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
65 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
66 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
68 config CC_CAN_LINK_STATIC
70 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
71 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
73 config CC_HAS_ASM_GOTO_OUTPUT
74 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)
76 config CC_HAS_ASM_GOTO_TIED_OUTPUT
77 depends on CC_HAS_ASM_GOTO_OUTPUT
78 # Detect buggy gcc and clang, fixed in gcc-11 clang-14.
79 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)
81 config TOOLS_SUPPORT_RELR
82 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
84 config CC_HAS_ASM_INLINE
85 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
87 config CC_HAS_NO_PROFILE_FN_ATTR
88 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
92 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
100 config BUILDTIME_TABLE_SORT
103 config THREAD_INFO_IN_TASK
106 Select this to move thread_info off the stack into task_struct. To
107 make this work, an arch will need to remove all thread_info fields
108 except flags and fix any runtime bugs.
110 One subtle change that will be needed is to use try_get_task_stack()
111 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
120 depends on BROKEN || !SMP
123 config INIT_ENV_ARG_LIMIT
128 Maximum of each of the number of arguments and environment
129 variables passed to init from the kernel command line.
132 bool "Compile also drivers which will not load"
135 Some drivers can be compiled on a different platform than they are
136 intended to be run on. Despite they cannot be loaded there (or even
137 when they load they cannot be used due to missing HW support),
138 developers still, opposing to distributors, might want to build such
139 drivers to compile-test them.
141 If you are a developer and want to build everything available, say Y
142 here. If you are a user/distributor, say N here to exclude useless
143 drivers to be distributed.
146 bool "Compile the kernel with warnings as errors"
149 A kernel build should not cause any compiler warnings, and this
150 enables the '-Werror' flag to enforce that rule by default.
152 However, if you have a new (or very old) compiler with odd and
153 unusual warnings, or you have some architecture with problems,
154 you may need to disable this config option in order to
155 successfully build the kernel.
159 config UAPI_HEADER_TEST
160 bool "Compile test UAPI headers"
161 depends on HEADERS_INSTALL && CC_CAN_LINK
163 Compile test headers exported to user-space to ensure they are
164 self-contained, i.e. compilable as standalone units.
166 If you are a developer or tester and want to ensure the exported
167 headers are self-contained, say Y here. Otherwise, choose N.
170 string "Local version - append to kernel release"
172 Append an extra string to the end of your kernel version.
173 This will show up when you type uname, for example.
174 The string you set here will be appended after the contents of
175 any files with a filename matching localversion* in your
176 object and source tree, in that order. Your total string can
177 be a maximum of 64 characters.
179 config LOCALVERSION_AUTO
180 bool "Automatically append version information to the version string"
182 depends on !COMPILE_TEST
184 This will try to automatically determine if the current tree is a
185 release tree by looking for git tags that belong to the current
186 top of tree revision.
188 A string of the format -gxxxxxxxx will be added to the localversion
189 if a git-based tree is found. The string generated by this will be
190 appended after any matching localversion* files, and after the value
191 set in CONFIG_LOCALVERSION.
193 (The actual string used here is the first eight characters produced
194 by running the command:
196 $ git rev-parse --verify HEAD
198 which is done within the script "scripts/setlocalversion".)
201 string "Build ID Salt"
204 The build ID is used to link binaries and their debug info. Setting
205 this option will use the value in the calculation of the build id.
206 This is mostly useful for distributions which want to ensure the
207 build is unique between builds. It's safe to leave the default.
209 config HAVE_KERNEL_GZIP
212 config HAVE_KERNEL_BZIP2
215 config HAVE_KERNEL_LZMA
218 config HAVE_KERNEL_XZ
221 config HAVE_KERNEL_LZO
224 config HAVE_KERNEL_LZ4
227 config HAVE_KERNEL_ZSTD
230 config HAVE_KERNEL_UNCOMPRESSED
234 prompt "Kernel compression mode"
236 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
238 The linux kernel is a kind of self-extracting executable.
239 Several compression algorithms are available, which differ
240 in efficiency, compression and decompression speed.
241 Compression speed is only relevant when building a kernel.
242 Decompression speed is relevant at each boot.
244 If you have any problems with bzip2 or lzma compressed
245 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
246 version of this functionality (bzip2 only), for 2.4, was
247 supplied by Christian Ludwig)
249 High compression options are mostly useful for users, who
250 are low on disk space (embedded systems), but for whom ram
253 If in doubt, select 'gzip'
257 depends on HAVE_KERNEL_GZIP
259 The old and tried gzip compression. It provides a good balance
260 between compression ratio and decompression speed.
264 depends on HAVE_KERNEL_BZIP2
266 Its compression ratio and speed is intermediate.
267 Decompression speed is slowest among the choices. The kernel
268 size is about 10% smaller with bzip2, in comparison to gzip.
269 Bzip2 uses a large amount of memory. For modern kernels you
270 will need at least 8MB RAM or more for booting.
274 depends on HAVE_KERNEL_LZMA
276 This compression algorithm's ratio is best. Decompression speed
277 is between gzip and bzip2. Compression is slowest.
278 The kernel size is about 33% smaller with LZMA in comparison to gzip.
282 depends on HAVE_KERNEL_XZ
284 XZ uses the LZMA2 algorithm and instruction set specific
285 BCJ filters which can improve compression ratio of executable
286 code. The size of the kernel is about 30% smaller with XZ in
287 comparison to gzip. On architectures for which there is a BCJ
288 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
289 will create a few percent smaller kernel than plain LZMA.
291 The speed is about the same as with LZMA: The decompression
292 speed of XZ is better than that of bzip2 but worse than gzip
293 and LZO. Compression is slow.
297 depends on HAVE_KERNEL_LZO
299 Its compression ratio is the poorest among the choices. The kernel
300 size is about 10% bigger than gzip; however its speed
301 (both compression and decompression) is the fastest.
305 depends on HAVE_KERNEL_LZ4
307 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
308 A preliminary version of LZ4 de/compression tool is available at
309 <https://code.google.com/p/lz4/>.
311 Its compression ratio is worse than LZO. The size of the kernel
312 is about 8% bigger than LZO. But the decompression speed is
317 depends on HAVE_KERNEL_ZSTD
319 ZSTD is a compression algorithm targeting intermediate compression
320 with fast decompression speed. It will compress better than GZIP and
321 decompress around the same speed as LZO, but slower than LZ4. You
322 will need at least 192 KB RAM or more for booting. The zstd command
323 line tool is required for compression.
