Paul E. McKenney d40011f601 rcu: Control grace-period duration from sysfs ... Although almost everyone is well-served by the defaults, some uses of RCU benefit from shorter grace periods, while others benefit more from the greater efficiency provided by longer grace periods. Situations requiring a large number of grace periods to elapse (and wireshark startup has been called out as an example of this) are helped by lower-latency grace periods. Furthermore, in some embedded applications, people are willing to accept a small degradation in update efficiency (due to there being more of the shorter grace-period operations) in order to gain the lower latency. In contrast, those few systems with thousands of CPUs need longer grace periods because the CPU overhead of a grace period rises roughly linearly with the number of CPUs. Such systems normally do not make much use of facilities that require large numbers of grace periods to elapse, so this is a good tradeoff. Therefore, this commit allows the durations to be controlled from sysfs. There are two sysfs parameters, one named "jiffies_till_first_fqs" that specifies the delay in jiffies from the end of grace-period initialization until the first attempt to force quiescent states, and the other named "jiffies_till_next_fqs" that specifies the delay (again in jiffies) between subsequent attempts to force quiescent states. They both default to three jiffies, which is compatible with the old hard-coded behavior. At some future time, it may be possible to automatically increase the grace-period length with the number of CPUs, but we do not yet have sufficient data to do a good job. Preliminary data indicates that we should add an addiitonal jiffy to each of the delays for every 200 CPUs in the system, but more experimentation is needed. For now, the number of systems with more than 1,000 CPUs is small enough that this can be relegated to boot-time hand tuning. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>		2012-09-23 07:41:54 -07:00
..
ABI	PCI/PM: Add ABI document for sysfs file d3cold_allowed	2012-08-21 17:36:33 -06:00
accounting
acpi	Update documentation for parameter *notrigger* in einj.txt	2012-03-30 03:30:19 -04:00
aoe	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
arm	[media] Documentation: Add newline at end-of-file to files lacking one	2012-07-30 20:37:01 -03:00
auxdisplay
backlight	backlight: new backlight driver for LP855x devices	2012-03-23 16:58:33 -07:00
blackfin	Documentation: Fix typo in multiple files in Documentation	2012-04-16 14:37:13 +02:00
block	Documentation: update tunable options in block/cfq-iosched.txt	2012-08-09 15:28:05 +02:00
blockdev	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
cdrom	doc: fix broken references	2011-09-27 18:08:04 +02:00
cgroups	mm/memcg: complete documentation for tcp memcg files	2012-07-31 18:42:43 -07:00
connector	connector: Move cn_test.c away from NLMSG_PUT().	2012-06-26 21:19:02 -07:00
console
cpu-freq	Doc: cpufreq: Fix typo and outdated line	2011-11-08 10:23:29 +01:00
cpuidle	cpuidle: add a sysfs entry to disable specific C state for debug purpose.	2012-03-30 01:52:58 -04:00
cris	CRIS: Update documentation	2012-04-03 13:09:18 +02:00
crypto
development-process	Documentation: Update stable address	2011-12-12 14:14:31 -08:00
device-mapper	Merge branch 'for-next' of git://neil.brown.name/md	2012-08-01 09:02:01 -07:00
devicetree	arm-soc fixes for v3.6-rc3	2012-08-25 17:33:33 -07:00
DocBook	Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media	2012-08-21 16:54:38 -07:00
driver-model	Pin control subsystem changes for kernel 3.5:	2012-05-21 16:58:23 -07:00
