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1	config ARCH
2	string
3	option env="ARCH"
4
5	config KERNELVERSION
6	string
7	option env="KERNELVERSION"
8
9	config DEFCONFIG_LIST
10	string
11	depends on !UML
12	option defconfig_list
13	default "/lib/modules/$UNAME_RELEASE/.config"
14	default "/etc/kernel-config"
15	default "/boot/config-$UNAME_RELEASE"
16	default "$ARCH_DEFCONFIG"
17	default "arch/$ARCH/defconfig"
18
19	config CONSTRUCTORS
20	bool
21	depends on !UML
22
23	config IRQ_WORK
24	bool
25
26	config BUILDTIME_EXTABLE_SORT
27	bool
28
29	menu "General setup"
30
31	config BROKEN
32	bool
33
34	config BROKEN_ON_SMP
35	bool
36	depends on BROKEN \|\| !SMP
37	default y
38
39	config INIT_ENV_ARG_LIMIT
40	int
41	default 32 if !UML
42	default 128 if UML
43	help
44	Maximum of each of the number of arguments and environment
45	variables passed to init from the kernel command line.
46
47
48	config CROSS_COMPILE
49	string "Cross-compiler tool prefix"
50	help
51	Same as running 'make CROSS_COMPILE=prefix-' but stored for
52	default make runs in this kernel build directory. You don't
53	need to set this unless you want the configured kernel build
54	directory to select the cross-compiler automatically.
55
56	config LOCALVERSION
57	string "Local version - append to kernel release"
58	help
59	Append an extra string to the end of your kernel version.
60	This will show up when you type uname, for example.
61	The string you set here will be appended after the contents of
62	any files with a filename matching localversion* in your
63	object and source tree, in that order. Your total string can
64	be a maximum of 64 characters.
65
66	config LOCALVERSION_AUTO
67	bool "Automatically append version information to the version string"
68	default y
69	help
70	This will try to automatically determine if the current tree is a
71	release tree by looking for git tags that belong to the current
72	top of tree revision.
73
74	A string of the format -gxxxxxxxx will be added to the localversion
75	if a git-based tree is found. The string generated by this will be
76	appended after any matching localversion* files, and after the value
77	set in CONFIG_LOCALVERSION.
78
79	(The actual string used here is the first eight characters produced
80	by running the command:
81
82	$ git rev-parse --verify HEAD
83
84	which is done within the script "scripts/setlocalversion".)
85
86	config HAVE_KERNEL_GZIP
87	bool
88
89	config HAVE_KERNEL_BZIP2
90	bool
91
92	config HAVE_KERNEL_LZMA
93	bool
94
95	config HAVE_KERNEL_XZ
96	bool
97
98	config HAVE_KERNEL_LZO
99	bool
100
101	choice
102	prompt "Kernel compression mode"
103	default KERNEL_GZIP
104	depends on HAVE_KERNEL_GZIP \|\| HAVE_KERNEL_BZIP2 \|\| HAVE_KERNEL_LZMA \|\| HAVE_KERNEL_XZ \|\| HAVE_KERNEL_LZO
105	help
106	The linux kernel is a kind of self-extracting executable.
107	Several compression algorithms are available, which differ
108	in efficiency, compression and decompression speed.
109	Compression speed is only relevant when building a kernel.
110	Decompression speed is relevant at each boot.
111
112	If you have any problems with bzip2 or lzma compressed
113	kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
114	version of this functionality (bzip2 only), for 2.4, was
115	supplied by Christian Ludwig)
116
117	High compression options are mostly useful for users, who
118	are low on disk space (embedded systems), but for whom ram
119	size matters less.
120
121	If in doubt, select 'gzip'
122
123	config KERNEL_GZIP
124	bool "Gzip"
125	depends on HAVE_KERNEL_GZIP
126	help
127	The old and tried gzip compression. It provides a good balance
128	between compression ratio and decompression speed.
129
130	config KERNEL_BZIP2
131	bool "Bzip2"
132	depends on HAVE_KERNEL_BZIP2
133	help
134	Its compression ratio and speed is intermediate.
135	Decompression speed is slowest among the choices. The kernel
136	size is about 10% smaller with bzip2, in comparison to gzip.
137	Bzip2 uses a large amount of memory. For modern kernels you
138	will need at least 8MB RAM or more for booting.
139
140	config KERNEL_LZMA
141	bool "LZMA"
142	depends on HAVE_KERNEL_LZMA
143	help
144	This compression algorithm's ratio is best. Decompression speed
145	is between gzip and bzip2. Compression is slowest.
146	The kernel size is about 33% smaller with LZMA in comparison to gzip.
147
148	config KERNEL_XZ
149	bool "XZ"
150	depends on HAVE_KERNEL_XZ
151	help
152	XZ uses the LZMA2 algorithm and instruction set specific
153	BCJ filters which can improve compression ratio of executable
154	code. The size of the kernel is about 30% smaller with XZ in
155	comparison to gzip. On architectures for which there is a BCJ
156	filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
157	will create a few percent smaller kernel than plain LZMA.
158
159	The speed is about the same as with LZMA: The decompression
160	speed of XZ is better than that of bzip2 but worse than gzip
161	and LZO. Compression is slow.
162
163	config KERNEL_LZO
164	bool "LZO"
165	depends on HAVE_KERNEL_LZO
166	help
167	Its compression ratio is the poorest among the choices. The kernel
168	size is about 10% bigger than gzip; however its speed
169	(both compression and decompression) is the fastest.
170
171	endchoice
172
173	config DEFAULT_HOSTNAME
174	string "Default hostname"
175	default "(none)"
176	help
177	This option determines the default system hostname before userspace
178	calls sethostname(2). The kernel traditionally uses "(none)" here,
179	but you may wish to use a different default here to make a minimal
180	system more usable with less configuration.
181
182	config SWAP
183	bool "Support for paging of anonymous memory (swap)"
184	depends on MMU && BLOCK
185	default y
186	help
187	This option allows you to choose whether you want to have support
188	for so called swap devices or swap files in your kernel that are
189	used to provide more virtual memory than the actual RAM present
190	in your computer. If unsure say Y.
191
192	config SYSVIPC
193	bool "System V IPC"
194	---help---
195	Inter Process Communication is a suite of library functions and
196	system calls which let processes (running programs) synchronize and
197	exchange information. It is generally considered to be a good thing,
198	and some programs won't run unless you say Y here. In particular, if
199	you want to run the DOS emulator dosemu under Linux (read the
200	DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
201	you'll need to say Y here.
202
203	You can find documentation about IPC with "info ipc" and also in
204	section 6.4 of the Linux Programmer's Guide, available from
205	<http://www.tldp.org/guides.html>.
206
207	config SYSVIPC_SYSCTL
208	bool
209	depends on SYSVIPC
210	depends on SYSCTL
211	default y
212
213	config POSIX_MQUEUE
214	bool "POSIX Message Queues"
215	depends on NET
216	---help---
217	POSIX variant of message queues is a part of IPC. In POSIX message
218	queues every message has a priority which decides about succession
219	of receiving it by a process. If you want to compile and run
220	programs written e.g. for Solaris with use of its POSIX message
221	queues (functions mq_*) say Y here.
222
223	POSIX message queues are visible as a filesystem called 'mqueue'
224	and can be mounted somewhere if you want to do filesystem
225	operations on message queues.
226
227	If unsure, say Y.
228
229	config POSIX_MQUEUE_SYSCTL
230	bool
231	depends on POSIX_MQUEUE
232	depends on SYSCTL
233	default y
234
235	config FHANDLE
236	bool "open by fhandle syscalls"
237	select EXPORTFS
238	help
239	If you say Y here, a user level program will be able to map
240	file names to handle and then later use the handle for
241	different file system operations. This is useful in implementing
242	userspace file servers, which now track files using handles instead
243	of names. The handle would remain the same even if file names
244	get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
245	syscalls.
