716 Accept the default if unsure.
719 bool "Offload RCU callback processing from boot-selected CPUs"
720 depends on TREE_RCU || PREEMPT_RCU
721 depends on RCU_EXPERT || NO_HZ_FULL
724 Use this option to reduce OS jitter for aggressive HPC or
725 real-time workloads. It can also be used to offload RCU
726 callback invocation to energy-efficient CPUs in battery-powered
727 asymmetric multiprocessors.
729 This option offloads callback invocation from the set of
730 CPUs specified at boot time by the rcu_nocbs parameter.
731 For each such CPU, a kthread ("rcuox/N") will be created to
732 invoke callbacks, where the "N" is the CPU being offloaded,
733 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
734 "s" for RCU-sched. Nothing prevents this kthread from running
735 on the specified CPUs, but (1) the kthreads may be preempted
736 between each callback, and (2) affinity or cgroups can be used
737 to force the kthreads to run on whatever set of CPUs is desired.
739 Say Y here if you want to help to debug reduced OS jitter.
740 Say N here if you are unsure.
743 prompt "Build-forced no-CBs CPUs"
744 default RCU_NOCB_CPU_NONE
745 depends on RCU_NOCB_CPU
747 This option allows no-CBs CPUs (whose RCU callbacks are invoked
748 from kthreads rather than from softirq context) to be specified
749 at build time. Additional no-CBs CPUs may be specified by
750 the rcu_nocbs= boot parameter.
752 config RCU_NOCB_CPU_NONE
753 bool "No build_forced no-CBs CPUs"
755 This option does not force any of the CPUs to be no-CBs CPUs.
756 Only CPUs designated by the rcu_nocbs= boot parameter will be
757 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
758 kthreads whose names begin with "rcuo". All other CPUs will
759 invoke their own RCU callbacks in softirq context.
761 Select this option if you want to choose no-CBs CPUs at
762 boot time, for example, to allow testing of different no-CBs
763 configurations without having to rebuild the kernel each time.
765 config RCU_NOCB_CPU_ZERO
766 bool "CPU 0 is a build_forced no-CBs CPU"
768 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
769 callbacks are invoked by a per-CPU kthread whose name begins
770 with "rcuo". Additional CPUs may be designated as no-CBs
771 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
772 All other CPUs will invoke their own RCU callbacks in softirq
775 Select this if CPU 0 needs to be a no-CBs CPU for real-time
776 or energy-efficiency reasons, but the real reason it exists
777 is to ensure that randconfig testing covers mixed systems.
779 config RCU_NOCB_CPU_ALL
780 bool "All CPUs are build_forced no-CBs CPUs"
782 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
783 boot parameter will be ignored. All CPUs' RCU callbacks will
784 be executed in the context of per-CPU rcuo kthreads created for
785 this purpose. Assuming that the kthreads whose names start with
786 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
787 on the remaining CPUs, but might decrease memory locality during
788 RCU-callback invocation, thus potentially degrading throughput.
790 Select this if all CPUs need to be no-CBs CPUs for real-time
791 or energy-efficiency reasons.
795 config RCU_EXPEDITE_BOOT
799 This option enables expedited grace periods at boot time,
800 as if rcu_expedite_gp() had been invoked early in boot.
801 The corresponding rcu_unexpedite_gp() is invoked from
802 rcu_end_inkernel_boot(), which is intended to be invoked
803 at the end of the kernel-only boot sequence, just before
806 Accept the default if unsure.
808 endmenu # "RCU Subsystem"
815 tristate "Kernel .config support"
818 This option enables the complete Linux kernel ".config" file
819 contents to be saved in the kernel. It provides documentation
820 of which kernel options are used in a running kernel or in an
821 on-disk kernel. This information can be extracted from the kernel
822 image file with the script scripts/extract-ikconfig and used as
823 input to rebuild the current kernel or to build another kernel.
824 It can also be extracted from a running kernel by reading
825 /proc/config.gz if enabled (below).
828 bool "Enable access to .config through /proc/config.gz"
829 depends on IKCONFIG && PROC_FS
831 This option enables access to the kernel configuration file
832 through /proc/config.gz.
835 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
840 Select the minimal kernel log buffer size as a power of 2.
841 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
842 parameter, see below. Any higher size also might be forced
843 by "log_buf_len" boot parameter.
853 config LOG_CPU_MAX_BUF_SHIFT
854 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
857 default 12 if !BASE_SMALL
858 default 0 if BASE_SMALL
861 This option allows to increase the default ring buffer size
862 according to the number of CPUs. The value defines the contribution
863 of each CPU as a power of 2. The used space is typically only few
864 lines however it might be much more when problems are reported,
867 The increased size means that a new buffer has to be allocated and
868 the original static one is unused. It makes sense only on systems
869 with more CPUs. Therefore this value is used only when the sum of
870 contributions is greater than the half of the default kernel ring
871 buffer as defined by LOG_BUF_SHIFT. The default values are set
872 so that more than 64 CPUs are needed to trigger the allocation.
874 Also this option is ignored when "log_buf_len" kernel parameter is
875 used as it forces an exact (power of two) size of the ring buffer.
