1 # SPDX-License-Identifier: GPL-2.0-only
4 default "$(CC_VERSION_TEXT)"
6 This is used in unclear ways:
8 - Re-run Kconfig when the compiler is updated
9 The 'default' property references the environment variable,
10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
11 When the compiler is updated, Kconfig will be invoked.
13 - Ensure full rebuild when the compiler is updated
14 include/linux/compiler-version.h contains this option in the comment
15 line so fixdep adds include/config/CC_VERSION_TEXT into the
16 auto-generated dependency. When the compiler is updated, syncconfig
17 will touch it and then every file will be rebuilt.
20 def_bool $(success,test "$(cc-name)" = GCC)
24 default $(cc-version) if CC_IS_GCC
28 def_bool $(success,test "$(cc-name)" = Clang)
32 default $(cc-version) if CC_IS_CLANG
36 def_bool $(success,test "$(as-name)" = GNU)
39 def_bool $(success,test "$(as-name)" = LLVM)
43 # Use clang version if this is the integrated assembler
44 default CLANG_VERSION if AS_IS_LLVM
48 def_bool $(success,test "$(ld-name)" = BFD)
52 default $(ld-version) if LD_IS_BFD
56 def_bool $(success,test "$(ld-name)" = LLD)
60 default $(ld-version) if LD_IS_LLD
63 config RUST_IS_AVAILABLE
64 def_bool $(success,$(srctree)/scripts/rust_is_available.sh)
66 This shows whether a suitable Rust toolchain is available (found).
68 Please see Documentation/rust/quick-start.rst for instructions on how
69 to satify the build requirements of Rust support.
71 In particular, the Makefile target 'rustavailable' is useful to check
72 why the Rust toolchain is not being detected.
76 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
77 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
79 config CC_CAN_LINK_STATIC
81 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
82 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
84 config CC_HAS_ASM_GOTO_OUTPUT
85 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
87 config CC_HAS_ASM_GOTO_TIED_OUTPUT
88 depends on CC_HAS_ASM_GOTO_OUTPUT
89 # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
90 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
92 config TOOLS_SUPPORT_RELR
93 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
95 config CC_HAS_ASM_INLINE
96 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
98 config CC_HAS_NO_PROFILE_FN_ATTR
99 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
101 config PAHOLE_VERSION
103 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
111 config BUILDTIME_TABLE_SORT
114 config THREAD_INFO_IN_TASK
117 Select this to move thread_info off the stack into task_struct. To
118 make this work, an arch will need to remove all thread_info fields
119 except flags and fix any runtime bugs.
121 One subtle change that will be needed is to use try_get_task_stack()
122 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
131 depends on BROKEN || !SMP
134 config INIT_ENV_ARG_LIMIT
139 Maximum of each of the number of arguments and environment
140 variables passed to init from the kernel command line.
143 bool "Compile also drivers which will not load"
146 Some drivers can be compiled on a different platform than they are
147 intended to be run on. Despite they cannot be loaded there (or even
148 when they load they cannot be used due to missing HW support),
149 developers still, opposing to distributors, might want to build such
150 drivers to compile-test them.
152 If you are a developer and want to build everything available, say Y
153 here. If you are a user/distributor, say N here to exclude useless
154 drivers to be distributed.
157 bool "Compile the kernel with warnings as errors"
160 A kernel build should not cause any compiler warnings, and this
161 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
162 to enforce that rule by default.
164 However, if you have a new (or very old) compiler with odd and
165 unusual warnings, or you have some architecture with problems,
166 you may need to disable this config option in order to
167 successfully build the kernel.
171 config UAPI_HEADER_TEST
172 bool "Compile test UAPI headers"
173 depends on HEADERS_INSTALL && CC_CAN_LINK
175 Compile test headers exported to user-space to ensure they are
176 self-contained, i.e. compilable as standalone units.
178 If you are a developer or tester and want to ensure the exported
179 headers are self-contained, say Y here. Otherwise, choose N.
182 string "Local version - append to kernel release"
184 Append an extra string to the end of your kernel version.
185 This will show up when you type uname, for example.
186 The string you set here will be appended after the contents of
187 any files with a filename matching localversion* in your
188 object and source tree, in that order. Your total string can
189 be a maximum of 64 characters.
191 config LOCALVERSION_AUTO
192 bool "Automatically append version information to the version string"
194 depends on !COMPILE_TEST
196 This will try to automatically determine if the current tree is a
197 release tree by looking for git tags that belong to the current
198 top of tree revision.
200 A string of the format -gxxxxxxxx will be added to the localversion
201 if a git-based tree is found. The string generated by this will be
202 appended after any matching localversion* files, and after the value
203 set in CONFIG_LOCALVERSION.
205 (The actual string used here is the first eight characters produced
206 by running the command:
208 $ git rev-parse --verify HEAD
210 which is done within the script "scripts/setlocalversion".)
213 string "Build ID Salt"
216 The build ID is used to link binaries and their debug info. Setting
217 this option will use the value in the calculation of the build id.
218 This is mostly useful for distributions which want to ensure the
219 build is unique between builds. It's safe to leave the default.
221 config HAVE_KERNEL_GZIP
224 config HAVE_KERNEL_BZIP2
227 config HAVE_KERNEL_LZMA
230 config HAVE_KERNEL_XZ
233 config HAVE_KERNEL_LZO
236 config HAVE_KERNEL_LZ4
239 config HAVE_KERNEL_ZSTD
242 config HAVE_KERNEL_UNCOMPRESSED
246 prompt "Kernel compression mode"
248 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
250 The linux kernel is a kind of self-extracting executable.
251 Several compression algorithms are available, which differ
252 in efficiency, compression and decompression speed.
253 Compression speed is only relevant when building a kernel.
254 Decompression speed is relevant at each boot.
256 If you have any problems with bzip2 or lzma compressed
257 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
258 version of this functionality (bzip2 only), for 2.4, was
259 supplied by Christian Ludwig)
261 High compression options are mostly useful for users, who
262 are low on disk space (embedded systems), but for whom ram
265 If in doubt, select 'gzip'
269 depends on HAVE_KERNEL_GZIP
271 The old and tried gzip compression. It provides a good balance
272 between compression ratio and decompression speed.
276 depends on HAVE_KERNEL_BZIP2
278 Its compression ratio and speed is intermediate.
279 Decompression speed is slowest among the choices. The kernel
280 size is about 10% smaller with bzip2, in comparison to gzip.
281 Bzip2 uses a large amount of memory. For modern kernels you
282 will need at least 8MB RAM or more for booting.
286 depends on HAVE_KERNEL_LZMA
288 This compression algorithm's ratio is best. Decompression speed
289 is between gzip and bzip2. Compression is slowest.