246
247	config AUDIT
248	bool "Auditing support"
249	depends on NET
250	help
251	Enable auditing infrastructure that can be used with another
252	kernel subsystem, such as SELinux (which requires this for
253	logging of avc messages output). Does not do system-call
254	auditing without CONFIG_AUDITSYSCALL.
255
256	config AUDITSYSCALL
257	bool "Enable system-call auditing support"
258	depends on AUDIT && (X86 \|\| PPC \|\| S390 \|\| IA64 \|\| UML \|\| SPARC64 \|\| SUPERH \|\| (ARM && AEABI && !OABI_COMPAT))
259	default y if SECURITY_SELINUX
260	help
261	Enable low-overhead system-call auditing infrastructure that
262	can be used independently or with another kernel subsystem,
263	such as SELinux.
264
265	config AUDIT_WATCH
266	def_bool y
267	depends on AUDITSYSCALL
268	select FSNOTIFY
269
270	config AUDIT_TREE
271	def_bool y
272	depends on AUDITSYSCALL
273	select FSNOTIFY
274
275	config AUDIT_LOGINUID_IMMUTABLE
276	bool "Make audit loginuid immutable"
277	depends on AUDIT
278	help
279	The config option toggles if a task setting its loginuid requires
280	CAP_SYS_AUDITCONTROL or if that task should require no special permissions
281	but should instead only allow setting its loginuid if it was never
282	previously set. On systems which use systemd or a similar central
283	process to restart login services this should be set to true. On older
284	systems in which an admin would typically have to directly stop and
285	start processes this should be set to false. Setting this to true allows
286	one to drop potentially dangerous capabilites from the login tasks,
287	but may not be backwards compatible with older init systems.
288
289	source "kernel/irq/Kconfig"
290	source "kernel/time/Kconfig"
291
292	menu "CPU/Task time and stats accounting"
293
294	config VIRT_CPU_ACCOUNTING
295	bool
296
297	choice
298	prompt "Cputime accounting"
299	default TICK_CPU_ACCOUNTING if !PPC64
300	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
301
302	# Kind of a stub config for the pure tick based cputime accounting
303	config TICK_CPU_ACCOUNTING
304	bool "Simple tick based cputime accounting"
305	depends on !S390
306	help
307	This is the basic tick based cputime accounting that maintains
308	statistics about user, system and idle time spent on per jiffies
309	granularity.
310
311	If unsure, say Y.
312
313	config VIRT_CPU_ACCOUNTING_NATIVE
314	bool "Deterministic task and CPU time accounting"
315	depends on HAVE_VIRT_CPU_ACCOUNTING
316	select VIRT_CPU_ACCOUNTING
317	help
318	Select this option to enable more accurate task and CPU time
319	accounting. This is done by reading a CPU counter on each
320	kernel entry and exit and on transitions within the kernel
321	between system, softirq and hardirq state, so there is a
322	small performance impact. In the case of s390 or IBM POWER > 5,
323	this also enables accounting of stolen time on logically-partitioned
324	systems.
325
326	config VIRT_CPU_ACCOUNTING_GEN
327	bool "Full dynticks CPU time accounting"
328	depends on HAVE_CONTEXT_TRACKING && 64BIT
329	select VIRT_CPU_ACCOUNTING
330	select CONTEXT_TRACKING
331	help
332	Select this option to enable task and CPU time accounting on full
333	dynticks systems. This accounting is implemented by watching every
334	kernel-user boundaries using the context tracking subsystem.
335	The accounting is thus performed at the expense of some significant
336	overhead.
337
338	For now this is only useful if you are working on the full
339	dynticks subsystem development.
340
341	If unsure, say N.
342
343	config IRQ_TIME_ACCOUNTING
344	bool "Fine granularity task level IRQ time accounting"
345	depends on HAVE_IRQ_TIME_ACCOUNTING
346	help
347	Select this option to enable fine granularity task irq time
348	accounting. This is done by reading a timestamp on each
349	transitions between softirq and hardirq state, so there can be a
350	small performance impact.
351
352	If in doubt, say N here.
353
354	endchoice
355
356	config BSD_PROCESS_ACCT
357	bool "BSD Process Accounting"
358	help
359	If you say Y here, a user level program will be able to instruct the
360	kernel (via a special system call) to write process accounting
361	information to a file: whenever a process exits, information about
362	that process will be appended to the file by the kernel. The
363	information includes things such as creation time, owning user,
364	command name, memory usage, controlling terminal etc. (the complete
365	list is in the struct acct in <file:include/linux/acct.h>). It is
366	up to the user level program to do useful things with this
367	information. This is generally a good idea, so say Y.
368
369	config BSD_PROCESS_ACCT_V3
370	bool "BSD Process Accounting version 3 file format"
371	depends on BSD_PROCESS_ACCT
372	default n
373	help
374	If you say Y here, the process accounting information is written
375	in a new file format that also logs the process IDs of each
376	process and it's parent. Note that this file format is incompatible
377	with previous v0/v1/v2 file formats, so you will need updated tools
378	for processing it. A preliminary version of these tools is available
379	at <http://www.gnu.org/software/acct/>.
380
381	config TASKSTATS
382	bool "Export task/process statistics through netlink"
383	depends on NET
384	default n
385	help
386	Export selected statistics for tasks/processes through the
387	generic netlink interface. Unlike BSD process accounting, the
388	statistics are available during the lifetime of tasks/processes as
389	responses to commands. Like BSD accounting, they are sent to user
390	space on task exit.
391
392	Say N if unsure.
393
394	config TASK_DELAY_ACCT
395	bool "Enable per-task delay accounting"
396	depends on TASKSTATS
397	help
398	Collect information on time spent by a task waiting for system
399	resources like cpu, synchronous block I/O completion and swapping
400	in pages. Such statistics can help in setting a task's priorities
401	relative to other tasks for cpu, io, rss limits etc.
402
403	Say N if unsure.
404
405	config TASK_XACCT
406	bool "Enable extended accounting over taskstats"
407	depends on TASKSTATS
408	help
409	Collect extended task accounting data and send the data
410	to userland for processing over the taskstats interface.
411
412	Say N if unsure.
413
414	config TASK_IO_ACCOUNTING
415	bool "Enable per-task storage I/O accounting"
416	depends on TASK_XACCT
417	help
418	Collect information on the number of bytes of storage I/O which this
419	task has caused.
420
421	Say N if unsure.
422
423	endmenu # "CPU/Task time and stats accounting"
424
425	menu "RCU Subsystem"
426
427	choice
428	prompt "RCU Implementation"
429	default TREE_RCU
430
431	config TREE_RCU
432	bool "Tree-based hierarchical RCU"
433	depends on !PREEMPT && SMP
434	help
435	This option selects the RCU implementation that is
436	designed for very large SMP system with hundreds or
437	thousands of CPUs. It also scales down nicely to
438	smaller systems.
439
440	config TREE_PREEMPT_RCU
441	bool "Preemptible tree-based hierarchical RCU"
442	depends on PREEMPT
443	help
444	This option selects the RCU implementation that is
445	designed for very large SMP systems with hundreds or
446	thousands of CPUs, but for which real-time response
447	is also required. It also scales down nicely to
448	smaller systems.
449
450	Select this option if you are unsure.
451
452	config TINY_RCU
453	bool "UP-only small-memory-footprint RCU"
454	depends on !PREEMPT && !SMP
455	help
456	This option selects the RCU implementation that is
457	designed for UP systems from which real-time response
458	is not required. This option greatly reduces the
459	memory footprint of RCU.
