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 satisfy 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]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
92 config GCC_ASM_GOTO_OUTPUT_WORKAROUND
94 depends on CC_IS_GCC && CC_HAS_ASM_GOTO_OUTPUT
95 # Fixed in GCC 14, 13.3, 12.4 and 11.5
96 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
97 default y if GCC_VERSION < 110500
98 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400
99 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300
101 config TOOLS_SUPPORT_RELR
102 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
104 config CC_HAS_ASM_INLINE
105 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
107 config CC_HAS_NO_PROFILE_FN_ATTR
108 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
110 config PAHOLE_VERSION
112 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
120 config BUILDTIME_TABLE_SORT
123 config THREAD_INFO_IN_TASK
126 Select this to move thread_info off the stack into task_struct. To
127 make this work, an arch will need to remove all thread_info fields
128 except flags and fix any runtime bugs.
130 One subtle change that will be needed is to use try_get_task_stack()
131 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
140 depends on BROKEN || !SMP
143 config INIT_ENV_ARG_LIMIT
148 Maximum of each of the number of arguments and environment
149 variables passed to init from the kernel command line.
152 bool "Compile also drivers which will not load"
155 Some drivers can be compiled on a different platform than they are
156 intended to be run on. Despite they cannot be loaded there (or even
157 when they load they cannot be used due to missing HW support),
158 developers still, opposing to distributors, might want to build such
159 drivers to compile-test them.
161 If you are a developer and want to build everything available, say Y
162 here. If you are a user/distributor, say N here to exclude useless
163 drivers to be distributed.
166 bool "Compile the kernel with warnings as errors"
169 A kernel build should not cause any compiler warnings, and this
170 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
171 to enforce that rule by default. Certain warnings from other tools
172 such as the linker may be upgraded to errors with this option as
175 However, if you have a new (or very old) compiler or linker with odd
176 and unusual warnings, or you have some architecture with problems,
177 you may need to disable this config option in order to
178 successfully build the kernel.
182 config UAPI_HEADER_TEST
183 bool "Compile test UAPI headers"
184 depends on HEADERS_INSTALL && CC_CAN_LINK
186 Compile test headers exported to user-space to ensure they are
187 self-contained, i.e. compilable as standalone units.
189 If you are a developer or tester and want to ensure the exported
190 headers are self-contained, say Y here. Otherwise, choose N.
193 string "Local version - append to kernel release"
195 Append an extra string to the end of your kernel version.
196 This will show up when you type uname, for example.
197 The string you set here will be appended after the contents of
198 any files with a filename matching localversion* in your
199 object and source tree, in that order. Your total string can
200 be a maximum of 64 characters.
202 config LOCALVERSION_AUTO
203 bool "Automatically append version information to the version string"
205 depends on !COMPILE_TEST
207 This will try to automatically determine if the current tree is a
208 release tree by looking for git tags that belong to the current
209 top of tree revision.
211 A string of the format -gxxxxxxxx will be added to the localversion
212 if a git-based tree is found. The string generated by this will be
213 appended after any matching localversion* files, and after the value
214 set in CONFIG_LOCALVERSION.
216 (The actual string used here is the first 12 characters produced
217 by running the command:
219 $ git rev-parse --verify HEAD
221 which is done within the script "scripts/setlocalversion".)
224 string "Build ID Salt"
227 The build ID is used to link binaries and their debug info. Setting
228 this option will use the value in the calculation of the build id.
229 This is mostly useful for distributions which want to ensure the
230 build is unique between builds. It's safe to leave the default.
232 config HAVE_KERNEL_GZIP
235 config HAVE_KERNEL_BZIP2
238 config HAVE_KERNEL_LZMA
241 config HAVE_KERNEL_XZ
244 config HAVE_KERNEL_LZO
247 config HAVE_KERNEL_LZ4
250 config HAVE_KERNEL_ZSTD
253 config HAVE_KERNEL_UNCOMPRESSED
257 prompt "Kernel compression mode"
259 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
261 The linux kernel is a kind of self-extracting executable.
262 Several compression algorithms are available, which differ
263 in efficiency, compression and decompression speed.
264 Compression speed is only relevant when building a kernel.
265 Decompression speed is relevant at each boot.
267 If you have any problems with bzip2 or lzma compressed
269 version of this functionality (bzip2 only), for 2.4, was
270 supplied by Christian Ludwig)
272 High compression options are mostly useful for users, who
273 are low on disk space (embedded systems), but for whom ram
276 If in doubt, select 'gzip'
280 depends on HAVE_KERNEL_GZIP
282 The old and tried gzip compression. It provides a good balance
283 between compression ratio and decompression speed.
287 depends on HAVE_KERNEL_BZIP2
289 Its compression ratio and speed is intermediate.
290 Decompression speed is slowest among the choices. The kernel
291 size is about 10% smaller with bzip2, in comparison to gzip.
292 Bzip2 uses a large amount of memory. For modern kernels you
293 will need at least 8MB RAM or more for booting.
297 depends on HAVE_KERNEL_LZMA
299 This compression algorithm's ratio is best. Decompression speed
300 is between gzip and bzip2. Compression is slowest.
301 The kernel size is about 33% smaller with LZMA in comparison to gzip.
305 depends on HAVE_KERNEL_XZ
307 XZ uses the LZMA2 algorithm and instruction set specific
308 BCJ filters which can improve compression ratio of executable
309 code. The size of the kernel is about 30% smaller with XZ in
310 comparison to gzip. On architectures for which there is a BCJ
311 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
312 will create a few percent smaller kernel than plain LZMA.
314 The speed is about the same as with LZMA: The decompression
315 speed of XZ is better than that of bzip2 but worse than gzip
316 and LZO. Compression is slow.
320 depends on HAVE_KERNEL_LZO
322 Its compression ratio is the poorest among the choices. The kernel
323 size is about 10% bigger than gzip; however its speed
324 (both compression and decompression) is the fastest.
328 depends on HAVE_KERNEL_LZ4
330 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
331 A preliminary version of LZ4 de/compression tool is available at
332 <https://code.google.com/p/lz4/>.
334 Its compression ratio is worse than LZO. The size of the kernel
335 is about 8% bigger than LZO. But the decompression speed is
340 depends on HAVE_KERNEL_ZSTD
342 ZSTD is a compression algorithm targeting intermediate compression
343 with fast decompression speed. It will compress better than GZIP and
344 decompress around the same speed as LZO, but slower than LZ4. You
345 will need at least 192 KB RAM or more for booting. The zstd command
346 line tool is required for compression.
