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authorYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 12:17:53 -0700
committerYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 15:44:42 -0700
commit9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch)
tree1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/init/Kconfig
parent98260f3884f4a202f9ca5eabed40b1354c489b29 (diff)
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
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+config ARCH
+ string
+ option env="ARCH"
+
+config KERNELVERSION
+ string
+ option env="KERNELVERSION"
+
+config DEFCONFIG_LIST
+ string
+ depends on !UML
+ option defconfig_list
+ default "/lib/modules/$UNAME_RELEASE/.config"
+ default "/etc/kernel-config"
+ default "/boot/config-$UNAME_RELEASE"
+ default "$ARCH_DEFCONFIG"
+ default "arch/$ARCH/defconfig"
+
+config CONSTRUCTORS
+ bool
+ depends on !UML
+
+config IRQ_WORK
+ bool
+
+config BUILDTIME_EXTABLE_SORT
+ bool
+
+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 CROSS_COMPILE
+ string "Cross-compiler tool prefix"
+ help
+ Same as running 'make CROSS_COMPILE=prefix-' but stored for
+ default make runs in this kernel build directory. You don't
+ need to set this unless you want the configured kernel build
+ directory to select the cross-compiler automatically.
+
+config COMPILE_TEST
+ bool "Compile also drivers which will not load"
+ default n
+ 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 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
+ 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 eight characters produced
+ by running the command:
+
+ $ git rev-parse --verify HEAD
+
+ which is done within the script "scripts/setlocalversion".)
+
+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
+
+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
+ 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.
+
+endchoice
+
+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 SWAP
+ bool "Support for paging of anonymous memory (swap)"
+ depends on MMU && BLOCK
+ default y
+ help
+ This option allows you to choose whether you want to have support
+ for so called swap devices or swap files in your kernel that are
+ used to provide more virtual memory than the actual RAM present
+ in your computer. If unsure say Y.
+
+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 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 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 FHANDLE
+ bool "open by fhandle syscalls"
+ select EXPORTFS
+ 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 USELIB
+ bool "uselib syscall"
+ default y
+ 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). Does not do system-call
+ auditing without CONFIG_AUDITSYSCALL.
+
+config HAVE_ARCH_AUDITSYSCALL
+ bool
+
+config AUDITSYSCALL
+ bool "Enable system-call auditing support"
+ depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
+ default y if SECURITY_SELINUX
+ help
+ Enable low-overhead system-call auditing infrastructure that
+ can be used independently or with another kernel subsystem,
+ such as SELinux.
+
+config AUDIT_WATCH
+ def_bool y
+ depends on AUDITSYSCALL
+ select FSNOTIFY
+
+config AUDIT_TREE
+ def_bool y
+ depends on AUDITSYSCALL
+ select FSNOTIFY
+
+source "kernel/irq/Kconfig"
+source "kernel/time/Kconfig"
+
+menu "CPU/Task time and stats accounting"
+
+config VIRT_CPU_ACCOUNTING
+ bool
+
+choice
+ prompt "Cputime accounting"
+ default TICK_CPU_ACCOUNTING if !PPC64
+ default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
+
+# 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
+ depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
+ select VIRT_CPU_ACCOUNTING
+ select CONTEXT_TRACKING
+ 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.
+
+config IRQ_TIME_ACCOUNTING
+ bool "Fine granularity task level IRQ time accounting"
+ depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
+ 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.
+
+endchoice
+
+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 it's 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
+ 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.
+
+endmenu # "CPU/Task time and stats accounting"
+
+menu "RCU Subsystem"
+
+choice
+ prompt "RCU Implementation"
+ default TREE_RCU
+
+config TREE_RCU
+ bool "Tree-based hierarchical RCU"
+ depends on !PREEMPT && SMP
+ help
+ This option selects the RCU implementation that is
+ designed for very large SMP system with hundreds or
+ thousands of CPUs. It also scales down nicely to
+ smaller systems.
+
+config PREEMPT_RCU
+ bool "Preemptible tree-based hierarchical RCU"
+ depends on PREEMPT
+ help
+ This option selects the RCU implementation that is
+ designed for very large SMP systems with hundreds or
+ thousands of CPUs, but for which real-time response
+ is also required. It also scales down nicely to
+ smaller systems.
+
+ Select this option if you are unsure.
+
+config TINY_RCU
+ bool "UP-only small-memory-footprint RCU"
+ depends on !PREEMPT && !SMP
+ help
+ This option selects the RCU implementation that is
+ designed for UP systems from which real-time response
+ is not required. This option greatly reduces the
+ memory footprint of RCU.
+
+endchoice
+
+config SRCU
+ bool
+ help
+ This option selects the sleepable version of RCU. This version
+ permits arbitrary sleeping or blocking within RCU read-side critical
+ sections.