877 The number of possible CPUs is used for this computation ignoring
878 hotplugging making the compuation optimal for the the worst case
879 scenerio while allowing a simple algorithm to be used from bootup.
881 Examples shift values and their meaning:
882 17 => 128 KB for each CPU
883 16 => 64 KB for each CPU
884 15 => 32 KB for each CPU
885 14 => 16 KB for each CPU
886 13 => 8 KB for each CPU
887 12 => 4 KB for each CPU
890 # Architectures with an unreliable sched_clock() should select this:
892 config HAVE_UNSTABLE_SCHED_CLOCK
895 config GENERIC_SCHED_CLOCK
899 # For architectures that want to enable the support for NUMA-affine scheduler
902 config ARCH_SUPPORTS_NUMA_BALANCING
906 # For architectures that prefer to flush all TLBs after a number of pages
907 # are unmapped instead of sending one IPI per page to flush. The architecture
908 # must provide guarantees on what happens if a clean TLB cache entry is
909 # written after the unmap. Details are in mm/rmap.c near the check for
910 # should_defer_flush. The architecture should also consider if the full flush
911 # and the refill costs are offset by the savings of sending fewer IPIs.
912 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
916 # For architectures that know their GCC __int128 support is sound
918 config ARCH_SUPPORTS_INT128
921 # For architectures that (ab)use NUMA to represent different memory regions
922 # all cpu-local but of different latencies, such as SuperH.
924 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
927 config NUMA_BALANCING
928 bool "Memory placement aware NUMA scheduler"
929 depends on ARCH_SUPPORTS_NUMA_BALANCING
930 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
931 depends on SMP && NUMA && MIGRATION
933 This option adds support for automatic NUMA aware memory/task placement.
934 The mechanism is quite primitive and is based on migrating memory when
935 it has references to the node the task is running on.
937 This system will be inactive on UMA systems.
939 config NUMA_BALANCING_DEFAULT_ENABLED
940 bool "Automatically enable NUMA aware memory/task placement"
942 depends on NUMA_BALANCING
944 If set, automatic NUMA balancing will be enabled if running on a NUMA
948 bool "Control Group support"
951 This option adds support for grouping sets of processes together, for
952 use with process control subsystems such as Cpusets, CFS, memory
953 controls or device isolation.
955 - Documentation/scheduler/sched-design-CFS.txt (CFS)
956 - Documentation/cgroups/ (features for grouping, isolation
957 and resource control)
964 bool "Example debug cgroup subsystem"
967 This option enables a simple cgroup subsystem that
968 exports useful debugging information about the cgroups
973 config CGROUP_FREEZER
974 bool "Freezer cgroup subsystem"
976 Provides a way to freeze and unfreeze all tasks in a
980 bool "PIDs cgroup subsystem"
982 Provides enforcement of process number limits in the scope of a
983 cgroup. Any attempt to fork more processes than is allowed in the
984 cgroup will fail. PIDs are fundamentally a global resource because it
985 is fairly trivial to reach PID exhaustion before you reach even a
986 conservative kmemcg limit. As a result, it is possible to grind a
987 system to halt without being limited by other cgroup policies. The
988 PIDs cgroup subsystem is designed to stop this from happening.
990 It should be noted that organisational operations (such as attaching
991 to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
992 since the PIDs limit only affects a process's ability to fork, not to
996 bool "Device controller for cgroups"
998 Provides a cgroup implementing whitelists for devices which
999 a process in the cgroup can mknod or open.
1002 bool "Cpuset support"
1004 This option will let you create and manage CPUSETs which
1005 allow dynamically partitioning a system into sets of CPUs and
1006 Memory Nodes and assigning tasks to run only within those sets.
1007 This is primarily useful on large SMP or NUMA systems.
1011 config PROC_PID_CPUSET
1012 bool "Include legacy /proc/<pid>/cpuset file"
1016 config CGROUP_CPUACCT
1017 bool "Simple CPU accounting cgroup subsystem"
1019 Provides a simple Resource Controller for monitoring the
1020 total CPU consumed by the tasks in a cgroup.
1022 config CGROUP_SCHEDTUNE
1023 bool "CFS tasks boosting cgroup subsystem (EXPERIMENTAL)"
1024 depends on SCHED_TUNE
1026 This option provides the "schedtune" controller which improves the
1027 flexibility of the task boosting mechanism by introducing the support
1028 to define "per task" boost values.
1030 This new controller:
1031 1. allows only a two layers hierarchy, where the root defines the
1032 system-wide boost value and its direct childrens define each one a
1033 different "class of tasks" to be boosted with a different value
1034 2. supports up to 16 different task classes, each one which could be
1035 configured with a different boost value
1043 bool "Memory Resource Controller for Control Groups"
1047 Provides a memory resource controller that manages both anonymous
1048 memory and page cache. (See Documentation/cgroups/memory.txt)
1051 bool "Memory Resource Controller Swap Extension"
1052 depends on MEMCG && SWAP
1054 Add swap management feature to memory resource controller. When you
1055 enable this, you can limit mem+swap usage per cgroup. In other words,
1056 when you disable this, memory resource controller has no cares to
1057 usage of swap...a process can exhaust all of the swap. This extension
1058 is useful when you want to avoid exhaustion swap but this itself
1059 adds more overheads and consumes memory for remembering information.