290 The kernel size is about 33% smaller with LZMA in comparison to gzip.
294 depends on HAVE_KERNEL_XZ
296 XZ uses the LZMA2 algorithm and instruction set specific
297 BCJ filters which can improve compression ratio of executable
298 code. The size of the kernel is about 30% smaller with XZ in
299 comparison to gzip. On architectures for which there is a BCJ
300 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
301 will create a few percent smaller kernel than plain LZMA.
303 The speed is about the same as with LZMA: The decompression
304 speed of XZ is better than that of bzip2 but worse than gzip
305 and LZO. Compression is slow.
309 depends on HAVE_KERNEL_LZO
311 Its compression ratio is the poorest among the choices. The kernel
312 size is about 10% bigger than gzip; however its speed
313 (both compression and decompression) is the fastest.
317 depends on HAVE_KERNEL_LZ4
319 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
320 A preliminary version of LZ4 de/compression tool is available at
321 <https://code.google.com/p/lz4/>.
323 Its compression ratio is worse than LZO. The size of the kernel
324 is about 8% bigger than LZO. But the decompression speed is
329 depends on HAVE_KERNEL_ZSTD
331 ZSTD is a compression algorithm targeting intermediate compression
332 with fast decompression speed. It will compress better than GZIP and
333 decompress around the same speed as LZO, but slower than LZ4. You
334 will need at least 192 KB RAM or more for booting. The zstd command
335 line tool is required for compression.
337 config KERNEL_UNCOMPRESSED
339 depends on HAVE_KERNEL_UNCOMPRESSED
341 Produce uncompressed kernel image. This option is usually not what
342 you want. It is useful for debugging the kernel in slow simulation
343 environments, where decompressing and moving the kernel is awfully
344 slow. This option allows early boot code to skip the decompressor
345 and jump right at uncompressed kernel image.
350 string "Default init path"
353 This option determines the default init for the system if no init=
354 option is passed on the kernel command line. If the requested path is
355 not present, we will still then move on to attempting further
356 locations (e.g. /sbin/init, etc). If this is empty, we will just use
357 the fallback list when init= is not passed.
359 config DEFAULT_HOSTNAME
360 string "Default hostname"
363 This option determines the default system hostname before userspace
364 calls sethostname(2). The kernel traditionally uses "(none)" here,
365 but you may wish to use a different default here to make a minimal
366 system more usable with less configuration.
371 Inter Process Communication is a suite of library functions and
372 system calls which let processes (running programs) synchronize and
373 exchange information. It is generally considered to be a good thing,
374 and some programs won't run unless you say Y here. In particular, if
375 you want to run the DOS emulator dosemu under Linux (read the
376 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
377 you'll need to say Y here.
379 You can find documentation about IPC with "info ipc" and also in
380 section 6.4 of the Linux Programmer's Guide, available from
381 <http://www.tldp.org/guides.html>.
383 config SYSVIPC_SYSCTL
389 config SYSVIPC_COMPAT
391 depends on COMPAT && SYSVIPC
394 bool "POSIX Message Queues"
397 POSIX variant of message queues is a part of IPC. In POSIX message
398 queues every message has a priority which decides about succession
399 of receiving it by a process. If you want to compile and run
400 programs written e.g. for Solaris with use of its POSIX message
401 queues (functions mq_*) say Y here.
403 POSIX message queues are visible as a filesystem called 'mqueue'
404 and can be mounted somewhere if you want to do filesystem
405 operations on message queues.
409 config POSIX_MQUEUE_SYSCTL
411 depends on POSIX_MQUEUE
416 bool "General notification queue"
420 This is a general notification queue for the kernel to pass events to
421 userspace by splicing them into pipes. It can be used in conjunction
422 with watches for key/keyring change notifications and device
425 See Documentation/core-api/watch_queue.rst
427 config CROSS_MEMORY_ATTACH
428 bool "Enable process_vm_readv/writev syscalls"
432 Enabling this option adds the system calls process_vm_readv and
433 process_vm_writev which allow a process with the correct privileges
434 to directly read from or write to another process' address space.
435 See the man page for more details.
438 bool "uselib syscall (for libc5 and earlier)"
439 default ALPHA || M68K || SPARC
441 This option enables the uselib syscall, a system call used in the
442 dynamic linker from libc5 and earlier. glibc does not use this
443 system call. If you intend to run programs built on libc5 or
444 earlier, you may need to enable this syscall. Current systems
445 running glibc can safely disable this.
448 bool "Auditing support"
451 Enable auditing infrastructure that can be used with another
452 kernel subsystem, such as SELinux (which requires this for
453 logging of avc messages output). System call auditing is included
454 on architectures which support it.
456 config HAVE_ARCH_AUDITSYSCALL
461 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
464 source "kernel/irq/Kconfig"
465 source "kernel/time/Kconfig"
466 source "kernel/bpf/Kconfig"
467 source "kernel/Kconfig.preempt"
469 menu "CPU/Task time and stats accounting"
471 config VIRT_CPU_ACCOUNTING
475 prompt "Cputime accounting"
476 default TICK_CPU_ACCOUNTING
478 # Kind of a stub config for the pure tick based cputime accounting
479 config TICK_CPU_ACCOUNTING
480 bool "Simple tick based cputime accounting"
481 depends on !S390 && !NO_HZ_FULL
483 This is the basic tick based cputime accounting that maintains
484 statistics about user, system and idle time spent on per jiffies
489 config VIRT_CPU_ACCOUNTING_NATIVE
490 bool "Deterministic task and CPU time accounting"
491 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
492 select VIRT_CPU_ACCOUNTING
494 Select this option to enable more accurate task and CPU time
495 accounting. This is done by reading a CPU counter on each
496 kernel entry and exit and on transitions within the kernel
497 between system, softirq and hardirq state, so there is a
498 small performance impact. In the case of s390 or IBM POWER > 5,
499 this also enables accounting of stolen time on logically-partitioned
502 config VIRT_CPU_ACCOUNTING_GEN
503 bool "Full dynticks CPU time accounting"
504 depends on HAVE_CONTEXT_TRACKING_USER
505 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
506 depends on GENERIC_CLOCKEVENTS
507 select VIRT_CPU_ACCOUNTING
508 select CONTEXT_TRACKING_USER
510 Select this option to enable task and CPU time accounting on full
511 dynticks systems. This accounting is implemented by watching every
512 kernel-user boundaries using the context tracking subsystem.
513 The accounting is thus performed at the expense of some significant
516 For now this is only useful if you are working on the full
517 dynticks subsystem development.