+
+config TASKS_RCU
+ bool "Task_based RCU implementation using voluntary context switch"
+ default n
+ select SRCU
+ help
+ This option enables a task-based RCU implementation that uses
+ only voluntary context switch (not preemption!), idle, and
+ user-mode execution as quiescent states.
+
+ If unsure, say N.
+
+config RCU_STALL_COMMON
+ def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
+ help
+ This option enables RCU CPU stall code that is common between
+ the TINY and TREE variants of RCU. The purpose is to allow
+ the tiny variants to disable RCU CPU stall warnings, while
+ making these warnings mandatory for the tree variants.
+
+config CONTEXT_TRACKING
+ bool
+
+config RCU_USER_QS
+ bool "Consider userspace as in RCU extended quiescent state"
+ depends on HAVE_CONTEXT_TRACKING && SMP
+ select CONTEXT_TRACKING
+ help
+ This option sets hooks on kernel / userspace boundaries and
+ puts RCU in extended quiescent state when the CPU runs in
+ userspace. It means that when a CPU runs in userspace, it is
+ excluded from the global RCU state machine and thus doesn't
+ try to keep the timer tick on for RCU.
+
+ Unless you want to hack and help the development of the full
+ dynticks mode, you shouldn't enable this option. It also
+ adds unnecessary overhead.
+
+ If unsure say N
+
+config CONTEXT_TRACKING_FORCE
+ bool "Force context tracking"
+ depends on CONTEXT_TRACKING
+ default y if !NO_HZ_FULL
+ help
+ The major pre-requirement for full dynticks to work is to
+ support the context tracking subsystem. But there are also
+ other dependencies to provide in order to make the full
+ dynticks working.
+
+ This option stands for testing when an arch implements the
+ context tracking backend but doesn't yet fullfill all the
+ requirements to make the full dynticks feature working.
+ Without the full dynticks, there is no way to test the support
+ for context tracking and the subsystems that rely on it: RCU
+ userspace extended quiescent state and tickless cputime
+ accounting. This option copes with the absence of the full
+ dynticks subsystem by forcing the context tracking on all
+ CPUs in the system.
+
+ Say Y only if you're working on the development of an
+ architecture backend for the context tracking.
+
+ Say N otherwise, this option brings an overhead that you
+ don't want in production.
+
+
+config RCU_FANOUT
+ int "Tree-based hierarchical RCU fanout value"
+ range 2 64 if 64BIT
+ range 2 32 if !64BIT
+ depends on TREE_RCU || PREEMPT_RCU
+ default 64 if 64BIT
+ default 32 if !64BIT
+ help
+ This option controls the fanout of hierarchical implementations
+ of RCU, allowing RCU to work efficiently on machines with
+ large numbers of CPUs. This value must be at least the fourth
+ root of NR_CPUS, which allows NR_CPUS to be insanely large.
+ The default value of RCU_FANOUT should be used for production
+ systems, but if you are stress-testing the RCU implementation
+ itself, small RCU_FANOUT values allow you to test large-system
+ code paths on small(er) systems.
+
+ Select a specific number if testing RCU itself.
+ Take the default if unsure.
+
+config RCU_FANOUT_LEAF
+ int "Tree-based hierarchical RCU leaf-level fanout value"
+ range 2 RCU_FANOUT if 64BIT
+ range 2 RCU_FANOUT if !64BIT
+ depends on TREE_RCU || PREEMPT_RCU
+ default 16
+ help
+ This option controls the leaf-level fanout of hierarchical
+ implementations of RCU, and allows trading off cache misses
+ against lock contention. Systems that synchronize their
+ scheduling-clock interrupts for energy-efficiency reasons will
+ want the default because the smaller leaf-level fanout keeps
+ lock contention levels acceptably low. Very large systems
+ (hundreds or thousands of CPUs) will instead want to set this
+ value to the maximum value possible in order to reduce the
+ number of cache misses incurred during RCU's grace-period
+ initialization. These systems tend to run CPU-bound, and thus
+ are not helped by synchronized interrupts, and thus tend to
+ skew them, which reduces lock contention enough that large
+ leaf-level fanouts work well.
+
+ Select a specific number if testing RCU itself.
+
+ Select the maximum permissible value for large systems.
+
+ Take the default if unsure.
+
+config RCU_FANOUT_EXACT
+ bool "Disable tree-based hierarchical RCU auto-balancing"
+ depends on TREE_RCU || PREEMPT_RCU
+ default n
+ help
+ This option forces use of the exact RCU_FANOUT value specified,
+ regardless of imbalances in the hierarchy. This is useful for
+ testing RCU itself, and might one day be useful on systems with
+ strong NUMA behavior.
+
+ Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
+
+ Say N if unsure.