460
461	config TINY_PREEMPT_RCU
462	bool "Preemptible UP-only small-memory-footprint RCU"
463	depends on PREEMPT && !SMP
464	help
465	This option selects the RCU implementation that is designed
466	for real-time UP systems. This option greatly reduces the
467	memory footprint of RCU.
468
469	endchoice
470
471	config PREEMPT_RCU
472	def_bool ( TREE_PREEMPT_RCU \|\| TINY_PREEMPT_RCU )
473	help
474	This option enables preemptible-RCU code that is common between
475	the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
476
477	config RCU_STALL_COMMON
478	def_bool ( TREE_RCU \|\| TREE_PREEMPT_RCU \|\| RCU_TRACE )
479	help
480	This option enables RCU CPU stall code that is common between
481	the TINY and TREE variants of RCU. The purpose is to allow
482	the tiny variants to disable RCU CPU stall warnings, while
483	making these warnings mandatory for the tree variants.
484
485	config CONTEXT_TRACKING
486	bool
487
488	config RCU_USER_QS
489	bool "Consider userspace as in RCU extended quiescent state"
490	depends on HAVE_CONTEXT_TRACKING && SMP
491	select CONTEXT_TRACKING
492	help
493	This option sets hooks on kernel / userspace boundaries and
494	puts RCU in extended quiescent state when the CPU runs in
495	userspace. It means that when a CPU runs in userspace, it is
496	excluded from the global RCU state machine and thus doesn't
497	try to keep the timer tick on for RCU.
498
499	Unless you want to hack and help the development of the full
500	dynticks mode, you shouldn't enable this option. It also
501	adds unnecessary overhead.
502
503	If unsure say N
504
505	config CONTEXT_TRACKING_FORCE
506	bool "Force context tracking"
507	depends on CONTEXT_TRACKING
508	help
509	Probe on user/kernel boundaries by default in order to
510	test the features that rely on it such as userspace RCU extended
511	quiescent states.
512	This test is there for debugging until we have a real user like the
513	full dynticks mode.
514
515	config RCU_FANOUT
516	int "Tree-based hierarchical RCU fanout value"
517	range 2 64 if 64BIT
518	range 2 32 if !64BIT
519	depends on TREE_RCU \|\| TREE_PREEMPT_RCU
520	default 64 if 64BIT
521	default 32 if !64BIT
522	help
523	This option controls the fanout of hierarchical implementations
524	of RCU, allowing RCU to work efficiently on machines with
525	large numbers of CPUs. This value must be at least the fourth
526	root of NR_CPUS, which allows NR_CPUS to be insanely large.
527	The default value of RCU_FANOUT should be used for production
528	systems, but if you are stress-testing the RCU implementation
529	itself, small RCU_FANOUT values allow you to test large-system
530	code paths on small(er) systems.
531
532	Select a specific number if testing RCU itself.
533	Take the default if unsure.
534
535	config RCU_FANOUT_LEAF
536	int "Tree-based hierarchical RCU leaf-level fanout value"
537	range 2 RCU_FANOUT if 64BIT
538	range 2 RCU_FANOUT if !64BIT
539	depends on TREE_RCU \|\| TREE_PREEMPT_RCU
540	default 16
541	help
542	This option controls the leaf-level fanout of hierarchical
543	implementations of RCU, and allows trading off cache misses
544	against lock contention. Systems that synchronize their
545	scheduling-clock interrupts for energy-efficiency reasons will
546	want the default because the smaller leaf-level fanout keeps
547	lock contention levels acceptably low. Very large systems
548	(hundreds or thousands of CPUs) will instead want to set this
549	value to the maximum value possible in order to reduce the
550	number of cache misses incurred during RCU's grace-period
551	initialization. These systems tend to run CPU-bound, and thus
552	are not helped by synchronized interrupts, and thus tend to
553	skew them, which reduces lock contention enough that large
554	leaf-level fanouts work well.
555
556	Select a specific number if testing RCU itself.
557
558	Select the maximum permissible value for large systems.
559
560	Take the default if unsure.
561
562	config RCU_FANOUT_EXACT
563	bool "Disable tree-based hierarchical RCU auto-balancing"
564	depends on TREE_RCU \|\| TREE_PREEMPT_RCU
565	default n
566	help
567	This option forces use of the exact RCU_FANOUT value specified,
568	regardless of imbalances in the hierarchy. This is useful for
569	testing RCU itself, and might one day be useful on systems with
570	strong NUMA behavior.
571
572	Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
573
574	Say N if unsure.
575
576	config RCU_FAST_NO_HZ
577	bool "Accelerate last non-dyntick-idle CPU's grace periods"
578	depends on NO_HZ && SMP
579	default n
580	help
581	This option causes RCU to attempt to accelerate grace periods in
582	order to allow CPUs to enter dynticks-idle state more quickly.
583	On the other hand, this option increases the overhead of the
584	dynticks-idle checking, thus degrading scheduling latency.
585
586	Say Y if energy efficiency is critically important, and you don't
587	care about real-time response.
588
589	Say N if you are unsure.
590
591	config TREE_RCU_TRACE
592	def_bool RCU_TRACE && ( TREE_RCU \|\| TREE_PREEMPT_RCU )
593	select DEBUG_FS
594	help
595	This option provides tracing for the TREE_RCU and
596	TREE_PREEMPT_RCU implementations, permitting Makefile to
597	trivially select kernel/rcutree_trace.c.
598
599	config RCU_BOOST
600	bool "Enable RCU priority boosting"
601	depends on RT_MUTEXES && PREEMPT_RCU
602	default n
603	help
604	This option boosts the priority of preempted RCU readers that
605	block the current preemptible RCU grace period for too long.
606	This option also prevents heavy loads from blocking RCU
607	callback invocation for all flavors of RCU.
608
609	Say Y here if you are working with real-time apps or heavy loads
610	Say N here if you are unsure.
611
612	config RCU_BOOST_PRIO
613	int "Real-time priority to boost RCU readers to"
614	range 1 99
615	depends on RCU_BOOST
616	default 1
617	help
618	This option specifies the real-time priority to which long-term
619	preempted RCU readers are to be boosted. If you are working
620	with a real-time application that has one or more CPU-bound
621	threads running at a real-time priority level, you should set
622	RCU_BOOST_PRIO to a priority higher then the highest-priority
623	real-time CPU-bound thread. The default RCU_BOOST_PRIO value
624	of 1 is appropriate in the common case, which is real-time
625	applications that do not have any CPU-bound threads.
626
627	Some real-time applications might not have a single real-time
628	thread that saturates a given CPU, but instead might have
629	multiple real-time threads that, taken together, fully utilize
630	that CPU. In this case, you should set RCU_BOOST_PRIO to
631	a priority higher than the lowest-priority thread that is
632	conspiring to prevent the CPU from running any non-real-time
633	tasks. For example, if one thread at priority 10 and another
634	thread at priority 5 are between themselves fully consuming
635	the CPU time on a given CPU, then RCU_BOOST_PRIO should be
636	set to priority 6 or higher.
637
638	Specify the real-time priority, or take the default if unsure.
639
640	config RCU_BOOST_DELAY
641	int "Milliseconds to delay boosting after RCU grace-period start"
642	range 0 3000
643	depends on RCU_BOOST
644	default 500
645	help
646	This option specifies the time to wait after the beginning of
647	a given grace period before priority-boosting preempted RCU
648	readers blocking that grace period. Note that any RCU reader
649	blocking an expedited RCU grace period is boosted immediately.