523 config IRQ_TIME_ACCOUNTING
524 bool "Fine granularity task level IRQ time accounting"
525 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
527 Select this option to enable fine granularity task irq time
528 accounting. This is done by reading a timestamp on each
529 transitions between softirq and hardirq state, so there can be a
530 small performance impact.
532 If in doubt, say N here.
534 config HAVE_SCHED_AVG_IRQ
536 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
539 config SCHED_THERMAL_PRESSURE
541 default y if ARM && ARM_CPU_TOPOLOGY
544 depends on CPU_FREQ_THERMAL
546 Select this option to enable thermal pressure accounting in the
547 scheduler. Thermal pressure is the value conveyed to the scheduler
548 that reflects the reduction in CPU compute capacity resulted from
549 thermal throttling. Thermal throttling occurs when the performance of
550 a CPU is capped due to high operating temperatures.
552 If selected, the scheduler will be able to balance tasks accordingly,
553 i.e. put less load on throttled CPUs than on non/less throttled ones.
555 This requires the architecture to implement
556 arch_update_thermal_pressure() and arch_scale_thermal_pressure().
558 config BSD_PROCESS_ACCT
559 bool "BSD Process Accounting"
562 If you say Y here, a user level program will be able to instruct the
563 kernel (via a special system call) to write process accounting
564 information to a file: whenever a process exits, information about
565 that process will be appended to the file by the kernel. The
566 information includes things such as creation time, owning user,
567 command name, memory usage, controlling terminal etc. (the complete
568 list is in the struct acct in <file:include/linux/acct.h>). It is
569 up to the user level program to do useful things with this
570 information. This is generally a good idea, so say Y.
572 config BSD_PROCESS_ACCT_V3
573 bool "BSD Process Accounting version 3 file format"
574 depends on BSD_PROCESS_ACCT
577 If you say Y here, the process accounting information is written
578 in a new file format that also logs the process IDs of each
579 process and its parent. Note that this file format is incompatible
580 with previous v0/v1/v2 file formats, so you will need updated tools
581 for processing it. A preliminary version of these tools is available
582 at <http://www.gnu.org/software/acct/>.
585 bool "Export task/process statistics through netlink"
590 Export selected statistics for tasks/processes through the
591 generic netlink interface. Unlike BSD process accounting, the
592 statistics are available during the lifetime of tasks/processes as
593 responses to commands. Like BSD accounting, they are sent to user
598 config TASK_DELAY_ACCT
599 bool "Enable per-task delay accounting"
603 Collect information on time spent by a task waiting for system
604 resources like cpu, synchronous block I/O completion and swapping
605 in pages. Such statistics can help in setting a task's priorities
606 relative to other tasks for cpu, io, rss limits etc.
611 bool "Enable extended accounting over taskstats"
614 Collect extended task accounting data and send the data
615 to userland for processing over the taskstats interface.
619 config TASK_IO_ACCOUNTING
620 bool "Enable per-task storage I/O accounting"
621 depends on TASK_XACCT
623 Collect information on the number of bytes of storage I/O which this
629 bool "Pressure stall information tracking"
631 Collect metrics that indicate how overcommitted the CPU, memory,
632 and IO capacity are in the system.
634 If you say Y here, the kernel will create /proc/pressure/ with the
635 pressure statistics files cpu, memory, and io. These will indicate
636 the share of walltime in which some or all tasks in the system are
637 delayed due to contention of the respective resource.
639 In kernels with cgroup support, cgroups (cgroup2 only) will
640 have cpu.pressure, memory.pressure, and io.pressure files,
641 which aggregate pressure stalls for the grouped tasks only.
643 For more details see Documentation/accounting/psi.rst.
647 config PSI_DEFAULT_DISABLED
648 bool "Require boot parameter to enable pressure stall information tracking"
652 If set, pressure stall information tracking will be disabled
653 per default but can be enabled through passing psi=1 on the
654 kernel commandline during boot.
656 This feature adds some code to the task wakeup and sleep
657 paths of the scheduler. The overhead is too low to affect
658 common scheduling-intense workloads in practice (such as
659 webservers, memcache), but it does show up in artificial
660 scheduler stress tests, such as hackbench.
662 If you are paranoid and not sure what the kernel will be
667 endmenu # "CPU/Task time and stats accounting"
671 depends on SMP || COMPILE_TEST
674 Make sure that CPUs running critical tasks are not disturbed by
675 any source of "noise" such as unbound workqueues, timers, kthreads...
676 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
677 the "isolcpus=" boot parameter.
681 source "kernel/rcu/Kconfig"
688 tristate "Kernel .config support"
690 This option enables the complete Linux kernel ".config" file
691 contents to be saved in the kernel. It provides documentation
692 of which kernel options are used in a running kernel or in an
693 on-disk kernel. This information can be extracted from the kernel
694 image file with the script scripts/extract-ikconfig and used as
695 input to rebuild the current kernel or to build another kernel.
696 It can also be extracted from a running kernel by reading
697 /proc/config.gz if enabled (below).
700 bool "Enable access to .config through /proc/config.gz"
701 depends on IKCONFIG && PROC_FS
703 This option enables access to the kernel configuration file
704 through /proc/config.gz.
707 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
710 This option enables access to the in-kernel headers that are generated during
711 the build process. These can be used to build eBPF tracing programs,
712 or similar programs. If you build the headers as a module, a module called
713 kheaders.ko is built which can be loaded on-demand to get access to headers.
716 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
721 Select the minimal kernel log buffer size as a power of 2.
722 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
723 parameter, see below. Any higher size also might be forced
724 by "log_buf_len" boot parameter.
734 config LOG_CPU_MAX_BUF_SHIFT
735 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
738 default 12 if !BASE_SMALL
739 default 0 if BASE_SMALL
742 This option allows to increase the default ring buffer size
743 according to the number of CPUs. The value defines the contribution
744 of each CPU as a power of 2. The used space is typically only few
745 lines however it might be much more when problems are reported,
748 The increased size means that a new buffer has to be allocated and
749 the original static one is unused. It makes sense only on systems
750 with more CPUs. Therefore this value is used only when the sum of
751 contributions is greater than the half of the default kernel ring
752 buffer as defined by LOG_BUF_SHIFT. The default values are set
753 so that more than 16 CPUs are needed to trigger the allocation.
755 Also this option is ignored when "log_buf_len" kernel parameter is
756 used as it forces an exact (power of two) size of the ring buffer.
758 The number of possible CPUs is used for this computation ignoring
759 hotplugging making the computation optimal for the worst case
760 scenario while allowing a simple algorithm to be used from bootup.