+
+config RCU_FAST_NO_HZ
+ bool "Accelerate last non-dyntick-idle CPU's grace periods"
+ depends on NO_HZ_COMMON && SMP && !PREEMPT_RT_FULL
+ default n
+ help
+ This option permits CPUs to enter dynticks-idle state even if
+ they have RCU callbacks queued, and prevents RCU from waking
+ these CPUs up more than roughly once every four jiffies (by
+ default, you can adjust this using the rcutree.rcu_idle_gp_delay
+ parameter), thus improving energy efficiency. On the other
+ hand, this option increases the duration of RCU grace periods,
+ for example, slowing down synchronize_rcu().
+
+ Say Y if energy efficiency is critically important, and you
+ don't care about increased grace-period durations.
+
+ Say N if you are unsure.
+
+config TREE_RCU_TRACE
+ def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
+ select DEBUG_FS
+ help
+ This option provides tracing for the TREE_RCU and
+ PREEMPT_RCU implementations, permitting Makefile to
+ trivially select kernel/rcutree_trace.c.
+
+config RCU_BOOST
+ bool "Enable RCU priority boosting"
+ depends on RT_MUTEXES && PREEMPT_RCU
+ default y if PREEMPT_RT_FULL
+ help
+ This option boosts the priority of preempted RCU readers that
+ block the current preemptible RCU grace period for too long.
+ This option also prevents heavy loads from blocking RCU
+ callback invocation for all flavors of RCU.
+
+ Say Y here if you are working with real-time apps or heavy loads
+ Say N here if you are unsure.
+
+config RCU_KTHREAD_PRIO
+ int "Real-time priority to use for RCU worker threads"
+ range 1 99 if RCU_BOOST
+ range 0 99 if !RCU_BOOST
+ default 1 if RCU_BOOST
+ default 0 if !RCU_BOOST
+ help
+ This option specifies the SCHED_FIFO priority value that will be
+ assigned to the rcuc/n and rcub/n threads and is also the value
+ used for RCU_BOOST (if enabled). If you are working with a
+ real-time application that has one or more CPU-bound threads
+ running at a real-time priority level, you should set
+ RCU_KTHREAD_PRIO to a priority higher than the highest-priority
+ real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
+ value of 1 is appropriate in the common case, which is real-time
+ applications that do not have any CPU-bound threads.
+
+ Some real-time applications might not have a single real-time
+ thread that saturates a given CPU, but instead might have
+ multiple real-time threads that, taken together, fully utilize
+ that CPU. In this case, you should set RCU_KTHREAD_PRIO to
+ a priority higher than the lowest-priority thread that is
+ conspiring to prevent the CPU from running any non-real-time
+ tasks. For example, if one thread at priority 10 and another
+ thread at priority 5 are between themselves fully consuming
+ the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
+ set to priority 6 or higher.
+
+ Specify the real-time priority, or take the default if unsure.
+
+config RCU_BOOST_DELAY
+ int "Milliseconds to delay boosting after RCU grace-period start"
+ range 0 3000
+ depends on RCU_BOOST
+ default 500
+ help
+ This option specifies the time to wait after the beginning of
+ a given grace period before priority-boosting preempted RCU
+ readers blocking that grace period. Note that any RCU reader
+ blocking an expedited RCU grace period is boosted immediately.
+
+ Accept the default if unsure.
+
+config RCU_NOCB_CPU
+ bool "Offload RCU callback processing from boot-selected CPUs"
+ depends on TREE_RCU || PREEMPT_RCU
+ default n
+ help
+ Use this option to reduce OS jitter for aggressive HPC or
+ real-time workloads. It can also be used to offload RCU
+ callback invocation to energy-efficient CPUs in battery-powered
+ asymmetric multiprocessors.
+
+ This option offloads callback invocation from the set of
+ CPUs specified at boot time by the rcu_nocbs parameter.
+ For each such CPU, a kthread ("rcuox/N") will be created to
+ invoke callbacks, where the "N" is the CPU being offloaded,
+ and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
+ "s" for RCU-sched. Nothing prevents this kthread from running
+ on the specified CPUs, but (1) the kthreads may be preempted
+ between each callback, and (2) affinity or cgroups can be used
+ to force the kthreads to run on whatever set of CPUs is desired.
+
+ Say Y here if you want to help to debug reduced OS jitter.
+ Say N here if you are unsure.
+
+choice
+ prompt "Build-forced no-CBs CPUs"
+ default RCU_NOCB_CPU_NONE
+ depends on RCU_NOCB_CPU
+ help
+ This option allows no-CBs CPUs (whose RCU callbacks are invoked
+ from kthreads rather than from softirq context) to be specified
+ at build time. Additional no-CBs CPUs may be specified by
+ the rcu_nocbs= boot parameter.
+
+config RCU_NOCB_CPU_NONE
+ bool "No build_forced no-CBs CPUs"
+ help
+ This option does not force any of the CPUs to be no-CBs CPUs.