650
651	Accept the default if unsure.
652
653	config RCU_NOCB_CPU
654	bool "Offload RCU callback processing from boot-selected CPUs"
655	depends on TREE_RCU \|\| TREE_PREEMPT_RCU
656	default n
657	help
658	Use this option to reduce OS jitter for aggressive HPC or
659	real-time workloads. It can also be used to offload RCU
660	callback invocation to energy-efficient CPUs in battery-powered
661	asymmetric multiprocessors.
662
663	This option offloads callback invocation from the set of
664	CPUs specified at boot time by the rcu_nocbs parameter.
665	For each such CPU, a kthread ("rcuoN") will be created to
666	invoke callbacks, where the "N" is the CPU being offloaded.
667	Nothing prevents this kthread from running on the specified
668	CPUs, but (1) the kthreads may be preempted between each
669	callback, and (2) affinity or cgroups can be used to force
670	the kthreads to run on whatever set of CPUs is desired.
671
672	Say Y here if you want reduced OS jitter on selected CPUs.
673	Say N here if you are unsure.
674
675	endmenu # "RCU Subsystem"
676
677	config IKCONFIG
678	tristate "Kernel .config support"
679	---help---
680	This option enables the complete Linux kernel ".config" file
681	contents to be saved in the kernel. It provides documentation
682	of which kernel options are used in a running kernel or in an
683	on-disk kernel. This information can be extracted from the kernel
684	image file with the script scripts/extract-ikconfig and used as
685	input to rebuild the current kernel or to build another kernel.
686	It can also be extracted from a running kernel by reading
687	/proc/config.gz if enabled (below).
688
689	config IKCONFIG_PROC
690	bool "Enable access to .config through /proc/config.gz"
691	depends on IKCONFIG && PROC_FS
692	---help---
693	This option enables access to the kernel configuration file
694	through /proc/config.gz.
695
696	config LOG_BUF_SHIFT
697	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
698	range 12 21
699	default 17
700	help
701	Select kernel log buffer size as a power of 2.
702	Examples:
703	17 => 128 KB
704	16 => 64 KB
705	15 => 32 KB
706	14 => 16 KB
707	13 => 8 KB
708	12 => 4 KB
709
710	#
711	# Architectures with an unreliable sched_clock() should select this:
712	#
713	config HAVE_UNSTABLE_SCHED_CLOCK
714	bool
715
716	#
717	# For architectures that want to enable the support for NUMA-affine scheduler
718	# balancing logic:
719	#
720	config ARCH_SUPPORTS_NUMA_BALANCING
721	bool
722
723	# For architectures that (ab)use NUMA to represent different memory regions
724	# all cpu-local but of different latencies, such as SuperH.
725	#
726	config ARCH_WANT_NUMA_VARIABLE_LOCALITY
727	bool
728
729	#
730	# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
731	config ARCH_WANTS_PROT_NUMA_PROT_NONE
732	bool
733
734	config ARCH_USES_NUMA_PROT_NONE
735	bool
736	default y
737	depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
738	depends on NUMA_BALANCING
739
740	config NUMA_BALANCING_DEFAULT_ENABLED
741	bool "Automatically enable NUMA aware memory/task placement"
742	default y
743	depends on NUMA_BALANCING
744	help
745	If set, autonumic NUMA balancing will be enabled if running on a NUMA
746	machine.
747
748	config NUMA_BALANCING
749	bool "Memory placement aware NUMA scheduler"
750	depends on ARCH_SUPPORTS_NUMA_BALANCING
751	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
752	depends on SMP && NUMA && MIGRATION
753	help
754	This option adds support for automatic NUMA aware memory/task placement.
755	The mechanism is quite primitive and is based on migrating memory when
756	it is references to the node the task is running on.
757
758	This system will be inactive on UMA systems.
759
760	menuconfig CGROUPS
761	boolean "Control Group support"
762	depends on EVENTFD
763	help
764	This option adds support for grouping sets of processes together, for
765	use with process control subsystems such as Cpusets, CFS, memory
766	controls or device isolation.
767	See
768	- Documentation/scheduler/sched-design-CFS.txt (CFS)
769	- Documentation/cgroups/ (features for grouping, isolation
770	and resource control)
771
772	Say N if unsure.
773
774	if CGROUPS
775
776	config CGROUP_DEBUG
777	bool "Example debug cgroup subsystem"
778	default n
779	help
780	This option enables a simple cgroup subsystem that
781	exports useful debugging information about the cgroups
782	framework.
783
784	Say N if unsure.
785
786	config CGROUP_FREEZER
787	bool "Freezer cgroup subsystem"
788	help
789	Provides a way to freeze and unfreeze all tasks in a
790	cgroup.
791
792	config CGROUP_DEVICE
793	bool "Device controller for cgroups"
794	help
795	Provides a cgroup implementing whitelists for devices which
796	a process in the cgroup can mknod or open.
797
798	config CPUSETS
799	bool "Cpuset support"
800	help
801	This option will let you create and manage CPUSETs which
802	allow dynamically partitioning a system into sets of CPUs and
803	Memory Nodes and assigning tasks to run only within those sets.
804	This is primarily useful on large SMP or NUMA systems.
805
806	Say N if unsure.
807
808	config PROC_PID_CPUSET
809	bool "Include legacy /proc/<pid>/cpuset file"
810	depends on CPUSETS
811	default y
812
813	config CGROUP_CPUACCT
814	bool "Simple CPU accounting cgroup subsystem"
815	help
816	Provides a simple Resource Controller for monitoring the
817	total CPU consumed by the tasks in a cgroup.
818
819	config RESOURCE_COUNTERS
820	bool "Resource counters"
821	help
822	This option enables controller independent resource accounting
823	infrastructure that works with cgroups.
824
825	config MEMCG
826	bool "Memory Resource Controller for Control Groups"
827	depends on RESOURCE_COUNTERS
828	select MM_OWNER
829	help
830	Provides a memory resource controller that manages both anonymous
831	memory and page cache. (See Documentation/cgroups/memory.txt)
832
833	Note that setting this option increases fixed memory overhead
834	associated with each page of memory in the system. By this,
835	20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
836	usage tracking struct at boot. Total amount of this is printed out
837	at boot.
838
839	Only enable when you're ok with these trade offs and really
840	sure you need the memory resource controller. Even when you enable
841	this, you can set "cgroup_disable=memory" at your boot option to
842	disable memory resource controller and you can avoid overheads.
843	(and lose benefits of memory resource controller)
844
845	This config option also selects MM_OWNER config option, which
846	could in turn add some fork/exit overhead.
847
848	config MEMCG_SWAP
849	bool "Memory Resource Controller Swap Extension"
850	depends on MEMCG && SWAP
851	help
852	Add swap management feature to memory resource controller. When you
853	enable this, you can limit mem+swap usage per cgroup. In other words,
854	when you disable this, memory resource controller has no cares to
855	usage of swap...a process can exhaust all of the swap. This extension
856	is useful when you want to avoid exhaustion swap but this itself
857	adds more overheads and consumes memory for remembering information.
858	Especially if you use 32bit system or small memory system, please
859	be careful about enabling this. When memory resource controller
860	is disabled by boot option, this will be automatically disabled and
861	there will be no overhead from this. Even when you set this config=y,
862	if boot option "swapaccount=0" is set, swap will not be accounted.
863	Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
864	size is 4096bytes, 512k per 1Gbytes of swap.
865	config MEMCG_SWAP_ENABLED
866	bool "Memory Resource Controller Swap Extension enabled by default"
867	depends on MEMCG_SWAP
868	default y
869	help
870	Memory Resource Controller Swap Extension comes with its price in
871	a bigger memory consumption. General purpose distribution kernels
872	which want to enable the feature but keep it disabled by default
873	and let the user enable it by swapaccount boot command line
874	parameter should have this option unselected.
875	For those who want to have the feature enabled by default should
876	select this option (if, for some reason, they need to disable it
877	then swapaccount=0 does the trick).
