| # SPDX-License-Identifier: GPL-2.0-only |
| config CC_VERSION_TEXT |
| string |
| default "$(CC_VERSION_TEXT)" |
| help |
| This is used in unclear ways: |
| |
| - Re-run Kconfig when the compiler is updated |
| The 'default' property references the environment variable, |
| CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. |
| When the compiler is updated, Kconfig will be invoked. |
| |
| - Ensure full rebuild when the compiler is updated |
| include/linux/compiler-version.h contains this option in the comment |
| line so fixdep adds include/config/CC_VERSION_TEXT into the |
| auto-generated dependency. When the compiler is updated, syncconfig |
| will touch it and then every file will be rebuilt. |
| |
| config CC_IS_GCC |
| def_bool $(success,test "$(cc-name)" = GCC) |
| |
| config GCC_VERSION |
| int |
| default $(cc-version) if CC_IS_GCC |
| default 0 |
| |
| config CC_IS_CLANG |
| def_bool $(success,test "$(cc-name)" = Clang) |
| |
| config CLANG_VERSION |
| int |
| default $(cc-version) if CC_IS_CLANG |
| default 0 |
| |
| config AS_IS_GNU |
| def_bool $(success,test "$(as-name)" = GNU) |
| |
| config AS_IS_LLVM |
| def_bool $(success,test "$(as-name)" = LLVM) |
| |
| config AS_VERSION |
| int |
| # Use clang version if this is the integrated assembler |
| default CLANG_VERSION if AS_IS_LLVM |
| default $(as-version) |
| |
| config LD_IS_BFD |
| def_bool $(success,test "$(ld-name)" = BFD) |
| |
| config LD_VERSION |
| int |
| default $(ld-version) if LD_IS_BFD |
| default 0 |
| |
| config LD_IS_LLD |
| def_bool $(success,test "$(ld-name)" = LLD) |
| |
| config LLD_VERSION |
| int |
| default $(ld-version) if LD_IS_LLD |
| default 0 |
| |
| config RUST_IS_AVAILABLE |
| def_bool $(success,$(srctree)/scripts/rust_is_available.sh) |
| help |
| This shows whether a suitable Rust toolchain is available (found). |
| |
| Please see Documentation/rust/quick-start.rst for instructions on how |
| to satisfy the build requirements of Rust support. |
| |
| In particular, the Makefile target 'rustavailable' is useful to check |
| why the Rust toolchain is not being detected. |
| |
| config CC_CAN_LINK |
| bool |
| default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT |
| default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) |
| |
| config CC_CAN_LINK_STATIC |
| bool |
| default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT |
| default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) |
| |
| config CC_HAS_ASM_GOTO_OUTPUT |
| 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) |
| |
| config CC_HAS_ASM_GOTO_TIED_OUTPUT |
| depends on CC_HAS_ASM_GOTO_OUTPUT |
| # Detect buggy gcc and clang, fixed in gcc-11 clang-14. |
| 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) |
| |
| config GCC_ASM_GOTO_OUTPUT_WORKAROUND |
| bool |
| depends on CC_IS_GCC && CC_HAS_ASM_GOTO_OUTPUT |
| # Fixed in GCC 14, 13.3, 12.4 and 11.5 |
| # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 |
| default y if GCC_VERSION < 110500 |
| default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400 |
| default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300 |
| |
| config TOOLS_SUPPORT_RELR |
| def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) |
| |
| config CC_HAS_ASM_INLINE |
| def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) |
| |
| config CC_HAS_NO_PROFILE_FN_ATTR |
| def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) |
| |
| config PAHOLE_VERSION |
| int |
| default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) |
| |
| config CONSTRUCTORS |
| bool |
| |
| config IRQ_WORK |
| def_bool y if SMP |
| |
| config BUILDTIME_TABLE_SORT |
| bool |
| |
| config THREAD_INFO_IN_TASK |
| bool |
| help |
| Select this to move thread_info off the stack into task_struct. To |
| make this work, an arch will need to remove all thread_info fields |
| except flags and fix any runtime bugs. |
| |
| One subtle change that will be needed is to use try_get_task_stack() |
| and put_task_stack() in save_thread_stack_tsk() and get_wchan(). |
| |
| menu "General setup" |
| |
| config BROKEN |
| bool |
| |
| config BROKEN_ON_SMP |
| bool |
| depends on BROKEN || !SMP |
| default y |
| |
| config INIT_ENV_ARG_LIMIT |
| int |
| default 32 if !UML |
| default 128 if UML |
| help |
| Maximum of each of the number of arguments and environment |
| variables passed to init from the kernel command line. |
| |
| config COMPILE_TEST |
| bool "Compile also drivers which will not load" |
| depends on HAS_IOMEM |
| help |
| Some drivers can be compiled on a different platform than they are |
| intended to be run on. Despite they cannot be loaded there (or even |
| when they load they cannot be used due to missing HW support), |
| developers still, opposing to distributors, might want to build such |
| drivers to compile-test them. |
| |
| If you are a developer and want to build everything available, say Y |
| here. If you are a user/distributor, say N here to exclude useless |
| drivers to be distributed. |
| |
| config WERROR |
| bool "Compile the kernel with warnings as errors" |
| default COMPILE_TEST |
| help |
| A kernel build should not cause any compiler warnings, and this |
| enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags |
| to enforce that rule by default. Certain warnings from other tools |
| such as the linker may be upgraded to errors with this option as |
| well. |
| |
| However, if you have a new (or very old) compiler or linker with odd |
| and unusual warnings, or you have some architecture with problems, |
| you may need to disable this config option in order to |
| successfully build the kernel. |
| |
| If in doubt, say Y. |
| |
| config UAPI_HEADER_TEST |
| bool "Compile test UAPI headers" |
| depends on HEADERS_INSTALL && CC_CAN_LINK |
| help |
| Compile test headers exported to user-space to ensure they are |
| self-contained, i.e. compilable as standalone units. |
| |
| If you are a developer or tester and want to ensure the exported |
| headers are self-contained, say Y here. Otherwise, choose N. |
| |
| config LOCALVERSION |
| string "Local version - append to kernel release" |
| help |
| Append an extra string to the end of your kernel version. |
| This will show up when you type uname, for example. |
| The string you set here will be appended after the contents of |
| any files with a filename matching localversion* in your |
| object and source tree, in that order. Your total string can |
| be a maximum of 64 characters. |
| |
| config LOCALVERSION_AUTO |
| bool "Automatically append version information to the version string" |
| default y |
| depends on !COMPILE_TEST |
| help |
| This will try to automatically determine if the current tree is a |
| release tree by looking for git tags that belong to the current |
| top of tree revision. |
| |
| A string of the format -gxxxxxxxx will be added to the localversion |
| if a git-based tree is found. The string generated by this will be |
| appended after any matching localversion* files, and after the value |
| set in CONFIG_LOCALVERSION. |
| |
| (The actual string used here is the first 12 characters produced |
| by running the command: |
| |
| $ git rev-parse --verify HEAD |
| |
| which is done within the script "scripts/setlocalversion".) |
| |
| config BUILD_SALT |
| string "Build ID Salt" |
| default "" |
| help |
| The build ID is used to link binaries and their debug info. Setting |
| this option will use the value in the calculation of the build id. |
| This is mostly useful for distributions which want to ensure the |
| build is unique between builds. It's safe to leave the default. |
| |
| config HAVE_KERNEL_GZIP |
| bool |
| |
| config HAVE_KERNEL_BZIP2 |
| bool |
| |
| config HAVE_KERNEL_LZMA |
| bool |
| |
| config HAVE_KERNEL_XZ |
| bool |
| |
| config HAVE_KERNEL_LZO |
| bool |
| |
| config HAVE_KERNEL_LZ4 |
| bool |
| |
| config HAVE_KERNEL_ZSTD |
| bool |
| |
| config HAVE_KERNEL_UNCOMPRESSED |
| bool |
| |
| choice |
| prompt "Kernel compression mode" |
| default KERNEL_GZIP |
| 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 |
| help |
| The linux kernel is a kind of self-extracting executable. |
| Several compression algorithms are available, which differ |
| in efficiency, compression and decompression speed. |
| Compression speed is only relevant when building a kernel. |
| Decompression speed is relevant at each boot. |
| |
| If you have any problems with bzip2 or lzma compressed |
| kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older |