+ Only CPUs designated by the rcu_nocbs= boot parameter will be
+ no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
+ kthreads whose names begin with "rcuo". All other CPUs will
+ invoke their own RCU callbacks in softirq context.
+
+ Select this option if you want to choose no-CBs CPUs at
+ boot time, for example, to allow testing of different no-CBs
+ configurations without having to rebuild the kernel each time.
+
+config RCU_NOCB_CPU_ZERO
+ bool "CPU 0 is a build_forced no-CBs CPU"
+ help
+ This option forces CPU 0 to be a no-CBs CPU, so that its RCU
+ callbacks are invoked by a per-CPU kthread whose name begins
+ with "rcuo". Additional CPUs may be designated as no-CBs
+ CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
+ All other CPUs will invoke their own RCU callbacks in softirq
+ context.
+
+ Select this if CPU 0 needs to be a no-CBs CPU for real-time
+ or energy-efficiency reasons, but the real reason it exists
+ is to ensure that randconfig testing covers mixed systems.
+
+config RCU_NOCB_CPU_ALL
+ bool "All CPUs are build_forced no-CBs CPUs"
+ help
+ This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
+ boot parameter will be ignored. All CPUs' RCU callbacks will
+ be executed in the context of per-CPU rcuo kthreads created for
+ this purpose. Assuming that the kthreads whose names start with
+ "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
+ on the remaining CPUs, but might decrease memory locality during
+ RCU-callback invocation, thus potentially degrading throughput.
+
+ Select this if all CPUs need to be no-CBs CPUs for real-time
+ or energy-efficiency reasons.
+
+endchoice
+
+config RCU_EXPEDITE_BOOT
+ bool
+ default n
+ help
+ This option enables expedited grace periods at boot time,
+ as if rcu_expedite_gp() had been invoked early in boot.
+ The corresponding rcu_unexpedite_gp() is invoked from
+ rcu_end_inkernel_boot(), which is intended to be invoked
+ at the end of the kernel-only boot sequence, just before
+ init is exec'ed.
+
+ Accept the default if unsure.
+
+endmenu # "RCU Subsystem"
+
+config BUILD_BIN2C
+ bool
+ default n
+
+config IKCONFIG
+ tristate "Kernel .config support"
+ select BUILD_BIN2C
+ ---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 LOG_BUF_SHIFT
+ int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
+ range 12 21
+ 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 12 if !BASE_SMALL
+ default 0 if BASE_SMALL
+ 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 64 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 compuation optimal for the the worst case
+ scenerio 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
+
+#
+# Architectures with an unreliable sched_clock() should select this:
+#
+config HAVE_UNSTABLE_SCHED_CLOCK
+ bool
+
+config GENERIC_SCHED_CLOCK
+ bool
+
+#
+# For architectures that want to enable the support for NUMA-affine scheduler
+# balancing logic:
+#
+config ARCH_SUPPORTS_NUMA_BALANCING
+ bool
+
+#
+# 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
+ 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.txt (CFS)
+ - Documentation/cgroups/ (features for grouping, isolation
+ and resource control)
+
+ Say N if unsure.
+
+if CGROUPS
+
+config CGROUP_DEBUG
+ bool "Example debug cgroup subsystem"
+ default n
+ help
+ This option enables a simple cgroup subsystem that
+ exports useful debugging information about the cgroups
+ framework.
+
+ Say N if unsure.
+
+config CGROUP_FREEZER
+ bool "Freezer cgroup subsystem"
+ help
+ Provides a way to freeze and unfreeze all tasks in a
+ cgroup.
+
+config CGROUP_DEVICE
+ bool "Device controller for cgroups"
+ help
+ Provides a cgroup implementing whitelists for devices which
+ a process in the cgroup can mknod or open.
+
+config CPUSETS
+ bool "Cpuset support"
+ 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_CPUACCT
+ bool "Simple CPU accounting cgroup subsystem"
+ help
+ Provides a simple Resource Controller for monitoring the
+ total CPU consumed by the tasks in a cgroup.
+
+config PAGE_COUNTER
+ bool
+
+config MEMCG
+ bool "Memory Resource Controller for Control Groups"
+ select PAGE_COUNTER
+ select EVENTFD
+ help
+ Provides a memory resource controller that manages both anonymous
+ memory and page cache. (See Documentation/cgroups/memory.txt)
+
+config MEMCG_SWAP
+ bool "Memory Resource Controller Swap Extension"
+ depends on MEMCG && SWAP
+ help
+ Add swap management feature to memory resource controller. When you
+ enable this, you can limit mem+swap usage per cgroup. In other words,
+ when you disable this, memory resource controller has no cares to
+ usage of swap...a process can exhaust all of the swap. This extension
+ is useful when you want to avoid exhaustion swap but this itself
+ adds more overheads and consumes memory for remembering information.