762 Examples shift values and their meaning:
763 17 => 128 KB for each CPU
764 16 => 64 KB for each CPU
765 15 => 32 KB for each CPU
766 14 => 16 KB for each CPU
767 13 => 8 KB for each CPU
768 12 => 4 KB for each CPU
770 config PRINTK_SAFE_LOG_BUF_SHIFT
771 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
776 Select the size of an alternate printk per-CPU buffer where messages
777 printed from usafe contexts are temporary stored. One example would
778 be NMI messages, another one - printk recursion. The messages are
779 copied to the main log buffer in a safe context to avoid a deadlock.
780 The value defines the size as a power of 2.
782 Those messages are rare and limited. The largest one is when
783 a backtrace is printed. It usually fits into 4KB. Select
784 8KB if you want to be on the safe side.
787 17 => 128 KB for each CPU
788 16 => 64 KB for each CPU
789 15 => 32 KB for each CPU
790 14 => 16 KB for each CPU
791 13 => 8 KB for each CPU
792 12 => 4 KB for each CPU
795 bool "Printk indexing debugfs interface"
796 depends on PRINTK && DEBUG_FS
798 Add support for indexing of all printk formats known at compile time
799 at <debugfs>/printk/index/<module>.
801 This can be used as part of maintaining daemons which monitor
802 /dev/kmsg, as it permits auditing the printk formats present in a
803 kernel, allowing detection of cases where monitored printks are
804 changed or no longer present.
806 There is no additional runtime cost to printk with this enabled.
809 # Architectures with an unreliable sched_clock() should select this:
811 config HAVE_UNSTABLE_SCHED_CLOCK
814 config GENERIC_SCHED_CLOCK
817 menu "Scheduler features"
820 bool "Enable utilization clamping for RT/FAIR tasks"
821 depends on CPU_FREQ_GOV_SCHEDUTIL
823 This feature enables the scheduler to track the clamped utilization
824 of each CPU based on RUNNABLE tasks scheduled on that CPU.
826 With this option, the user can specify the min and max CPU
827 utilization allowed for RUNNABLE tasks. The max utilization defines
828 the maximum frequency a task should use while the min utilization
829 defines the minimum frequency it should use.
831 Both min and max utilization clamp values are hints to the scheduler,
832 aiming at improving its frequency selection policy, but they do not
833 enforce or grant any specific bandwidth for tasks.
837 config UCLAMP_BUCKETS_COUNT
838 int "Number of supported utilization clamp buckets"
841 depends on UCLAMP_TASK
843 Defines the number of clamp buckets to use. The range of each bucket
844 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
845 number of clamp buckets the finer their granularity and the higher
846 the precision of clamping aggregation and tracking at run-time.
848 For example, with the minimum configuration value we will have 5
849 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
850 be refcounted in the [20..39]% bucket and will set the bucket clamp
851 effective value to 25%.
852 If a second 30% boosted task should be co-scheduled on the same CPU,
853 that task will be refcounted in the same bucket of the first task and
854 it will boost the bucket clamp effective value to 30%.
855 The clamp effective value of a bucket is reset to its nominal value
856 (20% in the example above) when there are no more tasks refcounted in
859 An additional boost/capping margin can be added to some tasks. In the
860 example above the 25% task will be boosted to 30% until it exits the
861 CPU. If that should be considered not acceptable on certain systems,
862 it's always possible to reduce the margin by increasing the number of
863 clamp buckets to trade off used memory for run-time tracking
866 If in doubt, use the default value.
871 # For architectures that want to enable the support for NUMA-affine scheduler
874 config ARCH_SUPPORTS_NUMA_BALANCING
878 # For architectures that prefer to flush all TLBs after a number of pages
879 # are unmapped instead of sending one IPI per page to flush. The architecture
880 # must provide guarantees on what happens if a clean TLB cache entry is
881 # written after the unmap. Details are in mm/rmap.c near the check for
882 # should_defer_flush. The architecture should also consider if the full flush
883 # and the refill costs are offset by the savings of sending fewer IPIs.
884 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
888 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
890 config CC_IMPLICIT_FALLTHROUGH
892 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
893 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
895 # Currently, disable gcc-12 array-bounds globally.
896 # We may want to target only particular configurations some day.
897 config GCC12_NO_ARRAY_BOUNDS
900 config CC_NO_ARRAY_BOUNDS
902 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS
905 # For architectures that know their GCC __int128 support is sound
907 config ARCH_SUPPORTS_INT128
910 # For architectures that (ab)use NUMA to represent different memory regions
911 # all cpu-local but of different latencies, such as SuperH.
913 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
916 config NUMA_BALANCING
917 bool "Memory placement aware NUMA scheduler"
918 depends on ARCH_SUPPORTS_NUMA_BALANCING
919 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
920 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
922 This option adds support for automatic NUMA aware memory/task placement.
923 The mechanism is quite primitive and is based on migrating memory when
924 it has references to the node the task is running on.
926 This system will be inactive on UMA systems.
928 config NUMA_BALANCING_DEFAULT_ENABLED
929 bool "Automatically enable NUMA aware memory/task placement"
931 depends on NUMA_BALANCING
933 If set, automatic NUMA balancing will be enabled if running on a NUMA
937 bool "Control Group support"
940 This option adds support for grouping sets of processes together, for
941 use with process control subsystems such as Cpusets, CFS, memory
942 controls or device isolation.
944 - Documentation/scheduler/sched-design-CFS.rst (CFS)
945 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
946 and resource control)
955 config CGROUP_FAVOR_DYNMODS
956 bool "Favor dynamic modification latency reduction by default"
958 This option enables the "favordynmods" mount option by default
959 which reduces the latencies of dynamic cgroup modifications such
960 as task migrations and controller on/offs at the cost of making
961 hot path operations such as forks and exits more expensive.
966 bool "Memory controller"
970 Provides control over the memory footprint of tasks in a cgroup.
974 depends on MEMCG && SWAP
979 depends on MEMCG && !SLOB
987 Generic block IO controller cgroup interface. This is the common
988 cgroup interface which should be used by various IO controlling
991 Currently, CFQ IO scheduler uses it to recognize task groups and
992 control disk bandwidth allocation (proportional time slice allocation)
993 to such task groups. It is also used by bio throttling logic in
994 block layer to implement upper limit in IO rates on a device.
996 This option only enables generic Block IO controller infrastructure.
997 One needs to also enable actual IO controlling logic/policy. For
998 enabling proportional weight division of disk bandwidth in CFQ, set
999 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1000 CONFIG_BLK_DEV_THROTTLING=y.