| version of this functionality (bzip2 only), for 2.4, was |
| supplied by Christian Ludwig) |
| |
| High compression options are mostly useful for users, who |
| are low on disk space (embedded systems), but for whom ram |
| size matters less. |
| |
| If in doubt, select 'gzip' |
| |
| config KERNEL_GZIP |
| bool "Gzip" |
| depends on HAVE_KERNEL_GZIP |
| help |
| The old and tried gzip compression. It provides a good balance |
| between compression ratio and decompression speed. |
| |
| config KERNEL_BZIP2 |
| bool "Bzip2" |
| depends on HAVE_KERNEL_BZIP2 |
| help |
| Its compression ratio and speed is intermediate. |
| Decompression speed is slowest among the choices. The kernel |
| size is about 10% smaller with bzip2, in comparison to gzip. |
| Bzip2 uses a large amount of memory. For modern kernels you |
| will need at least 8MB RAM or more for booting. |
| |
| config KERNEL_LZMA |
| bool "LZMA" |
| depends on HAVE_KERNEL_LZMA |
| help |
| This compression algorithm's ratio is best. Decompression speed |
| is between gzip and bzip2. Compression is slowest. |
| The kernel size is about 33% smaller with LZMA in comparison to gzip. |
| |
| config KERNEL_XZ |
| bool "XZ" |
| depends on HAVE_KERNEL_XZ |
| help |
| XZ uses the LZMA2 algorithm and instruction set specific |
| BCJ filters which can improve compression ratio of executable |
| code. The size of the kernel is about 30% smaller with XZ in |
| comparison to gzip. On architectures for which there is a BCJ |
| filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ |
| will create a few percent smaller kernel than plain LZMA. |
| |
| The speed is about the same as with LZMA: The decompression |
| speed of XZ is better than that of bzip2 but worse than gzip |
| and LZO. Compression is slow. |
| |
| config KERNEL_LZO |
| bool "LZO" |
| depends on HAVE_KERNEL_LZO |
| help |
| Its compression ratio is the poorest among the choices. The kernel |
| size is about 10% bigger than gzip; however its speed |
| (both compression and decompression) is the fastest. |
| |
| config KERNEL_LZ4 |
| bool "LZ4" |
| depends on HAVE_KERNEL_LZ4 |
| help |
| LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. |
| A preliminary version of LZ4 de/compression tool is available at |
| <https://code.google.com/p/lz4/>. |
| |
| Its compression ratio is worse than LZO. The size of the kernel |
| is about 8% bigger than LZO. But the decompression speed is |
| faster than LZO. |
| |
| config KERNEL_ZSTD |
| bool "ZSTD" |
| depends on HAVE_KERNEL_ZSTD |
| help |
| ZSTD is a compression algorithm targeting intermediate compression |
| with fast decompression speed. It will compress better than GZIP and |
| decompress around the same speed as LZO, but slower than LZ4. You |
| will need at least 192 KB RAM or more for booting. The zstd command |
| line tool is required for compression. |
| |
| config KERNEL_UNCOMPRESSED |
| bool "None" |
| depends on HAVE_KERNEL_UNCOMPRESSED |
| help |
| Produce uncompressed kernel image. This option is usually not what |
| you want. It is useful for debugging the kernel in slow simulation |
| environments, where decompressing and moving the kernel is awfully |
| slow. This option allows early boot code to skip the decompressor |
| and jump right at uncompressed kernel image. |
| |
| endchoice |
| |
| config DEFAULT_INIT |
| string "Default init path" |
| default "" |
| help |
| This option determines the default init for the system if no init= |
| option is passed on the kernel command line. If the requested path is |
| not present, we will still then move on to attempting further |
| locations (e.g. /sbin/init, etc). If this is empty, we will just use |
| the fallback list when init= is not passed. |
| |
| config DEFAULT_HOSTNAME |
| string "Default hostname" |
| default "(none)" |
| help |
| This option determines the default system hostname before userspace |
| calls sethostname(2). The kernel traditionally uses "(none)" here, |
| but you may wish to use a different default here to make a minimal |
| system more usable with less configuration. |
| |
| config SYSVIPC |
| bool "System V IPC" |
| help |
| Inter Process Communication is a suite of library functions and |
| system calls which let processes (running programs) synchronize and |
| exchange information. It is generally considered to be a good thing, |
| and some programs won't run unless you say Y here. In particular, if |
| you want to run the DOS emulator dosemu under Linux (read the |
| DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), |
| you'll need to say Y here. |
| |
| You can find documentation about IPC with "info ipc" and also in |
| section 6.4 of the Linux Programmer's Guide, available from |
| <http://www.tldp.org/guides.html>. |
| |
| config SYSVIPC_SYSCTL |
| bool |
| depends on SYSVIPC |
| depends on SYSCTL |
| default y |
| |
| config SYSVIPC_COMPAT |
| def_bool y |
| depends on COMPAT && SYSVIPC |
| |
| config POSIX_MQUEUE |
| bool "POSIX Message Queues" |
| depends on NET |
| help |
| POSIX variant of message queues is a part of IPC. In POSIX message |
| queues every message has a priority which decides about succession |
| of receiving it by a process. If you want to compile and run |
| programs written e.g. for Solaris with use of its POSIX message |
| queues (functions mq_*) say Y here. |
| |
| POSIX message queues are visible as a filesystem called 'mqueue' |
| and can be mounted somewhere if you want to do filesystem |
| operations on message queues. |
| |
| If unsure, say Y. |
| |
| config POSIX_MQUEUE_SYSCTL |
| bool |
| depends on POSIX_MQUEUE |
| depends on SYSCTL |
| default y |
| |
| config WATCH_QUEUE |
| bool "General notification queue" |
| default n |
| help |
| |
| This is a general notification queue for the kernel to pass events to |
| userspace by splicing them into pipes. It can be used in conjunction |
| with watches for key/keyring change notifications and device |
| notifications. |
| |
| See Documentation/core-api/watch_queue.rst |
| |
| config CROSS_MEMORY_ATTACH |
| bool "Enable process_vm_readv/writev syscalls" |
| depends on MMU |
| default y |
| help |
| Enabling this option adds the system calls process_vm_readv and |
| process_vm_writev which allow a process with the correct privileges |
| to directly read from or write to another process' address space. |
| See the man page for more details. |
| |
| config USELIB |
| bool "uselib syscall (for libc5 and earlier)" |
| default ALPHA || M68K || SPARC |
| help |
| This option enables the uselib syscall, a system call used in the |
| dynamic linker from libc5 and earlier. glibc does not use this |
| system call. If you intend to run programs built on libc5 or |
| earlier, you may need to enable this syscall. Current systems |
| running glibc can safely disable this. |
| |
| config AUDIT |
| bool "Auditing support" |
| depends on NET |
| help |
| Enable auditing infrastructure that can be used with another |
| kernel subsystem, such as SELinux (which requires this for |
| logging of avc messages output). System call auditing is included |
| on architectures which support it. |
| |
| config HAVE_ARCH_AUDITSYSCALL |
| bool |
| |
| config AUDITSYSCALL |
| def_bool y |
| depends on AUDIT && HAVE_ARCH_AUDITSYSCALL |
| select FSNOTIFY |
| |
| source "kernel/irq/Kconfig" |
| source "kernel/time/Kconfig" |
| source "kernel/bpf/Kconfig" |
| source "kernel/Kconfig.preempt" |
| |
| menu "CPU/Task time and stats accounting" |
| |
| config VIRT_CPU_ACCOUNTING |
| bool |
| |
| choice |
| prompt "Cputime accounting" |
| default TICK_CPU_ACCOUNTING |
| |
| # Kind of a stub config for the pure tick based cputime accounting |
| config TICK_CPU_ACCOUNTING |
| bool "Simple tick based cputime accounting" |
| depends on !S390 && !NO_HZ_FULL |
| help |
| This is the basic tick based cputime accounting that maintains |
| statistics about user, system and idle time spent on per jiffies |
| granularity. |
| |
| If unsure, say Y. |
| |
| config VIRT_CPU_ACCOUNTING_NATIVE |
| bool "Deterministic task and CPU time accounting" |
| depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL |
| select VIRT_CPU_ACCOUNTING |
| help |
| Select this option to enable more accurate task and CPU time |
| accounting. This is done by reading a CPU counter on each |
| kernel entry and exit and on transitions within the kernel |
| between system, softirq and hardirq state, so there is a |
| small performance impact. In the case of s390 or IBM POWER > 5, |
| this also enables accounting of stolen time on logically-partitioned |