+ Especially if you use 32bit system or small memory system, please
+ be careful about enabling this. When memory resource controller
+ is disabled by boot option, this will be automatically disabled and
+ there will be no overhead from this. Even when you set this config=y,
+ if boot option "swapaccount=0" is set, swap will not be accounted.
+ Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
+ size is 4096bytes, 512k per 1Gbytes of swap.
+config MEMCG_SWAP_ENABLED
+ bool "Memory Resource Controller Swap Extension enabled by default"
+ depends on MEMCG_SWAP
+ default y
+ help
+ Memory Resource Controller Swap Extension comes with its price in
+ a bigger memory consumption. General purpose distribution kernels
+ which want to enable the feature but keep it disabled by default
+ and let the user enable it by swapaccount=1 boot command line
+ parameter should have this option unselected.
+ For those who want to have the feature enabled by default should
+ select this option (if, for some reason, they need to disable it
+ then swapaccount=0 does the trick).
+config MEMCG_KMEM
+ bool "Memory Resource Controller Kernel Memory accounting"
+ depends on MEMCG
+ depends on SLUB || SLAB
+ help
+ The Kernel Memory extension for Memory Resource Controller can limit
+ the amount of memory used by kernel objects in the system. Those are
+ fundamentally different from the entities handled by the standard
+ Memory Controller, which are page-based, and can be swapped. Users of
+ the kmem extension can use it to guarantee that no group of processes
+ will ever exhaust kernel resources alone.
+
+config CGROUP_HUGETLB
+ bool "HugeTLB Resource Controller for Control Groups"
+ depends on HUGETLB_PAGE
+ select PAGE_COUNTER
+ default n
+ help
+ Provides a cgroup Resource 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 CGROUP_PERF
+ bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
+ depends on PERF_EVENTS && CGROUPS
+ help
+ This option extends the per-cpu mode to restrict monitoring to
+ threads which belong to the cgroup specified and run on the
+ designated cpu.
+
+ Say N if unsure.
+
+menuconfig CGROUP_SCHED
+ bool "Group CPU scheduler"
+ 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 tip/Documentation/scheduler/sched-bwc.txt for more information.
+
+config RT_GROUP_SCHED
+ bool "Group scheduling for SCHED_RR/FIFO"
+ depends on CGROUP_SCHED
+ depends on !PREEMPT_RT_FULL
+ 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.txt for more information.
+
+endif #CGROUP_SCHED
+
+config BLK_CGROUP
+ bool "Block 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_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
+ CONFIG_BLK_DEV_THROTTLING=y.
+
+ See Documentation/cgroups/blkio-controller.txt for more information.
+
+config DEBUG_BLK_CGROUP
+ bool "Enable Block IO controller debugging"
+ depends on BLK_CGROUP
+ default n
+ ---help---
+ Enable some debugging help. Currently it exports additional stat
+ files in a cgroup which can be useful for debugging.
+
+endif # CGROUPS
+
+config CHECKPOINT_RESTORE
+ bool "Checkpoint/restore support" if EXPERT
+ 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.
+
+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 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 and MEMCG_KMEM options 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 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 SYSFS_DEPRECATED
+ bool "Enable deprecated sysfs features to support old userspace tools"
+ depends on SYSFS
+ default n
+ help
+ This option adds code that switches the layout of the "block" class
+ devices, to not show up in /sys/class/block/, but only in
+ /sys/block/.
+
+ This switch is only active when the sysfs.deprecated=1 boot option is
+ passed or the SYSFS_DEPRECATED_V2 option is set.
+
+ This option allows new kernels to run on old distributions and tools,
+ which might get confused by /sys/class/block/. Since 2007/2008 all
+ major distributions and tools handle this just fine.
+
+ Recent distributions and userspace tools after 2009/2010 depend on
+ the existence of /sys/class/block/, and will not work with this
+ option enabled.
+
+ Only if you are using a new kernel on an old distribution, you might
+ need to say Y here.
+
+config SYSFS_DEPRECATED_V2
+ bool "Enable deprecated sysfs features by default"
+ default n
+ depends on SYSFS
+ depends on SYSFS_DEPRECATED
+ help
+ Enable deprecated sysfs by default.
+
+ See the CONFIG_SYSFS_DEPRECATED option for more details about this
+ option.
+
+ Only if you are using a new kernel on an old distribution, you might
+ need to say Y here. Even then, odds are you would not need it
+ enabled, you can always pass the boot option if absolutely necessary.
+
+config RELAY
+ bool "Kernel->user space relay support (formerly relayfs)"
+ 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"
+ depends on BROKEN || !FRV
+ 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/initrd.txt> 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 CC_OPTIMIZE_FOR_SIZE
+ bool "Optimize for size"
+ help
+ Enabling this option will pass "-Os" instead of "-O2" to
+ your compiler resulting in a smaller kernel.
+
+ If unsure, say N.