1060 Especially if you use 32bit system or small memory system, please
1061 be careful about enabling this. When memory resource controller
1062 is disabled by boot option, this will be automatically disabled and
1063 there will be no overhead from this. Even when you set this config=y,
1064 if boot option "swapaccount=0" is set, swap will not be accounted.
1065 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1066 size is 4096bytes, 512k per 1Gbytes of swap.
1068 config MEMCG_SWAP_ENABLED
1069 bool "Memory Resource Controller Swap Extension enabled by default"
1070 depends on MEMCG_SWAP
1073 Memory Resource Controller Swap Extension comes with its price in
1074 a bigger memory consumption. General purpose distribution kernels
1075 which want to enable the feature but keep it disabled by default
1076 and let the user enable it by swapaccount=1 boot command line
1077 parameter should have this option unselected.
1078 For those who want to have the feature enabled by default should
1079 select this option (if, for some reason, they need to disable it
1080 then swapaccount=0 does the trick).
1082 config MEMCG_FORCE_USE_VM_SWAPPINESS
1083 bool "Force to use vm_swappiness instead of memcg->swappiness"
1084 depends on MEMCG_SWAP
1088 bool "Memory Resource Controller Kernel Memory accounting"
1090 depends on SLUB || SLAB
1092 The Kernel Memory extension for Memory Resource Controller can limit
1093 the amount of memory used by kernel objects in the system. Those are
1094 fundamentally different from the entities handled by the standard
1095 Memory Controller, which are page-based, and can be swapped. Users of
1096 the kmem extension can use it to guarantee that no group of processes
1097 will ever exhaust kernel resources alone.
1099 config CGROUP_HUGETLB
1100 bool "HugeTLB Resource Controller for Control Groups"
1101 depends on HUGETLB_PAGE
1105 Provides a cgroup Resource Controller for HugeTLB pages.
1106 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1107 The limit is enforced during page fault. Since HugeTLB doesn't
1108 support page reclaim, enforcing the limit at page fault time implies
1109 that, the application will get SIGBUS signal if it tries to access
1110 HugeTLB pages beyond its limit. This requires the application to know
1111 beforehand how much HugeTLB pages it would require for its use. The
1112 control group is tracked in the third page lru pointer. This means
1113 that we cannot use the controller with huge page less than 3 pages.
1116 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1117 depends on PERF_EVENTS && CGROUPS
1119 This option extends the per-cpu mode to restrict monitoring to
1120 threads which belong to the cgroup specified and run on the
1125 menuconfig CGROUP_SCHED
1126 bool "Group CPU scheduler"
1129 This feature lets CPU scheduler recognize task groups and control CPU
1130 bandwidth allocation to such task groups. It uses cgroups to group
1134 config FAIR_GROUP_SCHED
1135 bool "Group scheduling for SCHED_OTHER"
1136 depends on CGROUP_SCHED
1137 default CGROUP_SCHED
1139 config CFS_BANDWIDTH
1140 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1141 depends on FAIR_GROUP_SCHED
1144 This option allows users to define CPU bandwidth rates (limits) for
1145 tasks running within the fair group scheduler. Groups with no limit
1146 set are considered to be unconstrained and will run with no
1148 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1150 config RT_GROUP_SCHED
1151 bool "Group scheduling for SCHED_RR/FIFO"
1152 depends on CGROUP_SCHED
1155 This feature lets you explicitly allocate real CPU bandwidth
1156 to task groups. If enabled, it will also make it impossible to
1157 schedule realtime tasks for non-root users until you allocate
1158 realtime bandwidth for them.
1159 See Documentation/scheduler/sched-rt-group.txt for more information.
1164 bool "Block IO controller"
1168 Generic block IO controller cgroup interface. This is the common
1169 cgroup interface which should be used by various IO controlling
1172 Currently, CFQ IO scheduler uses it to recognize task groups and
1173 control disk bandwidth allocation (proportional time slice allocation)
1174 to such task groups. It is also used by bio throttling logic in
1175 block layer to implement upper limit in IO rates on a device.
1177 This option only enables generic Block IO controller infrastructure.
1178 One needs to also enable actual IO controlling logic/policy. For
1179 enabling proportional weight division of disk bandwidth in CFQ, set
1180 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1181 CONFIG_BLK_DEV_THROTTLING=y.
1183 See Documentation/cgroups/blkio-controller.txt for more information.
1185 config DEBUG_BLK_CGROUP
1186 bool "Enable Block IO controller debugging"
1187 depends on BLK_CGROUP
1190 Enable some debugging help. Currently it exports additional stat
1191 files in a cgroup which can be useful for debugging.