dvb	Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media	2012-07-30 19:03:41 -07:00
early-userspace
EDID	drm: allow loading an EDID as firmware to override broken monitor	2012-03-20 10:09:28 +00:00
extcon	Documentation/extcon: porting guide for Android kernel switch driver.	2012-04-20 09:24:27 -07:00
fault-injection	fault-injection: add tool to run command with failslab or fail_page_alloc	2012-07-30 17:25:22 -07:00
fb	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
filesystems	Documentation: update mount option in filesystem/vfat.txt	2012-08-21 16:45:02 -07:00
firmware_class
frv	doc: fix broken references	2011-09-27 18:08:04 +02:00
hid	HID: uhid: add documentation	2012-06-18 13:42:03 +02:00
hwmon	hwmon: Honeywell Humidicon HIH-6130/HIH-6131 humidity and temperature sensor driver	2012-07-21 21:48:44 -07:00
i2c	i2c-i801: Enable IRQ for SMBus transactions	2012-07-24 14:13:58 +02:00
i2o	Documentation: Fix multiple typo in Documentation	2012-03-07 16:08:24 +01:00
ia64
ide	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
infiniband
input	Input: add driver for FT5x06 based EDT displays	2012-07-24 23:55:03 -07:00
ioctl	vfio: VFIO core	2012-07-31 08:16:22 -06:00
isdn	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
ja_JP
kbuild	Merge branch 'kconfig' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild	2012-05-28 10:37:56 -07:00
kdump	kexec: update URL of kexec homepage	2012-07-18 18:35:57 -07:00
ko_KR	driver-core: documentation: fix up Greg's email address	2012-02-15 14:48:01 -08:00
laptops	Documentation: fix the VM knobs descritpion WRT pdflush	2012-08-04 12:15:09 +04:00
leds	LEDS: add BlinkM RGB LED driver, documentation and update MAINTAINERS	2012-07-24 16:00:51 +08:00
m68k
make
memory-devices	memory: emif: add basic infrastructure for EMIF driver	2012-05-02 00:10:49 -07:00
mips
misc-devices	mei: mei.txt: minor grammar fixes	2012-06-13 13:38:25 -07:00
mmc	mmc: core: Fixup delayed work clock gating patch	2012-01-11 23:58:43 -05:00
mn10300
mtd
namespaces
netlabel
networking	netconsole.txt: revision of examples for the receiver of kernel messages	2012-08-14 14:33:33 -07:00
nfc	NFC: Error management documentation	2012-07-09 16:42:11 -04:00
parisc	Documentation: Fix typo in multiple files in Documentation	2012-04-16 14:37:13 +02:00
PCI	doc: fix broken references	2011-09-27 18:08:04 +02:00
pcmcia
power	The tag contains just a few battery-related changes for v3.6. It's is	2012-07-31 18:08:25 -07:00
powerpc	Revert "powerpc/hw-breakpoint: Use generic hw-breakpoint interfaces for new PPC ptrace flags"	2012-05-22 14:37:24 +10:00
pps
prctl	security: Minor improvements to no_new_privs documentation	2012-07-08 00:25:48 +10:00
pti
ptp
rapidio	RapidIO: documentation update	2011-11-02 16:07:02 -07:00
RCU	rcu: Adjust debugfs tracing for kthread-based quiescent-state forcing	2012-09-23 07:41:54 -07:00
s390	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
scheduler	sched: Remove stale power aware scheduling remnants and dysfunctional knobs	2012-05-17 13:48:56 +02:00
scsi	Merge branch 'delete-mca' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux	2012-05-23 17:12:06 -07:00
security	Yama: higher restrictions should block PTRACE_TRACEME	2012-08-10 19:58:07 +10:00
serial	serial: delete the MCA specific 8250 support.	2012-05-17 19:02:14 -04:00
sh
sound	Sound fixes for 3.6-rc1	2012-08-01 10:42:26 -07:00
spi	spi: create a message queueing infrastructure	2012-03-07 19:19:48 -07:00
sysctl	Documentation: fix the VM knobs descritpion WRT pdflush	2012-08-04 12:15:09 +04:00
target	Documentation: Fix typo in tcm_mod_builder.py	2012-02-10 09:52:18 +01:00
telephony
thermal	Thermal: Documentation update	2012-07-24 23:20:40 -04:00