+
+config SYSCTL
+ bool
+
+config ANON_INODES
+ 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
+
+# interpreter that classic socket filters depend on
+config BPF
+ 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 || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || 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 SYSCTL_SYSCALL
+ bool "Sysctl syscall support" if EXPERT
+ depends on PROC_SYSCTL
+ default n
+ select SYSCTL
+ ---help---
+ sys_sysctl uses binary paths that have been found challenging
+ to properly maintain and use. The interface in /proc/sys
+ using paths with ascii names is now the primary path to this
+ information.
+
+ Almost nothing using the binary sysctl interface so if you are
+ trying to save some space it is probably safe to disable this,
+ making your kernel marginally smaller.
+
+ If unsure say N here.
+
+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_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 in very rare
+ cases (e.g., when a debugger is used) all symbols are required (e.g.,
+ 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.
+
+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
+ default y
+ select 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 HAVE_FUTEX_CMPXCHG
+ bool
+ depends on FUTEX
+ help
+ Architectures should select this if futex_atomic_cmpxchg_inatomic()
+ is implemented and always working. This removes a couple of runtime
+ checks.
+
+config EPOLL
+ bool "Enable eventpoll support" if EXPERT
+ default y
+ select ANON_INODES
+ 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
+ select ANON_INODES
+ 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
+ select ANON_INODES
+ 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
+ select ANON_INODES
+ default y
+ help
+ Enable the eventfd() system call that allows to receive both
+ kernel notification (ie. KAIO) or userspace notifications.
+
+ If unsure, say Y.
+
+# syscall, maps, verifier
+config BPF_SYSCALL
+ bool "Enable bpf() system call"
+ select ANON_INODES
+ select BPF
+ default n
+ help
+ Enable the bpf() system call that allows to manipulate eBPF
+ programs and maps via file descriptors.
+
+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 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 PCI_QUIRKS
+ default y
+ bool "Enable PCI quirk workarounds" if EXPERT
+ depends on PCI
+ help
+ This enables workarounds for various PCI chipset
+ bugs/quirks. Disable this only if your target machine is
+ unaffected by PCI quirks.
+
+config EMBEDDED
+ bool "Embedded system"
+ option allnoconfig_y
+ select EXPERT
+ help
+ This option should be enabled if compiling the kernel for
+ an embedded system so certain expert options are available
+ for configuration.
+
+config HAVE_PERF_EVENTS
+ bool
+ help
+ See tools/perf/design.txt for details.
+
+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 ANON_INODES
+ select IRQ_WORK
+ select SRCU
+ 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
+ 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 VM_EVENT_COUNTERS
+ default y
+ bool "Enable VM event counters for /proc/vmstat" if EXPERT
+ help
+ VM event counters are needed for event counts to be shown.
+ This option allows the disabling of the VM event counters
+ on EXPERT systems. /proc/vmstat will only show page counts
+ if VM event counters are disabled.
+
+config SLUB_DEBUG
+ default y
+ bool "Enable SLUB debugging support" if EXPERT
+ depends on SLUB && SYSFS
+ help
+ SLUB has extensive debug support features. Disabling these can
+ result in significant savings in code size. This also disables
+ SLUB sysfs support. /sys/slab will not exist and there will be
+ no support for cache validation etc.
+
+config COMPAT_BRK
+ bool "Disable heap randomization"
+ default y
+ help
+ Randomizing heap placement makes heap exploits harder, but it
+ also breaks ancient binaries (including anything libc5 based).
+ This option changes the bootup default to heap randomization
+ disabled, and can be overridden at runtime by setting
+ /proc/sys/kernel/randomize_va_space to 2.
+
+ On non-ancient distros (post-2000 ones) N is usually a safe choice.
+
+choice
+ prompt "Choose SLAB allocator"
+ default SLUB
+ help
+ This option allows to select a slab allocator.
+
+config SLAB
+ bool "SLAB"
+ depends on !PREEMPT_RT_FULL
+ help
+ The regular slab allocator that is established and known to work
+ well in all environments. It organizes cache hot objects in
+ per cpu and per node queues.
+
+config SLUB
+ bool "SLUB (Unqueued Allocator)"
+ help
+ SLUB is a slab allocator that minimizes cache line usage
+ instead of managing queues of cached objects (SLAB approach).
+ Per cpu caching is realized using slabs of objects instead
+ of queues of objects. SLUB can use memory efficiently
+ and has enhanced diagnostics. SLUB is the default choice for
+ a slab allocator.
+
+config SLOB
+ depends on EXPERT
+ bool "SLOB (Simple Allocator)"
+ depends on !PREEMPT_RT_FULL
+ help
+ SLOB replaces the stock allocator with a drastically simpler
+ allocator. SLOB is generally more space efficient but
+ does not perform as well on large systems.