348 config KERNEL_UNCOMPRESSED
350 depends on HAVE_KERNEL_UNCOMPRESSED
352 Produce uncompressed kernel image. This option is usually not what
353 you want. It is useful for debugging the kernel in slow simulation
354 environments, where decompressing and moving the kernel is awfully
355 slow. This option allows early boot code to skip the decompressor
356 and jump right at uncompressed kernel image.
361 string "Default init path"
364 This option determines the default init for the system if no init=
365 option is passed on the kernel command line. If the requested path is
366 not present, we will still then move on to attempting further
367 locations (e.g. /sbin/init, etc). If this is empty, we will just use
368 the fallback list when init= is not passed.
370 config DEFAULT_HOSTNAME
371 string "Default hostname"
374 This option determines the default system hostname before userspace
375 calls sethostname(2). The kernel traditionally uses "(none)" here,
376 but you may wish to use a different default here to make a minimal
377 system more usable with less configuration.
382 Inter Process Communication is a suite of library functions and
383 system calls which let processes (running programs) synchronize and
384 exchange information. It is generally considered to be a good thing,
385 and some programs won't run unless you say Y here. In particular, if
386 you want to run the DOS emulator dosemu under Linux (read the
387 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
388 you'll need to say Y here.
390 You can find documentation about IPC with "info ipc" and also in
391 section 6.4 of the Linux Programmer's Guide, available from
392 <http://www.tldp.org/guides.html>.
394 config SYSVIPC_SYSCTL
400 config SYSVIPC_COMPAT
402 depends on COMPAT && SYSVIPC
405 bool "POSIX Message Queues"
408 POSIX variant of message queues is a part of IPC. In POSIX message
409 queues every message has a priority which decides about succession
410 of receiving it by a process. If you want to compile and run
411 programs written e.g. for Solaris with use of its POSIX message
412 queues (functions mq_*) say Y here.
414 POSIX message queues are visible as a filesystem called 'mqueue'
415 and can be mounted somewhere if you want to do filesystem
416 operations on message queues.
420 config POSIX_MQUEUE_SYSCTL
422 depends on POSIX_MQUEUE
427 bool "General notification queue"
431 This is a general notification queue for the kernel to pass events to
432 userspace by splicing them into pipes. It can be used in conjunction
433 with watches for key/keyring change notifications and device
436 See Documentation/core-api/watch_queue.rst
438 config CROSS_MEMORY_ATTACH
439 bool "Enable process_vm_readv/writev syscalls"
443 Enabling this option adds the system calls process_vm_readv and
444 process_vm_writev which allow a process with the correct privileges
445 to directly read from or write to another process' address space.
446 See the man page for more details.
449 bool "uselib syscall (for libc5 and earlier)"
450 default ALPHA || M68K || SPARC
452 This option enables the uselib syscall, a system call used in the
453 dynamic linker from libc5 and earlier. glibc does not use this
454 system call. If you intend to run programs built on libc5 or
455 earlier, you may need to enable this syscall. Current systems
456 running glibc can safely disable this.
459 bool "Auditing support"
462 Enable auditing infrastructure that can be used with another
463 kernel subsystem, such as SELinux (which requires this for
464 logging of avc messages output). System call auditing is included
465 on architectures which support it.
467 config HAVE_ARCH_AUDITSYSCALL
472 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
475 source "kernel/irq/Kconfig"
476 source "kernel/time/Kconfig"
477 source "kernel/bpf/Kconfig"
478 source "kernel/Kconfig.preempt"
480 menu "CPU/Task time and stats accounting"
482 config VIRT_CPU_ACCOUNTING
486 prompt "Cputime accounting"
487 default TICK_CPU_ACCOUNTING
489 # Kind of a stub config for the pure tick based cputime accounting
490 config TICK_CPU_ACCOUNTING
491 bool "Simple tick based cputime accounting"
492 depends on !S390 && !NO_HZ_FULL
494 This is the basic tick based cputime accounting that maintains
495 statistics about user, system and idle time spent on per jiffies
500 config VIRT_CPU_ACCOUNTING_NATIVE
501 bool "Deterministic task and CPU time accounting"
502 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
503 select VIRT_CPU_ACCOUNTING
505 Select this option to enable more accurate task and CPU time
506 accounting. This is done by reading a CPU counter on each
507 kernel entry and exit and on transitions within the kernel
508 between system, softirq and hardirq state, so there is a
509 small performance impact. In the case of s390 or IBM POWER > 5,
510 this also enables accounting of stolen time on logically-partitioned
513 config VIRT_CPU_ACCOUNTING_GEN
514 bool "Full dynticks CPU time accounting"
515 depends on HAVE_CONTEXT_TRACKING_USER
516 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
517 depends on GENERIC_CLOCKEVENTS
518 select VIRT_CPU_ACCOUNTING
519 select CONTEXT_TRACKING_USER
521 Select this option to enable task and CPU time accounting on full
522 dynticks systems. This accounting is implemented by watching every
523 kernel-user boundaries using the context tracking subsystem.
524 The accounting is thus performed at the expense of some significant
527 For now this is only useful if you are working on the full
528 dynticks subsystem development.
534 config IRQ_TIME_ACCOUNTING
535 bool "Fine granularity task level IRQ time accounting"
536 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
538 Select this option to enable fine granularity task irq time
539 accounting. This is done by reading a timestamp on each
540 transitions between softirq and hardirq state, so there can be a
541 small performance impact.
543 If in doubt, say N here.
545 config HAVE_SCHED_AVG_IRQ
547 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
550 config SCHED_HW_PRESSURE
552 default y if ARM && ARM_CPU_TOPOLOGY
555 depends on CPU_FREQ_THERMAL
557 Select this option to enable HW pressure accounting in the
558 scheduler. HW pressure is the value conveyed to the scheduler
559 that reflects the reduction in CPU compute capacity resulted from
560 HW throttling. HW throttling occurs when the performance of
561 a CPU is capped due to high operating temperatures as an example.
563 If selected, the scheduler will be able to balance tasks accordingly,
564 i.e. put less load on throttled CPUs than on non/less throttled ones.