| systems. |
| |
| config VIRT_CPU_ACCOUNTING_GEN |
| bool "Full dynticks CPU time accounting" |
| depends on HAVE_CONTEXT_TRACKING_USER |
| depends on HAVE_VIRT_CPU_ACCOUNTING_GEN |
| depends on GENERIC_CLOCKEVENTS |
| select VIRT_CPU_ACCOUNTING |
| select CONTEXT_TRACKING_USER |
| help |
| Select this option to enable task and CPU time accounting on full |
| dynticks systems. This accounting is implemented by watching every |
| kernel-user boundaries using the context tracking subsystem. |
| The accounting is thus performed at the expense of some significant |
| overhead. |
| |
| For now this is only useful if you are working on the full |
| dynticks subsystem development. |
| |
| If unsure, say N. |
| |
| endchoice |
| |
| config IRQ_TIME_ACCOUNTING |
| bool "Fine granularity task level IRQ time accounting" |
| depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE |
| help |
| Select this option to enable fine granularity task irq time |
| accounting. This is done by reading a timestamp on each |
| transitions between softirq and hardirq state, so there can be a |
| small performance impact. |
| |
| If in doubt, say N here. |
| |
| config HAVE_SCHED_AVG_IRQ |
| def_bool y |
| depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING |
| depends on SMP |
| |
| config SCHED_THERMAL_PRESSURE |
| bool |
| default y if ARM && ARM_CPU_TOPOLOGY |
| default y if ARM64 |
| depends on SMP |
| depends on CPU_FREQ_THERMAL |
| help |
| Select this option to enable thermal pressure accounting in the |
| scheduler. Thermal pressure is the value conveyed to the scheduler |
| that reflects the reduction in CPU compute capacity resulted from |
| thermal throttling. Thermal throttling occurs when the performance of |
| a CPU is capped due to high operating temperatures. |
| |
| If selected, the scheduler will be able to balance tasks accordingly, |
| i.e. put less load on throttled CPUs than on non/less throttled ones. |
| |
| This requires the architecture to implement |
| arch_update_thermal_pressure() and arch_scale_thermal_pressure(). |
| |
| config BSD_PROCESS_ACCT |
| bool "BSD Process Accounting" |
| depends on MULTIUSER |
| help |
| If you say Y here, a user level program will be able to instruct the |
| kernel (via a special system call) to write process accounting |
| information to a file: whenever a process exits, information about |
| that process will be appended to the file by the kernel. The |
| information includes things such as creation time, owning user, |
| command name, memory usage, controlling terminal etc. (the complete |
| list is in the struct acct in <file:include/linux/acct.h>). It is |
| up to the user level program to do useful things with this |
| information. This is generally a good idea, so say Y. |
| |
| config BSD_PROCESS_ACCT_V3 |
| bool "BSD Process Accounting version 3 file format" |
| depends on BSD_PROCESS_ACCT |
| default n |
| help |
| If you say Y here, the process accounting information is written |
| in a new file format that also logs the process IDs of each |
| process and its parent. Note that this file format is incompatible |
| with previous v0/v1/v2 file formats, so you will need updated tools |
| for processing it. A preliminary version of these tools is available |
| at <http://www.gnu.org/software/acct/>. |
| |
| config TASKSTATS |
| bool "Export task/process statistics through netlink" |
| depends on NET |
| depends on MULTIUSER |
| default n |
| help |
| Export selected statistics for tasks/processes through the |
| generic netlink interface. Unlike BSD process accounting, the |
| statistics are available during the lifetime of tasks/processes as |
| responses to commands. Like BSD accounting, they are sent to user |
| space on task exit. |
| |
| Say N if unsure. |
| |
| config TASK_DELAY_ACCT |
| bool "Enable per-task delay accounting" |
| depends on TASKSTATS |
| select SCHED_INFO |
| help |
| Collect information on time spent by a task waiting for system |
| resources like cpu, synchronous block I/O completion and swapping |
| in pages. Such statistics can help in setting a task's priorities |
| relative to other tasks for cpu, io, rss limits etc. |
| |
| Say N if unsure. |
| |
| config TASK_XACCT |
| bool "Enable extended accounting over taskstats" |
| depends on TASKSTATS |
| help |
| Collect extended task accounting data and send the data |
| to userland for processing over the taskstats interface. |
| |
| Say N if unsure. |
| |
| config TASK_IO_ACCOUNTING |
| bool "Enable per-task storage I/O accounting" |
| depends on TASK_XACCT |
| help |
| Collect information on the number of bytes of storage I/O which this |
| task has caused. |
| |
| Say N if unsure. |
| |
| config PSI |
| bool "Pressure stall information tracking" |
| select KERNFS |
| help |
| Collect metrics that indicate how overcommitted the CPU, memory, |
| and IO capacity are in the system. |
| |
| If you say Y here, the kernel will create /proc/pressure/ with the |
| pressure statistics files cpu, memory, and io. These will indicate |
| the share of walltime in which some or all tasks in the system are |
| delayed due to contention of the respective resource. |
| |
| In kernels with cgroup support, cgroups (cgroup2 only) will |
| have cpu.pressure, memory.pressure, and io.pressure files, |
| which aggregate pressure stalls for the grouped tasks only. |
| |
| For more details see Documentation/accounting/psi.rst. |
| |
| Say N if unsure. |
| |
| config PSI_DEFAULT_DISABLED |
| bool "Require boot parameter to enable pressure stall information tracking" |
| default n |
| depends on PSI |
| help |
| If set, pressure stall information tracking will be disabled |
| per default but can be enabled through passing psi=1 on the |
| kernel commandline during boot. |
| |
| This feature adds some code to the task wakeup and sleep |
| paths of the scheduler. The overhead is too low to affect |
| common scheduling-intense workloads in practice (such as |
| webservers, memcache), but it does show up in artificial |
| scheduler stress tests, such as hackbench. |
| |
| If you are paranoid and not sure what the kernel will be |
| used for, say Y. |
| |
| Say N if unsure. |
| |
| endmenu # "CPU/Task time and stats accounting" |
| |
| config CPU_ISOLATION |
| bool "CPU isolation" |
| depends on SMP || COMPILE_TEST |
| default y |
| help |
| Make sure that CPUs running critical tasks are not disturbed by |
| any source of "noise" such as unbound workqueues, timers, kthreads... |
| Unbound jobs get offloaded to housekeeping CPUs. This is driven by |
| the "isolcpus=" boot parameter. |
| |
| Say Y if unsure. |
| |
| source "kernel/rcu/Kconfig" |
| |
| config IKCONFIG |
| tristate "Kernel .config support" |
| help |
| This option enables the complete Linux kernel ".config" file |
| contents to be saved in the kernel. It provides documentation |
| of which kernel options are used in a running kernel or in an |
| on-disk kernel. This information can be extracted from the kernel |
| image file with the script scripts/extract-ikconfig and used as |
| input to rebuild the current kernel or to build another kernel. |
| It can also be extracted from a running kernel by reading |
| /proc/config.gz if enabled (below). |
| |
| config IKCONFIG_PROC |
| bool "Enable access to .config through /proc/config.gz" |
| depends on IKCONFIG && PROC_FS |
| help |
| This option enables access to the kernel configuration file |
| through /proc/config.gz. |
| |
| config IKHEADERS |
| tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" |
| depends on SYSFS |
| help |
| This option enables access to the in-kernel headers that are generated during |
| the build process. These can be used to build eBPF tracing programs, |
| or similar programs. If you build the headers as a module, a module called |
| kheaders.ko is built which can be loaded on-demand to get access to headers. |
| |
| config LOG_BUF_SHIFT |
| int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" |
| range 12 25 |
| default 17 |
| depends on PRINTK |
| help |
| Select the minimal kernel log buffer size as a power of 2. |
| The final size is affected by LOG_CPU_MAX_BUF_SHIFT config |
| parameter, see below. Any higher size also might be forced |
| by "log_buf_len" boot parameter. |
| |
| Examples: |
| 17 => 128 KB |
| 16 => 64 KB |
| 15 => 32 KB |
| 14 => 16 KB |
| 13 => 8 KB |
| 12 => 4 KB |
| |
| config LOG_CPU_MAX_BUF_SHIFT |
| int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" |
| depends on SMP |
| range 0 21 |
