Paul E. McKenney fbce7497ee rcu: Parallelize and economize NOCB kthread wakeups ... An 80-CPU system with a context-switch-heavy workload can require so many NOCB kthread wakeups that the RCU grace-period kthreads spend several tens of percent of a CPU just awakening things. This clearly will not scale well: If you add enough CPUs, the RCU grace-period kthreads would get behind, increasing grace-period latency. To avoid this problem, this commit divides the NOCB kthreads into leaders and followers, where the grace-period kthreads awaken the leaders each of whom in turn awakens its followers. By default, the number of groups of kthreads is the square root of the number of CPUs, but this default may be overridden using the rcutree.rcu_nocb_leader_stride boot parameter. This reduces the number of wakeups done per grace period by the RCU grace-period kthread by the square root of the number of CPUs, but of course by shifting those wakeups to the leaders. In addition, because the leaders do grace periods on behalf of their respective followers, the number of wakeups of the followers decreases by up to a factor of two. Instead of being awakened once when new callbacks arrive and again at the end of the grace period, the followers are awakened only at the end of the grace period. For a numerical example, in a 4096-CPU system, the grace-period kthread would awaken 64 leaders, each of which would awaken its 63 followers at the end of the grace period. This compares favorably with the 79 wakeups for the grace-period kthread on an 80-CPU system. Reported-by: Rik van Riel <riel@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>		2014-07-07 15:13:44 -07:00
..
debug	kernel/printk: use symbolic defines for console loglevels	2014-06-04 16:54:17 -07:00
events	Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-06-12 19:18:49 -07:00
gcov	gcov: add support for GCC 4.9	2014-06-10 15:34:46 -07:00
irq	genirq: Improve documentation to match current implementation	2014-05-27 10:16:44 +02:00
locking	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-06-12 18:48:15 -07:00
power	Merge branch 'pm-sleep'	2014-06-12 13:43:08 +02:00
printk	kernel/printk: use symbolic defines for console loglevels	2014-06-04 16:54:17 -07:00
rcu	rcu: Parallelize and economize NOCB kthread wakeups	2014-07-07 15:13:44 -07:00
sched	rcu: Reduce overhead of cond_resched() checks for RCU	2014-06-23 11:19:32 -07:00
time	Merge branch 'akpm' (patchbomb from Andrew) into next	2014-06-04 16:55:13 -07:00
trace	One bug fix that goes back to 3.10. Accessing a non existent buffer	2014-06-12 21:07:25 -07:00
.gitignore	Ignore generated file kernel/x509_certificate_list	2013-12-10 18:21:34 +00:00
Kconfig.freezer	…
Kconfig.hz	kernel: remove CONFIG_USE_GENERIC_SMP_HELPERS	2013-11-15 09:32:22 +09:00
Kconfig.locks	locking/rwlocks: Introduce 'qrwlocks' - fair, queued rwlocks	2014-06-06 07:58:28 +02:00
Kconfig.preempt	…
Makefile	Merge branch 'x86-asmlinkage-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-03-31 14:13:25 -07:00
acct.c	ipc, kernel: clear whitespace	2014-06-06 16:08:14 -07:00
async.c	…
audit.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2014-06-12 14:27:40 -07:00
audit.h	audit: Use struct net not pid_t to remember the network namespce to reply in	2014-03-20 10:10:53 -04:00
audit_tree.c	inotify: Fix reporting of cookies for inotify events	2014-02-18 11:17:17 +01:00
audit_watch.c	inotify: Fix reporting of cookies for inotify events	2014-02-18 11:17:17 +01:00
auditfilter.c	Merge git://git.infradead.org/users/eparis/audit	2014-04-12 12:38:53 -07:00
auditsc.c	auditsc: audit_krule mask accesses need bounds checking	2014-06-10 08:44:40 -07:00