1193 config CGROUP_WRITEBACK
1195 depends on MEMCG && BLK_CGROUP
1200 config CHECKPOINT_RESTORE
1201 bool "Checkpoint/restore support" if EXPERT
1202 select PROC_CHILDREN
1205 Enables additional kernel features in a sake of checkpoint/restore.
1206 In particular it adds auxiliary prctl codes to setup process text,
1207 data and heap segment sizes, and a few additional /proc filesystem
1210 If unsure, say N here.
1212 menuconfig NAMESPACES
1213 bool "Namespaces support" if EXPERT
1214 depends on MULTIUSER
1217 Provides the way to make tasks work with different objects using
1218 the same id. For example same IPC id may refer to different objects
1219 or same user id or pid may refer to different tasks when used in
1220 different namespaces.
1225 bool "UTS namespace"
1228 In this namespace tasks see different info provided with the
1232 bool "IPC namespace"
1233 depends on (SYSVIPC || POSIX_MQUEUE)
1236 In this namespace tasks work with IPC ids which correspond to
1237 different IPC objects in different namespaces.
1240 bool "User namespace"
1243 This allows containers, i.e. vservers, to use user namespaces
1244 to provide different user info for different servers.
1246 When user namespaces are enabled in the kernel it is
1247 recommended that the MEMCG and MEMCG_KMEM options also be
1248 enabled and that user-space use the memory control groups to
1249 limit the amount of memory a memory unprivileged users can
1255 bool "PID Namespaces"
1258 Support process id namespaces. This allows having multiple
1259 processes with the same pid as long as they are in different
1260 pid namespaces. This is a building block of containers.
1263 bool "Network namespace"
1267 Allow user space to create what appear to be multiple instances
1268 of the network stack.
1272 config SCHED_AUTOGROUP
1273 bool "Automatic process group scheduling"
1276 select FAIR_GROUP_SCHED
1278 This option optimizes the scheduler for common desktop workloads by
1279 automatically creating and populating task groups. This separation
1280 of workloads isolates aggressive CPU burners (like build jobs) from
1281 desktop applications. Task group autogeneration is currently based
1285 bool "Boosting for CFS tasks (EXPERIMENTAL)"
1286 depends on CPU_FREQ_GOV_SCHEDUTIL
1288 This option enables the system-wide support for task boosting.
1289 When this support is enabled a new sysctl interface is exposed to
1291 /proc/sys/kernel/sched_cfs_boost
1292 which allows to set a system-wide boost value in range [0..100].
1294 The currently boosting strategy is implemented in such a way that:
1295 - a 0% boost value requires to operate in "standard" mode by
1296 scheduling all tasks at the minimum capacities required by their
1298 - a 100% boost value requires to push at maximum the task
1299 performances, "regardless" of the incurred energy consumption
1301 A boost value in between these two boundaries is used to bias the
1302 power/performance trade-off, the higher the boost value the more the
1303 scheduler is biased toward performance boosting instead of energy
1306 Since this support exposes a single system-wide knob, the specified
1307 boost value is applied to all (CFS) tasks in the system.
1311 config SCHED_USE_FLUID_RT
1312 bool "Enable Fluid RT scheduler feature"
1316 Basically, the Fluid RT selects the core by a task priority as usual.
1317 But beyond the basic behavior, FRT performs the load balancing of
1318 RT task by core selection with reference to utilization of rq.
1319 And in some circumstances, she allows the task with lower priority
1320 to preempt the higher one based on weighted load.
1324 config SYSFS_DEPRECATED
1325 bool "Enable deprecated sysfs features to support old userspace tools"
1329 This option adds code that switches the layout of the "block" class
1330 devices, to not show up in /sys/class/block/, but only in
1333 This switch is only active when the sysfs.deprecated=1 boot option is
1334 passed or the SYSFS_DEPRECATED_V2 option is set.
1336 This option allows new kernels to run on old distributions and tools,
1337 which might get confused by /sys/class/block/. Since 2007/2008 all
1338 major distributions and tools handle this just fine.
1340 Recent distributions and userspace tools after 2009/2010 depend on
1341 the existence of /sys/class/block/, and will not work with this
1344 Only if you are using a new kernel on an old distribution, you might
1347 config SYSFS_DEPRECATED_V2
1348 bool "Enable deprecated sysfs features by default"
1351 depends on SYSFS_DEPRECATED
1353 Enable deprecated sysfs by default.
1355 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1358 Only if you are using a new kernel on an old distribution, you might
1359 need to say Y here. Even then, odds are you would not need it
1360 enabled, you can always pass the boot option if absolutely necessary.
1363 bool "Kernel->user space relay support (formerly relayfs)"
1365 This option enables support for relay interface support in
1366 certain file systems (such as debugfs).
1367 It is designed to provide an efficient mechanism for tools and
1368 facilities to relay large amounts of data from kernel space to
1373 config BLK_DEV_INITRD
1374 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1375 depends on BROKEN || !FRV
1377 The initial RAM filesystem is a ramfs which is loaded by the
1378 boot loader (loadlin or lilo) and that is mounted as root
1379 before the normal boot procedure. It is typically used to
1380 load modules needed to mount the "real" root file system,
1381 etc. See <file:Documentation/initrd.txt> for details.