566 This requires the architecture to implement
567 arch_update_hw_pressure() and arch_scale_thermal_pressure().
569 config BSD_PROCESS_ACCT
570 bool "BSD Process Accounting"
573 If you say Y here, a user level program will be able to instruct the
574 kernel (via a special system call) to write process accounting
575 information to a file: whenever a process exits, information about
576 that process will be appended to the file by the kernel. The
577 information includes things such as creation time, owning user,
578 command name, memory usage, controlling terminal etc. (the complete
579 list is in the struct acct in <file:include/linux/acct.h>). It is
580 up to the user level program to do useful things with this
581 information. This is generally a good idea, so say Y.
583 config BSD_PROCESS_ACCT_V3
584 bool "BSD Process Accounting version 3 file format"
585 depends on BSD_PROCESS_ACCT
588 If you say Y here, the process accounting information is written
589 in a new file format that also logs the process IDs of each
590 process and its parent. Note that this file format is incompatible
591 with previous v0/v1/v2 file formats, so you will need updated tools
592 for processing it. A preliminary version of these tools is available
593 at <http://www.gnu.org/software/acct/>.
596 bool "Export task/process statistics through netlink"
601 Export selected statistics for tasks/processes through the
602 generic netlink interface. Unlike BSD process accounting, the
603 statistics are available during the lifetime of tasks/processes as
604 responses to commands. Like BSD accounting, they are sent to user
609 config TASK_DELAY_ACCT
610 bool "Enable per-task delay accounting"
614 Collect information on time spent by a task waiting for system
615 resources like cpu, synchronous block I/O completion and swapping
616 in pages. Such statistics can help in setting a task's priorities
617 relative to other tasks for cpu, io, rss limits etc.
622 bool "Enable extended accounting over taskstats"
625 Collect extended task accounting data and send the data
626 to userland for processing over the taskstats interface.
630 config TASK_IO_ACCOUNTING
631 bool "Enable per-task storage I/O accounting"
632 depends on TASK_XACCT
634 Collect information on the number of bytes of storage I/O which this
640 bool "Pressure stall information tracking"
643 Collect metrics that indicate how overcommitted the CPU, memory,
644 and IO capacity are in the system.
646 If you say Y here, the kernel will create /proc/pressure/ with the
647 pressure statistics files cpu, memory, and io. These will indicate
648 the share of walltime in which some or all tasks in the system are
649 delayed due to contention of the respective resource.
651 In kernels with cgroup support, cgroups (cgroup2 only) will
652 have cpu.pressure, memory.pressure, and io.pressure files,
653 which aggregate pressure stalls for the grouped tasks only.
655 For more details see Documentation/accounting/psi.rst.
659 config PSI_DEFAULT_DISABLED
660 bool "Require boot parameter to enable pressure stall information tracking"
664 If set, pressure stall information tracking will be disabled
665 per default but can be enabled through passing psi=1 on the
666 kernel commandline during boot.
668 This feature adds some code to the task wakeup and sleep
669 paths of the scheduler. The overhead is too low to affect
670 common scheduling-intense workloads in practice (such as
671 webservers, memcache), but it does show up in artificial
672 scheduler stress tests, such as hackbench.
674 If you are paranoid and not sure what the kernel will be
679 endmenu # "CPU/Task time and stats accounting"
683 depends on SMP || COMPILE_TEST
686 Make sure that CPUs running critical tasks are not disturbed by
687 any source of "noise" such as unbound workqueues, timers, kthreads...
688 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
689 the "isolcpus=" boot parameter.
693 source "kernel/rcu/Kconfig"
696 tristate "Kernel .config support"
698 This option enables the complete Linux kernel ".config" file
699 contents to be saved in the kernel. It provides documentation
700 of which kernel options are used in a running kernel or in an
701 on-disk kernel. This information can be extracted from the kernel
702 image file with the script scripts/extract-ikconfig and used as
703 input to rebuild the current kernel or to build another kernel.
704 It can also be extracted from a running kernel by reading
705 /proc/config.gz if enabled (below).
708 bool "Enable access to .config through /proc/config.gz"
709 depends on IKCONFIG && PROC_FS
711 This option enables access to the kernel configuration file
712 through /proc/config.gz.
715 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
718 This option enables access to the in-kernel headers that are generated during
719 the build process. These can be used to build eBPF tracing programs,
720 or similar programs. If you build the headers as a module, a module called
721 kheaders.ko is built which can be loaded on-demand to get access to headers.
724 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
729 Select the minimal kernel log buffer size as a power of 2.
730 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
731 parameter, see below. Any higher size also might be forced
732 by "log_buf_len" boot parameter.
742 config LOG_CPU_MAX_BUF_SHIFT
743 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
746 default 0 if BASE_SMALL
750 This option allows to increase the default ring buffer size
751 according to the number of CPUs. The value defines the contribution
752 of each CPU as a power of 2. The used space is typically only few
753 lines however it might be much more when problems are reported,
756 The increased size means that a new buffer has to be allocated and
757 the original static one is unused. It makes sense only on systems
758 with more CPUs. Therefore this value is used only when the sum of
759 contributions is greater than the half of the default kernel ring
760 buffer as defined by LOG_BUF_SHIFT. The default values are set
761 so that more than 16 CPUs are needed to trigger the allocation.
763 Also this option is ignored when "log_buf_len" kernel parameter is
764 used as it forces an exact (power of two) size of the ring buffer.
766 The number of possible CPUs is used for this computation ignoring
767 hotplugging making the computation optimal for the worst case
768 scenario while allowing a simple algorithm to be used from bootup.
770 Examples shift values and their meaning:
771 17 => 128 KB for each CPU
772 16 => 64 KB for each CPU
773 15 => 32 KB for each CPU
774 14 => 16 KB for each CPU
775 13 => 8 KB for each CPU
776 12 => 4 KB for each CPU
779 bool "Printk indexing debugfs interface"
780 depends on PRINTK && DEBUG_FS
782 Add support for indexing of all printk formats known at compile time
783 at <debugfs>/printk/index/<module>.
785 This can be used as part of maintaining daemons which monitor
786 /dev/kmsg, as it permits auditing the printk formats present in a
787 kernel, allowing detection of cases where monitored printks are
788 changed or no longer present.