timers	doc: fix broken references	2011-09-27 18:08:04 +02:00
trace	tracing: Fix kconfig warning due to a typo	2012-05-08 14:17:25 +02:00
usb	usb: gadget: mass_storage: add documentation	2012-06-15 14:32:30 +03:00
vDSO
video4linux	Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media	2012-07-31 18:47:44 -07:00
virtual	KVM updates for the 3.6 merge window	2012-07-24 12:01:20 -07:00
vm	hugetlb: update hugetlbpage.txt	2012-08-21 16:45:03 -07:00
w1	1-Wire: Add support for the maxim ds1825 temperature sensor	2012-08-16 12:33:59 -07:00
watchdog	watchdog: fix watchdog-test.c build warning	2012-08-29 17:12:58 +02:00
wimax
x86	Merge branch 'x86-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2012-07-26 13:13:25 -07:00
zh_CN	Fix a mistake sentence in the file 'Documentation/zh_CN/magic-number.txt'	2012-05-07 17:20:27 -07:00
.gitignore
00-INDEX	MCA: delete all remaining traces of microchannel bus support.	2012-05-17 19:06:13 -04:00
applying-patches.txt
atomic_ops.txt	doc: Add load/store guarantees to Documentation/atomic-ops.txt	2011-12-11 10:31:58 -08:00
bad_memory.txt
basic_profiling.txt
binfmt_misc.txt
braille-console.txt
bt8xxgpio.txt
btmrvl.txt
BUG-HUNTING
bus-virt-phys-mapping.txt	doc: fix broken references	2011-09-27 18:08:04 +02:00
cachetlb.txt
Changes
circular-buffers.txt
clk.txt	Documentation: common clk API	2012-03-16 20:35:01 +00:00
coccinelle.txt	coccinelle.txt: update documentation to include M= option	2012-01-14 22:25:56 +01:00
CodingStyle	CodingStyle: add kmalloc_array() to memory allocators	2012-05-31 17:49:26 -07:00
cpu-hotplug.txt	documentation: remove references to cpu_*_map.	2012-03-29 15:38:31 +10:30
cpu-load.txt
cputopology.txt
crc32.txt	crc32: move long comment about crc32 fundamentals to Documentation/	2012-03-23 16:58:37 -07:00
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt
dell_rbu.txt
devices.txt	Doc: document max raw dev number	2012-06-03 12:05:50 +02:00
digsig.txt	crypto: digital signature verification support	2011-11-09 12:10:37 +02:00
DMA-API-HOWTO.txt
DMA-API.txt	include/linux/dma-mapping.h: add dma_zalloc_coherent()	2011-11-02 16:07:02 -07:00
DMA-attributes.txt	common: DMA-mapping: add DMA_ATTR_SKIP_CPU_SYNC attribute	2012-07-30 12:25:47 +02:00
dma-buf-sharing.txt	dma-buf: add initial vmap documentation	2012-05-25 12:51:11 +05:30
DMA-ISA-LPC.txt
dmaengine.txt	Documentation: Fix multiple typo in Documentation	2012-03-07 16:08:24 +01:00
dontdiff	kconfig: remove lkc_defs.h from .gitignore and dontdiff	2012-07-13 15:08:25 +02:00
dynamic-debug-howto.txt	dynamic_debug: update Documentation/*, Kconfig.debug	2012-04-30 16:26:30 -04:00
edac.txt	Merge branch 'devel'	2012-07-29 21:11:05 -03:00
eisa.txt	MCA: delete all remaining traces of microchannel bus support.	2012-05-17 19:06:13 -04:00
email-clients.txt	Documentation: email-clients: Add better Thunderbird information	2011-08-13 18:34:03 -07:00
feature-removal-schedule.txt	ARM: at91/feature-removal-schedule: delay at91_mci removal	2012-08-27 09:59:36 +02:00
flexible-arrays.txt
futex-requeue-pi.txt
gcov.txt
gpio.txt	gpio: add flags to export GPIOs when requesting	2012-04-05 21:24:06 -07:00
highuid.txt
HOWTO	docs: update HOWTO for 2.6.x -> 3.x versioning	2012-04-19 19:13:08 -07:00
hw_random.txt
hwspinlock.txt	hwspinlock/core: register a bank of hwspinlocks in a single API call	2011-09-21 19:45:34 +03:00
init.txt
initrd.txt	Documentation/initrd.txt: Change the location of util-linux	2012-05-25 16:18:34 +02:00
intel_txt.txt
Intel-IOMMU.txt
io_ordering.txt
io-mapping.txt
iostats.txt
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt	irq_domain: Standardise legacy/linear domain selection	2012-07-11 14:59:17 +01:00
IRQ.txt
irqflags-tracing.txt