1383 If RAM disk support (BLK_DEV_RAM) is also included, this
1384 also enables initial RAM disk (initrd) support and adds
1385 15 Kbytes (more on some other architectures) to the kernel size.
1391 source "usr/Kconfig"
1395 config CC_OPTIMIZE_FOR_SIZE
1396 bool "Optimize for size"
1398 Enabling this option will pass "-Os" instead of "-O2" to
1399 your compiler resulting in a smaller kernel.
1412 config SYSCTL_EXCEPTION_TRACE
1415 Enable support for /proc/sys/debug/exception-trace.
1417 config SYSCTL_ARCH_UNALIGN_NO_WARN
1420 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1421 Allows arch to define/use @no_unaligned_warning to possibly warn
1422 about unaligned access emulation going on under the hood.
1424 config SYSCTL_ARCH_UNALIGN_ALLOW
1427 Enable support for /proc/sys/kernel/unaligned-trap
1428 Allows arches to define/use @unaligned_enabled to runtime toggle
1429 the unaligned access emulation.
1430 see arch/parisc/kernel/unaligned.c for reference
1432 config HAVE_PCSPKR_PLATFORM
1435 # interpreter that classic socket filters depend on
1440 bool "Configure standard kernel features (expert users)"
1441 # Unhide debug options, to make the on-by-default options visible
1444 This option allows certain base kernel options and settings
1445 to be disabled or tweaked. This is for specialized
1446 environments which can tolerate a "non-standard" kernel.
1447 Only use this if you really know what you are doing.
1450 bool "Enable 16-bit UID system calls" if EXPERT
1451 depends on HAVE_UID16 && MULTIUSER
1454 This enables the legacy 16-bit UID syscall wrappers.
1457 bool "Multiple users, groups and capabilities support" if EXPERT
1460 This option enables support for non-root users, groups and
1463 If you say N here, all processes will run with UID 0, GID 0, and all
1464 possible capabilities. Saying N here also compiles out support for
1465 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1468 If unsure, say Y here.
1470 config SGETMASK_SYSCALL
1471 bool "sgetmask/ssetmask syscalls support" if EXPERT
1472 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1474 sys_sgetmask and sys_ssetmask are obsolete system calls
1475 no longer supported in libc but still enabled by default in some
1478 If unsure, leave the default option here.
1480 config SYSFS_SYSCALL
1481 bool "Sysfs syscall support" if EXPERT
1484 sys_sysfs is an obsolete system call no longer supported in libc.
1485 Note that disabling this option is more secure but might break
1486 compatibility with some systems.
1488 If unsure say Y here.
1490 config SYSCTL_SYSCALL
1491 bool "Sysctl syscall support" if EXPERT
1492 depends on PROC_SYSCTL
1496 sys_sysctl uses binary paths that have been found challenging
1497 to properly maintain and use. The interface in /proc/sys
1498 using paths with ascii names is now the primary path to this
1501 Almost nothing using the binary sysctl interface so if you are
1502 trying to save some space it is probably safe to disable this,
1503 making your kernel marginally smaller.
1505 If unsure say N here.
1508 bool "Load all symbols for debugging/ksymoops" if EXPERT
1511 Say Y here to let the kernel print out symbolic crash information and
1512 symbolic stack backtraces. This increases the size of the kernel
1513 somewhat, as all symbols have to be loaded into the kernel image.
1516 bool "Include all symbols in kallsyms"
1517 depends on DEBUG_KERNEL && KALLSYMS
1519 Normally kallsyms only contains the symbols of functions for nicer
1520 OOPS messages and backtraces (i.e., symbols from the text and inittext
1521 sections). This is sufficient for most cases. And only in very rare
1522 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1523 names of variables from the data sections, etc).
1525 This option makes sure that all symbols are loaded into the kernel
1526 image (i.e., symbols from all sections) in cost of increased kernel
1527 size (depending on the kernel configuration, it may be 300KiB or
1528 something like this).
1530 Say N unless you really need all symbols.
1534 bool "Enable support for printk" if EXPERT
1537 This option enables normal printk support. Removing it
1538 eliminates most of the message strings from the kernel image
1539 and makes the kernel more or less silent. As this makes it
1540 very difficult to diagnose system problems, saying N here is
1541 strongly discouraged.
1544 bool "BUG() support" if EXPERT
1547 Disabling this option eliminates support for BUG and WARN, reducing
1548 the size of your kernel image and potentially quietly ignoring
1549 numerous fatal conditions. You should only consider disabling this
1550 option for embedded systems with no facilities for reporting errors.
1556 bool "Enable ELF core dumps" if EXPERT
1558 Enable support for generating core dumps. Disabling saves about 4k.
1561 config PCSPKR_PLATFORM
1562 bool "Enable PC-Speaker support" if EXPERT
1563 depends on HAVE_PCSPKR_PLATFORM
1567 This option allows to disable the internal PC-Speaker
1568 support, saving some memory.
1572 bool "Enable full-sized data structures for core" if EXPERT
1574 Disabling this option reduces the size of miscellaneous core
1575 kernel data structures. This saves memory on small machines,
1576 but may reduce performance.