325 config KERNEL_UNCOMPRESSED
327 depends on HAVE_KERNEL_UNCOMPRESSED
329 Produce uncompressed kernel image. This option is usually not what
330 you want. It is useful for debugging the kernel in slow simulation
331 environments, where decompressing and moving the kernel is awfully
332 slow. This option allows early boot code to skip the decompressor
333 and jump right at uncompressed kernel image.
338 string "Default init path"
341 This option determines the default init for the system if no init=
342 option is passed on the kernel command line. If the requested path is
343 not present, we will still then move on to attempting further
344 locations (e.g. /sbin/init, etc). If this is empty, we will just use
345 the fallback list when init= is not passed.
347 config DEFAULT_HOSTNAME
348 string "Default hostname"
351 This option determines the default system hostname before userspace
352 calls sethostname(2). The kernel traditionally uses "(none)" here,
353 but you may wish to use a different default here to make a minimal
354 system more usable with less configuration.
359 Inter Process Communication is a suite of library functions and
360 system calls which let processes (running programs) synchronize and
361 exchange information. It is generally considered to be a good thing,
362 and some programs won't run unless you say Y here. In particular, if
363 you want to run the DOS emulator dosemu under Linux (read the
364 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
365 you'll need to say Y here.
367 You can find documentation about IPC with "info ipc" and also in
368 section 6.4 of the Linux Programmer's Guide, available from
369 <http://www.tldp.org/guides.html>.
371 config SYSVIPC_SYSCTL
377 config SYSVIPC_COMPAT
379 depends on COMPAT && SYSVIPC
382 bool "POSIX Message Queues"
385 POSIX variant of message queues is a part of IPC. In POSIX message
386 queues every message has a priority which decides about succession
387 of receiving it by a process. If you want to compile and run
388 programs written e.g. for Solaris with use of its POSIX message
389 queues (functions mq_*) say Y here.
391 POSIX message queues are visible as a filesystem called 'mqueue'
392 and can be mounted somewhere if you want to do filesystem
393 operations on message queues.
397 config POSIX_MQUEUE_SYSCTL
399 depends on POSIX_MQUEUE
404 bool "General notification queue"
408 This is a general notification queue for the kernel to pass events to
409 userspace by splicing them into pipes. It can be used in conjunction
410 with watches for key/keyring change notifications and device
413 See Documentation/core-api/watch_queue.rst
415 config CROSS_MEMORY_ATTACH
416 bool "Enable process_vm_readv/writev syscalls"
420 Enabling this option adds the system calls process_vm_readv and
421 process_vm_writev which allow a process with the correct privileges
422 to directly read from or write to another process' address space.
423 See the man page for more details.
426 bool "uselib syscall (for libc5 and earlier)"
427 default ALPHA || M68K || SPARC
429 This option enables the uselib syscall, a system call used in the
430 dynamic linker from libc5 and earlier. glibc does not use this
431 system call. If you intend to run programs built on libc5 or
432 earlier, you may need to enable this syscall. Current systems
433 running glibc can safely disable this.
436 bool "Auditing support"
439 Enable auditing infrastructure that can be used with another
440 kernel subsystem, such as SELinux (which requires this for
441 logging of avc messages output). System call auditing is included
442 on architectures which support it.
444 config HAVE_ARCH_AUDITSYSCALL
449 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
452 source "kernel/irq/Kconfig"
453 source "kernel/time/Kconfig"
454 source "kernel/bpf/Kconfig"
455 source "kernel/Kconfig.preempt"
457 menu "CPU/Task time and stats accounting"
459 config VIRT_CPU_ACCOUNTING
463 prompt "Cputime accounting"
464 default TICK_CPU_ACCOUNTING if !PPC64
465 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
467 # Kind of a stub config for the pure tick based cputime accounting
468 config TICK_CPU_ACCOUNTING
469 bool "Simple tick based cputime accounting"
470 depends on !S390 && !NO_HZ_FULL
472 This is the basic tick based cputime accounting that maintains
473 statistics about user, system and idle time spent on per jiffies
478 config VIRT_CPU_ACCOUNTING_NATIVE
479 bool "Deterministic task and CPU time accounting"
480 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
481 select VIRT_CPU_ACCOUNTING
483 Select this option to enable more accurate task and CPU time
484 accounting. This is done by reading a CPU counter on each
485 kernel entry and exit and on transitions within the kernel
486 between system, softirq and hardirq state, so there is a
487 small performance impact. In the case of s390 or IBM POWER > 5,
488 this also enables accounting of stolen time on logically-partitioned
491 config VIRT_CPU_ACCOUNTING_GEN
492 bool "Full dynticks CPU time accounting"
493 depends on HAVE_CONTEXT_TRACKING_USER
494 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
495 depends on GENERIC_CLOCKEVENTS
496 select VIRT_CPU_ACCOUNTING
497 select CONTEXT_TRACKING_USER
499 Select this option to enable task and CPU time accounting on full
500 dynticks systems. This accounting is implemented by watching every
501 kernel-user boundaries using the context tracking subsystem.
502 The accounting is thus performed at the expense of some significant
505 For now this is only useful if you are working on the full
506 dynticks subsystem development.
512 config IRQ_TIME_ACCOUNTING
513 bool "Fine granularity task level IRQ time accounting"
514 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
516 Select this option to enable fine granularity task irq time
517 accounting. This is done by reading a timestamp on each
518 transitions between softirq and hardirq state, so there can be a
519 small performance impact.
521 If in doubt, say N here.
523 config HAVE_SCHED_AVG_IRQ
525 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
528 config SCHED_THERMAL_PRESSURE
530 default y if ARM && ARM_CPU_TOPOLOGY
533 depends on CPU_FREQ_THERMAL
535 Select this option to enable thermal pressure accounting in the
536 scheduler. Thermal pressure is the value conveyed to the scheduler
537 that reflects the reduction in CPU compute capacity resulted from
538 thermal throttling. Thermal throttling occurs when the performance of
539 a CPU is capped due to high operating temperatures.
541 If selected, the scheduler will be able to balance tasks accordingly,
542 i.e. put less load on throttled CPUs than on non/less throttled ones.
544 This requires the architecture to implement
545 arch_update_thermal_pressure() and arch_scale_thermal_pressure().