backtracetest.c	kernel/backtracetest.c: replace no level printk by pr_info()	2014-06-04 16:54:14 -07:00
bounds.c	mm: do not allocate page->ptl dynamically, if spinlock_t fits to long	2013-12-20 12:25:45 -08:00
capability.c	fs,userns: Change inode_capable to capable_wrt_inode_uidgid	2014-06-10 13:57:22 -07:00
cgroup.c	Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2014-06-09 15:03:33 -07:00
cgroup_freezer.c	cgroup: remove css_parent()	2014-05-16 13:22:48 -04:00
compat.c	kernel/compat.c: use sizeof() instead of sizeof	2014-06-04 16:54:19 -07:00
configs.c	proc: Supply PDE attribute setting accessor functions	2013-05-01 17:29:18 -04:00
context_tracking.c	asmlinkage: Add explicit __visible to drivers/*, lib/*, kernel/*	2014-05-05 16:07:46 -07:00
cpu.c	More ACPI and power management updates for 3.16-rc1	2014-06-12 13:14:19 -07:00
cpu_pm.c	…
cpuset.c	Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2014-06-09 15:03:33 -07:00
crash_dump.c	…
cred.c	…
delayacct.c	kernel/delayacct.c: remove redundant checking in __delayacct_add_tsk()	2013-11-13 12:09:12 +09:00
dma.c	…
elfcore.c	switch elf_core_write_extra_phdrs() to dump_emit()	2013-11-09 00:16:23 -05:00
exec_domain.c	kernel/exec_domain.c: code clean-up	2014-06-04 16:54:15 -07:00
exit.c	signals: mv {dis,}allow_signal() from sched.h/exit.c to signal.[ch]	2014-06-06 16:08:11 -07:00
extable.c	asmlinkage: Make main_extable_sort_needed visible	2014-02-13 18:13:22 -08:00
fork.c	ptrace: fix fork event messages across pid namespaces	2014-06-06 16:08:11 -07:00
freezer.c	libata, freezer: avoid block device removal while system is frozen	2013-12-19 13:50:32 -05:00
futex.c	Merge branch 'next' (accumulated 3.16 merge window patches) into master	2014-06-08 11:31:16 -07:00
futex_compat.c	compat: Get rid of (get|put)_compat_time(val|spec)	2014-02-02 14:09:12 -08:00
groups.c	kernel/groups.c: remove return value of set_groups	2014-04-03 16:21:05 -07:00
hrtimer.c	Merge branch 'perf/urgent' into perf/core, to resolve conflict and to prepare for new patches	2014-06-06 07:55:06 +02:00
hung_task.c	kernel/hung_task.c: convert simple_strtoul to kstrtouint	2014-06-04 16:54:15 -07:00
irq_work.c	perf/x86: Warn to early_printk() in case irq_work is too slow	2014-02-21 21:49:07 +01:00
itimer.c	…
jump_label.c	static_key: WARN on usage before jump_label_init was called	2013-10-19 19:45:35 -04:00
kallsyms.c	kernel: use macros from compiler.h instead of __attribute__((...))	2014-04-07 16:36:11 -07:00
kcmp.c	…
kexec.c	kernel/kexec.c: convert printk to pr_foo()	2014-06-06 16:08:12 -07:00
kmod.c	signals: change wait_for_helper() to use kernel_sigaction()	2014-06-06 16:08:12 -07:00
kprobes.c	kprobes: Show blacklist entries via debugfs	2014-04-24 10:26:41 +02:00
ksysfs.c	kobject: Make support for uevent_helper optional.	2014-04-25 12:00:49 -07:00
kthread.c	kthread: fix return value of kthread_create() upon SIGKILL.	2014-06-04 16:53:51 -07:00
latencytop.c	kernel/latencytop.c: convert seq_printf to seq_puts	2014-06-04 16:54:15 -07:00
module-internal.h	KEYS: Separate the kernel signature checking keyring from module signing	2013-09-25 17:17:01 +01:00
module.c	Most of this is cleaning up various driver sysfs permissions so we can	2014-06-11 16:09:14 -07:00
module_signing.c	keys: change asymmetric keys to use common hash definitions	2013-10-25 17:15:18 -04:00
notifier.c	kprobes, notifier: Use NOKPROBE_SYMBOL macro in notifier	2014-04-24 10:26:39 +02:00
nsproxy.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2013-09-07 14:35:32 -07:00
padata.c	padata: Fix wrong usage of rcu_dereference()	2013-12-05 21:28:42 +08:00
panic.c	kernel/panic.c: add "crash_kexec_post_notifiers" option for kdump after panic_notifers	2014-06-06 16:08:12 -07:00
params.c	param: hand arguments after -- straight to init	2014-04-28 11:48:34 +09:30