878	config MEMCG_KMEM
879	bool "Memory Resource Controller Kernel Memory accounting"
880	depends on MEMCG
881	depends on SLUB \|\| SLAB
882	help
883	The Kernel Memory extension for Memory Resource Controller can limit
884	the amount of memory used by kernel objects in the system. Those are
885	fundamentally different from the entities handled by the standard
886	Memory Controller, which are page-based, and can be swapped. Users of
887	the kmem extension can use it to guarantee that no group of processes
888	will ever exhaust kernel resources alone.
889
890	config CGROUP_HUGETLB
891	bool "HugeTLB Resource Controller for Control Groups"
892	depends on RESOURCE_COUNTERS && HUGETLB_PAGE
893	default n
894	help
895	Provides a cgroup Resource Controller for HugeTLB pages.
896	When you enable this, you can put a per cgroup limit on HugeTLB usage.
897	The limit is enforced during page fault. Since HugeTLB doesn't
898	support page reclaim, enforcing the limit at page fault time implies
899	that, the application will get SIGBUS signal if it tries to access
900	HugeTLB pages beyond its limit. This requires the application to know
901	beforehand how much HugeTLB pages it would require for its use. The
902	control group is tracked in the third page lru pointer. This means
903	that we cannot use the controller with huge page less than 3 pages.
904
905	config CGROUP_PERF
906	bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
907	depends on PERF_EVENTS && CGROUPS
908	help
909	This option extends the per-cpu mode to restrict monitoring to
910	threads which belong to the cgroup specified and run on the
911	designated cpu.
912
913	Say N if unsure.
914
915	menuconfig CGROUP_SCHED
916	bool "Group CPU scheduler"
917	default n
918	help
919	This feature lets CPU scheduler recognize task groups and control CPU
920	bandwidth allocation to such task groups. It uses cgroups to group
921	tasks.
922
923	if CGROUP_SCHED
924	config FAIR_GROUP_SCHED
925	bool "Group scheduling for SCHED_OTHER"
926	depends on CGROUP_SCHED
927	default CGROUP_SCHED
928
929	config CFS_BANDWIDTH
930	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
931	depends on FAIR_GROUP_SCHED
932	default n
933	help
934	This option allows users to define CPU bandwidth rates (limits) for
935	tasks running within the fair group scheduler. Groups with no limit
936	set are considered to be unconstrained and will run with no
937	restriction.
938	See tip/Documentation/scheduler/sched-bwc.txt for more information.
939
940	config RT_GROUP_SCHED
941	bool "Group scheduling for SCHED_RR/FIFO"
942	depends on CGROUP_SCHED
943	default n
944	help
945	This feature lets you explicitly allocate real CPU bandwidth
946	to task groups. If enabled, it will also make it impossible to
947	schedule realtime tasks for non-root users until you allocate
948	realtime bandwidth for them.
949	See Documentation/scheduler/sched-rt-group.txt for more information.
950
951	endif #CGROUP_SCHED
952
953	config BLK_CGROUP
954	bool "Block IO controller"
955	depends on BLOCK
956	default n
957	---help---
958	Generic block IO controller cgroup interface. This is the common
959	cgroup interface which should be used by various IO controlling
960	policies.
961
962	Currently, CFQ IO scheduler uses it to recognize task groups and
963	control disk bandwidth allocation (proportional time slice allocation)
964	to such task groups. It is also used by bio throttling logic in
965	block layer to implement upper limit in IO rates on a device.
966
967	This option only enables generic Block IO controller infrastructure.
968	One needs to also enable actual IO controlling logic/policy. For
969	enabling proportional weight division of disk bandwidth in CFQ, set
970	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
971	CONFIG_BLK_DEV_THROTTLING=y.
972
973	See Documentation/cgroups/blkio-controller.txt for more information.
974
975	config DEBUG_BLK_CGROUP
976	bool "Enable Block IO controller debugging"
977	depends on BLK_CGROUP
978	default n
979	---help---
980	Enable some debugging help. Currently it exports additional stat
981	files in a cgroup which can be useful for debugging.
982
983	endif # CGROUPS
984
985	config CHECKPOINT_RESTORE
986	bool "Checkpoint/restore support" if EXPERT
987	default n
988	help
989	Enables additional kernel features in a sake of checkpoint/restore.
990	In particular it adds auxiliary prctl codes to setup process text,
991	data and heap segment sizes, and a few additional /proc filesystem
992	entries.
993
994	If unsure, say N here.
995
996	menuconfig NAMESPACES
997	bool "Namespaces support" if EXPERT
998	default !EXPERT
999	help
1000	Provides the way to make tasks work with different objects using
1001	the same id. For example same IPC id may refer to different objects
1002	or same user id or pid may refer to different tasks when used in
1003	different namespaces.
1004
1005	if NAMESPACES
1006
1007	config UTS_NS
1008	bool "UTS namespace"
1009	default y
1010	help
1011	In this namespace tasks see different info provided with the
1012	uname() system call
1013
1014	config IPC_NS
1015	bool "IPC namespace"
1016	depends on (SYSVIPC \|\| POSIX_MQUEUE)
1017	default y
1018	help
1019	In this namespace tasks work with IPC ids which correspond to
1020	different IPC objects in different namespaces.
1021
1022	config USER_NS
1023	bool "User namespace"
1024	depends on UIDGID_CONVERTED
1025	select UIDGID_STRICT_TYPE_CHECKS
1026
1027	default n
1028	help
1029	This allows containers, i.e. vservers, to use user namespaces
1030	to provide different user info for different servers.
1031
1032	When user namespaces are enabled in the kernel it is
1033	recommended that the MEMCG and MEMCG_KMEM options also be
1034	enabled and that user-space use the memory control groups to
1035	limit the amount of memory a memory unprivileged users can
1036	use.
1037
1038	If unsure, say N.
1039
1040	config PID_NS
1041	bool "PID Namespaces"
1042	default y
1043	help
1044	Support process id namespaces. This allows having multiple
1045	processes with the same pid as long as they are in different
1046	pid namespaces. This is a building block of containers.
1047
1048	config NET_NS
1049	bool "Network namespace"
1050	depends on NET
1051	default y
1052	help
1053	Allow user space to create what appear to be multiple instances
1054	of the network stack.
1055
1056	endif # NAMESPACES
1057
1058	config UIDGID_CONVERTED
1059	# True if all of the selected software conmponents are known
1060	# to have uid_t and gid_t converted to kuid_t and kgid_t
1061	# where appropriate and are otherwise safe to use with
1062	# the user namespace.
1063	bool
1064	default y
1065
1066	# Filesystems
1067	depends on XFS_FS = n
1068
1069	config UIDGID_STRICT_TYPE_CHECKS
1070	bool "Require conversions between uid/gids and their internal representation"
1071	depends on UIDGID_CONVERTED
1072	default n
1073	help
1074	While the nececessary conversions are being added to all subsystems this option allows
1075	the code to continue to build for unconverted subsystems.
1076
1077	Say Y here if you want the strict type checking enabled
1078
1079	config SCHED_AUTOGROUP
1080	bool "Automatic process group scheduling"
1081	select EVENTFD
1082	select CGROUPS
1083	select CGROUP_SCHED
1084	select FAIR_GROUP_SCHED
1085	help
1086	This option optimizes the scheduler for common desktop workloads by
1087	automatically creating and populating task groups. This separation
1088	of workloads isolates aggressive CPU burners (like build jobs) from
1089	desktop applications. Task group autogeneration is currently based
1090	upon task session.