547 config BSD_PROCESS_ACCT
548 bool "BSD Process Accounting"
551 If you say Y here, a user level program will be able to instruct the
552 kernel (via a special system call) to write process accounting
553 information to a file: whenever a process exits, information about
554 that process will be appended to the file by the kernel. The
555 information includes things such as creation time, owning user,
556 command name, memory usage, controlling terminal etc. (the complete
557 list is in the struct acct in <file:include/linux/acct.h>). It is
558 up to the user level program to do useful things with this
559 information. This is generally a good idea, so say Y.
561 config BSD_PROCESS_ACCT_V3
562 bool "BSD Process Accounting version 3 file format"
563 depends on BSD_PROCESS_ACCT
566 If you say Y here, the process accounting information is written
567 in a new file format that also logs the process IDs of each
568 process and its parent. Note that this file format is incompatible
569 with previous v0/v1/v2 file formats, so you will need updated tools
570 for processing it. A preliminary version of these tools is available
571 at <http://www.gnu.org/software/acct/>.
574 bool "Export task/process statistics through netlink"
579 Export selected statistics for tasks/processes through the
580 generic netlink interface. Unlike BSD process accounting, the
581 statistics are available during the lifetime of tasks/processes as
582 responses to commands. Like BSD accounting, they are sent to user
587 config TASK_DELAY_ACCT
588 bool "Enable per-task delay accounting"
592 Collect information on time spent by a task waiting for system
593 resources like cpu, synchronous block I/O completion and swapping
594 in pages. Such statistics can help in setting a task's priorities
595 relative to other tasks for cpu, io, rss limits etc.
600 bool "Enable extended accounting over taskstats"
603 Collect extended task accounting data and send the data
604 to userland for processing over the taskstats interface.
608 config TASK_IO_ACCOUNTING
609 bool "Enable per-task storage I/O accounting"
610 depends on TASK_XACCT
612 Collect information on the number of bytes of storage I/O which this
618 bool "Pressure stall information tracking"
620 Collect metrics that indicate how overcommitted the CPU, memory,
621 and IO capacity are in the system.
623 If you say Y here, the kernel will create /proc/pressure/ with the
624 pressure statistics files cpu, memory, and io. These will indicate
625 the share of walltime in which some or all tasks in the system are
626 delayed due to contention of the respective resource.
628 In kernels with cgroup support, cgroups (cgroup2 only) will
629 have cpu.pressure, memory.pressure, and io.pressure files,
630 which aggregate pressure stalls for the grouped tasks only.
632 For more details see Documentation/accounting/psi.rst.
636 config PSI_DEFAULT_DISABLED
637 bool "Require boot parameter to enable pressure stall information tracking"
641 If set, pressure stall information tracking will be disabled
642 per default but can be enabled through passing psi=1 on the
643 kernel commandline during boot.
645 This feature adds some code to the task wakeup and sleep
646 paths of the scheduler. The overhead is too low to affect
647 common scheduling-intense workloads in practice (such as
648 webservers, memcache), but it does show up in artificial
649 scheduler stress tests, such as hackbench.
651 If you are paranoid and not sure what the kernel will be
656 endmenu # "CPU/Task time and stats accounting"
660 depends on SMP || COMPILE_TEST
663 Make sure that CPUs running critical tasks are not disturbed by
664 any source of "noise" such as unbound workqueues, timers, kthreads...
665 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
666 the "isolcpus=" boot parameter.
670 source "kernel/rcu/Kconfig"
677 tristate "Kernel .config support"
679 This option enables the complete Linux kernel ".config" file
680 contents to be saved in the kernel. It provides documentation
681 of which kernel options are used in a running kernel or in an
682 on-disk kernel. This information can be extracted from the kernel
683 image file with the script scripts/extract-ikconfig and used as
684 input to rebuild the current kernel or to build another kernel.
685 It can also be extracted from a running kernel by reading
686 /proc/config.gz if enabled (below).
689 bool "Enable access to .config through /proc/config.gz"
690 depends on IKCONFIG && PROC_FS
692 This option enables access to the kernel configuration file
693 through /proc/config.gz.
696 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
699 This option enables access to the in-kernel headers that are generated during
700 the build process. These can be used to build eBPF tracing programs,
701 or similar programs. If you build the headers as a module, a module called
702 kheaders.ko is built which can be loaded on-demand to get access to headers.
705 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
710 Select the minimal kernel log buffer size as a power of 2.
711 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
712 parameter, see below. Any higher size also might be forced
713 by "log_buf_len" boot parameter.
723 config LOG_CPU_MAX_BUF_SHIFT
724 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
727 default 12 if !BASE_SMALL
728 default 0 if BASE_SMALL
731 This option allows to increase the default ring buffer size
732 according to the number of CPUs. The value defines the contribution
733 of each CPU as a power of 2. The used space is typically only few
734 lines however it might be much more when problems are reported,
737 The increased size means that a new buffer has to be allocated and
738 the original static one is unused. It makes sense only on systems
739 with more CPUs. Therefore this value is used only when the sum of
740 contributions is greater than the half of the default kernel ring
741 buffer as defined by LOG_BUF_SHIFT. The default values are set
742 so that more than 16 CPUs are needed to trigger the allocation.
744 Also this option is ignored when "log_buf_len" kernel parameter is
745 used as it forces an exact (power of two) size of the ring buffer.
747 The number of possible CPUs is used for this computation ignoring
748 hotplugging making the computation optimal for the worst case
749 scenario while allowing a simple algorithm to be used from bootup.
751 Examples shift values and their meaning:
752 17 => 128 KB for each CPU
753 16 => 64 KB for each CPU
754 15 => 32 KB for each CPU
755 14 => 16 KB for each CPU
756 13 => 8 KB for each CPU
757 12 => 4 KB for each CPU
759 config PRINTK_SAFE_LOG_BUF_SHIFT
760 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
765 Select the size of an alternate printk per-CPU buffer where messages
766 printed from usafe contexts are temporary stored. One example would
767 be NMI messages, another one - printk recursion. The messages are
768 copied to the main log buffer in a safe context to avoid a deadlock.
769 The value defines the size as a power of 2.
771 Those messages are rare and limited. The largest one is when
772 a backtrace is printed. It usually fits into 4KB. Select
773 8KB if you want to be on the safe side.