790 There is no additional runtime cost to printk with this enabled.
793 # Architectures with an unreliable sched_clock() should select this:
795 config HAVE_UNSTABLE_SCHED_CLOCK
798 config GENERIC_SCHED_CLOCK
801 menu "Scheduler features"
804 bool "Enable utilization clamping for RT/FAIR tasks"
805 depends on CPU_FREQ_GOV_SCHEDUTIL
807 This feature enables the scheduler to track the clamped utilization
808 of each CPU based on RUNNABLE tasks scheduled on that CPU.
810 With this option, the user can specify the min and max CPU
811 utilization allowed for RUNNABLE tasks. The max utilization defines
812 the maximum frequency a task should use while the min utilization
813 defines the minimum frequency it should use.
815 Both min and max utilization clamp values are hints to the scheduler,
816 aiming at improving its frequency selection policy, but they do not
817 enforce or grant any specific bandwidth for tasks.
821 config UCLAMP_BUCKETS_COUNT
822 int "Number of supported utilization clamp buckets"
825 depends on UCLAMP_TASK
827 Defines the number of clamp buckets to use. The range of each bucket
828 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
829 number of clamp buckets the finer their granularity and the higher
830 the precision of clamping aggregation and tracking at run-time.
832 For example, with the minimum configuration value we will have 5
833 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
834 be refcounted in the [20..39]% bucket and will set the bucket clamp
835 effective value to 25%.
836 If a second 30% boosted task should be co-scheduled on the same CPU,
837 that task will be refcounted in the same bucket of the first task and
838 it will boost the bucket clamp effective value to 30%.
839 The clamp effective value of a bucket is reset to its nominal value
840 (20% in the example above) when there are no more tasks refcounted in
843 An additional boost/capping margin can be added to some tasks. In the
844 example above the 25% task will be boosted to 30% until it exits the
845 CPU. If that should be considered not acceptable on certain systems,
846 it's always possible to reduce the margin by increasing the number of
847 clamp buckets to trade off used memory for run-time tracking
850 If in doubt, use the default value.
855 # For architectures that want to enable the support for NUMA-affine scheduler
858 config ARCH_SUPPORTS_NUMA_BALANCING
862 # For architectures that prefer to flush all TLBs after a number of pages
863 # are unmapped instead of sending one IPI per page to flush. The architecture
864 # must provide guarantees on what happens if a clean TLB cache entry is
865 # written after the unmap. Details are in mm/rmap.c near the check for
866 # should_defer_flush. The architecture should also consider if the full flush
867 # and the refill costs are offset by the savings of sending fewer IPIs.
868 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
872 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
874 config CC_IMPLICIT_FALLTHROUGH
876 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
877 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
879 # Currently, disable gcc-10+ array-bounds globally.
880 # It's still broken in gcc-13, so no upper bound yet.
881 config GCC10_NO_ARRAY_BOUNDS
884 config CC_NO_ARRAY_BOUNDS
886 default y if CC_IS_GCC && GCC_VERSION >= 100000 && GCC10_NO_ARRAY_BOUNDS
888 # Currently, disable -Wstringop-overflow for GCC globally.
889 config GCC_NO_STRINGOP_OVERFLOW
892 config CC_NO_STRINGOP_OVERFLOW
894 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW
896 config CC_STRINGOP_OVERFLOW
898 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
901 # For architectures that know their GCC __int128 support is sound
903 config ARCH_SUPPORTS_INT128
906 # For architectures that (ab)use NUMA to represent different memory regions
907 # all cpu-local but of different latencies, such as SuperH.
909 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
912 config NUMA_BALANCING
913 bool "Memory placement aware NUMA scheduler"
914 depends on ARCH_SUPPORTS_NUMA_BALANCING
915 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
916 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT
918 This option adds support for automatic NUMA aware memory/task placement.
919 The mechanism is quite primitive and is based on migrating memory when
920 it has references to the node the task is running on.
922 This system will be inactive on UMA systems.
924 config NUMA_BALANCING_DEFAULT_ENABLED
925 bool "Automatically enable NUMA aware memory/task placement"
927 depends on NUMA_BALANCING
929 If set, automatic NUMA balancing will be enabled if running on a NUMA
936 bool "Control Group support"
939 This option adds support for grouping sets of processes together, for
940 use with process control subsystems such as Cpusets, CFS, memory
941 controls or device isolation.
943 - Documentation/scheduler/sched-design-CFS.rst (CFS)
944 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
945 and resource control)
954 config CGROUP_FAVOR_DYNMODS
955 bool "Favor dynamic modification latency reduction by default"
957 This option enables the "favordynmods" mount option by default
958 which reduces the latencies of dynamic cgroup modifications such
959 as task migrations and controller on/offs at the cost of making
960 hot path operations such as forks and exits more expensive.
965 bool "Memory controller"
970 Provides control over the memory footprint of tasks in a cgroup.
982 Generic block IO controller cgroup interface. This is the common
983 cgroup interface which should be used by various IO controlling
986 Currently, CFQ IO scheduler uses it to recognize task groups and
987 control disk bandwidth allocation (proportional time slice allocation)
988 to such task groups. It is also used by bio throttling logic in
989 block layer to implement upper limit in IO rates on a device.
991 This option only enables generic Block IO controller infrastructure.
992 One needs to also enable actual IO controlling logic/policy. For
993 enabling proportional weight division of disk bandwidth in CFQ, set
994 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
995 CONFIG_BLK_DEV_THROTTLING=y.
997 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
999 config CGROUP_WRITEBACK
1001 depends on MEMCG && BLK_CGROUP
1004 menuconfig CGROUP_SCHED
1005 bool "CPU controller"
1008 This feature lets CPU scheduler recognize task groups and control CPU
1009 bandwidth allocation to such task groups. It uses cgroups to group
1013 config FAIR_GROUP_SCHED
1014 bool "Group scheduling for SCHED_OTHER"
1015 depends on CGROUP_SCHED
1016 default CGROUP_SCHED
1018 config CFS_BANDWIDTH
1019 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1020 depends on FAIR_GROUP_SCHED
1023 This option allows users to define CPU bandwidth rates (limits) for
1024 tasks running within the fair group scheduler. Groups with no limit
1025 set are considered to be unconstrained and will run with no
1027 See Documentation/scheduler/sched-bwc.rst for more information.
1029 config RT_GROUP_SCHED
1030 bool "Group scheduling for SCHED_RR/FIFO"
1031 depends on CGROUP_SCHED
1034 This feature lets you explicitly allocate real CPU bandwidth
1035 to task groups. If enabled, it will also make it impossible to
1036 schedule realtime tasks for non-root users until you allocate
1037 realtime bandwidth for them.