+
+endchoice
+
+config SLUB_CPU_PARTIAL
+ default y
+ depends on SLUB && SMP && !PREEMPT_RT_FULL
+ bool "SLUB per cpu partial cache"
+ help
+ Per cpu partial caches accellerate objects allocation and freeing
+ that is local to a processor at the price of more indeterminism
+ in the latency of the free. On overflow these caches will be cleared
+ which requires the taking of locks that may cause latency spikes.
+ Typically one would choose no for a realtime system.
+
+config MMAP_ALLOW_UNINITIALIZED
+ bool "Allow mmapped anonymous memory to be uninitialized"
+ depends on EXPERT && !MMU
+ default n
+ help
+ Normally, and according to the Linux spec, anonymous memory obtained
+ from mmap() has it's contents cleared before it is passed to
+ userspace. Enabling this config option allows you to request that
+ mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
+ providing a huge performance boost. If this option is not enabled,
+ then the flag will be ignored.
+
+ This is taken advantage of by uClibc's malloc(), and also by
+ ELF-FDPIC binfmt's brk and stack allocator.
+
+ Because of the obvious security issues, this option should only be
+ enabled on embedded devices where you control what is run in
+ userspace. Since that isn't generally a problem on no-MMU systems,
+ it is normally safe to say Y here.
+
+ See Documentation/nommu-mmap.txt for more information.
+
+config SYSTEM_TRUSTED_KEYRING
+ bool "Provide system-wide ring of trusted keys"
+ depends on KEYS
+ help
+ Provide a system keyring to which trusted keys can be added. Keys in
+ the keyring are considered to be trusted. Keys may be added at will
+ by the kernel from compiled-in data and from hardware key stores, but
+ userspace may only add extra keys if those keys can be verified by
+ keys already in the keyring.
+
+ Keys in this keyring are used by module signature checking.
+
+config PROFILING
+ bool "Profiling support"
+ help
+ Say Y here to enable the extended profiling support mechanisms used
+ by profilers such as OProfile.
+
+#
+# Place an empty function call at each tracepoint site. Can be
+# dynamically changed for a probe function.
+#
+config TRACEPOINTS
+ bool
+
+source "arch/Kconfig"
+
+endmenu # General setup
+
+config HAVE_GENERIC_DMA_COHERENT
+ bool
+ default n
+
+config SLABINFO
+ bool
+ depends on PROC_FS
+ depends on SLAB || SLUB_DEBUG
+ default y
+
+config RT_MUTEXES
+ bool
+
+config BASE_SMALL
+ int
+ default 0 if BASE_FULL
+ default 1 if !BASE_FULL
+
+menuconfig MODULES
+ bool "Enable loadable module support"
+ option modules
+ help
+ Kernel modules are small pieces of compiled code which can
+ be inserted in the running kernel, rather than being
+ permanently built into the kernel. You use the "modprobe"
+ tool to add (and sometimes remove) them. If you say Y here,
+ many parts of the kernel can be built as modules (by
+ answering M instead of Y where indicated): this is most
+ useful for infrequently used options which are not required
+ for booting. For more information, see the man pages for
+ modprobe, lsmod, modinfo, insmod and rmmod.
+
+ If you say Y here, you will need to run "make
+ modules_install" to put the modules under /lib/modules/
+ where modprobe can find them (you may need to be root to do
+ this).
+
+ If unsure, say Y.
+
+if MODULES
+
+config MODULE_FORCE_LOAD
+ bool "Forced module loading"
+ default n
+ help
+ Allow loading of modules without version information (ie. modprobe
+ --force). Forced module loading sets the 'F' (forced) taint flag and
+ is usually a really bad idea.
+
+config MODULE_UNLOAD
+ bool "Module unloading"
+ help
+ Without this option you will not be able to unload any
+ modules (note that some modules may not be unloadable
+ anyway), which makes your kernel smaller, faster
+ and simpler. If unsure, say Y.
+
+config MODULE_FORCE_UNLOAD
+ bool "Forced module unloading"
+ depends on MODULE_UNLOAD
+ help
+ This option allows you to force a module to unload, even if the
+ kernel believes it is unsafe: the kernel will remove the module
+ without waiting for anyone to stop using it (using the -f option to
+ rmmod). This is mainly for kernel developers and desperate users.
+ If unsure, say N.
+
+config MODVERSIONS
+ bool "Module versioning support"
+ help
+ Usually, you have to use modules compiled with your kernel.
+ Saying Y here makes it sometimes possible to use modules
+ compiled for different kernels, by adding enough information
+ to the modules to (hopefully) spot any changes which would
+ make them incompatible with the kernel you are running. If
+ unsure, say N.
+
+config MODULE_SRCVERSION_ALL
+ bool "Source checksum for all modules"
+ help
+ Modules which contain a MODULE_VERSION get an extra "srcversion"
+ field inserted into their modinfo section, which contains a
+ sum of the source files which made it. This helps maintainers
+ see exactly which source was used to build a module (since
+ others sometimes change the module source without updating
+ the version). With this option, such a "srcversion" field
+ will be created for all modules. If unsure, say N.