776 17 => 128 KB for each CPU
777 16 => 64 KB for each CPU
778 15 => 32 KB for each CPU
779 14 => 16 KB for each CPU
780 13 => 8 KB for each CPU
781 12 => 4 KB for each CPU
784 bool "Printk indexing debugfs interface"
785 depends on PRINTK && DEBUG_FS
787 Add support for indexing of all printk formats known at compile time
788 at <debugfs>/printk/index/<module>.
790 This can be used as part of maintaining daemons which monitor
791 /dev/kmsg, as it permits auditing the printk formats present in a
792 kernel, allowing detection of cases where monitored printks are
793 changed or no longer present.
795 There is no additional runtime cost to printk with this enabled.
798 # Architectures with an unreliable sched_clock() should select this:
800 config HAVE_UNSTABLE_SCHED_CLOCK
803 config GENERIC_SCHED_CLOCK
806 menu "Scheduler features"
809 bool "Enable utilization clamping for RT/FAIR tasks"
810 depends on CPU_FREQ_GOV_SCHEDUTIL
812 This feature enables the scheduler to track the clamped utilization
813 of each CPU based on RUNNABLE tasks scheduled on that CPU.
815 With this option, the user can specify the min and max CPU
816 utilization allowed for RUNNABLE tasks. The max utilization defines
817 the maximum frequency a task should use while the min utilization
818 defines the minimum frequency it should use.
820 Both min and max utilization clamp values are hints to the scheduler,
821 aiming at improving its frequency selection policy, but they do not
822 enforce or grant any specific bandwidth for tasks.
826 config UCLAMP_BUCKETS_COUNT
827 int "Number of supported utilization clamp buckets"
830 depends on UCLAMP_TASK
832 Defines the number of clamp buckets to use. The range of each bucket
833 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
834 number of clamp buckets the finer their granularity and the higher
835 the precision of clamping aggregation and tracking at run-time.
837 For example, with the minimum configuration value we will have 5
838 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
839 be refcounted in the [20..39]% bucket and will set the bucket clamp
840 effective value to 25%.
841 If a second 30% boosted task should be co-scheduled on the same CPU,
842 that task will be refcounted in the same bucket of the first task and
843 it will boost the bucket clamp effective value to 30%.
844 The clamp effective value of a bucket is reset to its nominal value
845 (20% in the example above) when there are no more tasks refcounted in
848 An additional boost/capping margin can be added to some tasks. In the
849 example above the 25% task will be boosted to 30% until it exits the
850 CPU. If that should be considered not acceptable on certain systems,
851 it's always possible to reduce the margin by increasing the number of
852 clamp buckets to trade off used memory for run-time tracking
855 If in doubt, use the default value.
860 # For architectures that want to enable the support for NUMA-affine scheduler
863 config ARCH_SUPPORTS_NUMA_BALANCING
867 # For architectures that prefer to flush all TLBs after a number of pages
868 # are unmapped instead of sending one IPI per page to flush. The architecture
869 # must provide guarantees on what happens if a clean TLB cache entry is
870 # written after the unmap. Details are in mm/rmap.c near the check for
871 # should_defer_flush. The architecture should also consider if the full flush
872 # and the refill costs are offset by the savings of sending fewer IPIs.
873 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
877 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
879 config CC_IMPLICIT_FALLTHROUGH
881 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
882 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
884 # Currently, disable gcc-12 array-bounds globally.
885 # We may want to target only particular configurations some day.
886 config GCC12_NO_ARRAY_BOUNDS
889 config CC_NO_ARRAY_BOUNDS
891 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS
894 # For architectures that know their GCC __int128 support is sound
896 config ARCH_SUPPORTS_INT128
899 # For architectures that (ab)use NUMA to represent different memory regions
900 # all cpu-local but of different latencies, such as SuperH.
902 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
905 config NUMA_BALANCING
906 bool "Memory placement aware NUMA scheduler"
907 depends on ARCH_SUPPORTS_NUMA_BALANCING
908 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
909 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
911 This option adds support for automatic NUMA aware memory/task placement.
912 The mechanism is quite primitive and is based on migrating memory when
913 it has references to the node the task is running on.
915 This system will be inactive on UMA systems.
917 config NUMA_BALANCING_DEFAULT_ENABLED
918 bool "Automatically enable NUMA aware memory/task placement"
920 depends on NUMA_BALANCING
922 If set, automatic NUMA balancing will be enabled if running on a NUMA
926 bool "Control Group support"
929 This option adds support for grouping sets of processes together, for
930 use with process control subsystems such as Cpusets, CFS, memory
931 controls or device isolation.
933 - Documentation/scheduler/sched-design-CFS.rst (CFS)
934 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
935 and resource control)
944 config CGROUP_FAVOR_DYNMODS
945 bool "Favor dynamic modification latency reduction by default"
947 This option enables the "favordynmods" mount option by default
948 which reduces the latencies of dynamic cgroup modifications such
949 as task migrations and controller on/offs at the cost of making
950 hot path operations such as forks and exits more expensive.
955 bool "Memory controller"
959 Provides control over the memory footprint of tasks in a cgroup.
963 depends on MEMCG && SWAP
968 depends on MEMCG && !SLOB
976 Generic block IO controller cgroup interface. This is the common
977 cgroup interface which should be used by various IO controlling
980 Currently, CFQ IO scheduler uses it to recognize task groups and
981 control disk bandwidth allocation (proportional time slice allocation)
982 to such task groups. It is also used by bio throttling logic in
983 block layer to implement upper limit in IO rates on a device.
985 This option only enables generic Block IO controller infrastructure.
986 One needs to also enable actual IO controlling logic/policy. For
987 enabling proportional weight division of disk bandwidth in CFQ, set
988 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
989 CONFIG_BLK_DEV_THROTTLING=y.
991 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
993 config CGROUP_WRITEBACK
995 depends on MEMCG && BLK_CGROUP
998 menuconfig CGROUP_SCHED
999 bool "CPU controller"
1002 This feature lets CPU scheduler recognize task groups and control CPU
1003 bandwidth allocation to such task groups. It uses cgroups to group
1007 config FAIR_GROUP_SCHED
1008 bool "Group scheduling for SCHED_OTHER"
1009 depends on CGROUP_SCHED
1010 default CGROUP_SCHED
1012 config CFS_BANDWIDTH
1013 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1014 depends on FAIR_GROUP_SCHED
1017 This option allows users to define CPU bandwidth rates (limits) for
1018 tasks running within the fair group scheduler. Groups with no limit
1019 set are considered to be unconstrained and will run with no
1021 See Documentation/scheduler/sched-bwc.rst for more information.
1023 config RT_GROUP_SCHED
1024 bool "Group scheduling for SCHED_RR/FIFO"
1025 depends on CGROUP_SCHED
1028 This feature lets you explicitly allocate real CPU bandwidth
1029 to task groups. If enabled, it will also make it impossible to
1030 schedule realtime tasks for non-root users until you allocate
1031 realtime bandwidth for them.