1579 bool "Enable futex support" if EXPERT
1583 Disabling this option will cause the kernel to be built without
1584 support for "fast userspace mutexes". The resulting kernel may not
1585 run glibc-based applications correctly.
1587 config HAVE_FUTEX_CMPXCHG
1591 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1592 is implemented and always working. This removes a couple of runtime
1596 bool "Enable eventpoll support" if EXPERT
1600 Disabling this option will cause the kernel to be built without
1601 support for epoll family of system calls.
1604 bool "Enable signalfd() system call" if EXPERT
1608 Enable the signalfd() system call that allows to receive signals
1609 on a file descriptor.
1614 bool "Enable timerfd() system call" if EXPERT
1618 Enable the timerfd() system call that allows to receive timer
1619 events on a file descriptor.
1624 bool "Enable eventfd() system call" if EXPERT
1628 Enable the eventfd() system call that allows to receive both
1629 kernel notification (ie. KAIO) or userspace notifications.
1633 # syscall, maps, verifier
1635 bool "Enable bpf() system call"
1640 Enable the bpf() system call that allows to manipulate eBPF
1641 programs and maps via file descriptors.
1644 bool "Use full shmem filesystem" if EXPERT
1648 The shmem is an internal filesystem used to manage shared memory.
1649 It is backed by swap and manages resource limits. It is also exported
1650 to userspace as tmpfs if TMPFS is enabled. Disabling this
1651 option replaces shmem and tmpfs with the much simpler ramfs code,
1652 which may be appropriate on small systems without swap.
1655 bool "Enable AIO support" if EXPERT
1658 This option enables POSIX asynchronous I/O which may by used
1659 by some high performance threaded applications. Disabling
1660 this option saves about 7k.
1662 config ADVISE_SYSCALLS
1663 bool "Enable madvise/fadvise syscalls" if EXPERT
1666 This option enables the madvise and fadvise syscalls, used by
1667 applications to advise the kernel about their future memory or file
1668 usage, improving performance. If building an embedded system where no
1669 applications use these syscalls, you can disable this option to save
1673 bool "Enable userfaultfd() system call"
1677 Enable the userfaultfd() system call that allows to intercept and
1678 handle page faults in userland.
1682 bool "Enable PCI quirk workarounds" if EXPERT
1685 This enables workarounds for various PCI chipset
1686 bugs/quirks. Disable this only if your target machine is
1687 unaffected by PCI quirks.
1690 bool "Enable membarrier() system call" if EXPERT
1693 Enable the membarrier() system call that allows issuing memory
1694 barriers across all running threads, which can be used to distribute
1695 the cost of user-space memory barriers asymmetrically by transforming
1696 pairs of memory barriers into pairs consisting of membarrier() and a
1702 bool "Embedded system"
1703 option allnoconfig_y
1706 This option should be enabled if compiling the kernel for
1707 an embedded system so certain expert options are available
1710 config HAVE_PERF_EVENTS
1713 See tools/perf/design.txt for details.
1715 config PERF_USE_VMALLOC
1718 See tools/perf/design.txt for details
1720 menu "Kernel Performance Events And Counters"
1723 bool "Kernel performance events and counters"
1724 default y if PROFILING
1725 depends on HAVE_PERF_EVENTS
1730 Enable kernel support for various performance events provided
1731 by software and hardware.
1733 Software events are supported either built-in or via the
1734 use of generic tracepoints.
1736 Most modern CPUs support performance events via performance
1737 counter registers. These registers count the number of certain
1738 types of hw events: such as instructions executed, cachemisses
1739 suffered, or branches mis-predicted - without slowing down the
1740 kernel or applications. These registers can also trigger interrupts
1741 when a threshold number of events have passed - and can thus be
1742 used to profile the code that runs on that CPU.
1744 The Linux Performance Event subsystem provides an abstraction of
1745 these software and hardware event capabilities, available via a
1746 system call and used by the "perf" utility in tools/perf/. It
1747 provides per task and per CPU counters, and it provides event
1748 capabilities on top of those.
1752 config DEBUG_PERF_USE_VMALLOC
1754 bool "Debug: use vmalloc to back perf mmap() buffers"
1755 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1756 select PERF_USE_VMALLOC
1758 Use vmalloc memory to back perf mmap() buffers.
1760 Mostly useful for debugging the vmalloc code on platforms
1761 that don't require it.
1767 config VM_EVENT_COUNTERS
1769 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1771 VM event counters are needed for event counts to be shown.
1772 This option allows the disabling of the VM event counters
1773 on EXPERT systems. /proc/vmstat will only show page counts
1774 if VM event counters are disabled.
1778 bool "Enable SLUB debugging support" if EXPERT
1779 depends on SLUB && SYSFS
1781 SLUB has extensive debug support features. Disabling these can
1782 result in significant savings in code size. This also disables
1783 SLUB sysfs support. /sys/slab will not exist and there will be
1784 no support for cache validation etc.
1787 bool "Disable heap randomization"
1790 Randomizing heap placement makes heap exploits harder, but it
1791 also breaks ancient binaries (including anything libc5 based).