1091
1092	config MM_OWNER
1093	bool
1094
1095	config SYSFS_DEPRECATED
1096	bool "Enable deprecated sysfs features to support old userspace tools"
1097	depends on SYSFS
1098	default n
1099	help
1100	This option adds code that switches the layout of the "block" class
1101	devices, to not show up in /sys/class/block/, but only in
1102	/sys/block/.
1103
1104	This switch is only active when the sysfs.deprecated=1 boot option is
1105	passed or the SYSFS_DEPRECATED_V2 option is set.
1106
1107	This option allows new kernels to run on old distributions and tools,
1108	which might get confused by /sys/class/block/. Since 2007/2008 all
1109	major distributions and tools handle this just fine.
1110
1111	Recent distributions and userspace tools after 2009/2010 depend on
1112	the existence of /sys/class/block/, and will not work with this
1113	option enabled.
1114
1115	Only if you are using a new kernel on an old distribution, you might
1116	need to say Y here.
1117
1118	config SYSFS_DEPRECATED_V2
1119	bool "Enable deprecated sysfs features by default"
1120	default n
1121	depends on SYSFS
1122	depends on SYSFS_DEPRECATED
1123	help
1124	Enable deprecated sysfs by default.
1125
1126	See the CONFIG_SYSFS_DEPRECATED option for more details about this
1127	option.
1128
1129	Only if you are using a new kernel on an old distribution, you might
1130	need to say Y here. Even then, odds are you would not need it
1131	enabled, you can always pass the boot option if absolutely necessary.
1132
1133	config RELAY
1134	bool "Kernel->user space relay support (formerly relayfs)"
1135	help
1136	This option enables support for relay interface support in
1137	certain file systems (such as debugfs).
1138	It is designed to provide an efficient mechanism for tools and
1139	facilities to relay large amounts of data from kernel space to
1140	user space.
1141
1142	If unsure, say N.
1143
1144	config BLK_DEV_INITRD
1145	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1146	depends on BROKEN \|\| !FRV
1147	help
1148	The initial RAM filesystem is a ramfs which is loaded by the
1149	boot loader (loadlin or lilo) and that is mounted as root
1150	before the normal boot procedure. It is typically used to
1151	load modules needed to mount the "real" root file system,
1152	etc. See <file:Documentation/initrd.txt> for details.
1153
1154	If RAM disk support (BLK_DEV_RAM) is also included, this
1155	also enables initial RAM disk (initrd) support and adds
1156	15 Kbytes (more on some other architectures) to the kernel size.
1157
1158	If unsure say Y.
1159
1160	if BLK_DEV_INITRD
1161
1162	source "usr/Kconfig"
1163
1164	endif
1165
1166	config CC_OPTIMIZE_FOR_SIZE
1167	bool "Optimize for size"
1168	help
1169	Enabling this option will pass "-Os" instead of "-O2" to gcc
1170	resulting in a smaller kernel.
1171
1172	If unsure, say N.
1173
1174	config SYSCTL
1175	bool
1176
1177	config ANON_INODES
1178	bool
1179
1180	menuconfig EXPERT
1181	bool "Configure standard kernel features (expert users)"
1182	# Unhide debug options, to make the on-by-default options visible
1183	select DEBUG_KERNEL
1184	help
1185	This option allows certain base kernel options and settings
1186	to be disabled or tweaked. This is for specialized
1187	environments which can tolerate a "non-standard" kernel.
1188	Only use this if you really know what you are doing.
1189
1190	config HAVE_UID16
1191	bool
1192
1193	config UID16
1194	bool "Enable 16-bit UID system calls" if EXPERT
1195	depends on HAVE_UID16
1196	default y
1197	help
1198	This enables the legacy 16-bit UID syscall wrappers.
1199
1200	config SYSCTL_SYSCALL
1201	bool "Sysctl syscall support" if EXPERT
1202	depends on PROC_SYSCTL
1203	default n
1204	select SYSCTL
1205	---help---
1206	sys_sysctl uses binary paths that have been found challenging
1207	to properly maintain and use. The interface in /proc/sys
1208	using paths with ascii names is now the primary path to this
1209	information.
1210
1211	Almost nothing using the binary sysctl interface so if you are
1212	trying to save some space it is probably safe to disable this,
1213	making your kernel marginally smaller.
1214
1215	If unsure say N here.
1216
1217	config SYSCTL_EXCEPTION_TRACE
1218	bool
1219	help
1220	Enable support for /proc/sys/debug/exception-trace.
1221
1222	config SYSCTL_ARCH_UNALIGN_NO_WARN
1223	bool
1224	help
1225	Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1226	Allows arch to define/use @no_unaligned_warning to possibly warn
1227	about unaligned access emulation going on under the hood.
1228
1229	config SYSCTL_ARCH_UNALIGN_ALLOW
1230	bool
1231	help
1232	Enable support for /proc/sys/kernel/unaligned-trap
1233	Allows arches to define/use @unaligned_enabled to runtime toggle
1234	the unaligned access emulation.
1235	see arch/parisc/kernel/unaligned.c for reference
1236
1237	config KALLSYMS
1238	bool "Load all symbols for debugging/ksymoops" if EXPERT
1239	default y
1240	help
1241	Say Y here to let the kernel print out symbolic crash information and
1242	symbolic stack backtraces. This increases the size of the kernel
1243	somewhat, as all symbols have to be loaded into the kernel image.
1244
1245	config KALLSYMS_ALL
1246	bool "Include all symbols in kallsyms"
1247	depends on DEBUG_KERNEL && KALLSYMS
1248	help
1249	Normally kallsyms only contains the symbols of functions for nicer
1250	OOPS messages and backtraces (i.e., symbols from the text and inittext
1251	sections). This is sufficient for most cases. And only in very rare
1252	cases (e.g., when a debugger is used) all symbols are required (e.g.,
1253	names of variables from the data sections, etc).
1254
1255	This option makes sure that all symbols are loaded into the kernel
1256	image (i.e., symbols from all sections) in cost of increased kernel
1257	size (depending on the kernel configuration, it may be 300KiB or
1258	something like this).
1259
1260	Say N unless you really need all symbols.
1261
1262	config HOTPLUG
1263	def_bool y
1264
1265	config PRINTK
1266	default y
1267	bool "Enable support for printk" if EXPERT
1268	select IRQ_WORK
1269	help
1270	This option enables normal printk support. Removing it
1271	eliminates most of the message strings from the kernel image
1272	and makes the kernel more or less silent. As this makes it
1273	very difficult to diagnose system problems, saying N here is
1274	strongly discouraged.
1275
1276	config BUG
1277	bool "BUG() support" if EXPERT
1278	default y
1279	help
1280	Disabling this option eliminates support for BUG and WARN, reducing
1281	the size of your kernel image and potentially quietly ignoring
1282	numerous fatal conditions. You should only consider disabling this
1283	option for embedded systems with no facilities for reporting errors.
1284	Just say Y.
1285
1286	config ELF_CORE
1287	depends on COREDUMP
1288	default y
1289	bool "Enable ELF core dumps" if EXPERT
1290	help
1291	Enable support for generating core dumps. Disabling saves about 4k.
1292
1293
1294	config PCSPKR_PLATFORM
1295	bool "Enable PC-Speaker support" if EXPERT
1296	depends on HAVE_PCSPKR_PLATFORM
1297	select I8253_LOCK
1298	default y
1299	help
1300	This option allows to disable the internal PC-Speaker
1301	support, saving some memory.
1302
1303	config HAVE_PCSPKR_PLATFORM
1304	bool
1305
1306	config BASE_FULL
1307	default y
1308	bool "Enable full-sized data structures for core" if EXPERT
1309	help
1310	Disabling this option reduces the size of miscellaneous core
1311	kernel data structures. This saves memory on small machines,
1312	but may reduce performance.