1038 See Documentation/scheduler/sched-rt-group.rst for more information.
1044 depends on SMP && RSEQ
1046 config UCLAMP_TASK_GROUP
1047 bool "Utilization clamping per group of tasks"
1048 depends on CGROUP_SCHED
1049 depends on UCLAMP_TASK
1052 This feature enables the scheduler to track the clamped utilization
1053 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
1055 When this option is enabled, the user can specify a min and max
1056 CPU bandwidth which is allowed for each single task in a group.
1057 The max bandwidth allows to clamp the maximum frequency a task
1058 can use, while the min bandwidth allows to define a minimum
1059 frequency a task will always use.
1061 When task group based utilization clamping is enabled, an eventually
1062 specified task-specific clamp value is constrained by the cgroup
1063 specified clamp value. Both minimum and maximum task clamping cannot
1064 be bigger than the corresponding clamping defined at task group level.
1069 bool "PIDs controller"
1071 Provides enforcement of process number limits in the scope of a
1072 cgroup. Any attempt to fork more processes than is allowed in the
1073 cgroup will fail. PIDs are fundamentally a global resource because it
1074 is fairly trivial to reach PID exhaustion before you reach even a
1075 conservative kmemcg limit. As a result, it is possible to grind a
1076 system to halt without being limited by other cgroup policies. The
1077 PIDs controller is designed to stop this from happening.
1079 It should be noted that organisational operations (such as attaching
1080 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1081 since the PIDs limit only affects a process's ability to fork, not to
1085 bool "RDMA controller"
1087 Provides enforcement of RDMA resources defined by IB stack.
1088 It is fairly easy for consumers to exhaust RDMA resources, which
1089 can result into resource unavailability to other consumers.
1090 RDMA controller is designed to stop this from happening.
1091 Attaching processes with active RDMA resources to the cgroup
1092 hierarchy is allowed even if can cross the hierarchy's limit.
1094 config CGROUP_FREEZER
1095 bool "Freezer controller"
1097 Provides a way to freeze and unfreeze all tasks in a
1100 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1101 controller includes important in-kernel memory consumers per default.
1103 If you're using cgroup2, say N.
1105 config CGROUP_HUGETLB
1106 bool "HugeTLB controller"
1107 depends on HUGETLB_PAGE
1111 Provides a cgroup controller for HugeTLB pages.
1112 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1113 The limit is enforced during page fault. Since HugeTLB doesn't
1114 support page reclaim, enforcing the limit at page fault time implies
1115 that, the application will get SIGBUS signal if it tries to access
1116 HugeTLB pages beyond its limit. This requires the application to know
1117 beforehand how much HugeTLB pages it would require for its use. The
1118 control group is tracked in the third page lru pointer. This means
1119 that we cannot use the controller with huge page less than 3 pages.
1122 bool "Cpuset controller"
1125 This option will let you create and manage CPUSETs which
1126 allow dynamically partitioning a system into sets of CPUs and
1127 Memory Nodes and assigning tasks to run only within those sets.
1128 This is primarily useful on large SMP or NUMA systems.
1132 config PROC_PID_CPUSET
1133 bool "Include legacy /proc/<pid>/cpuset file"
1137 config CGROUP_DEVICE
1138 bool "Device controller"
1140 Provides a cgroup controller implementing whitelists for
1141 devices which a process in the cgroup can mknod or open.
1143 config CGROUP_CPUACCT
1144 bool "Simple CPU accounting controller"
1146 Provides a simple controller for monitoring the
1147 total CPU consumed by the tasks in a cgroup.
1150 bool "Perf controller"
1151 depends on PERF_EVENTS
1153 This option extends the perf per-cpu mode to restrict monitoring
1154 to threads which belong to the cgroup specified and run on the
1155 designated cpu. Or this can be used to have cgroup ID in samples
1156 so that it can monitor performance events among cgroups.
1161 bool "Support for eBPF programs attached to cgroups"
1162 depends on BPF_SYSCALL
1163 select SOCK_CGROUP_DATA
1165 Allow attaching eBPF programs to a cgroup using the bpf(2)
1166 syscall command BPF_PROG_ATTACH.
1168 In which context these programs are accessed depends on the type
1169 of attachment. For instance, programs that are attached using
1170 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1174 bool "Misc resource controller"
1177 Provides a controller for miscellaneous resources on a host.
1179 Miscellaneous scalar resources are the resources on the host system
1180 which cannot be abstracted like the other cgroups. This controller
1181 tracks and limits the miscellaneous resources used by a process
1182 attached to a cgroup hierarchy.
1184 For more information, please check misc cgroup section in
1185 /Documentation/admin-guide/cgroup-v2.rst.
1188 bool "Debug controller"
1190 depends on DEBUG_KERNEL
1192 This option enables a simple controller that exports
1193 debugging information about the cgroups framework. This
1194 controller is for control cgroup debugging only. Its
1195 interfaces are not stable.
1199 config SOCK_CGROUP_DATA
1205 menuconfig NAMESPACES
1206 bool "Namespaces support" if EXPERT
1207 depends on MULTIUSER
1210 Provides the way to make tasks work with different objects using
1211 the same id. For example same IPC id may refer to different objects
1212 or same user id or pid may refer to different tasks when used in
1213 different namespaces.
1218 bool "UTS namespace"
1221 In this namespace tasks see different info provided with the
1225 bool "TIME namespace"
1226 depends on GENERIC_VDSO_TIME_NS
1229 In this namespace boottime and monotonic clocks can be set.
1230 The time will keep going with the same pace.
1233 bool "IPC namespace"
1234 depends on (SYSVIPC || POSIX_MQUEUE)
1237 In this namespace tasks work with IPC ids which correspond to
1238 different IPC objects in different namespaces.
1241 bool "User namespace"
1244 This allows containers, i.e. vservers, to use user namespaces
1245 to provide different user info for different servers.
1247 When user namespaces are enabled in the kernel it is
1248 recommended that the MEMCG option also be enabled and that
1249 user-space use the memory control groups to limit the amount
1250 of memory a memory unprivileged users can use.