1792 This option changes the bootup default to heap randomization
1793 disabled, and can be overridden at runtime by setting
1794 /proc/sys/kernel/randomize_va_space to 2.
1796 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1799 prompt "Choose SLAB allocator"
1802 This option allows to select a slab allocator.
1806 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1808 The regular slab allocator that is established and known to work
1809 well in all environments. It organizes cache hot objects in
1810 per cpu and per node queues.
1813 bool "SLUB (Unqueued Allocator)"
1814 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1816 SLUB is a slab allocator that minimizes cache line usage
1817 instead of managing queues of cached objects (SLAB approach).
1818 Per cpu caching is realized using slabs of objects instead
1819 of queues of objects. SLUB can use memory efficiently
1820 and has enhanced diagnostics. SLUB is the default choice for
1825 bool "SLOB (Simple Allocator)"
1827 SLOB replaces the stock allocator with a drastically simpler
1828 allocator. SLOB is generally more space efficient but
1829 does not perform as well on large systems.
1833 config SLUB_CPU_PARTIAL
1835 depends on SLUB && SMP
1836 bool "SLUB per cpu partial cache"
1838 Per cpu partial caches accellerate objects allocation and freeing
1839 that is local to a processor at the price of more indeterminism
1840 in the latency of the free. On overflow these caches will be cleared
1841 which requires the taking of locks that may cause latency spikes.
1842 Typically one would choose no for a realtime system.
1844 config MMAP_ALLOW_UNINITIALIZED
1845 bool "Allow mmapped anonymous memory to be uninitialized"
1846 depends on EXPERT && !MMU
1849 Normally, and according to the Linux spec, anonymous memory obtained
1850 from mmap() has it's contents cleared before it is passed to
1851 userspace. Enabling this config option allows you to request that
1852 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1853 providing a huge performance boost. If this option is not enabled,
1854 then the flag will be ignored.
1856 This is taken advantage of by uClibc's malloc(), and also by
1857 ELF-FDPIC binfmt's brk and stack allocator.
1859 Because of the obvious security issues, this option should only be
1860 enabled on embedded devices where you control what is run in
1861 userspace. Since that isn't generally a problem on no-MMU systems,
1862 it is normally safe to say Y here.
1864 See Documentation/nommu-mmap.txt for more information.
1866 config SYSTEM_DATA_VERIFICATION
1868 select SYSTEM_TRUSTED_KEYRING
1871 select ASYMMETRIC_KEY_TYPE
1872 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1873 select PUBLIC_KEY_ALGO_RSA
1876 select X509_CERTIFICATE_PARSER
1877 select PKCS7_MESSAGE_PARSER
1879 Provide PKCS#7 message verification using the contents of the system
1880 trusted keyring to provide public keys. This then can be used for
1881 module verification, kexec image verification and firmware blob
1884 config DEFERRED_INITCALLS
1885 bool "Deferred initcalls support"
1888 Say 'y' here to include support for deferred initcalls
1891 bool "Profiling support"
1893 Say Y here to enable the extended profiling support mechanisms used
1894 by profilers such as OProfile.
1897 # Place an empty function call at each tracepoint site. Can be
1898 # dynamically changed for a probe function.
1903 source "arch/Kconfig"
1905 endmenu # General setup
1907 config HAVE_GENERIC_DMA_COHERENT
1914 depends on SLAB || SLUB_DEBUG
1922 default 0 if BASE_FULL
1923 default 1 if !BASE_FULL
1926 bool "Enable loadable module support"
1929 Kernel modules are small pieces of compiled code which can
1930 be inserted in the running kernel, rather than being
1931 permanently built into the kernel. You use the "modprobe"
1932 tool to add (and sometimes remove) them. If you say Y here,
1933 many parts of the kernel can be built as modules (by
1934 answering M instead of Y where indicated): this is most
1935 useful for infrequently used options which are not required
1936 for booting. For more information, see the man pages for
1937 modprobe, lsmod, modinfo, insmod and rmmod.
1939 If you say Y here, you will need to run "make
1940 modules_install" to put the modules under /lib/modules/
1941 where modprobe can find them (you may need to be root to do
1948 config MODULE_FORCE_LOAD
1949 bool "Forced module loading"
1952 Allow loading of modules without version information (ie. modprobe
1953 --force). Forced module loading sets the 'F' (forced) taint flag and
1954 is usually a really bad idea.
1956 config MODULE_UNLOAD
1957 bool "Module unloading"
1959 Without this option you will not be able to unload any
1960 modules (note that some modules may not be unloadable
1961 anyway), which makes your kernel smaller, faster
1962 and simpler. If unsure, say Y.
1964 config MODULE_FORCE_UNLOAD
1965 bool "Forced module unloading"
1966 depends on MODULE_UNLOAD
1968 This option allows you to force a module to unload, even if the
1969 kernel believes it is unsafe: the kernel will remove the module
1970 without waiting for anyone to stop using it (using the -f option to
1971 rmmod). This is mainly for kernel developers and desperate users.