1313
1314	config FUTEX
1315	bool "Enable futex support" if EXPERT
1316	default y
1317	select RT_MUTEXES
1318	help
1319	Disabling this option will cause the kernel to be built without
1320	support for "fast userspace mutexes". The resulting kernel may not
1321	run glibc-based applications correctly.
1322
1323	config EPOLL
1324	bool "Enable eventpoll support" if EXPERT
1325	default y
1326	select ANON_INODES
1327	help
1328	Disabling this option will cause the kernel to be built without
1329	support for epoll family of system calls.
1330
1331	config SIGNALFD
1332	bool "Enable signalfd() system call" if EXPERT
1333	select ANON_INODES
1334	default y
1335	help
1336	Enable the signalfd() system call that allows to receive signals
1337	on a file descriptor.
1338
1339	If unsure, say Y.
1340
1341	config TIMERFD
1342	bool "Enable timerfd() system call" if EXPERT
1343	select ANON_INODES
1344	default y
1345	help
1346	Enable the timerfd() system call that allows to receive timer
1347	events on a file descriptor.
1348
1349	If unsure, say Y.
1350
1351	config EVENTFD
1352	bool "Enable eventfd() system call" if EXPERT
1353	select ANON_INODES
1354	default y
1355	help
1356	Enable the eventfd() system call that allows to receive both
1357	kernel notification (ie. KAIO) or userspace notifications.
1358
1359	If unsure, say Y.
1360
1361	config SHMEM
1362	bool "Use full shmem filesystem" if EXPERT
1363	default y
1364	depends on MMU
1365	help
1366	The shmem is an internal filesystem used to manage shared memory.
1367	It is backed by swap and manages resource limits. It is also exported
1368	to userspace as tmpfs if TMPFS is enabled. Disabling this
1369	option replaces shmem and tmpfs with the much simpler ramfs code,
1370	which may be appropriate on small systems without swap.
1371
1372	config AIO
1373	bool "Enable AIO support" if EXPERT
1374	default y
1375	help
1376	This option enables POSIX asynchronous I/O which may by used
1377	by some high performance threaded applications. Disabling
1378	this option saves about 7k.
1379
1380	config EMBEDDED
1381	bool "Embedded system"
1382	select EXPERT
1383	help
1384	This option should be enabled if compiling the kernel for
1385	an embedded system so certain expert options are available
1386	for configuration.
1387
1388	config HAVE_PERF_EVENTS
1389	bool
1390	help
1391	See tools/perf/design.txt for details.
1392
1393	config PERF_USE_VMALLOC
1394	bool
1395	help
1396	See tools/perf/design.txt for details
1397
1398	menu "Kernel Performance Events And Counters"
1399
1400	config PERF_EVENTS
1401	bool "Kernel performance events and counters"
1402	default y if PROFILING
1403	depends on HAVE_PERF_EVENTS
1404	select ANON_INODES
1405	select IRQ_WORK
1406	help
1407	Enable kernel support for various performance events provided
1408	by software and hardware.
1409
1410	Software events are supported either built-in or via the
1411	use of generic tracepoints.
1412
1413	Most modern CPUs support performance events via performance
1414	counter registers. These registers count the number of certain
1415	types of hw events: such as instructions executed, cachemisses
1416	suffered, or branches mis-predicted - without slowing down the
1417	kernel or applications. These registers can also trigger interrupts
1418	when a threshold number of events have passed - and can thus be
1419	used to profile the code that runs on that CPU.
1420
1421	The Linux Performance Event subsystem provides an abstraction of
1422	these software and hardware event capabilities, available via a
1423	system call and used by the "perf" utility in tools/perf/. It
1424	provides per task and per CPU counters, and it provides event
1425	capabilities on top of those.
1426
1427	Say Y if unsure.
1428
1429	config DEBUG_PERF_USE_VMALLOC
1430	default n
1431	bool "Debug: use vmalloc to back perf mmap() buffers"
1432	depends on PERF_EVENTS && DEBUG_KERNEL
1433	select PERF_USE_VMALLOC
1434	help
1435	Use vmalloc memory to back perf mmap() buffers.
1436
1437	Mostly useful for debugging the vmalloc code on platforms
1438	that don't require it.
1439
1440	Say N if unsure.
1441
1442	endmenu
1443
1444	config VM_EVENT_COUNTERS
1445	default y
1446	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1447	help
1448	VM event counters are needed for event counts to be shown.
1449	This option allows the disabling of the VM event counters
1450	on EXPERT systems. /proc/vmstat will only show page counts
1451	if VM event counters are disabled.
1452
1453	config PCI_QUIRKS
1454	default y
1455	bool "Enable PCI quirk workarounds" if EXPERT
1456	depends on PCI
1457	help
1458	This enables workarounds for various PCI chipset
1459	bugs/quirks. Disable this only if your target machine is
1460	unaffected by PCI quirks.
1461
1462	config SLUB_DEBUG
1463	default y
1464	bool "Enable SLUB debugging support" if EXPERT
1465	depends on SLUB && SYSFS
1466	help
1467	SLUB has extensive debug support features. Disabling these can
1468	result in significant savings in code size. This also disables
1469	SLUB sysfs support. /sys/slab will not exist and there will be
1470	no support for cache validation etc.
1471
1472	config COMPAT_BRK
1473	bool "Disable heap randomization"
1474	default y
1475	help
1476	Randomizing heap placement makes heap exploits harder, but it
1477	also breaks ancient binaries (including anything libc5 based).
1478	This option changes the bootup default to heap randomization
1479	disabled, and can be overridden at runtime by setting
1480	/proc/sys/kernel/randomize_va_space to 2.
1481
1482	On non-ancient distros (post-2000 ones) N is usually a safe choice.
1483
1484	choice
1485	prompt "Choose SLAB allocator"
1486	default SLUB
1487	help
1488	This option allows to select a slab allocator.
1489
1490	config SLAB
1491	bool "SLAB"
1492	help
1493	The regular slab allocator that is established and known to work
1494	well in all environments. It organizes cache hot objects in
1495	per cpu and per node queues.
1496
1497	config SLUB
1498	bool "SLUB (Unqueued Allocator)"
1499	help
1500	SLUB is a slab allocator that minimizes cache line usage
1501	instead of managing queues of cached objects (SLAB approach).
1502	Per cpu caching is realized using slabs of objects instead
1503	of queues of objects. SLUB can use memory efficiently
1504	and has enhanced diagnostics. SLUB is the default choice for
1505	a slab allocator.
1506
1507	config SLOB
1508	depends on EXPERT
1509	bool "SLOB (Simple Allocator)"
1510	help
1511	SLOB replaces the stock allocator with a drastically simpler
1512	allocator. SLOB is generally more space efficient but
1513	does not perform as well on large systems.
1514
1515	endchoice
1516
1517	config MMAP_ALLOW_UNINITIALIZED
1518	bool "Allow mmapped anonymous memory to be uninitialized"
1519	depends on EXPERT && !MMU
1520	default n
1521	help
1522	Normally, and according to the Linux spec, anonymous memory obtained
1523	from mmap() has it's contents cleared before it is passed to
1524	userspace. Enabling this config option allows you to request that
1525	mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1526	providing a huge performance boost. If this option is not enabled,
1527	then the flag will be ignored.
1528
1529	This is taken advantage of by uClibc's malloc(), and also by
1530	ELF-FDPIC binfmt's brk and stack allocator.
1531
1532	Because of the obvious security issues, this option should only be
1533	enabled on embedded devices where you control what is run in
1534	userspace. Since that isn't generally a problem on no-MMU systems,
1535	it is normally safe to say Y here.
1536
1537	See Documentation/nommu-mmap.txt for more information.
1538
1539	config PROFILING
1540	bool "Profiling support"
1541	help
1542	Say Y here to enable the extended profiling support mechanisms used
1543	by profilers such as OProfile.