1032 See Documentation/scheduler/sched-rt-group.rst for more information.
1036 config UCLAMP_TASK_GROUP
1037 bool "Utilization clamping per group of tasks"
1038 depends on CGROUP_SCHED
1039 depends on UCLAMP_TASK
1042 This feature enables the scheduler to track the clamped utilization
1043 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1045 When this option is enabled, the user can specify a min and max
1046 CPU bandwidth which is allowed for each single task in a group.
1047 The max bandwidth allows to clamp the maximum frequency a task
1048 can use, while the min bandwidth allows to define a minimum
1049 frequency a task will always use.
1051 When task group based utilization clamping is enabled, an eventually
1052 specified task-specific clamp value is constrained by the cgroup
1053 specified clamp value. Both minimum and maximum task clamping cannot
1054 be bigger than the corresponding clamping defined at task group level.
1059 bool "PIDs controller"
1061 Provides enforcement of process number limits in the scope of a
1062 cgroup. Any attempt to fork more processes than is allowed in the
1063 cgroup will fail. PIDs are fundamentally a global resource because it
1064 is fairly trivial to reach PID exhaustion before you reach even a
1065 conservative kmemcg limit. As a result, it is possible to grind a
1066 system to halt without being limited by other cgroup policies. The
1067 PIDs controller is designed to stop this from happening.
1069 It should be noted that organisational operations (such as attaching
1070 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1071 since the PIDs limit only affects a process's ability to fork, not to
1075 bool "RDMA controller"
1077 Provides enforcement of RDMA resources defined by IB stack.
1078 It is fairly easy for consumers to exhaust RDMA resources, which
1079 can result into resource unavailability to other consumers.
1080 RDMA controller is designed to stop this from happening.
1081 Attaching processes with active RDMA resources to the cgroup
1082 hierarchy is allowed even if can cross the hierarchy's limit.
1084 config CGROUP_FREEZER
1085 bool "Freezer controller"
1087 Provides a way to freeze and unfreeze all tasks in a
1090 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1091 controller includes important in-kernel memory consumers per default.
1093 If you're using cgroup2, say N.
1095 config CGROUP_HUGETLB
1096 bool "HugeTLB controller"
1097 depends on HUGETLB_PAGE
1101 Provides a cgroup controller for HugeTLB pages.
1102 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1103 The limit is enforced during page fault. Since HugeTLB doesn't
1104 support page reclaim, enforcing the limit at page fault time implies
1105 that, the application will get SIGBUS signal if it tries to access
1106 HugeTLB pages beyond its limit. This requires the application to know
1107 beforehand how much HugeTLB pages it would require for its use. The
1108 control group is tracked in the third page lru pointer. This means
1109 that we cannot use the controller with huge page less than 3 pages.
1112 bool "Cpuset controller"
1115 This option will let you create and manage CPUSETs which
1116 allow dynamically partitioning a system into sets of CPUs and
1117 Memory Nodes and assigning tasks to run only within those sets.
1118 This is primarily useful on large SMP or NUMA systems.
1122 config PROC_PID_CPUSET
1123 bool "Include legacy /proc/<pid>/cpuset file"
1127 config CGROUP_DEVICE
1128 bool "Device controller"
1130 Provides a cgroup controller implementing whitelists for
1131 devices which a process in the cgroup can mknod or open.
1133 config CGROUP_CPUACCT
1134 bool "Simple CPU accounting controller"
1136 Provides a simple controller for monitoring the
1137 total CPU consumed by the tasks in a cgroup.
1140 bool "Perf controller"
1141 depends on PERF_EVENTS
1143 This option extends the perf per-cpu mode to restrict monitoring
1144 to threads which belong to the cgroup specified and run on the
1145 designated cpu. Or this can be used to have cgroup ID in samples
1146 so that it can monitor performance events among cgroups.
1151 bool "Support for eBPF programs attached to cgroups"
1152 depends on BPF_SYSCALL
1153 select SOCK_CGROUP_DATA
1155 Allow attaching eBPF programs to a cgroup using the bpf(2)
1156 syscall command BPF_PROG_ATTACH.
1158 In which context these programs are accessed depends on the type
1159 of attachment. For instance, programs that are attached using
1160 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1164 bool "Misc resource controller"
1167 Provides a controller for miscellaneous resources on a host.
1169 Miscellaneous scalar resources are the resources on the host system
1170 which cannot be abstracted like the other cgroups. This controller
1171 tracks and limits the miscellaneous resources used by a process
1172 attached to a cgroup hierarchy.
1174 For more information, please check misc cgroup section in
1175 /Documentation/admin-guide/cgroup-v2.rst.
1178 bool "Debug controller"
1180 depends on DEBUG_KERNEL
1182 This option enables a simple controller that exports
1183 debugging information about the cgroups framework. This
1184 controller is for control cgroup debugging only. Its
1185 interfaces are not stable.
1189 config SOCK_CGROUP_DATA
1195 menuconfig NAMESPACES
1196 bool "Namespaces support" if EXPERT
1197 depends on MULTIUSER
1200 Provides the way to make tasks work with different objects using
1201 the same id. For example same IPC id may refer to different objects
1202 or same user id or pid may refer to different tasks when used in
1203 different namespaces.
1208 bool "UTS namespace"
1211 In this namespace tasks see different info provided with the
1215 bool "TIME namespace"
1216 depends on GENERIC_VDSO_TIME_NS
1219 In this namespace boottime and monotonic clocks can be set.
1220 The time will keep going with the same pace.
1223 bool "IPC namespace"
1224 depends on (SYSVIPC || POSIX_MQUEUE)
1227 In this namespace tasks work with IPC ids which correspond to
1228 different IPC objects in different namespaces.
1231 bool "User namespace"
1234 This allows containers, i.e. vservers, to use user namespaces
1235 to provide different user info for different servers.
1237 When user namespaces are enabled in the kernel it is
1238 recommended that the MEMCG option also be enabled and that
1239 user-space use the memory control groups to limit the amount
1240 of memory a memory unprivileged users can use.