| default 0 if BASE_SMALL != 0 |
| default 12 |
| depends on PRINTK |
| help |
| This option allows to increase the default ring buffer size |
| according to the number of CPUs. The value defines the contribution |
| of each CPU as a power of 2. The used space is typically only few |
| lines however it might be much more when problems are reported, |
| e.g. backtraces. |
| |
| The increased size means that a new buffer has to be allocated and |
| the original static one is unused. It makes sense only on systems |
| with more CPUs. Therefore this value is used only when the sum of |
| contributions is greater than the half of the default kernel ring |
| buffer as defined by LOG_BUF_SHIFT. The default values are set |
| so that more than 16 CPUs are needed to trigger the allocation. |
| |
| Also this option is ignored when "log_buf_len" kernel parameter is |
| used as it forces an exact (power of two) size of the ring buffer. |
| |
| The number of possible CPUs is used for this computation ignoring |
| hotplugging making the computation optimal for the worst case |
| scenario while allowing a simple algorithm to be used from bootup. |
| |
| Examples shift values and their meaning: |
| 17 => 128 KB for each CPU |
| 16 => 64 KB for each CPU |
| 15 => 32 KB for each CPU |
| 14 => 16 KB for each CPU |
| 13 => 8 KB for each CPU |
| 12 => 4 KB for each CPU |
| |
| config PRINTK_INDEX |
| bool "Printk indexing debugfs interface" |
| depends on PRINTK && DEBUG_FS |
| help |
| Add support for indexing of all printk formats known at compile time |
| at <debugfs>/printk/index/<module>. |
| |
| This can be used as part of maintaining daemons which monitor |
| /dev/kmsg, as it permits auditing the printk formats present in a |
| kernel, allowing detection of cases where monitored printks are |
| changed or no longer present. |
| |
| There is no additional runtime cost to printk with this enabled. |
| |
| # |
| # Architectures with an unreliable sched_clock() should select this: |
| # |
| config HAVE_UNSTABLE_SCHED_CLOCK |
| bool |
| |
| config GENERIC_SCHED_CLOCK |
| bool |
| |
| menu "Scheduler features" |
| |
| config UCLAMP_TASK |
| bool "Enable utilization clamping for RT/FAIR tasks" |
| depends on CPU_FREQ_GOV_SCHEDUTIL |
| help |
| This feature enables the scheduler to track the clamped utilization |
| of each CPU based on RUNNABLE tasks scheduled on that CPU. |
| |
| With this option, the user can specify the min and max CPU |
| utilization allowed for RUNNABLE tasks. The max utilization defines |
| the maximum frequency a task should use while the min utilization |
| defines the minimum frequency it should use. |
| |
| Both min and max utilization clamp values are hints to the scheduler, |
| aiming at improving its frequency selection policy, but they do not |
| enforce or grant any specific bandwidth for tasks. |
| |
| If in doubt, say N. |
| |
| config UCLAMP_BUCKETS_COUNT |
| int "Number of supported utilization clamp buckets" |
| range 5 20 |
| default 5 |
| depends on UCLAMP_TASK |
| help |
| Defines the number of clamp buckets to use. The range of each bucket |
| will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the |
| number of clamp buckets the finer their granularity and the higher |
| the precision of clamping aggregation and tracking at run-time. |
| |
| For example, with the minimum configuration value we will have 5 |
| clamp buckets tracking 20% utilization each. A 25% boosted tasks will |
| be refcounted in the [20..39]% bucket and will set the bucket clamp |
| effective value to 25%. |
| If a second 30% boosted task should be co-scheduled on the same CPU, |
| that task will be refcounted in the same bucket of the first task and |
| it will boost the bucket clamp effective value to 30%. |
| The clamp effective value of a bucket is reset to its nominal value |
| (20% in the example above) when there are no more tasks refcounted in |
| that bucket. |
| |
| An additional boost/capping margin can be added to some tasks. In the |
| example above the 25% task will be boosted to 30% until it exits the |
| CPU. If that should be considered not acceptable on certain systems, |
| it's always possible to reduce the margin by increasing the number of |
| clamp buckets to trade off used memory for run-time tracking |
| precision. |
| |
| If in doubt, use the default value. |
| |
| endmenu |
| |
| # |
| # For architectures that want to enable the support for NUMA-affine scheduler |
| # balancing logic: |
| # |
| config ARCH_SUPPORTS_NUMA_BALANCING |
| bool |
| |
| # |
| # For architectures that prefer to flush all TLBs after a number of pages |
| # are unmapped instead of sending one IPI per page to flush. The architecture |
| # must provide guarantees on what happens if a clean TLB cache entry is |
| # written after the unmap. Details are in mm/rmap.c near the check for |
| # should_defer_flush. The architecture should also consider if the full flush |
| # and the refill costs are offset by the savings of sending fewer IPIs. |
| config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH |
| bool |
| |
| config CC_HAS_INT128 |
| def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT |
| |
| config CC_IMPLICIT_FALLTHROUGH |
| string |
| default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) |
| default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) |
| |
| # Currently, disable gcc-10+ array-bounds globally. |
| # It's still broken in gcc-13, so no upper bound yet. |
| config GCC10_NO_ARRAY_BOUNDS |
| def_bool y |
| |
| config CC_NO_ARRAY_BOUNDS |
| bool |
| default y if CC_IS_GCC && GCC_VERSION >= 100000 && GCC10_NO_ARRAY_BOUNDS |
| |
| # Currently, disable -Wstringop-overflow for GCC globally. |
| config GCC_NO_STRINGOP_OVERFLOW |
| def_bool y |
| |
| config CC_NO_STRINGOP_OVERFLOW |
| bool |
| default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW |
| |
| config CC_STRINGOP_OVERFLOW |
| bool |
| default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW |
| |
| # |
| # For architectures that know their GCC __int128 support is sound |
| # |
| config ARCH_SUPPORTS_INT128 |
| bool |
| |
| # For architectures that (ab)use NUMA to represent different memory regions |
| # all cpu-local but of different latencies, such as SuperH. |
| # |
| config ARCH_WANT_NUMA_VARIABLE_LOCALITY |
| bool |
| |
| config NUMA_BALANCING |
| bool "Memory placement aware NUMA scheduler" |
| depends on ARCH_SUPPORTS_NUMA_BALANCING |
| depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY |
| depends on SMP && NUMA && MIGRATION && !PREEMPT_RT |
| help |
| This option adds support for automatic NUMA aware memory/task placement. |
| The mechanism is quite primitive and is based on migrating memory when |
| it has references to the node the task is running on. |
| |
| This system will be inactive on UMA systems. |
| |
| config NUMA_BALANCING_DEFAULT_ENABLED |
| bool "Automatically enable NUMA aware memory/task placement" |
| default y |
| depends on NUMA_BALANCING |
| help |
| If set, automatic NUMA balancing will be enabled if running on a NUMA |
| machine. |
| |
| menuconfig CGROUPS |
| bool "Control Group support" |
| select KERNFS |
| help |
| This option adds support for grouping sets of processes together, for |
| use with process control subsystems such as Cpusets, CFS, memory |
| controls or device isolation. |
| See |
| - Documentation/scheduler/sched-design-CFS.rst (CFS) |
| - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation |
| and resource control) |
| |
| Say N if unsure. |
| |
| if CGROUPS |
| |
| config PAGE_COUNTER |
| bool |
| |
| config CGROUP_FAVOR_DYNMODS |
| bool "Favor dynamic modification latency reduction by default" |
| help |
| This option enables the "favordynmods" mount option by default |
| which reduces the latencies of dynamic cgroup modifications such |
| as task migrations and controller on/offs at the cost of making |
| hot path operations such as forks and exits more expensive. |
| |
| Say N if unsure. |
| |
| config MEMCG |
| bool "Memory controller" |
| select PAGE_COUNTER |
| select EVENTFD |
| help |
| Provides control over the memory footprint of tasks in a cgroup. |
| |
| config MEMCG_KMEM |
| bool |
| depends on MEMCG |
| default y |
| |
| config BLK_CGROUP |
| bool "IO controller" |
| depends on BLOCK |
| default n |
| help |
| Generic block IO controller cgroup interface. This is the common |
| cgroup interface which should be used by various IO controlling |
| policies. |
| |
| Currently, CFQ IO scheduler uses it to recognize task groups and |