1002 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
1004 config CGROUP_WRITEBACK
1006 depends on MEMCG && BLK_CGROUP
1009 menuconfig CGROUP_SCHED
1010 bool "CPU controller"
1013 This feature lets CPU scheduler recognize task groups and control CPU
1014 bandwidth allocation to such task groups. It uses cgroups to group
1018 config FAIR_GROUP_SCHED
1019 bool "Group scheduling for SCHED_OTHER"
1020 depends on CGROUP_SCHED
1021 default CGROUP_SCHED
1023 config CFS_BANDWIDTH
1024 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1025 depends on FAIR_GROUP_SCHED
1028 This option allows users to define CPU bandwidth rates (limits) for
1029 tasks running within the fair group scheduler. Groups with no limit
1030 set are considered to be unconstrained and will run with no
1032 See Documentation/scheduler/sched-bwc.rst for more information.
1034 config RT_GROUP_SCHED
1035 bool "Group scheduling for SCHED_RR/FIFO"
1036 depends on CGROUP_SCHED
1039 This feature lets you explicitly allocate real CPU bandwidth
1040 to task groups. If enabled, it will also make it impossible to
1041 schedule realtime tasks for non-root users until you allocate
1042 realtime bandwidth for them.
1043 See Documentation/scheduler/sched-rt-group.rst for more information.
1047 config UCLAMP_TASK_GROUP
1048 bool "Utilization clamping per group of tasks"
1049 depends on CGROUP_SCHED
1050 depends on UCLAMP_TASK
1053 This feature enables the scheduler to track the clamped utilization
1054 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1056 When this option is enabled, the user can specify a min and max
1057 CPU bandwidth which is allowed for each single task in a group.
1058 The max bandwidth allows to clamp the maximum frequency a task
1059 can use, while the min bandwidth allows to define a minimum
1060 frequency a task will always use.
1062 When task group based utilization clamping is enabled, an eventually
1063 specified task-specific clamp value is constrained by the cgroup
1064 specified clamp value. Both minimum and maximum task clamping cannot
1065 be bigger than the corresponding clamping defined at task group level.
1070 bool "PIDs controller"
1072 Provides enforcement of process number limits in the scope of a
1073 cgroup. Any attempt to fork more processes than is allowed in the
1074 cgroup will fail. PIDs are fundamentally a global resource because it
1075 is fairly trivial to reach PID exhaustion before you reach even a
1076 conservative kmemcg limit. As a result, it is possible to grind a
1077 system to halt without being limited by other cgroup policies. The
1078 PIDs controller is designed to stop this from happening.
1080 It should be noted that organisational operations (such as attaching
1081 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1082 since the PIDs limit only affects a process's ability to fork, not to
1086 bool "RDMA controller"
1088 Provides enforcement of RDMA resources defined by IB stack.
1089 It is fairly easy for consumers to exhaust RDMA resources, which
1090 can result into resource unavailability to other consumers.
1091 RDMA controller is designed to stop this from happening.
1092 Attaching processes with active RDMA resources to the cgroup
1093 hierarchy is allowed even if can cross the hierarchy's limit.
1095 config CGROUP_FREEZER
1096 bool "Freezer controller"
1098 Provides a way to freeze and unfreeze all tasks in a
1101 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1102 controller includes important in-kernel memory consumers per default.
1104 If you're using cgroup2, say N.
1106 config CGROUP_HUGETLB
1107 bool "HugeTLB controller"
1108 depends on HUGETLB_PAGE
1112 Provides a cgroup controller for HugeTLB pages.
1113 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1114 The limit is enforced during page fault. Since HugeTLB doesn't
1115 support page reclaim, enforcing the limit at page fault time implies
1116 that, the application will get SIGBUS signal if it tries to access
1117 HugeTLB pages beyond its limit. This requires the application to know
1118 beforehand how much HugeTLB pages it would require for its use. The
1119 control group is tracked in the third page lru pointer. This means
1120 that we cannot use the controller with huge page less than 3 pages.
1123 bool "Cpuset controller"
1126 This option will let you create and manage CPUSETs which
1127 allow dynamically partitioning a system into sets of CPUs and
1128 Memory Nodes and assigning tasks to run only within those sets.
1129 This is primarily useful on large SMP or NUMA systems.
1133 config PROC_PID_CPUSET
1134 bool "Include legacy /proc/<pid>/cpuset file"
1138 config CGROUP_DEVICE
1139 bool "Device controller"
1141 Provides a cgroup controller implementing whitelists for
1142 devices which a process in the cgroup can mknod or open.
1144 config CGROUP_CPUACCT
1145 bool "Simple CPU accounting controller"
1147 Provides a simple controller for monitoring the
1148 total CPU consumed by the tasks in a cgroup.
1151 bool "Perf controller"
1152 depends on PERF_EVENTS
1154 This option extends the perf per-cpu mode to restrict monitoring
1155 to threads which belong to the cgroup specified and run on the
1156 designated cpu. Or this can be used to have cgroup ID in samples
1157 so that it can monitor performance events among cgroups.
1162 bool "Support for eBPF programs attached to cgroups"
1163 depends on BPF_SYSCALL
1164 select SOCK_CGROUP_DATA
1166 Allow attaching eBPF programs to a cgroup using the bpf(2)
1167 syscall command BPF_PROG_ATTACH.
1169 In which context these programs are accessed depends on the type
1170 of attachment. For instance, programs that are attached using
1171 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1175 bool "Misc resource controller"
1178 Provides a controller for miscellaneous resources on a host.
1180 Miscellaneous scalar resources are the resources on the host system
1181 which cannot be abstracted like the other cgroups. This controller
1182 tracks and limits the miscellaneous resources used by a process
1183 attached to a cgroup hierarchy.
1185 For more information, please check misc cgroup section in
1186 /Documentation/admin-guide/cgroup-v2.rst.
1189 bool "Debug controller"
1191 depends on DEBUG_KERNEL
1193 This option enables a simple controller that exports
1194 debugging information about the cgroups framework. This
1195 controller is for control cgroup debugging only. Its
1196 interfaces are not stable.
1200 config SOCK_CGROUP_DATA
1206 menuconfig NAMESPACES
1207 bool "Namespaces support" if EXPERT
1208 depends on MULTIUSER
1211 Provides the way to make tasks work with different objects using
1212 the same id. For example same IPC id may refer to different objects
1213 or same user id or pid may refer to different tasks when used in
1214 different namespaces.
1219 bool "UTS namespace"
1222 In this namespace tasks see different info provided with the
1226 bool "TIME namespace"
1227 depends on GENERIC_VDSO_TIME_NS
1230 In this namespace boottime and monotonic clocks can be set.
1231 The time will keep going with the same pace.
1234 bool "IPC namespace"
1235 depends on (SYSVIPC || POSIX_MQUEUE)
1238 In this namespace tasks work with IPC ids which correspond to
1239 different IPC objects in different namespaces.