1255 bool "PID Namespaces"
1258 Support process id namespaces. This allows having multiple
1259 processes with the same pid as long as they are in different
1260 pid namespaces. This is a building block of containers.
1263 bool "Network namespace"
1267 Allow user space to create what appear to be multiple instances
1268 of the network stack.
1272 config CHECKPOINT_RESTORE
1273 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
1299 bool "Kernel->user space relay support (formerly relayfs)"
1302 This option enables support for relay interface support in
1303 certain file systems (such as debugfs).
1304 It is designed to provide an efficient mechanism for tools and
1305 facilities to relay large amounts of data from kernel space to
1310 config BLK_DEV_INITRD
1311 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1313 The initial RAM filesystem is a ramfs which is loaded by the
1314 boot loader (loadlin or lilo) and that is mounted as root
1315 before the normal boot procedure. It is typically used to
1316 load modules needed to mount the "real" root file system,
1317 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1319 If RAM disk support (BLK_DEV_RAM) is also included, this
1320 also enables initial RAM disk (initrd) support and adds
1321 15 Kbytes (more on some other architectures) to the kernel size.
1327 source "usr/Kconfig"
1332 bool "Boot config support"
1333 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
1335 Extra boot config allows system admin to pass a config file as
1336 complemental extension of kernel cmdline when booting.
1337 The boot config file must be attached at the end of initramfs
1338 with checksum, size and magic word.
1339 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1343 config BOOT_CONFIG_FORCE
1344 bool "Force unconditional bootconfig processing"
1345 depends on BOOT_CONFIG
1346 default y if BOOT_CONFIG_EMBED
1348 With this Kconfig option set, BOOT_CONFIG processing is carried
1349 out even when the "bootconfig" kernel-boot parameter is omitted.
1350 In fact, with this Kconfig option set, there is no way to
1351 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot
1356 config BOOT_CONFIG_EMBED
1357 bool "Embed bootconfig file in the kernel"
1358 depends on BOOT_CONFIG
1360 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
1361 kernel. Usually, the bootconfig file is loaded with the initrd
1362 image. But if the system doesn't support initrd, this option will
1363 help you by embedding a bootconfig file while building the kernel.
1367 config BOOT_CONFIG_EMBED_FILE
1368 string "Embedded bootconfig file path"
1369 depends on BOOT_CONFIG_EMBED
1371 Specify a bootconfig file which will be embedded to the kernel.
1372 This bootconfig will be used if there is no initrd or no other
1373 bootconfig in the initrd.
1375 config INITRAMFS_PRESERVE_MTIME
1376 bool "Preserve cpio archive mtimes in initramfs"
1379 Each entry in an initramfs cpio archive carries an mtime value. When
1380 enabled, extracted cpio items take this mtime, with directory mtime
1381 setting deferred until after creation of any child entries.
1386 prompt "Compiler optimization level"
1387 default CC_OPTIMIZE_FOR_PERFORMANCE
1389 config CC_OPTIMIZE_FOR_PERFORMANCE
1390 bool "Optimize for performance (-O2)"
1392 This is the default optimization level for the kernel, building
1393 with the "-O2" compiler flag for best performance and most
1394 helpful compile-time warnings.
1396 config CC_OPTIMIZE_FOR_SIZE
1397 bool "Optimize for size (-Os)"
1399 Choosing this option will pass "-Os" to your compiler resulting
1400 in a smaller kernel.
1404 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1407 This requires that the arch annotates or otherwise protects
1408 its external entry points from being discarded. Linker scripts
1409 must also merge .text.*, .data.*, and .bss.* correctly into
1410 output sections. Care must be taken not to pull in unrelated
1411 sections (e.g., '.text.init'). Typically '.' in section names
1412 is used to distinguish them from label names / C identifiers.
1414 config LD_DEAD_CODE_DATA_ELIMINATION
1415 bool "Dead code and data elimination (EXPERIMENTAL)"
1416 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1418 depends on $(cc-option,-ffunction-sections -fdata-sections)
1419 depends on $(ld-option,--gc-sections)
1421 Enable this if you want to do dead code and data elimination with
1422 the linker by compiling with -ffunction-sections -fdata-sections,
1423 and linking with --gc-sections.
1425 This can reduce on disk and in-memory size of the kernel
1426 code and static data, particularly for small configs and
1427 on small systems. This has the possibility of introducing
1428 silently broken kernel if the required annotations are not
1429 present. This option is not well tested yet, so use at your
1432 config LD_ORPHAN_WARN
1434 depends on ARCH_WANT_LD_ORPHAN_WARN
1435 depends on $(ld-option,--orphan-handling=warn)
1436 depends on $(ld-option,--orphan-handling=error)
1438 config LD_ORPHAN_WARN_LEVEL
1440 depends on LD_ORPHAN_WARN
1441 default "error" if WERROR
1450 config SYSCTL_EXCEPTION_TRACE
1453 Enable support for /proc/sys/debug/exception-trace.
1455 config SYSCTL_ARCH_UNALIGN_NO_WARN
1458 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1459 Allows arch to define/use @no_unaligned_warning to possibly warn
1460 about unaligned access emulation going on under the hood.
1462 config SYSCTL_ARCH_UNALIGN_ALLOW
1465 Enable support for /proc/sys/kernel/unaligned-trap
1466 Allows arches to define/use @unaligned_enabled to runtime toggle
1467 the unaligned access emulation.
1468 see arch/parisc/kernel/unaligned.c for reference
1470 config HAVE_PCSPKR_PLATFORM
1474 bool "Configure standard kernel features (expert users)"
1475 # Unhide debug options, to make the on-by-default options visible
1478 This option allows certain base kernel options and settings
1479 to be disabled or tweaked. This is for specialized
1480 environments which can tolerate a "non-standard" kernel.
1481 Only use this if you really know what you are doing.
1484 bool "Enable 16-bit UID system calls" if EXPERT
1485 depends on HAVE_UID16 && MULTIUSER
1488 This enables the legacy 16-bit UID syscall wrappers.
1491 bool "Multiple users, groups and capabilities support" if EXPERT
1494 This option enables support for non-root users, groups and
1497 If you say N here, all processes will run with UID 0, GID 0, and all
1498 possible capabilities. Saying N here also compiles out support for
1499 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1502 If unsure, say Y here.