1245 bool "PID Namespaces"
1248 Support process id namespaces. This allows having multiple
1249 processes with the same pid as long as they are in different
1250 pid namespaces. This is a building block of containers.
1253 bool "Network namespace"
1257 Allow user space to create what appear to be multiple instances
1258 of the network stack.
1262 config CHECKPOINT_RESTORE
1263 bool "Checkpoint/restore support"
1264 select PROC_CHILDREN
1268 Enables additional kernel features in a sake of checkpoint/restore.
1269 In particular it adds auxiliary prctl codes to setup process text,
1270 data and heap segment sizes, and a few additional /proc filesystem
1273 If unsure, say N here.
1275 config SCHED_AUTOGROUP
1276 bool "Automatic process group scheduling"
1279 select FAIR_GROUP_SCHED
1281 This option optimizes the scheduler for common desktop workloads by
1282 automatically creating and populating task groups. This separation
1283 of workloads isolates aggressive CPU burners (like build jobs) from
1284 desktop applications. Task group autogeneration is currently based
1287 config SYSFS_DEPRECATED
1288 bool "Enable deprecated sysfs features to support old userspace tools"
1292 This option adds code that switches the layout of the "block" class
1293 devices, to not show up in /sys/class/block/, but only in
1296 This switch is only active when the sysfs.deprecated=1 boot option is
1297 passed or the SYSFS_DEPRECATED_V2 option is set.
1299 This option allows new kernels to run on old distributions and tools,
1300 which might get confused by /sys/class/block/. Since 2007/2008 all
1301 major distributions and tools handle this just fine.
1303 Recent distributions and userspace tools after 2009/2010 depend on
1304 the existence of /sys/class/block/, and will not work with this
1307 Only if you are using a new kernel on an old distribution, you might
1310 config SYSFS_DEPRECATED_V2
1311 bool "Enable deprecated sysfs features by default"
1314 depends on SYSFS_DEPRECATED
1316 Enable deprecated sysfs by default.
1318 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1321 Only if you are using a new kernel on an old distribution, you might
1322 need to say Y here. Even then, odds are you would not need it
1323 enabled, you can always pass the boot option if absolutely necessary.
1326 bool "Kernel->user space relay support (formerly relayfs)"
1329 This option enables support for relay interface support in
1330 certain file systems (such as debugfs).
1331 It is designed to provide an efficient mechanism for tools and
1332 facilities to relay large amounts of data from kernel space to
1337 config BLK_DEV_INITRD
1338 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1340 The initial RAM filesystem is a ramfs which is loaded by the
1341 boot loader (loadlin or lilo) and that is mounted as root
1342 before the normal boot procedure. It is typically used to
1343 load modules needed to mount the "real" root file system,
1344 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1346 If RAM disk support (BLK_DEV_RAM) is also included, this
1347 also enables initial RAM disk (initrd) support and adds
1348 15 Kbytes (more on some other architectures) to the kernel size.
1354 source "usr/Kconfig"
1359 bool "Boot config support"
1360 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1362 Extra boot config allows system admin to pass a config file as
1363 complemental extension of kernel cmdline when booting.
1364 The boot config file must be attached at the end of initramfs
1365 with checksum, size and magic word.
1366 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1370 config BOOT_CONFIG_EMBED
1371 bool "Embed bootconfig file in the kernel"
1372 depends on BOOT_CONFIG
1374 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1375 kernel. Usually, the bootconfig file is loaded with the initrd
1376 image. But if the system doesn't support initrd, this option will
1377 help you by embedding a bootconfig file while building the kernel.
1381 config BOOT_CONFIG_EMBED_FILE
1382 string "Embedded bootconfig file path"
1383 depends on BOOT_CONFIG_EMBED
1385 Specify a bootconfig file which will be embedded to the kernel.
1386 This bootconfig will be used if there is no initrd or no other
1387 bootconfig in the initrd.
1389 config INITRAMFS_PRESERVE_MTIME
1390 bool "Preserve cpio archive mtimes in initramfs"
1393 Each entry in an initramfs cpio archive carries an mtime value. When
1394 enabled, extracted cpio items take this mtime, with directory mtime
1395 setting deferred until after creation of any child entries.
1400 prompt "Compiler optimization level"
1401 default CC_OPTIMIZE_FOR_PERFORMANCE
1403 config CC_OPTIMIZE_FOR_PERFORMANCE
1404 bool "Optimize for performance (-O2)"
1406 This is the default optimization level for the kernel, building
1407 with the "-O2" compiler flag for best performance and most
1408 helpful compile-time warnings.
1410 config CC_OPTIMIZE_FOR_SIZE
1411 bool "Optimize for size (-Os)"
1413 Choosing this option will pass "-Os" to your compiler resulting
1414 in a smaller kernel.
1418 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1421 This requires that the arch annotates or otherwise protects
1422 its external entry points from being discarded. Linker scripts
1423 must also merge .text.*, .data.*, and .bss.* correctly into
1424 output sections. Care must be taken not to pull in unrelated
1425 sections (e.g., '.text.init'). Typically '.' in section names
1426 is used to distinguish them from label names / C identifiers.
1428 config LD_DEAD_CODE_DATA_ELIMINATION
1429 bool "Dead code and data elimination (EXPERIMENTAL)"
1430 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1432 depends on $(cc-option,-ffunction-sections -fdata-sections)
1433 depends on $(ld-option,--gc-sections)
1435 Enable this if you want to do dead code and data elimination with
1436 the linker by compiling with -ffunction-sections -fdata-sections,
1437 and linking with --gc-sections.
1439 This can reduce on disk and in-memory size of the kernel
1440 code and static data, particularly for small configs and
1441 on small systems. This has the possibility of introducing
1442 silently broken kernel if the required annotations are not
1443 present. This option is not well tested yet, so use at your
1446 config LD_ORPHAN_WARN
1448 depends on ARCH_WANT_LD_ORPHAN_WARN
1449 depends on $(ld-option,--orphan-handling=warn)
1457 config SYSCTL_EXCEPTION_TRACE
1460 Enable support for /proc/sys/debug/exception-trace.
1462 config SYSCTL_ARCH_UNALIGN_NO_WARN
1465 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1466 Allows arch to define/use @no_unaligned_warning to possibly warn
1467 about unaligned access emulation going on under the hood.