1242 bool "User namespace"
1245 This allows containers, i.e. vservers, to use user namespaces
1246 to provide different user info for different servers.
1248 When user namespaces are enabled in the kernel it is
1249 recommended that the MEMCG option also be enabled and that
1250 user-space use the memory control groups to limit the amount
1251 of memory a memory unprivileged users can use.
1256 bool "PID Namespaces"
1259 Support process id namespaces. This allows having multiple
1260 processes with the same pid as long as they are in different
1261 pid namespaces. This is a building block of containers.
1264 bool "Network namespace"
1268 Allow user space to create what appear to be multiple instances
1269 of the network stack.
1273 config CHECKPOINT_RESTORE
1274 bool "Checkpoint/restore support"
1275 select PROC_CHILDREN
1279 Enables additional kernel features in a sake of checkpoint/restore.
1280 In particular it adds auxiliary prctl codes to setup process text,
1281 data and heap segment sizes, and a few additional /proc filesystem
1284 If unsure, say N here.
1286 config SCHED_AUTOGROUP
1287 bool "Automatic process group scheduling"
1290 select FAIR_GROUP_SCHED
1292 This option optimizes the scheduler for common desktop workloads by
1293 automatically creating and populating task groups. This separation
1294 of workloads isolates aggressive CPU burners (like build jobs) from
1295 desktop applications. Task group autogeneration is currently based
1298 config SYSFS_DEPRECATED
1299 bool "Enable deprecated sysfs features to support old userspace tools"
1303 This option adds code that switches the layout of the "block" class
1304 devices, to not show up in /sys/class/block/, but only in
1307 This switch is only active when the sysfs.deprecated=1 boot option is
1308 passed or the SYSFS_DEPRECATED_V2 option is set.
1310 This option allows new kernels to run on old distributions and tools,
1311 which might get confused by /sys/class/block/. Since 2007/2008 all
1312 major distributions and tools handle this just fine.
1314 Recent distributions and userspace tools after 2009/2010 depend on
1315 the existence of /sys/class/block/, and will not work with this
1318 Only if you are using a new kernel on an old distribution, you might
1321 config SYSFS_DEPRECATED_V2
1322 bool "Enable deprecated sysfs features by default"
1325 depends on SYSFS_DEPRECATED
1327 Enable deprecated sysfs by default.
1329 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1332 Only if you are using a new kernel on an old distribution, you might
1333 need to say Y here. Even then, odds are you would not need it
1334 enabled, you can always pass the boot option if absolutely necessary.
1337 bool "Kernel->user space relay support (formerly relayfs)"
1340 This option enables support for relay interface support in
1341 certain file systems (such as debugfs).
1342 It is designed to provide an efficient mechanism for tools and
1343 facilities to relay large amounts of data from kernel space to
1348 config BLK_DEV_INITRD
1349 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1351 The initial RAM filesystem is a ramfs which is loaded by the
1352 boot loader (loadlin or lilo) and that is mounted as root
1353 before the normal boot procedure. It is typically used to
1354 load modules needed to mount the "real" root file system,
1355 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1357 If RAM disk support (BLK_DEV_RAM) is also included, this
1358 also enables initial RAM disk (initrd) support and adds
1359 15 Kbytes (more on some other architectures) to the kernel size.
1365 source "usr/Kconfig"
1370 bool "Boot config support"
1371 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1373 Extra boot config allows system admin to pass a config file as
1374 complemental extension of kernel cmdline when booting.
1375 The boot config file must be attached at the end of initramfs
1376 with checksum, size and magic word.
1377 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1381 config BOOT_CONFIG_EMBED
1382 bool "Embed bootconfig file in the kernel"
1383 depends on BOOT_CONFIG
1385 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1386 kernel. Usually, the bootconfig file is loaded with the initrd
1387 image. But if the system doesn't support initrd, this option will
1388 help you by embedding a bootconfig file while building the kernel.
1392 config BOOT_CONFIG_EMBED_FILE
1393 string "Embedded bootconfig file path"
1394 depends on BOOT_CONFIG_EMBED
1396 Specify a bootconfig file which will be embedded to the kernel.
1397 This bootconfig will be used if there is no initrd or no other
1398 bootconfig in the initrd.
1400 config INITRAMFS_PRESERVE_MTIME
1401 bool "Preserve cpio archive mtimes in initramfs"
1404 Each entry in an initramfs cpio archive carries an mtime value. When
1405 enabled, extracted cpio items take this mtime, with directory mtime
1406 setting deferred until after creation of any child entries.
1411 prompt "Compiler optimization level"
1412 default CC_OPTIMIZE_FOR_PERFORMANCE
1414 config CC_OPTIMIZE_FOR_PERFORMANCE
1415 bool "Optimize for performance (-O2)"
1417 This is the default optimization level for the kernel, building
1418 with the "-O2" compiler flag for best performance and most
1419 helpful compile-time warnings.
1421 config CC_OPTIMIZE_FOR_SIZE
1422 bool "Optimize for size (-Os)"
1424 Choosing this option will pass "-Os" to your compiler resulting
1425 in a smaller kernel.
1429 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1432 This requires that the arch annotates or otherwise protects
1433 its external entry points from being discarded. Linker scripts
1434 must also merge .text.*, .data.*, and .bss.* correctly into
1435 output sections. Care must be taken not to pull in unrelated
1436 sections (e.g., '.text.init'). Typically '.' in section names
1437 is used to distinguish them from label names / C identifiers.
1439 config LD_DEAD_CODE_DATA_ELIMINATION
1440 bool "Dead code and data elimination (EXPERIMENTAL)"
1441 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1443 depends on $(cc-option,-ffunction-sections -fdata-sections)
1444 depends on $(ld-option,--gc-sections)
1446 Enable this if you want to do dead code and data elimination with
1447 the linker by compiling with -ffunction-sections -fdata-sections,
1448 and linking with --gc-sections.
1450 This can reduce on disk and in-memory size of the kernel
1451 code and static data, particularly for small configs and
1452 on small systems. This has the possibility of introducing
1453 silently broken kernel if the required annotations are not
1454 present. This option is not well tested yet, so use at your
1457 config LD_ORPHAN_WARN
1459 depends on ARCH_WANT_LD_ORPHAN_WARN
1460 depends on $(ld-option,--orphan-handling=warn)
1468 config SYSCTL_EXCEPTION_TRACE
1471 Enable support for /proc/sys/debug/exception-trace.
1473 config SYSCTL_ARCH_UNALIGN_NO_WARN
1476 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1477 Allows arch to define/use @no_unaligned_warning to possibly warn
1478 about unaligned access emulation going on under the hood.