1504 config SGETMASK_SYSCALL
1505 bool "sgetmask/ssetmask syscalls support" if EXPERT
1506 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1508 sys_sgetmask and sys_ssetmask are obsolete system calls
1509 no longer supported in libc but still enabled by default in some
1512 If unsure, leave the default option here.
1514 config SYSFS_SYSCALL
1515 bool "Sysfs syscall support" if EXPERT
1518 sys_sysfs is an obsolete system call no longer supported in libc.
1519 Note that disabling this option is more secure but might break
1520 compatibility with some systems.
1522 If unsure say Y here.
1525 bool "open by fhandle syscalls" if EXPERT
1529 If you say Y here, a user level program will be able to map
1530 file names to handle and then later use the handle for
1531 different file system operations. This is useful in implementing
1532 userspace file servers, which now track files using handles instead
1533 of names. The handle would remain the same even if file names
1534 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1538 bool "Posix Clocks & timers" if EXPERT
1541 This includes native support for POSIX timers to the kernel.
1542 Some embedded systems have no use for them and therefore they
1543 can be configured out to reduce the size of the kernel image.
1545 When this option is disabled, the following syscalls won't be
1546 available: timer_create, timer_gettime: timer_getoverrun,
1547 timer_settime, timer_delete, clock_adjtime, getitimer,
1548 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1549 clock_getres and clock_nanosleep syscalls will be limited to
1550 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1556 bool "Enable support for printk" if EXPERT
1559 This option enables normal printk support. Removing it
1560 eliminates most of the message strings from the kernel image
1561 and makes the kernel more or less silent. As this makes it
1562 very difficult to diagnose system problems, saying N here is
1563 strongly discouraged.
1566 bool "BUG() support" if EXPERT
1569 Disabling this option eliminates support for BUG and WARN, reducing
1570 the size of your kernel image and potentially quietly ignoring
1571 numerous fatal conditions. You should only consider disabling this
1572 option for embedded systems with no facilities for reporting errors.
1578 bool "Enable ELF core dumps" if EXPERT
1580 Enable support for generating core dumps. Disabling saves about 4k.
1583 config PCSPKR_PLATFORM
1584 bool "Enable PC-Speaker support" if EXPERT
1585 depends on HAVE_PCSPKR_PLATFORM
1589 This option allows to disable the internal PC-Speaker
1590 support, saving some memory.
1593 bool "Enable smaller-sized data structures for core" if EXPERT
1595 Enabling this option reduces the size of miscellaneous core
1596 kernel data structures. This saves memory on small machines,
1597 but may reduce performance.
1600 bool "Enable futex support" if EXPERT
1601 depends on !(SPARC32 && SMP)
1605 Disabling this option will cause the kernel to be built without
1606 support for "fast userspace mutexes". The resulting kernel may not
1607 run glibc-based applications correctly.
1611 depends on FUTEX && RT_MUTEXES
1615 bool "Enable eventpoll support" if EXPERT
1618 Disabling this option will cause the kernel to be built without
1619 support for epoll family of system calls.
1622 bool "Enable signalfd() system call" if EXPERT
1625 Enable the signalfd() system call that allows to receive signals
1626 on a file descriptor.
1631 bool "Enable timerfd() system call" if EXPERT
1634 Enable the timerfd() system call that allows to receive timer
1635 events on a file descriptor.
1640 bool "Enable eventfd() system call" if EXPERT
1643 Enable the eventfd() system call that allows to receive both
1644 kernel notification (ie. KAIO) or userspace notifications.
1649 bool "Use full shmem filesystem" if EXPERT
1653 The shmem is an internal filesystem used to manage shared memory.
1654 It is backed by swap and manages resource limits. It is also exported
1655 to userspace as tmpfs if TMPFS is enabled. Disabling this
1656 option replaces shmem and tmpfs with the much simpler ramfs code,
1657 which may be appropriate on small systems without swap.
1660 bool "Enable AIO support" if EXPERT
1663 This option enables POSIX asynchronous I/O which may by used
1664 by some high performance threaded applications. Disabling
1665 this option saves about 7k.
1668 bool "Enable IO uring support" if EXPERT
1672 This option enables support for the io_uring interface, enabling
1673 applications to submit and complete IO through submission and
1674 completion rings that are shared between the kernel and application.
1676 config ADVISE_SYSCALLS
1677 bool "Enable madvise/fadvise syscalls" if EXPERT
1680 This option enables the madvise and fadvise syscalls, used by
1681 applications to advise the kernel about their future memory or file
1682 usage, improving performance. If building an embedded system where no
1683 applications use these syscalls, you can disable this option to save
1687 bool "Enable membarrier() system call" if EXPERT
1690 Enable the membarrier() system call that allows issuing memory
1691 barriers across all running threads, which can be used to distribute
1692 the cost of user-space memory barriers asymmetrically by transforming
1693 pairs of memory barriers into pairs consisting of membarrier() and a
1699 bool "Enable kcmp() system call" if EXPERT
1701 Enable the kernel resource comparison system call. It provides
1702 user-space with the ability to compare two processes to see if they
1703 share a common resource, such as a file descriptor or even virtual
1709 bool "Enable rseq() system call" if EXPERT
1711 depends on HAVE_RSEQ
1714 Enable the restartable sequences system call. It provides a
1715 user-space cache for the current CPU number value, which
1716 speeds up getting the current CPU number from user-space,
1717 as well as an ABI to speed up user-space operations on
1724 bool "Enable debugging of rseq() system call" if EXPERT
1725 depends on RSEQ && DEBUG_KERNEL
1727 Enable extra debugging checks for the rseq system call.
1731 config CACHESTAT_SYSCALL
1732 bool "Enable cachestat() system call" if EXPERT
1735 Enable the cachestat system call, which queries the page cache
1736 statistics of a file (number of cached pages, dirty pages,
1737 pages marked for writeback, (recently) evicted pages).
1739 If unsure say Y here.
1742 bool "PC/104 support" if EXPERT
1744 Expose PC/104 form factor device drivers and options available for
1745 selection and configuration. Enable this option if your target
1746 machine has a PC/104 bus.
1749 bool "Load all symbols for debugging/ksymoops" if EXPERT
1752 Say Y here to let the kernel print out symbolic crash information and
1753 symbolic stack backtraces. This increases the size of the kernel
1754 somewhat, as all symbols have to be loaded into the kernel image.