1469 config SYSCTL_ARCH_UNALIGN_ALLOW
1472 Enable support for /proc/sys/kernel/unaligned-trap
1473 Allows arches to define/use @unaligned_enabled to runtime toggle
1474 the unaligned access emulation.
1475 see arch/parisc/kernel/unaligned.c for reference
1477 config HAVE_PCSPKR_PLATFORM
1480 # interpreter that classic socket filters depend on
1483 select CRYPTO_LIB_SHA1
1486 bool "Configure standard kernel features (expert users)"
1487 # Unhide debug options, to make the on-by-default options visible
1490 This option allows certain base kernel options and settings
1491 to be disabled or tweaked. This is for specialized
1492 environments which can tolerate a "non-standard" kernel.
1493 Only use this if you really know what you are doing.
1496 bool "Enable 16-bit UID system calls" if EXPERT
1497 depends on HAVE_UID16 && MULTIUSER
1500 This enables the legacy 16-bit UID syscall wrappers.
1503 bool "Multiple users, groups and capabilities support" if EXPERT
1506 This option enables support for non-root users, groups and
1509 If you say N here, all processes will run with UID 0, GID 0, and all
1510 possible capabilities. Saying N here also compiles out support for
1511 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1514 If unsure, say Y here.
1516 config SGETMASK_SYSCALL
1517 bool "sgetmask/ssetmask syscalls support" if EXPERT
1518 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1520 sys_sgetmask and sys_ssetmask are obsolete system calls
1521 no longer supported in libc but still enabled by default in some
1524 If unsure, leave the default option here.
1526 config SYSFS_SYSCALL
1527 bool "Sysfs syscall support" if EXPERT
1530 sys_sysfs is an obsolete system call no longer supported in libc.
1531 Note that disabling this option is more secure but might break
1532 compatibility with some systems.
1534 If unsure say Y here.
1537 bool "open by fhandle syscalls" if EXPERT
1541 If you say Y here, a user level program will be able to map
1542 file names to handle and then later use the handle for
1543 different file system operations. This is useful in implementing
1544 userspace file servers, which now track files using handles instead
1545 of names. The handle would remain the same even if file names
1546 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1550 bool "Posix Clocks & timers" if EXPERT
1553 This includes native support for POSIX timers to the kernel.
1554 Some embedded systems have no use for them and therefore they
1555 can be configured out to reduce the size of the kernel image.
1557 When this option is disabled, the following syscalls won't be
1558 available: timer_create, timer_gettime: timer_getoverrun,
1559 timer_settime, timer_delete, clock_adjtime, getitimer,
1560 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1561 clock_getres and clock_nanosleep syscalls will be limited to
1562 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1568 bool "Enable support for printk" if EXPERT
1571 This option enables normal printk support. Removing it
1572 eliminates most of the message strings from the kernel image
1573 and makes the kernel more or less silent. As this makes it
1574 very difficult to diagnose system problems, saying N here is
1575 strongly discouraged.
1578 bool "BUG() support" if EXPERT
1581 Disabling this option eliminates support for BUG and WARN, reducing
1582 the size of your kernel image and potentially quietly ignoring
1583 numerous fatal conditions. You should only consider disabling this
1584 option for embedded systems with no facilities for reporting errors.
1590 bool "Enable ELF core dumps" if EXPERT
1592 Enable support for generating core dumps. Disabling saves about 4k.
1595 config PCSPKR_PLATFORM
1596 bool "Enable PC-Speaker support" if EXPERT
1597 depends on HAVE_PCSPKR_PLATFORM
1601 This option allows to disable the internal PC-Speaker
1602 support, saving some memory.
1606 bool "Enable full-sized data structures for core" if EXPERT
1608 Disabling this option reduces the size of miscellaneous core
1609 kernel data structures. This saves memory on small machines,
1610 but may reduce performance.
1613 bool "Enable futex support" if EXPERT
1614 depends on !(SPARC32 && SMP)
1618 Disabling this option will cause the kernel to be built without
1619 support for "fast userspace mutexes". The resulting kernel may not
1620 run glibc-based applications correctly.
1624 depends on FUTEX && RT_MUTEXES
1628 bool "Enable eventpoll support" if EXPERT
1631 Disabling this option will cause the kernel to be built without
1632 support for epoll family of system calls.
1635 bool "Enable signalfd() system call" if EXPERT
1638 Enable the signalfd() system call that allows to receive signals
1639 on a file descriptor.
1644 bool "Enable timerfd() system call" if EXPERT
1647 Enable the timerfd() system call that allows to receive timer
1648 events on a file descriptor.
1653 bool "Enable eventfd() system call" if EXPERT
1656 Enable the eventfd() system call that allows to receive both
1657 kernel notification (ie. KAIO) or userspace notifications.
1662 bool "Use full shmem filesystem" if EXPERT
1666 The shmem is an internal filesystem used to manage shared memory.
1667 It is backed by swap and manages resource limits. It is also exported
1668 to userspace as tmpfs if TMPFS is enabled. Disabling this
1669 option replaces shmem and tmpfs with the much simpler ramfs code,
1670 which may be appropriate on small systems without swap.
1673 bool "Enable AIO support" if EXPERT
1676 This option enables POSIX asynchronous I/O which may by used
1677 by some high performance threaded applications. Disabling
1678 this option saves about 7k.
1681 bool "Enable IO uring support" if EXPERT
1685 This option enables support for the io_uring interface, enabling
1686 applications to submit and complete IO through submission and
1687 completion rings that are shared between the kernel and application.
1689 config ADVISE_SYSCALLS
1690 bool "Enable madvise/fadvise syscalls" if EXPERT
1693 This option enables the madvise and fadvise syscalls, used by
1694 applications to advise the kernel about their future memory or file
1695 usage, improving performance. If building an embedded system where no
1696 applications use these syscalls, you can disable this option to save
1700 bool "Enable membarrier() system call" if EXPERT
1703 Enable the membarrier() system call that allows issuing memory
1704 barriers across all running threads, which can be used to distribute
1705 the cost of user-space memory barriers asymmetrically by transforming
1706 pairs of memory barriers into pairs consisting of membarrier() and a
1712 bool "Load all symbols for debugging/ksymoops" if EXPERT
1715 Say Y here to let the kernel print out symbolic crash information and
1716 symbolic stack backtraces. This increases the size of the kernel
1717 somewhat, as all symbols have to be loaded into the kernel image.