+
+config MODULE_SIG
+ bool "Module signature verification"
+ depends on MODULES
+ select SYSTEM_TRUSTED_KEYRING
+ select KEYS
+ select CRYPTO
+ select ASYMMETRIC_KEY_TYPE
+ select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
+ select PUBLIC_KEY_ALGO_RSA
+ select ASN1
+ select OID_REGISTRY
+ select X509_CERTIFICATE_PARSER
+ help
+ Check modules for valid signatures upon load: the signature
+ is simply appended to the module. For more information see
+ Documentation/module-signing.txt.
+
+ !!!WARNING!!! If you enable this option, you MUST make sure that the
+ module DOES NOT get stripped after being signed. This includes the
+ debuginfo strip done by some packagers (such as rpmbuild) and
+ inclusion into an initramfs that wants the module size reduced.
+
+config MODULE_SIG_FORCE
+ bool "Require modules to be validly signed"
+ depends on MODULE_SIG
+ help
+ Reject unsigned modules or signed modules for which we don't have a
+ key. Without this, such modules will simply taint the kernel.
+
+config MODULE_SIG_ALL
+ bool "Automatically sign all modules"
+ default y
+ depends on MODULE_SIG
+ help
+ Sign all modules during make modules_install. Without this option,
+ modules must be signed manually, using the scripts/sign-file tool.
+
+comment "Do not forget to sign required modules with scripts/sign-file"
+ depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
+
+choice
+ prompt "Which hash algorithm should modules be signed with?"
+ depends on MODULE_SIG
+ help
+ This determines which sort of hashing algorithm will be used during
+ signature generation. This algorithm _must_ be built into the kernel
+ directly so that signature verification can take place. It is not
+ possible to load a signed module containing the algorithm to check
+ the signature on that module.
+
+config MODULE_SIG_SHA1
+ bool "Sign modules with SHA-1"
+ select CRYPTO_SHA1
+
+config MODULE_SIG_SHA224
+ bool "Sign modules with SHA-224"
+ select CRYPTO_SHA256
+
+config MODULE_SIG_SHA256
+ bool "Sign modules with SHA-256"
+ select CRYPTO_SHA256
+
+config MODULE_SIG_SHA384
+ bool "Sign modules with SHA-384"
+ select CRYPTO_SHA512
+
+config MODULE_SIG_SHA512
+ bool "Sign modules with SHA-512"
+ select CRYPTO_SHA512
+
+endchoice
+
+config MODULE_SIG_HASH
+ string
+ depends on MODULE_SIG
+ default "sha1" if MODULE_SIG_SHA1
+ default "sha224" if MODULE_SIG_SHA224
+ default "sha256" if MODULE_SIG_SHA256
+ default "sha384" if MODULE_SIG_SHA384
+ default "sha512" if MODULE_SIG_SHA512
+
+config MODULE_COMPRESS
+ bool "Compress modules on installation"
+ depends on MODULES
+ help
+ This option compresses the kernel modules when 'make
+ modules_install' is run.
+
+ The modules will be compressed either using gzip or xz depend on the
+ choice made in "Compression algorithm".
+
+ module-init-tools has support for gzip format while kmod handle gzip
+ and xz compressed modules.
+
+ When a kernel module is installed from outside of the main kernel
+ source and uses the Kbuild system for installing modules then that
+ kernel module will also be compressed when it is installed.
+
+ This option provides little benefit when the modules are to be used inside
+ an initrd or initramfs, it generally is more efficient to compress the whole
+ initrd or initramfs instead.
+
+ This is fully compatible with signed modules while the signed module is
+ compressed. module-init-tools or kmod handles decompression and provide to
+ other layer the uncompressed but signed payload.
+
+choice
+ prompt "Compression algorithm"
+ depends on MODULE_COMPRESS
+ default MODULE_COMPRESS_GZIP
+ help
+ This determines which sort of compression will be used during
+ 'make modules_install'.
+
+ GZIP (default) and XZ are supported.
+
+config MODULE_COMPRESS_GZIP
+ bool "GZIP"
+
+config MODULE_COMPRESS_XZ
+ bool "XZ"
+
+endchoice
+
+endif # MODULES
+
+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.
+
+config STOP_MACHINE
+ bool
+ default y
+ depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
+ help
+ Need stop_machine() primitive.
+
+source "block/Kconfig"
+
+config PREEMPT_NOTIFIERS
+ bool
+
+config PADATA
+ depends on SMP
+ bool
+
+# Can be selected by architectures with broken toolchains
+# that get confused by correct const<->read_only section
+# mappings
+config BROKEN_RODATA
+ 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"