isapnp.txt
java.txt
kernel-doc-nano-HOWTO.txt
kernel-docs.txt	doc: fix broken references	2011-09-27 18:08:04 +02:00
kernel-parameters.txt	rcu: Control grace-period duration from sysfs	2012-09-23 07:41:54 -07:00
kmemcheck.txt
kmemleak.txt	kmemleak: Handle percpu memory allocation	2011-12-02 16:12:42 +00:00
kobject.txt	driver-core: documentation: fix up Greg's email address	2012-02-15 14:48:01 -08:00
kprobes.txt
kref.txt
ldm.txt
local_ops.txt
lockdep-design.txt	lockdep: Update documentation for lock-class leak detection	2011-12-11 10:31:23 -08:00
lockstat.txt
lockup-watchdogs.txt	watchdog: Update documentation	2012-02-11 15:11:28 +01:00
logo.gif
logo.txt
magic-number.txt	drivers/net: fix up stale paths from driver reorg	2012-01-30 12:54:40 -05:00
Makefile	mei: move doc files Documentation/misc-devices/mei	2012-05-09 13:59:09 -07:00
ManagementStyle	Documentation: ManagementStyle: fixed typo	2012-06-28 12:03:15 +02:00
md.txt	md: create externally visible flags for supporting hot-replace.	2011-12-23 10:17:51 +11:00
media-framework.txt	[media] media: Add link_validate() op to check links to the sink pad	2012-05-14 08:44:11 -03:00
memory-barriers.txt	doc: fix broken references	2011-09-27 18:08:04 +02:00
memory-hotplug.txt	Documentation: Fix typo in multiple files in Documentation	2012-04-16 14:37:13 +02:00
memory.txt
mono.txt	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
mutex-design.txt
nommu-mmap.txt
numastat.txt	Doc: Update numastat.txt	2012-02-28 16:05:06 +01:00
oops-tracing.txt	module,bug: Add TAINT_OOT_MODULE flag for modules not built in-tree	2011-11-07 07:54:42 +10:30
padata.txt
parport-lowlevel.txt
parport.txt	Documentation: remove references to /etc/modprobe.conf	2012-03-30 16:03:15 -07:00
pi-futex.txt
pinctrl.txt	Documentation/pinctrl.txt: Fix some misspelled macros	2012-08-17 11:09:58 +02:00
pnp.txt
preempt-locking.txt
printk-formats.txt	vsprintf: add support of '%*ph[CDN]'	2012-07-30 17:25:14 -07:00
prio_tree.txt
pwm.txt	pwm: Add table-based lookup for static mappings	2012-06-15 12:56:53 +02:00
ramoops.txt	pstore/ram: Add ftrace messages handling	2012-07-17 10:14:17 -07:00
rbtree.txt
remoteproc.txt	remoteproc: adopt the driver core's alloc/add/del/put naming	2012-07-06 00:53:27 +03:00
rfkill.txt	doc: fix broken references	2011-09-27 18:08:04 +02:00
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt	rpmsg: add virtio-based remote processor messaging bus	2012-02-08 22:53:58 +02:00
rt-mutex-design.txt
rt-mutex.txt
rtc.txt
SAK.txt
SecurityBugs
serial-console.txt
sgi-ioc4.txt
sgi-visws.txt
SM501.txt
sparse.txt
spinlocks.txt
stable_api_nonsense.txt
stable_kernel_rules.txt	stable: Allow merging of backports for serious user-visible performance issues	2012-06-25 12:11:58 -07:00
static-keys.txt	Documentation: Fix typo in multiple files in Documentation	2012-04-16 14:37:13 +02:00
SubmitChecklist
SubmittingDrivers	Documentation: SubmittingDrivers: fix Linus's git tree URL	2011-08-13 18:34:03 -07:00
SubmittingPatches	Documentation/SubmittingPatches: suggested the use of scripts/get_maintainer.pl	2012-05-25 16:18:30 +02:00
svga.txt
sysfs-rules.txt
sysrq.txt	Documentation: sysrq: Crutcher Dunnavant is unavailable	2012-03-30 16:03:15 -07:00
unaligned-memory-access.txt
unicode.txt
unshare.txt
vfio.txt	vfio: Add documentation	2012-07-31 08:16:23 -06:00
VGA-softcursor.txt
vgaarbiter.txt	misc latin1 to utf8 conversions	2012-01-02 13:04:55 +01:00
video-output.txt
vme_api.txt	VME: Move API documentation to Documentation folder	2012-05-08 16:01:34 -07:00
volatile-considered-harmful.txt
workqueue.txt	workqueue: reimplement WQ_HIGHPRI using a separate worker_pool	2012-07-13 22:24:45 -07:00
xz.txt
zorro.txt