| control disk bandwidth allocation (proportional time slice allocation) |
| to such task groups. It is also used by bio throttling logic in |
| block layer to implement upper limit in IO rates on a device. |
| |
| This option only enables generic Block IO controller infrastructure. |
| One needs to also enable actual IO controlling logic/policy. For |
| enabling proportional weight division of disk bandwidth in CFQ, set |
| CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set |
| CONFIG_BLK_DEV_THROTTLING=y. |
| |
| See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. |
| |
| config CGROUP_WRITEBACK |
| bool |
| depends on MEMCG && BLK_CGROUP |
| default y |
| |
| menuconfig CGROUP_SCHED |
| bool "CPU controller" |
| default n |
| help |
| This feature lets CPU scheduler recognize task groups and control CPU |
| bandwidth allocation to such task groups. It uses cgroups to group |
| tasks. |
| |
| if CGROUP_SCHED |
| config FAIR_GROUP_SCHED |
| bool "Group scheduling for SCHED_OTHER" |
| depends on CGROUP_SCHED |
| default CGROUP_SCHED |
| |
| config CFS_BANDWIDTH |
| bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" |
| depends on FAIR_GROUP_SCHED |
| default n |
| help |
| This option allows users to define CPU bandwidth rates (limits) for |
| tasks running within the fair group scheduler. Groups with no limit |
| set are considered to be unconstrained and will run with no |
| restriction. |
| See Documentation/scheduler/sched-bwc.rst for more information. |
| |
| config RT_GROUP_SCHED |
| bool "Group scheduling for SCHED_RR/FIFO" |
| depends on CGROUP_SCHED |
| default n |
| help |
| This feature lets you explicitly allocate real CPU bandwidth |
| to task groups. If enabled, it will also make it impossible to |
| schedule realtime tasks for non-root users until you allocate |
| realtime bandwidth for them. |
| See Documentation/scheduler/sched-rt-group.rst for more information. |
| |
| endif #CGROUP_SCHED |
| |
| config SCHED_MM_CID |
| def_bool y |
| depends on SMP && RSEQ |
| |
| config UCLAMP_TASK_GROUP |
| bool "Utilization clamping per group of tasks" |
| depends on CGROUP_SCHED |
| depends on UCLAMP_TASK |
| default n |
| help |
| This feature enables the scheduler to track the clamped utilization |
| of each CPU based on RUNNABLE tasks currently scheduled on that CPU. |
| |
| When this option is enabled, the user can specify a min and max |
| CPU bandwidth which is allowed for each single task in a group. |
| The max bandwidth allows to clamp the maximum frequency a task |
| can use, while the min bandwidth allows to define a minimum |
| frequency a task will always use. |
| |
| When task group based utilization clamping is enabled, an eventually |
| specified task-specific clamp value is constrained by the cgroup |
| specified clamp value. Both minimum and maximum task clamping cannot |
| be bigger than the corresponding clamping defined at task group level. |
| |
| If in doubt, say N. |
| |
| config CGROUP_PIDS |
| bool "PIDs controller" |
| help |
| Provides enforcement of process number limits in the scope of a |
| cgroup. Any attempt to fork more processes than is allowed in the |
| cgroup will fail. PIDs are fundamentally a global resource because it |
| is fairly trivial to reach PID exhaustion before you reach even a |
| conservative kmemcg limit. As a result, it is possible to grind a |
| system to halt without being limited by other cgroup policies. The |
| PIDs controller is designed to stop this from happening. |
| |
| It should be noted that organisational operations (such as attaching |
| to a cgroup hierarchy) will *not* be blocked by the PIDs controller, |
| since the PIDs limit only affects a process's ability to fork, not to |
| attach to a cgroup. |
| |
| config CGROUP_RDMA |
| bool "RDMA controller" |
| help |
| Provides enforcement of RDMA resources defined by IB stack. |
| It is fairly easy for consumers to exhaust RDMA resources, which |
| can result into resource unavailability to other consumers. |
| RDMA controller is designed to stop this from happening. |
| Attaching processes with active RDMA resources to the cgroup |
| hierarchy is allowed even if can cross the hierarchy's limit. |
| |
| config CGROUP_FREEZER |
| bool "Freezer controller" |
| help |
| Provides a way to freeze and unfreeze all tasks in a |
| cgroup. |
| |
| This option affects the ORIGINAL cgroup interface. The cgroup2 memory |
| controller includes important in-kernel memory consumers per default. |
| |
| If you're using cgroup2, say N. |
| |
| config CGROUP_HUGETLB |
| bool "HugeTLB controller" |
| depends on HUGETLB_PAGE |
| select PAGE_COUNTER |
| default n |
| help |
| Provides a cgroup controller for HugeTLB pages. |
| When you enable this, you can put a per cgroup limit on HugeTLB usage. |
| The limit is enforced during page fault. Since HugeTLB doesn't |
| support page reclaim, enforcing the limit at page fault time implies |
| that, the application will get SIGBUS signal if it tries to access |
| HugeTLB pages beyond its limit. This requires the application to know |
| beforehand how much HugeTLB pages it would require for its use. The |
| control group is tracked in the third page lru pointer. This means |
| that we cannot use the controller with huge page less than 3 pages. |
| |
| config CPUSETS |
| bool "Cpuset controller" |
| depends on SMP |
| help |
| This option will let you create and manage CPUSETs which |
| allow dynamically partitioning a system into sets of CPUs and |
| Memory Nodes and assigning tasks to run only within those sets. |
| This is primarily useful on large SMP or NUMA systems. |
| |
| Say N if unsure. |
| |
| config PROC_PID_CPUSET |
| bool "Include legacy /proc/<pid>/cpuset file" |
| depends on CPUSETS |
| default y |
| |
| config CGROUP_DEVICE |
| bool "Device controller" |
| help |
| Provides a cgroup controller implementing whitelists for |
| devices which a process in the cgroup can mknod or open. |
| |
| config CGROUP_CPUACCT |
| bool "Simple CPU accounting controller" |
| help |
| Provides a simple controller for monitoring the |
| total CPU consumed by the tasks in a cgroup. |
| |
| config CGROUP_PERF |
| bool "Perf controller" |
| depends on PERF_EVENTS |
| help |
| This option extends the perf per-cpu mode to restrict monitoring |
| to threads which belong to the cgroup specified and run on the |
| designated cpu. Or this can be used to have cgroup ID in samples |
| so that it can monitor performance events among cgroups. |
| |
| Say N if unsure. |
| |
| config CGROUP_BPF |
| bool "Support for eBPF programs attached to cgroups" |
| depends on BPF_SYSCALL |
| select SOCK_CGROUP_DATA |
| help |
| Allow attaching eBPF programs to a cgroup using the bpf(2) |
| syscall command BPF_PROG_ATTACH. |
| |
| In which context these programs are accessed depends on the type |
| of attachment. For instance, programs that are attached using |
| BPF_CGROUP_INET_INGRESS will be executed on the ingress path of |
| inet sockets. |
| |
| config CGROUP_MISC |
| bool "Misc resource controller" |
| default n |
| help |
| Provides a controller for miscellaneous resources on a host. |
| |
| Miscellaneous scalar resources are the resources on the host system |
| which cannot be abstracted like the other cgroups. This controller |
| tracks and limits the miscellaneous resources used by a process |
| attached to a cgroup hierarchy. |
| |
| For more information, please check misc cgroup section in |
| /Documentation/admin-guide/cgroup-v2.rst. |
| |
| config CGROUP_DEBUG |
| bool "Debug controller" |
| default n |
| depends on DEBUG_KERNEL |
| help |
| This option enables a simple controller that exports |
| debugging information about the cgroups framework. This |
| controller is for control cgroup debugging only. Its |
| interfaces are not stable. |
| |
| Say N. |
| |
| config SOCK_CGROUP_DATA |
| bool |
| default n |
| |
| endif # CGROUPS |
| |
| menuconfig NAMESPACES |
| bool "Namespaces support" if EXPERT |
| depends on MULTIUSER |
| default !EXPERT |
| help |
| Provides the way to make tasks work with different objects using |
| the same id. For example same IPC id may refer to different objects |
| or same user id or pid may refer to different tasks when used in |
| different namespaces. |
| |
| if NAMESPACES |
| |
| config UTS_NS |
| bool "UTS namespace" |
| default y |
| help |
| In this namespace tasks see different info provided with the |
| uname() system call |
| |
| config TIME_NS |
| bool "TIME namespace" |
| depends on GENERIC_VDSO_TIME_NS |