1720 bool "Include all symbols in kallsyms"
1721 depends on DEBUG_KERNEL && KALLSYMS
1723 Normally kallsyms only contains the symbols of functions for nicer
1724 OOPS messages and backtraces (i.e., symbols from the text and inittext
1725 sections). This is sufficient for most cases. And only if you want to
1726 enable kernel live patching, or other less common use cases (e.g.,
1727 when a debugger is used) all symbols are required (i.e., names of
1728 variables from the data sections, etc).
1730 This option makes sure that all symbols are loaded into the kernel
1731 image (i.e., symbols from all sections) in cost of increased kernel
1732 size (depending on the kernel configuration, it may be 300KiB or
1733 something like this).
1735 Say N unless you really need all symbols, or kernel live patching.
1737 config KALLSYMS_ABSOLUTE_PERCPU
1740 default X86_64 && SMP
1742 config KALLSYMS_BASE_RELATIVE
1747 Instead of emitting them as absolute values in the native word size,
1748 emit the symbol references in the kallsyms table as 32-bit entries,
1749 each containing a relative value in the range [base, base + U32_MAX]
1750 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1751 an absolute value in the range [0, S32_MAX] or a relative value in the
1752 range [base, base + S32_MAX], where base is the lowest relative symbol
1753 address encountered in the image.
1755 On 64-bit builds, this reduces the size of the address table by 50%,
1756 but more importantly, it results in entries whose values are build
1757 time constants, and no relocation pass is required at runtime to fix
1758 up the entries based on the runtime load address of the kernel.
1760 # end of the "standard kernel features (expert users)" menu
1762 # syscall, maps, verifier
1764 config ARCH_HAS_MEMBARRIER_CALLBACKS
1767 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1771 bool "Enable kcmp() system call" if EXPERT
1773 Enable the kernel resource comparison system call. It provides
1774 user-space with the ability to compare two processes to see if they
1775 share a common resource, such as a file descriptor or even virtual
1781 bool "Enable rseq() system call" if EXPERT
1783 depends on HAVE_RSEQ
1786 Enable the restartable sequences system call. It provides a
1787 user-space cache for the current CPU number value, which
1788 speeds up getting the current CPU number from user-space,
1789 as well as an ABI to speed up user-space operations on
1796 bool "Enabled debugging of rseq() system call" if EXPERT
1797 depends on RSEQ && DEBUG_KERNEL
1799 Enable extra debugging checks for the rseq system call.
1804 bool "Embedded system"
1807 This option should be enabled if compiling the kernel for
1808 an embedded system so certain expert options are available
1811 config HAVE_PERF_EVENTS
1814 See tools/perf/design.txt for details.
1816 config GUEST_PERF_EVENTS
1818 depends on HAVE_PERF_EVENTS
1820 config PERF_USE_VMALLOC
1823 See tools/perf/design.txt for details
1826 bool "PC/104 support" if EXPERT
1828 Expose PC/104 form factor device drivers and options available for
1829 selection and configuration. Enable this option if your target
1830 machine has a PC/104 bus.
1832 menu "Kernel Performance Events And Counters"
1835 bool "Kernel performance events and counters"
1836 default y if PROFILING
1837 depends on HAVE_PERF_EVENTS
1841 Enable kernel support for various performance events provided
1842 by software and hardware.
1844 Software events are supported either built-in or via the
1845 use of generic tracepoints.
1847 Most modern CPUs support performance events via performance
1848 counter registers. These registers count the number of certain
1849 types of hw events: such as instructions executed, cachemisses
1850 suffered, or branches mis-predicted - without slowing down the
1851 kernel or applications. These registers can also trigger interrupts
1852 when a threshold number of events have passed - and can thus be
1853 used to profile the code that runs on that CPU.
1855 The Linux Performance Event subsystem provides an abstraction of
1856 these software and hardware event capabilities, available via a
1857 system call and used by the "perf" utility in tools/perf/. It
1858 provides per task and per CPU counters, and it provides event
1859 capabilities on top of those.
1863 config DEBUG_PERF_USE_VMALLOC
1865 bool "Debug: use vmalloc to back perf mmap() buffers"
1866 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1867 select PERF_USE_VMALLOC
1869 Use vmalloc memory to back perf mmap() buffers.
1871 Mostly useful for debugging the vmalloc code on platforms
1872 that don't require it.
1878 config SYSTEM_DATA_VERIFICATION
1880 select SYSTEM_TRUSTED_KEYRING
1884 select ASYMMETRIC_KEY_TYPE
1885 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1888 select X509_CERTIFICATE_PARSER
1889 select PKCS7_MESSAGE_PARSER
1891 Provide PKCS#7 message verification using the contents of the system
1892 trusted keyring to provide public keys. This then can be used for
1893 module verification, kexec image verification and firmware blob
1897 bool "Profiling support"
1899 Say Y here to enable the extended profiling support mechanisms used
1903 # Place an empty function call at each tracepoint site. Can be
1904 # dynamically changed for a probe function.
1909 endmenu # General setup
1911 source "arch/Kconfig"
1915 default y if PREEMPT_RT
1919 default 0 if BASE_FULL
1920 default 1 if !BASE_FULL
1922 config MODULE_SIG_FORMAT
1924 select SYSTEM_DATA_VERIFICATION
1926 source "kernel/module/Kconfig"
1928 config INIT_ALL_POSSIBLE
1931 Back when each arch used to define their own cpu_online_mask and
1932 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1933 with all 1s, and others with all 0s. When they were centralised,
1934 it was better to provide this option than to break all the archs
1935 and have several arch maintainers pursuing me down dark alleys.
1937 source "block/Kconfig"
1939 config PREEMPT_NOTIFIERS
1949 Build a simple ASN.1 grammar compiler that produces a bytecode output
1950 that can be interpreted by the ASN.1 stream decoder and used to
1951 inform it as to what tags are to be expected in a stream and what
1952 functions to call on what tags.
1954 source "kernel/Kconfig.locks"
1956 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
1959 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
1962 # It may be useful for an architecture to override the definitions of the
1963 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
1964 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
1965 # different calling convention for syscalls. They can also override the
1966 # macros for not-implemented syscalls in kernel/sys_ni.c and
1967 # kernel/time/posix-stubs.c. All these overrides need to be available in
1968 # <asm/syscall_wrapper.h>.
1969 config ARCH_HAS_SYSCALL_WRAPPER
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