1480 config SYSCTL_ARCH_UNALIGN_ALLOW
1483 Enable support for /proc/sys/kernel/unaligned-trap
1484 Allows arches to define/use @unaligned_enabled to runtime toggle
1485 the unaligned access emulation.
1486 see arch/parisc/kernel/unaligned.c for reference
1488 config HAVE_PCSPKR_PLATFORM
1491 # interpreter that classic socket filters depend on
1494 select CRYPTO_LIB_SHA1
1497 bool "Configure standard kernel features (expert users)"
1498 # Unhide debug options, to make the on-by-default options visible
1501 This option allows certain base kernel options and settings
1502 to be disabled or tweaked. This is for specialized
1503 environments which can tolerate a "non-standard" kernel.
1504 Only use this if you really know what you are doing.
1507 bool "Enable 16-bit UID system calls" if EXPERT
1508 depends on HAVE_UID16 && MULTIUSER
1511 This enables the legacy 16-bit UID syscall wrappers.
1514 bool "Multiple users, groups and capabilities support" if EXPERT
1517 This option enables support for non-root users, groups and
1520 If you say N here, all processes will run with UID 0, GID 0, and all
1521 possible capabilities. Saying N here also compiles out support for
1522 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1525 If unsure, say Y here.
1527 config SGETMASK_SYSCALL
1528 bool "sgetmask/ssetmask syscalls support" if EXPERT
1529 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1531 sys_sgetmask and sys_ssetmask are obsolete system calls
1532 no longer supported in libc but still enabled by default in some
1535 If unsure, leave the default option here.
1537 config SYSFS_SYSCALL
1538 bool "Sysfs syscall support" if EXPERT
1541 sys_sysfs is an obsolete system call no longer supported in libc.
1542 Note that disabling this option is more secure but might break
1543 compatibility with some systems.
1545 If unsure say Y here.
1548 bool "open by fhandle syscalls" if EXPERT
1552 If you say Y here, a user level program will be able to map
1553 file names to handle and then later use the handle for
1554 different file system operations. This is useful in implementing
1555 userspace file servers, which now track files using handles instead
1556 of names. The handle would remain the same even if file names
1557 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1561 bool "Posix Clocks & timers" if EXPERT
1564 This includes native support for POSIX timers to the kernel.
1565 Some embedded systems have no use for them and therefore they
1566 can be configured out to reduce the size of the kernel image.
1568 When this option is disabled, the following syscalls won't be
1569 available: timer_create, timer_gettime: timer_getoverrun,
1570 timer_settime, timer_delete, clock_adjtime, getitimer,
1571 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1572 clock_getres and clock_nanosleep syscalls will be limited to
1573 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1579 bool "Enable support for printk" if EXPERT
1582 This option enables normal printk support. Removing it
1583 eliminates most of the message strings from the kernel image
1584 and makes the kernel more or less silent. As this makes it
1585 very difficult to diagnose system problems, saying N here is
1586 strongly discouraged.
1589 bool "BUG() support" if EXPERT
1592 Disabling this option eliminates support for BUG and WARN, reducing
1593 the size of your kernel image and potentially quietly ignoring
1594 numerous fatal conditions. You should only consider disabling this
1595 option for embedded systems with no facilities for reporting errors.
1601 bool "Enable ELF core dumps" if EXPERT
1603 Enable support for generating core dumps. Disabling saves about 4k.
1606 config PCSPKR_PLATFORM
1607 bool "Enable PC-Speaker support" if EXPERT
1608 depends on HAVE_PCSPKR_PLATFORM
1612 This option allows to disable the internal PC-Speaker
1613 support, saving some memory.
1617 bool "Enable full-sized data structures for core" if EXPERT
1619 Disabling this option reduces the size of miscellaneous core
1620 kernel data structures. This saves memory on small machines,
1621 but may reduce performance.
1624 bool "Enable futex support" if EXPERT
1625 depends on !(SPARC32 && SMP)
1629 Disabling this option will cause the kernel to be built without
1630 support for "fast userspace mutexes". The resulting kernel may not
1631 run glibc-based applications correctly.
1635 depends on FUTEX && RT_MUTEXES
1639 bool "Enable eventpoll support" if EXPERT
1642 Disabling this option will cause the kernel to be built without
1643 support for epoll family of system calls.
1646 bool "Enable signalfd() system call" if EXPERT
1649 Enable the signalfd() system call that allows to receive signals
1650 on a file descriptor.
1655 bool "Enable timerfd() system call" if EXPERT
1658 Enable the timerfd() system call that allows to receive timer
1659 events on a file descriptor.
1664 bool "Enable eventfd() system call" if EXPERT
1667 Enable the eventfd() system call that allows to receive both
1668 kernel notification (ie. KAIO) or userspace notifications.
1673 bool "Use full shmem filesystem" if EXPERT
1677 The shmem is an internal filesystem used to manage shared memory.
1678 It is backed by swap and manages resource limits. It is also exported
1679 to userspace as tmpfs if TMPFS is enabled. Disabling this
1680 option replaces shmem and tmpfs with the much simpler ramfs code,
1681 which may be appropriate on small systems without swap.
1684 bool "Enable AIO support" if EXPERT
1687 This option enables POSIX asynchronous I/O which may by used
1688 by some high performance threaded applications. Disabling
1689 this option saves about 7k.
1692 bool "Enable IO uring support" if EXPERT
1696 This option enables support for the io_uring interface, enabling
1697 applications to submit and complete IO through submission and
1698 completion rings that are shared between the kernel and application.
1700 config ADVISE_SYSCALLS
1701 bool "Enable madvise/fadvise syscalls" if EXPERT
1704 This option enables the madvise and fadvise syscalls, used by
1705 applications to advise the kernel about their future memory or file
1706 usage, improving performance. If building an embedded system where no
1707 applications use these syscalls, you can disable this option to save
1711 bool "Enable membarrier() system call" if EXPERT
1714 Enable the membarrier() system call that allows issuing memory
1715 barriers across all running threads, which can be used to distribute
1716 the cost of user-space memory barriers asymmetrically by transforming
1717 pairs of memory barriers into pairs consisting of membarrier() and a
1723 bool "Load all symbols for debugging/ksymoops" if EXPERT
1726 Say Y here to let the kernel print out symbolic crash information and
1727 symbolic stack backtraces. This increases the size of the kernel
1728 somewhat, as all symbols have to be loaded into the kernel image.
1731 bool "Include all symbols in kallsyms"
1732 depends on DEBUG_KERNEL && KALLSYMS
1734 Normally kallsyms only contains the symbols of functions for nicer
1735 OOPS messages and backtraces (i.e., symbols from the text and inittext
1736 sections). This is sufficient for most cases. And only if you want to
1737 enable kernel live patching, or other less common use cases (e.g.,
1738 when a debugger is used) all symbols are required (i.e., names of
1739 variables from the data sections, etc).