| default y |
| help |
| In this namespace boottime and monotonic clocks can be set. |
| The time will keep going with the same pace. |
| |
| config IPC_NS |
| bool "IPC namespace" |
| depends on (SYSVIPC || POSIX_MQUEUE) |
| default y |
| help |
| In this namespace tasks work with IPC ids which correspond to |
| different IPC objects in different namespaces. |
| |
| config USER_NS |
| bool "User namespace" |
| default n |
| help |
| This allows containers, i.e. vservers, to use user namespaces |
| to provide different user info for different servers. |
| |
| When user namespaces are enabled in the kernel it is |
| recommended that the MEMCG option also be enabled and that |
| user-space use the memory control groups to limit the amount |
| of memory a memory unprivileged users can use. |
| |
| If unsure, say N. |
| |
| config PID_NS |
| bool "PID Namespaces" |
| default y |
| help |
| Support process id namespaces. This allows having multiple |
| processes with the same pid as long as they are in different |
| pid namespaces. This is a building block of containers. |
| |
| config NET_NS |
| bool "Network namespace" |
| depends on NET |
| default y |
| help |
| Allow user space to create what appear to be multiple instances |
| of the network stack. |
| |
| endif # NAMESPACES |
| |
| config CHECKPOINT_RESTORE |
| bool "Checkpoint/restore support" |
| depends on PROC_FS |
| select PROC_CHILDREN |
| select KCMP |
| default n |
| help |
| Enables additional kernel features in a sake of checkpoint/restore. |
| In particular it adds auxiliary prctl codes to setup process text, |
| data and heap segment sizes, and a few additional /proc filesystem |
| entries. |
| |
| If unsure, say N here. |
| |
| config SCHED_AUTOGROUP |
| bool "Automatic process group scheduling" |
| select CGROUPS |
| select CGROUP_SCHED |
| select FAIR_GROUP_SCHED |
| help |
| This option optimizes the scheduler for common desktop workloads by |
| automatically creating and populating task groups. This separation |
| of workloads isolates aggressive CPU burners (like build jobs) from |
| desktop applications. Task group autogeneration is currently based |
| upon task session. |
| |
| config RELAY |
| bool "Kernel->user space relay support (formerly relayfs)" |
| select IRQ_WORK |
| help |
| This option enables support for relay interface support in |
| certain file systems (such as debugfs). |
| It is designed to provide an efficient mechanism for tools and |
| facilities to relay large amounts of data from kernel space to |
| user space. |
| |
| If unsure, say N. |
| |
| config BLK_DEV_INITRD |
| bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" |
| help |
| The initial RAM filesystem is a ramfs which is loaded by the |
| boot loader (loadlin or lilo) and that is mounted as root |
| before the normal boot procedure. It is typically used to |
| load modules needed to mount the "real" root file system, |
| etc. See <file:Documentation/admin-guide/initrd.rst> for details. |
| |
| If RAM disk support (BLK_DEV_RAM) is also included, this |
| also enables initial RAM disk (initrd) support and adds |
| 15 Kbytes (more on some other architectures) to the kernel size. |
| |
| If unsure say Y. |
| |
| if BLK_DEV_INITRD |
| |
| source "usr/Kconfig" |
| |
| endif |
| |
| config BOOT_CONFIG |
| bool "Boot config support" |
| select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED |
| help |
| Extra boot config allows system admin to pass a config file as |
| complemental extension of kernel cmdline when booting. |
| The boot config file must be attached at the end of initramfs |
| with checksum, size and magic word. |
| See <file:Documentation/admin-guide/bootconfig.rst> for details. |
| |
| If unsure, say Y. |
| |
| config BOOT_CONFIG_FORCE |
| bool "Force unconditional bootconfig processing" |
| depends on BOOT_CONFIG |
| default y if BOOT_CONFIG_EMBED |
| help |
| With this Kconfig option set, BOOT_CONFIG processing is carried |
| out even when the "bootconfig" kernel-boot parameter is omitted. |
| In fact, with this Kconfig option set, there is no way to |
| make the kernel ignore the BOOT_CONFIG-supplied kernel-boot |
| parameters. |
| |
| If unsure, say N. |
| |
| config BOOT_CONFIG_EMBED |
| bool "Embed bootconfig file in the kernel" |
| depends on BOOT_CONFIG |
| help |
| Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the |
| kernel. Usually, the bootconfig file is loaded with the initrd |
| image. But if the system doesn't support initrd, this option will |
| help you by embedding a bootconfig file while building the kernel. |
| |
| If unsure, say N. |
| |
| config BOOT_CONFIG_EMBED_FILE |
| string "Embedded bootconfig file path" |
| depends on BOOT_CONFIG_EMBED |
| help |
| Specify a bootconfig file which will be embedded to the kernel. |
| This bootconfig will be used if there is no initrd or no other |
| bootconfig in the initrd. |
| |
| config INITRAMFS_PRESERVE_MTIME |
| bool "Preserve cpio archive mtimes in initramfs" |
| default y |
| help |
| Each entry in an initramfs cpio archive carries an mtime value. When |
| enabled, extracted cpio items take this mtime, with directory mtime |
| setting deferred until after creation of any child entries. |
| |
| If unsure, say Y. |
| |
| choice |
| prompt "Compiler optimization level" |
| default CC_OPTIMIZE_FOR_PERFORMANCE |
| |
| config CC_OPTIMIZE_FOR_PERFORMANCE |
| bool "Optimize for performance (-O2)" |
| help |
| This is the default optimization level for the kernel, building |
| with the "-O2" compiler flag for best performance and most |
| helpful compile-time warnings. |
| |
| config CC_OPTIMIZE_FOR_SIZE |
| bool "Optimize for size (-Os)" |
| help |
| Choosing this option will pass "-Os" to your compiler resulting |
| in a smaller kernel. |
| |
| endchoice |
| |
| config HAVE_LD_DEAD_CODE_DATA_ELIMINATION |
| bool |
| help |
| This requires that the arch annotates or otherwise protects |
| its external entry points from being discarded. Linker scripts |
| must also merge .text.*, .data.*, and .bss.* correctly into |
| output sections. Care must be taken not to pull in unrelated |
| sections (e.g., '.text.init'). Typically '.' in section names |
| is used to distinguish them from label names / C identifiers. |
| |
| config LD_DEAD_CODE_DATA_ELIMINATION |
| bool "Dead code and data elimination (EXPERIMENTAL)" |
| depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION |
| depends on EXPERT |
| depends on $(cc-option,-ffunction-sections -fdata-sections) |
| depends on $(ld-option,--gc-sections) |
| help |
| Enable this if you want to do dead code and data elimination with |
| the linker by compiling with -ffunction-sections -fdata-sections, |
| and linking with --gc-sections. |
| |
| This can reduce on disk and in-memory size of the kernel |
| code and static data, particularly for small configs and |
| on small systems. This has the possibility of introducing |
| silently broken kernel if the required annotations are not |
| present. This option is not well tested yet, so use at your |
| own risk. |
| |
| config LD_ORPHAN_WARN |
| def_bool y |
| depends on ARCH_WANT_LD_ORPHAN_WARN |
| depends on $(ld-option,--orphan-handling=warn) |
| depends on $(ld-option,--orphan-handling=error) |
| |
| config LD_ORPHAN_WARN_LEVEL |
| string |
| depends on LD_ORPHAN_WARN |
| default "error" if WERROR |
| default "warn" |
| |
| config SYSCTL |
| bool |
| |
| config HAVE_UID16 |
| bool |
| |
| config SYSCTL_EXCEPTION_TRACE |
| bool |
| help |
| Enable support for /proc/sys/debug/exception-trace. |
| |
| config SYSCTL_ARCH_UNALIGN_NO_WARN |
| bool |
| help |
| Enable support for /proc/sys/kernel/ignore-unaligned-usertrap |
| Allows arch to define/use @no_unaligned_warning to possibly warn |
| about unaligned access emulation going on under the hood. |
| |
| config SYSCTL_ARCH_UNALIGN_ALLOW |
| bool |
| help |
| Enable support for /proc/sys/kernel/unaligned-trap |
| Allows arches to define/use @unaligned_enabled to runtime toggle |
| the unaligned access emulation. |
| see arch/parisc/kernel/unaligned.c for reference |
| |
| config HAVE_PCSPKR_PLATFORM |
| bool |
| |
| menuconfig EXPERT |
| bool "Configure standard kernel features (expert users)" |
| # Unhide debug options, to make the on-by-default options visible |
| select DEBUG_KERNEL |
| help |
| This option allows certain base kernel options and settings |
| to be disabled or tweaked. This is for specialized |
| environments which can tolerate a "non-standard" kernel. |