1756 config KALLSYMS_SELFTEST
1757 bool "Test the basic functions and performance of kallsyms"
1761 Test the basic functions and performance of some interfaces, such as
1762 kallsyms_lookup_name. It also calculates the compression rate of the
1763 kallsyms compression algorithm for the current symbol set.
1765 Start self-test automatically after system startup. Suggest executing
1766 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is
1767 displayed in the last line, indicating that the test is complete.
1770 bool "Include all symbols in kallsyms"
1771 depends on DEBUG_KERNEL && KALLSYMS
1773 Normally kallsyms only contains the symbols of functions for nicer
1774 OOPS messages and backtraces (i.e., symbols from the text and inittext
1775 sections). This is sufficient for most cases. And only if you want to
1776 enable kernel live patching, or other less common use cases (e.g.,
1777 when a debugger is used) all symbols are required (i.e., names of
1778 variables from the data sections, etc).
1780 This option makes sure that all symbols are loaded into the kernel
1781 image (i.e., symbols from all sections) in cost of increased kernel
1782 size (depending on the kernel configuration, it may be 300KiB or
1783 something like this).
1785 Say N unless you really need all symbols, or kernel live patching.
1787 config KALLSYMS_ABSOLUTE_PERCPU
1790 default X86_64 && SMP
1792 config KALLSYMS_BASE_RELATIVE
1797 Instead of emitting them as absolute values in the native word size,
1798 emit the symbol references in the kallsyms table as 32-bit entries,
1799 each containing a relative value in the range [base, base + U32_MAX]
1800 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1801 an absolute value in the range [0, S32_MAX] or a relative value in the
1802 range [base, base + S32_MAX], where base is the lowest relative symbol
1803 address encountered in the image.
1805 On 64-bit builds, this reduces the size of the address table by 50%,
1806 but more importantly, it results in entries whose values are build
1807 time constants, and no relocation pass is required at runtime to fix
1808 up the entries based on the runtime load address of the kernel.
1810 # end of the "standard kernel features (expert users)" menu
1812 config ARCH_HAS_MEMBARRIER_CALLBACKS
1815 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1818 config HAVE_PERF_EVENTS
1821 See tools/perf/design.txt for details.
1823 config GUEST_PERF_EVENTS
1825 depends on HAVE_PERF_EVENTS
1827 config PERF_USE_VMALLOC
1830 See tools/perf/design.txt for details
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
1840 Enable kernel support for various performance events provided
1841 by software and hardware.
1843 Software events are supported either built-in or via the
1844 use of generic tracepoints.
1846 Most modern CPUs support performance events via performance
1847 counter registers. These registers count the number of certain
1848 types of hw events: such as instructions executed, cachemisses
1849 suffered, or branches mis-predicted - without slowing down the
1850 kernel or applications. These registers can also trigger interrupts
1851 when a threshold number of events have passed - and can thus be
1852 used to profile the code that runs on that CPU.
1854 The Linux Performance Event subsystem provides an abstraction of
1855 these software and hardware event capabilities, available via a
1856 system call and used by the "perf" utility in tools/perf/. It
1857 provides per task and per CPU counters, and it provides event
1858 capabilities on top of those.
1862 config DEBUG_PERF_USE_VMALLOC
1864 bool "Debug: use vmalloc to back perf mmap() buffers"
1865 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1866 select PERF_USE_VMALLOC
1868 Use vmalloc memory to back perf mmap() buffers.
1870 Mostly useful for debugging the vmalloc code on platforms
1871 that don't require it.
1877 config SYSTEM_DATA_VERIFICATION
1879 select SYSTEM_TRUSTED_KEYRING
1883 select ASYMMETRIC_KEY_TYPE
1884 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1887 select X509_CERTIFICATE_PARSER
1888 select PKCS7_MESSAGE_PARSER
1890 Provide PKCS#7 message verification using the contents of the system
1891 trusted keyring to provide public keys. This then can be used for
1892 module verification, kexec image verification and firmware blob
1896 bool "Profiling support"
1898 Say Y here to enable the extended profiling support mechanisms used
1903 depends on HAVE_RUST
1904 depends on RUST_IS_AVAILABLE
1905 depends on !CFI_CLANG
1906 depends on !MODVERSIONS
1907 depends on !GCC_PLUGINS
1908 depends on !RANDSTRUCT
1909 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
1911 Enables Rust support in the kernel.
1913 This allows other Rust-related options, like drivers written in Rust,
1916 It is also required to be able to load external kernel modules
1919 See Documentation/rust/ for more information.
1923 config RUSTC_VERSION_TEXT
1926 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n)
1928 config BINDGEN_VERSION_TEXT
1931 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
1934 # Place an empty function call at each tracepoint site. Can be
1935 # dynamically changed for a probe function.
1940 source "kernel/Kconfig.kexec"
1942 endmenu # General setup
1944 source "arch/Kconfig"
1948 default y if PREEMPT_RT
1950 config MODULE_SIG_FORMAT
1952 select SYSTEM_DATA_VERIFICATION
1954 source "kernel/module/Kconfig"
1956 config INIT_ALL_POSSIBLE
1959 Back when each arch used to define their own cpu_online_mask and
1960 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1961 with all 1s, and others with all 0s. When they were centralised,
1962 it was better to provide this option than to break all the archs
1963 and have several arch maintainers pursuing me down dark alleys.
1965 source "block/Kconfig"
1967 config PREEMPT_NOTIFIERS
1977 Build a simple ASN.1 grammar compiler that produces a bytecode output
1978 that can be interpreted by the ASN.1 stream decoder and used to
1979 inform it as to what tags are to be expected in a stream and what
1980 functions to call on what tags.
1982 source "kernel/Kconfig.locks"
1984 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
1987 config ARCH_HAS_PREPARE_SYNC_CORE_CMD
1990 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
1993 # It may be useful for an architecture to override the definitions of the
1994 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
1995 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
1996 # different calling convention for syscalls. They can also override the
1997 # macros for not-implemented syscalls in kernel/sys_ni.c and
1998 # kernel/time/posix-stubs.c. All these overrides need to be available in
1999 # <asm/syscall_wrapper.h>.
2000 config ARCH_HAS_SYSCALL_WRAPPER
projects / linux.git / blob