1544
1545	#
1546	# Place an empty function call at each tracepoint site. Can be
1547	# dynamically changed for a probe function.
1548	#
1549	config TRACEPOINTS
1550	bool
1551
1552	source "arch/Kconfig"
1553
1554	endmenu # General setup
1555
1556	config HAVE_GENERIC_DMA_COHERENT
1557	bool
1558	default n
1559
1560	config SLABINFO
1561	bool
1562	depends on PROC_FS
1563	depends on SLAB \|\| SLUB_DEBUG
1564	default y
1565
1566	config RT_MUTEXES
1567	boolean
1568
1569	config BASE_SMALL
1570	int
1571	default 0 if BASE_FULL
1572	default 1 if !BASE_FULL
1573
1574	menuconfig MODULES
1575	bool "Enable loadable module support"
1576	help
1577	Kernel modules are small pieces of compiled code which can
1578	be inserted in the running kernel, rather than being
1579	permanently built into the kernel. You use the "modprobe"
1580	tool to add (and sometimes remove) them. If you say Y here,
1581	many parts of the kernel can be built as modules (by
1582	answering M instead of Y where indicated): this is most
1583	useful for infrequently used options which are not required
1584	for booting. For more information, see the man pages for
1585	modprobe, lsmod, modinfo, insmod and rmmod.
1586
1587	If you say Y here, you will need to run "make
1588	modules_install" to put the modules under /lib/modules/
1589	where modprobe can find them (you may need to be root to do
1590	this).
1591
1592	If unsure, say Y.
1593
1594	if MODULES
1595
1596	config MODULE_FORCE_LOAD
1597	bool "Forced module loading"
1598	default n
1599	help
1600	Allow loading of modules without version information (ie. modprobe
1601	--force). Forced module loading sets the 'F' (forced) taint flag and
1602	is usually a really bad idea.
1603
1604	config MODULE_UNLOAD
1605	bool "Module unloading"
1606	help
1607	Without this option you will not be able to unload any
1608	modules (note that some modules may not be unloadable
1609	anyway), which makes your kernel smaller, faster
1610	and simpler. If unsure, say Y.
1611
1612	config MODULE_FORCE_UNLOAD
1613	bool "Forced module unloading"
1614	depends on MODULE_UNLOAD
1615	help
1616	This option allows you to force a module to unload, even if the
1617	kernel believes it is unsafe: the kernel will remove the module
1618	without waiting for anyone to stop using it (using the -f option to
1619	rmmod). This is mainly for kernel developers and desperate users.
1620	If unsure, say N.
1621
1622	config MODVERSIONS
1623	bool "Module versioning support"
1624	help
1625	Usually, you have to use modules compiled with your kernel.
1626	Saying Y here makes it sometimes possible to use modules
1627	compiled for different kernels, by adding enough information
1628	to the modules to (hopefully) spot any changes which would
1629	make them incompatible with the kernel you are running. If
1630	unsure, say N.
1631
1632	config MODULE_SRCVERSION_ALL
1633	bool "Source checksum for all modules"
1634	help
1635	Modules which contain a MODULE_VERSION get an extra "srcversion"
1636	field inserted into their modinfo section, which contains a
1637	sum of the source files which made it. This helps maintainers
1638	see exactly which source was used to build a module (since
1639	others sometimes change the module source without updating
1640	the version). With this option, such a "srcversion" field
1641	will be created for all modules. If unsure, say N.
1642
1643	config MODULE_SIG
1644	bool "Module signature verification"
1645	depends on MODULES
1646	select KEYS
1647	select CRYPTO
1648	select ASYMMETRIC_KEY_TYPE
1649	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1650	select PUBLIC_KEY_ALGO_RSA
1651	select ASN1
1652	select OID_REGISTRY
1653	select X509_CERTIFICATE_PARSER
1654	help
1655	Check modules for valid signatures upon load: the signature
1656	is simply appended to the module. For more information see
1657	Documentation/module-signing.txt.
1658
1659	!!!WARNING!!! If you enable this option, you MUST make sure that the
1660	module DOES NOT get stripped after being signed. This includes the
1661	debuginfo strip done by some packagers (such as rpmbuild) and
1662	inclusion into an initramfs that wants the module size reduced.
1663
1664	config MODULE_SIG_FORCE
1665	bool "Require modules to be validly signed"
1666	depends on MODULE_SIG
1667	help
1668	Reject unsigned modules or signed modules for which we don't have a
1669	key. Without this, such modules will simply taint the kernel.
1670
1671	config MODULE_SIG_ALL
1672	bool "Automatically sign all modules"
1673	default y
1674	depends on MODULE_SIG
1675	help
1676	Sign all modules during make modules_install. Without this option,
1677	modules must be signed manually, using the scripts/sign-file tool.
1678
1679	comment "Do not forget to sign required modules with scripts/sign-file"
1680	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1681
1682	choice
1683	prompt "Which hash algorithm should modules be signed with?"
1684	depends on MODULE_SIG
1685	help
1686	This determines which sort of hashing algorithm will be used during
1687	signature generation. This algorithm _must_ be built into the kernel
1688	directly so that signature verification can take place. It is not
1689	possible to load a signed module containing the algorithm to check
1690	the signature on that module.
1691
1692	config MODULE_SIG_SHA1
1693	bool "Sign modules with SHA-1"
1694	select CRYPTO_SHA1
1695
1696	config MODULE_SIG_SHA224
1697	bool "Sign modules with SHA-224"
1698	select CRYPTO_SHA256
1699
1700	config MODULE_SIG_SHA256
1701	bool "Sign modules with SHA-256"
1702	select CRYPTO_SHA256
1703
1704	config MODULE_SIG_SHA384
1705	bool "Sign modules with SHA-384"
1706	select CRYPTO_SHA512
1707
1708	config MODULE_SIG_SHA512
1709	bool "Sign modules with SHA-512"
1710	select CRYPTO_SHA512
1711
1712	endchoice
1713
1714	config MODULE_SIG_HASH
1715	string
1716	depends on MODULE_SIG
1717	default "sha1" if MODULE_SIG_SHA1
1718	default "sha224" if MODULE_SIG_SHA224
1719	default "sha256" if MODULE_SIG_SHA256
1720	default "sha384" if MODULE_SIG_SHA384
1721	default "sha512" if MODULE_SIG_SHA512
1722
1723	endif # MODULES
1724
1725	config INIT_ALL_POSSIBLE
1726	bool
1727	help
1728	Back when each arch used to define their own cpu_online_mask and
1729	cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1730	with all 1s, and others with all 0s. When they were centralised,
1731	it was better to provide this option than to break all the archs
1732	and have several arch maintainers pursuing me down dark alleys.
1733
1734	config STOP_MACHINE
1735	bool
1736	default y
1737	depends on (SMP && MODULE_UNLOAD) \|\| HOTPLUG_CPU
1738	help
1739	Need stop_machine() primitive.
1740
1741	source "block/Kconfig"
1742
1743	config PREEMPT_NOTIFIERS
1744	bool
1745
1746	config PADATA
1747	depends on SMP
1748	bool
1749
1750	# Can be selected by architectures with broken toolchains
1751	# that get confused by correct const<->read_only section
1752	# mappings
1753	config BROKEN_RODATA
1754	bool
1755
1756	config ASN1
1757	tristate
1758	help
1759	Build a simple ASN.1 grammar compiler that produces a bytecode output
1760	that can be interpreted by the ASN.1 stream decoder and used to
1761	inform it as to what tags are to be expected in a stream and what
1762	functions to call on what tags.
1763
1764	source "kernel/Kconfig.locks"
1765

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