| Only use this if you really know what you are doing. |
| |
| config UID16 |
| bool "Enable 16-bit UID system calls" if EXPERT |
| depends on HAVE_UID16 && MULTIUSER |
| default y |
| help |
| This enables the legacy 16-bit UID syscall wrappers. |
| |
| config MULTIUSER |
| bool "Multiple users, groups and capabilities support" if EXPERT |
| default y |
| help |
| This option enables support for non-root users, groups and |
| capabilities. |
| |
| If you say N here, all processes will run with UID 0, GID 0, and all |
| possible capabilities. Saying N here also compiles out support for |
| system calls related to UIDs, GIDs, and capabilities, such as setuid, |
| setgid, and capset. |
| |
| If unsure, say Y here. |
| |
| config SGETMASK_SYSCALL |
| bool "sgetmask/ssetmask syscalls support" if EXPERT |
| def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH |
| help |
| sys_sgetmask and sys_ssetmask are obsolete system calls |
| no longer supported in libc but still enabled by default in some |
| architectures. |
| |
| If unsure, leave the default option here. |
| |
| config SYSFS_SYSCALL |
| bool "Sysfs syscall support" if EXPERT |
| default y |
| help |
| sys_sysfs is an obsolete system call no longer supported in libc. |
| Note that disabling this option is more secure but might break |
| compatibility with some systems. |
| |
| If unsure say Y here. |
| |
| config FHANDLE |
| bool "open by fhandle syscalls" if EXPERT |
| select EXPORTFS |
| default y |
| help |
| If you say Y here, a user level program will be able to map |
| file names to handle and then later use the handle for |
| different file system operations. This is useful in implementing |
| userspace file servers, which now track files using handles instead |
| of names. The handle would remain the same even if file names |
| get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) |
| syscalls. |
| |
| config POSIX_TIMERS |
| bool "Posix Clocks & timers" if EXPERT |
| default y |
| help |
| This includes native support for POSIX timers to the kernel. |
| Some embedded systems have no use for them and therefore they |
| can be configured out to reduce the size of the kernel image. |
| |
| When this option is disabled, the following syscalls won't be |
| available: timer_create, timer_gettime: timer_getoverrun, |
| timer_settime, timer_delete, clock_adjtime, getitimer, |
| setitimer, alarm. Furthermore, the clock_settime, clock_gettime, |
| clock_getres and clock_nanosleep syscalls will be limited to |
| CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. |
| |
| If unsure say y. |
| |
| config PRINTK |
| default y |
| bool "Enable support for printk" if EXPERT |
| select IRQ_WORK |
| help |
| This option enables normal printk support. Removing it |
| eliminates most of the message strings from the kernel image |
| and makes the kernel more or less silent. As this makes it |
| very difficult to diagnose system problems, saying N here is |
| strongly discouraged. |
| |
| config BUG |
| bool "BUG() support" if EXPERT |
| default y |
| help |
| Disabling this option eliminates support for BUG and WARN, reducing |
| the size of your kernel image and potentially quietly ignoring |
| numerous fatal conditions. You should only consider disabling this |
| option for embedded systems with no facilities for reporting errors. |
| Just say Y. |
| |
| config ELF_CORE |
| depends on COREDUMP |
| default y |
| bool "Enable ELF core dumps" if EXPERT |
| help |
| Enable support for generating core dumps. Disabling saves about 4k. |
| |
| |
| config PCSPKR_PLATFORM |
| bool "Enable PC-Speaker support" if EXPERT |
| depends on HAVE_PCSPKR_PLATFORM |
| select I8253_LOCK |
| default y |
| help |
| This option allows to disable the internal PC-Speaker |
| support, saving some memory. |
| |
| config BASE_FULL |
| default y |
| bool "Enable full-sized data structures for core" if EXPERT |
| help |
| Disabling this option reduces the size of miscellaneous core |
| kernel data structures. This saves memory on small machines, |
| but may reduce performance. |
| |
| config FUTEX |
| bool "Enable futex support" if EXPERT |
| depends on !(SPARC32 && SMP) |
| default y |
| imply RT_MUTEXES |
| help |
| Disabling this option will cause the kernel to be built without |
| support for "fast userspace mutexes". The resulting kernel may not |
| run glibc-based applications correctly. |
| |
| config FUTEX_PI |
| bool |
| depends on FUTEX && RT_MUTEXES |
| default y |
| |
| config EPOLL |
| bool "Enable eventpoll support" if EXPERT |
| default y |
| help |
| Disabling this option will cause the kernel to be built without |
| support for epoll family of system calls. |
| |
| config SIGNALFD |
| bool "Enable signalfd() system call" if EXPERT |
| default y |
| help |
| Enable the signalfd() system call that allows to receive signals |
| on a file descriptor. |
| |
| If unsure, say Y. |
| |
| config TIMERFD |
| bool "Enable timerfd() system call" if EXPERT |
| default y |
| help |
| Enable the timerfd() system call that allows to receive timer |
| events on a file descriptor. |
| |
| If unsure, say Y. |
| |
| config EVENTFD |
| bool "Enable eventfd() system call" if EXPERT |
| default y |
| help |
| Enable the eventfd() system call that allows to receive both |
| kernel notification (ie. KAIO) or userspace notifications. |
| |
| If unsure, say Y. |
| |
| config SHMEM |
| bool "Use full shmem filesystem" if EXPERT |
| default y |
| depends on MMU |
| help |
| The shmem is an internal filesystem used to manage shared memory. |
| It is backed by swap and manages resource limits. It is also exported |
| to userspace as tmpfs if TMPFS is enabled. Disabling this |
| option replaces shmem and tmpfs with the much simpler ramfs code, |
| which may be appropriate on small systems without swap. |
| |
| config AIO |
| bool "Enable AIO support" if EXPERT |
| default y |
| help |
| This option enables POSIX asynchronous I/O which may by used |
| by some high performance threaded applications. Disabling |
| this option saves about 7k. |
| |
| config IO_URING |
| bool "Enable IO uring support" if EXPERT |
| select IO_WQ |
| default y |
| help |
| This option enables support for the io_uring interface, enabling |
| applications to submit and complete IO through submission and |
| completion rings that are shared between the kernel and application. |
| |
| config ADVISE_SYSCALLS |
| bool "Enable madvise/fadvise syscalls" if EXPERT |
| default y |
| help |
| This option enables the madvise and fadvise syscalls, used by |
| applications to advise the kernel about their future memory or file |
| usage, improving performance. If building an embedded system where no |
| applications use these syscalls, you can disable this option to save |
| space. |
| |
| config MEMBARRIER |
| bool "Enable membarrier() system call" if EXPERT |
| default y |
| help |
| Enable the membarrier() system call that allows issuing memory |
| barriers across all running threads, which can be used to distribute |
| the cost of user-space memory barriers asymmetrically by transforming |
| pairs of memory barriers into pairs consisting of membarrier() and a |
| compiler barrier. |
| |
| If unsure, say Y. |
| |
| config KCMP |
| bool "Enable kcmp() system call" if EXPERT |
| help |
| Enable the kernel resource comparison system call. It provides |
| user-space with the ability to compare two processes to see if they |
| share a common resource, such as a file descriptor or even virtual |
| memory space. |
| |
| If unsure, say N. |
| |
| config RSEQ |
| bool "Enable rseq() system call" if EXPERT |
| default y |
| depends on HAVE_RSEQ |
| select MEMBARRIER |
| help |
| Enable the restartable sequences system call. It provides a |
| user-space cache for the current CPU number value, which |
| speeds up getting the current CPU number from user-space, |
| as well as an ABI to speed up user-space operations on |
| per-CPU data. |
| |
| If unsure, say Y. |
| |
| config DEBUG_RSEQ |
| default n |
| bool "Enable debugging of rseq() system call" if EXPERT |
| depends on RSEQ && DEBUG_KERNEL |
| help |
| Enable extra debugging checks for the rseq system call. |
| |
| If unsure, say N. |
| |
| config CACHESTAT_SYSCALL |
| bool "Enable cachestat() system call" if EXPERT |
| default y |
| help |
| Enable the cachestat system call, which queries the page cache |
| statistics of a file (number of cached pages, dirty pages, |
| pages marked for writeback, (recently) evicted pages). |
| |
| If unsure say Y here. |
| |
| config PC104 |