1741 This option makes sure that all symbols are loaded into the kernel
1742 image (i.e., symbols from all sections) in cost of increased kernel
1743 size (depending on the kernel configuration, it may be 300KiB or
1744 something like this).
1746 Say N unless you really need all symbols, or kernel live patching.
1748 config KALLSYMS_ABSOLUTE_PERCPU
1751 default X86_64 && SMP
1753 config KALLSYMS_BASE_RELATIVE
1758 Instead of emitting them as absolute values in the native word size,
1759 emit the symbol references in the kallsyms table as 32-bit entries,
1760 each containing a relative value in the range [base, base + U32_MAX]
1761 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1762 an absolute value in the range [0, S32_MAX] or a relative value in the
1763 range [base, base + S32_MAX], where base is the lowest relative symbol
1764 address encountered in the image.
1766 On 64-bit builds, this reduces the size of the address table by 50%,
1767 but more importantly, it results in entries whose values are build
1768 time constants, and no relocation pass is required at runtime to fix
1769 up the entries based on the runtime load address of the kernel.
1771 # end of the "standard kernel features (expert users)" menu
1773 # syscall, maps, verifier
1775 config ARCH_HAS_MEMBARRIER_CALLBACKS
1778 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1782 bool "Enable kcmp() system call" if EXPERT
1784 Enable the kernel resource comparison system call. It provides
1785 user-space with the ability to compare two processes to see if they
1786 share a common resource, such as a file descriptor or even virtual
1792 bool "Enable rseq() system call" if EXPERT
1794 depends on HAVE_RSEQ
1797 Enable the restartable sequences system call. It provides a
1798 user-space cache for the current CPU number value, which
1799 speeds up getting the current CPU number from user-space,
1800 as well as an ABI to speed up user-space operations on
1807 bool "Enabled debugging of rseq() system call" if EXPERT
1808 depends on RSEQ && DEBUG_KERNEL
1810 Enable extra debugging checks for the rseq system call.
1815 bool "Embedded system"
1818 This option should be enabled if compiling the kernel for
1819 an embedded system so certain expert options are available
1822 config HAVE_PERF_EVENTS
1825 See tools/perf/design.txt for details.
1827 config GUEST_PERF_EVENTS
1829 depends on HAVE_PERF_EVENTS
1831 config PERF_USE_VMALLOC
1834 See tools/perf/design.txt for details
1837 bool "PC/104 support" if EXPERT
1839 Expose PC/104 form factor device drivers and options available for
1840 selection and configuration. Enable this option if your target
1841 machine has a PC/104 bus.
1843 menu "Kernel Performance Events And Counters"
1846 bool "Kernel performance events and counters"
1847 default y if PROFILING
1848 depends on HAVE_PERF_EVENTS
1852 Enable kernel support for various performance events provided
1853 by software and hardware.
1855 Software events are supported either built-in or via the
1856 use of generic tracepoints.
1858 Most modern CPUs support performance events via performance
1859 counter registers. These registers count the number of certain
1860 types of hw events: such as instructions executed, cachemisses
1861 suffered, or branches mis-predicted - without slowing down the
1862 kernel or applications. These registers can also trigger interrupts
1863 when a threshold number of events have passed - and can thus be
1864 used to profile the code that runs on that CPU.
1866 The Linux Performance Event subsystem provides an abstraction of
1867 these software and hardware event capabilities, available via a
1868 system call and used by the "perf" utility in tools/perf/. It
1869 provides per task and per CPU counters, and it provides event
1870 capabilities on top of those.
1874 config DEBUG_PERF_USE_VMALLOC
1876 bool "Debug: use vmalloc to back perf mmap() buffers"
1877 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1878 select PERF_USE_VMALLOC
1880 Use vmalloc memory to back perf mmap() buffers.
1882 Mostly useful for debugging the vmalloc code on platforms
1883 that don't require it.
1889 config SYSTEM_DATA_VERIFICATION
1891 select SYSTEM_TRUSTED_KEYRING
1895 select ASYMMETRIC_KEY_TYPE
1896 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1899 select X509_CERTIFICATE_PARSER
1900 select PKCS7_MESSAGE_PARSER
1902 Provide PKCS#7 message verification using the contents of the system
1903 trusted keyring to provide public keys. This then can be used for
1904 module verification, kexec image verification and firmware blob
1908 bool "Profiling support"
1910 Say Y here to enable the extended profiling support mechanisms used
1915 depends on HAVE_RUST
1916 depends on RUST_IS_AVAILABLE
1917 depends on !MODVERSIONS
1918 depends on !GCC_PLUGINS
1919 depends on !RANDSTRUCT
1920 depends on !DEBUG_INFO_BTF
1923 Enables Rust support in the kernel.
1925 This allows other Rust-related options, like drivers written in Rust,
1928 It is also required to be able to load external kernel modules
1931 See Documentation/rust/ for more information.
1935 config RUSTC_VERSION_TEXT
1938 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n)
1940 config BINDGEN_VERSION_TEXT
1943 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
1946 # Place an empty function call at each tracepoint site. Can be
1947 # dynamically changed for a probe function.
1952 endmenu # General setup
1954 source "arch/Kconfig"
1958 default y if PREEMPT_RT
1962 default 0 if BASE_FULL
1963 default 1 if !BASE_FULL
1965 config MODULE_SIG_FORMAT
1967 select SYSTEM_DATA_VERIFICATION
1969 source "kernel/module/Kconfig"
1971 config INIT_ALL_POSSIBLE
1974 Back when each arch used to define their own cpu_online_mask and
1975 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1976 with all 1s, and others with all 0s. When they were centralised,
1977 it was better to provide this option than to break all the archs
1978 and have several arch maintainers pursuing me down dark alleys.
1980 source "block/Kconfig"
1982 config PREEMPT_NOTIFIERS
1992 Build a simple ASN.1 grammar compiler that produces a bytecode output
1993 that can be interpreted by the ASN.1 stream decoder and used to
1994 inform it as to what tags are to be expected in a stream and what
1995 functions to call on what tags.
1997 source "kernel/Kconfig.locks"
1999 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2002 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2005 # It may be useful for an architecture to override the definitions of the
2006 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2007 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2008 # different calling convention for syscalls. They can also override the
2009 # macros for not-implemented syscalls in kernel/sys_ni.c and
2010 # kernel/time/posix-stubs.c. All these overrides need to be available in
2011 # <asm/syscall_wrapper.h>.
2012 config ARCH_HAS_SYSCALL_WRAPPER
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