1975 bool "Module versioning support"
1977 Usually, you have to use modules compiled with your kernel.
1978 Saying Y here makes it sometimes possible to use modules
1979 compiled for different kernels, by adding enough information
1980 to the modules to (hopefully) spot any changes which would
1981 make them incompatible with the kernel you are running. If
1984 config MODULE_SRCVERSION_ALL
1985 bool "Source checksum for all modules"
1987 Modules which contain a MODULE_VERSION get an extra "srcversion"
1988 field inserted into their modinfo section, which contains a
1989 sum of the source files which made it. This helps maintainers
1990 see exactly which source was used to build a module (since
1991 others sometimes change the module source without updating
1992 the version). With this option, such a "srcversion" field
1993 will be created for all modules. If unsure, say N.
1996 bool "Module signature verification"
1998 select SYSTEM_DATA_VERIFICATION
2000 Check modules for valid signatures upon load: the signature
2001 is simply appended to the module. For more information see
2002 Documentation/module-signing.txt.
2004 Note that this option adds the OpenSSL development packages as a
2005 kernel build dependency so that the signing tool can use its crypto
2008 !!!WARNING!!! If you enable this option, you MUST make sure that the
2009 module DOES NOT get stripped after being signed. This includes the
2010 debuginfo strip done by some packagers (such as rpmbuild) and
2011 inclusion into an initramfs that wants the module size reduced.
2013 config MODULE_SIG_FORCE
2014 bool "Require modules to be validly signed"
2015 depends on MODULE_SIG
2017 Reject unsigned modules or signed modules for which we don't have a
2018 key. Without this, such modules will simply taint the kernel.
2020 config MODULE_SIG_ALL
2021 bool "Automatically sign all modules"
2023 depends on MODULE_SIG
2025 Sign all modules during make modules_install. Without this option,
2026 modules must be signed manually, using the scripts/sign-file tool.
2028 comment "Do not forget to sign required modules with scripts/sign-file"
2029 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2032 prompt "Which hash algorithm should modules be signed with?"
2033 depends on MODULE_SIG
2035 This determines which sort of hashing algorithm will be used during
2036 signature generation. This algorithm _must_ be built into the kernel
2037 directly so that signature verification can take place. It is not
2038 possible to load a signed module containing the algorithm to check
2039 the signature on that module.
2041 config MODULE_SIG_SHA1
2042 bool "Sign modules with SHA-1"
2045 config MODULE_SIG_SHA224
2046 bool "Sign modules with SHA-224"
2047 select CRYPTO_SHA256
2049 config MODULE_SIG_SHA256
2050 bool "Sign modules with SHA-256"
2051 select CRYPTO_SHA256
2053 config MODULE_SIG_SHA384
2054 bool "Sign modules with SHA-384"
2055 select CRYPTO_SHA512
2057 config MODULE_SIG_SHA512
2058 bool "Sign modules with SHA-512"
2059 select CRYPTO_SHA512
2063 config MODULE_SIG_HASH
2065 depends on MODULE_SIG
2066 default "sha1" if MODULE_SIG_SHA1
2067 default "sha224" if MODULE_SIG_SHA224
2068 default "sha256" if MODULE_SIG_SHA256
2069 default "sha384" if MODULE_SIG_SHA384
2070 default "sha512" if MODULE_SIG_SHA512
2072 config MODULE_COMPRESS
2073 bool "Compress modules on installation"
2077 Compresses kernel modules when 'make modules_install' is run; gzip or
2078 xz depending on "Compression algorithm" below.
2080 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2082 Out-of-tree kernel modules installed using Kbuild will also be
2083 compressed upon installation.
2085 Note: for modules inside an initrd or initramfs, it's more efficient
2086 to compress the whole initrd or initramfs instead.
2088 Note: This is fully compatible with signed modules.
2093 prompt "Compression algorithm"
2094 depends on MODULE_COMPRESS
2095 default MODULE_COMPRESS_GZIP
2097 This determines which sort of compression will be used during
2098 'make modules_install'.
2100 GZIP (default) and XZ are supported.
2102 config MODULE_COMPRESS_GZIP
2105 config MODULE_COMPRESS_XZ
2112 config MODULES_TREE_LOOKUP
2114 depends on PERF_EVENTS || TRACING
2116 config INIT_ALL_POSSIBLE
2119 Back when each arch used to define their own cpu_online_mask and
2120 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2121 with all 1s, and others with all 0s. When they were centralised,
2122 it was better to provide this option than to break all the archs
2123 and have several arch maintainers pursuing me down dark alleys.
2125 source "block/Kconfig"
2127 config PREEMPT_NOTIFIERS
2134 # Can be selected by architectures with broken toolchains
2135 # that get confused by correct const<->read_only section
2137 config BROKEN_RODATA
2143 Build a simple ASN.1 grammar compiler that produces a bytecode output
2144 that can be interpreted by the ASN.1 stream decoder and used to
2145 inform it as to what tags are to be expected in a stream and what
2146 functions to call on what tags.
2148 source "kernel/Kconfig.locks"
projects / GitHub / exynos8895 / android_kernel_samsung_universal8895.git / blob