| bool "PC/104 support" if EXPERT |
| help |
| Expose PC/104 form factor device drivers and options available for |
| selection and configuration. Enable this option if your target |
| machine has a PC/104 bus. |
| |
| config KALLSYMS |
| bool "Load all symbols for debugging/ksymoops" if EXPERT |
| default y |
| help |
| Say Y here to let the kernel print out symbolic crash information and |
| symbolic stack backtraces. This increases the size of the kernel |
| somewhat, as all symbols have to be loaded into the kernel image. |
| |
| config KALLSYMS_SELFTEST |
| bool "Test the basic functions and performance of kallsyms" |
| depends on KALLSYMS |
| default n |
| help |
| Test the basic functions and performance of some interfaces, such as |
| kallsyms_lookup_name. It also calculates the compression rate of the |
| kallsyms compression algorithm for the current symbol set. |
| |
| Start self-test automatically after system startup. Suggest executing |
| "dmesg | grep kallsyms_selftest" to collect test results. "finish" is |
| displayed in the last line, indicating that the test is complete. |
| |
| config KALLSYMS_ALL |
| bool "Include all symbols in kallsyms" |
| depends on DEBUG_KERNEL && KALLSYMS |
| help |
| Normally kallsyms only contains the symbols of functions for nicer |
| OOPS messages and backtraces (i.e., symbols from the text and inittext |
| sections). This is sufficient for most cases. And only if you want to |
| enable kernel live patching, or other less common use cases (e.g., |
| when a debugger is used) all symbols are required (i.e., names of |
| variables from the data sections, etc). |
| |
| This option makes sure that all symbols are loaded into the kernel |
| image (i.e., symbols from all sections) in cost of increased kernel |
| size (depending on the kernel configuration, it may be 300KiB or |
| something like this). |
| |
| Say N unless you really need all symbols, or kernel live patching. |
| |
| config KALLSYMS_ABSOLUTE_PERCPU |
| bool |
| depends on KALLSYMS |
| default X86_64 && SMP |
| |
| config KALLSYMS_BASE_RELATIVE |
| bool |
| depends on KALLSYMS |
| default y |
| help |
| Instead of emitting them as absolute values in the native word size, |
| emit the symbol references in the kallsyms table as 32-bit entries, |
| each containing a relative value in the range [base, base + U32_MAX] |
| or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either |
| an absolute value in the range [0, S32_MAX] or a relative value in the |
| range [base, base + S32_MAX], where base is the lowest relative symbol |
| address encountered in the image. |
| |
| On 64-bit builds, this reduces the size of the address table by 50%, |
| but more importantly, it results in entries whose values are build |
| time constants, and no relocation pass is required at runtime to fix |
| up the entries based on the runtime load address of the kernel. |
| |
| # end of the "standard kernel features (expert users)" menu |
| |
| config ARCH_HAS_MEMBARRIER_CALLBACKS |
| bool |
| |
| config ARCH_HAS_MEMBARRIER_SYNC_CORE |
| bool |
| |
| config HAVE_PERF_EVENTS |
| bool |
| help |
| See tools/perf/design.txt for details. |
| |
| config GUEST_PERF_EVENTS |
| bool |
| depends on HAVE_PERF_EVENTS |
| |
| config PERF_USE_VMALLOC |
| bool |
| help |
| See tools/perf/design.txt for details |
| |
| menu "Kernel Performance Events And Counters" |
| |
| config PERF_EVENTS |
| bool "Kernel performance events and counters" |
| default y if PROFILING |
| depends on HAVE_PERF_EVENTS |
| select IRQ_WORK |
| help |
| Enable kernel support for various performance events provided |
| by software and hardware. |
| |
| Software events are supported either built-in or via the |
| use of generic tracepoints. |
| |
| Most modern CPUs support performance events via performance |
| counter registers. These registers count the number of certain |
| types of hw events: such as instructions executed, cachemisses |
| suffered, or branches mis-predicted - without slowing down the |
| kernel or applications. These registers can also trigger interrupts |
| when a threshold number of events have passed - and can thus be |
| used to profile the code that runs on that CPU. |
| |
| The Linux Performance Event subsystem provides an abstraction of |
| these software and hardware event capabilities, available via a |
| system call and used by the "perf" utility in tools/perf/. It |
| provides per task and per CPU counters, and it provides event |
| capabilities on top of those. |
| |
| Say Y if unsure. |
| |
| config DEBUG_PERF_USE_VMALLOC |
| default n |
| bool "Debug: use vmalloc to back perf mmap() buffers" |
| depends on PERF_EVENTS && DEBUG_KERNEL && !PPC |
| select PERF_USE_VMALLOC |
| help |
| Use vmalloc memory to back perf mmap() buffers. |
| |
| Mostly useful for debugging the vmalloc code on platforms |
| that don't require it. |
| |
| Say N if unsure. |
| |
| endmenu |
| |
| config SYSTEM_DATA_VERIFICATION |
| def_bool n |
| select SYSTEM_TRUSTED_KEYRING |
| select KEYS |
| select CRYPTO |
| select CRYPTO_RSA |
| select ASYMMETRIC_KEY_TYPE |
| select ASYMMETRIC_PUBLIC_KEY_SUBTYPE |
| select ASN1 |
| select OID_REGISTRY |
| select X509_CERTIFICATE_PARSER |
| select PKCS7_MESSAGE_PARSER |
| help |
| Provide PKCS#7 message verification using the contents of the system |
| trusted keyring to provide public keys. This then can be used for |
| module verification, kexec image verification and firmware blob |
| verification. |
| |
| config PROFILING |
| bool "Profiling support" |
| help |
| Say Y here to enable the extended profiling support mechanisms used |
| by profilers. |
| |
| config RUST |
| bool "Rust support" |
| depends on HAVE_RUST |
| depends on RUST_IS_AVAILABLE |
| depends on !MODVERSIONS |
| depends on !GCC_PLUGINS |
| depends on !RANDSTRUCT |
| depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE |
| select CONSTRUCTORS |
| help |
| Enables Rust support in the kernel. |
| |
| This allows other Rust-related options, like drivers written in Rust, |
| to be selected. |
| |
| It is also required to be able to load external kernel modules |
| written in Rust. |
| |
| See Documentation/rust/ for more information. |
| |
| If unsure, say N. |
| |
| config RUSTC_VERSION_TEXT |
| string |
| depends on RUST |
| default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) |
| |
| config BINDGEN_VERSION_TEXT |
| string |
| depends on RUST |
| default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) |
| |
| # |
| # Place an empty function call at each tracepoint site. Can be |
| # dynamically changed for a probe function. |
| # |
| config TRACEPOINTS |
| bool |
| |
| source "kernel/Kconfig.kexec" |
| |
| endmenu # General setup |
| |
| source "arch/Kconfig" |
| |
| config RT_MUTEXES |
| bool |
| default y if PREEMPT_RT |
| |
| config BASE_SMALL |
| int |
| default 0 if BASE_FULL |
| default 1 if !BASE_FULL |
| |
| config MODULE_SIG_FORMAT |
| def_bool n |
| select SYSTEM_DATA_VERIFICATION |
| |
| source "kernel/module/Kconfig" |
| |
| config INIT_ALL_POSSIBLE |
| bool |
| help |
| Back when each arch used to define their own cpu_online_mask and |
| cpu_possible_mask, some of them chose to initialize cpu_possible_mask |
| with all 1s, and others with all 0s. When they were centralised, |
| it was better to provide this option than to break all the archs |
| and have several arch maintainers pursuing me down dark alleys. |
| |
| source "block/Kconfig" |
| |
| config PREEMPT_NOTIFIERS |
| bool |
| |
| config PADATA |
| depends on SMP |
| bool |
| |
| config ASN1 |
| tristate |
| help |
| Build a simple ASN.1 grammar compiler that produces a bytecode output |
| that can be interpreted by the ASN.1 stream decoder and used to |
| inform it as to what tags are to be expected in a stream and what |
| functions to call on what tags. |
| |
| source "kernel/Kconfig.locks" |
| |
| config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE |
| bool |
| |
| config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE |
| bool |
| |
| # It may be useful for an architecture to override the definitions of the |
| # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> |
| # and the COMPAT_ variants in <linux/compat.h>, in particular to use a |
| # different calling convention for syscalls. They can also override the |
| # macros for not-implemented syscalls in kernel/sys_ni.c and |
| # kernel/time/posix-stubs.c. All these overrides need to be available in |
| # <asm/syscall_wrapper.h>. |
| config ARCH_HAS_SYSCALL_WRAPPER |
| def_bool n |