pid.c	pidns: fix free_pid() to handle the first fork failure	2013-09-30 14:31:03 -07:00
pid_namespace.c	pid_namespace: pidns_get() should check task_active_pid_ns() != NULL	2014-04-02 16:20:21 -07:00
posix-cpu-timers.c	posix-timers: Convert abuses of BUG_ON to WARN_ON	2013-12-09 16:56:29 +01:00
posix-timers.c	…
profile.c	kernel/profile.c: use static const char instead of static char	2014-06-06 16:08:13 -07:00
ptrace.c	kernel/compat: convert to COMPAT_SYSCALL_DEFINE	2014-03-06 15:35:10 +01:00
range.c	range: Do not add new blank slot with add_range_with_merge	2013-06-18 11:32:10 -05:00
reboot.c	kernel/reboot.c: convert simple_strtoul to kstrtoint	2014-06-04 16:54:15 -07:00
relay.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2014-04-12 14:49:50 -07:00
res_counter.c	kernel/res_counter.c: replace simple_strtoull by kstrtoull	2014-06-04 16:54:15 -07:00
resource.c	resources: Clarify sanity check message	2014-05-23 10:47:21 -06:00
seccomp.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2014-06-12 14:27:40 -07:00
signal.c	signals: introduce kernel_sigaction()	2014-06-06 16:08:12 -07:00
smp.c	smp: print more useful debug info upon receiving IPI on an offline CPU	2014-06-06 16:08:12 -07:00
smpboot.c	kernel: delete __cpuinit usage from all core kernel files	2013-07-14 19:36:59 -04:00
smpboot.h	…
softirq.c	Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu	2014-05-22 11:36:10 +02:00
stacktrace.c	…
stop_machine.c	kernel/stop_machine.c: kernel-doc warning fix	2014-06-04 16:54:15 -07:00
sys.c	sched: Consolidate open coded implementations of nice level frobbing into nice_to_rlimit() and rlimit_to_nice()	2014-05-22 11:16:36 +02:00
sys_ni.c	sys_sgetmask/sys_ssetmask: add CONFIG_SGETMASK_SYSCALL	2014-06-04 16:54:14 -07:00
sysctl.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2014-06-12 14:27:40 -07:00
sysctl_binary.c	kernel/sysctl_binary.c: use scnprintf() instead of snprintf()	2013-11-13 12:09:33 +09:00
system_certificates.S	KEYS: correct alignment of system_certificate_list content in assembly file	2013-12-10 18:25:28 +00:00
system_keyring.c	KEYS: correct alignment of system_certificate_list content in assembly file	2013-12-10 18:25:28 +00:00
task_work.c	task_work: documentation	2013-09-11 15:58:27 -07:00
taskstats.c	genetlink: only pass array to genl_register_family_with_ops()	2013-11-19 16:39:05 -05:00
test_kprobes.c	kernel/: rename random32() to prandom_u32()	2013-04-29 18:28:42 -07:00
time.c	sched: Rename sched.c as sched/core.c in comments and Documentation	2013-06-19 12:58:42 +02:00
timeconst.bc	…
timer.c	timer: Prevent overflow in apply_slack	2014-04-30 13:46:17 +02:00
torture.c	torture: Remove __init from torture_init_begin/end	2014-05-14 09:46:30 -07:00
tracepoint.c	kernel/tracepoint.c: kernel-doc fixes	2014-06-04 16:54:15 -07:00
tsacct.c	…
uid16.c	userns: Kill nsown_capable it makes the wrong thing easy	2013-08-30 23:44:11 -07:00
up.c	smp: Rename __smp_call_function_single() to smp_call_function_single_async()	2014-02-24 14:47:15 -08:00
user-return-notifier.c	…
user.c	kernel/user.c: drop unused field 'files' from user_struct	2014-06-04 16:54:16 -07:00
user_namespace.c	kernel/user_namespace.c: kernel-doc/checkpatch fixes	2014-06-06 16:08:13 -07:00
utsname.c	userns: Kill nsown_capable it makes the wrong thing easy	2013-08-30 23:44:11 -07:00
utsname_sysctl.c	sysctl: convert use of typedef ctl_table to struct ctl_table	2014-06-06 16:08:16 -07:00
watchdog.c	kernel/watchdog.c:touch_softlockup_watchdog(): use raw_cpu_write()	2014-04-18 16:40:08 -07:00
workqueue.c	Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq	2014-06-09 14:56:49 -07:00
workqueue_internal.h	workqueue: rename manager_mutex to attach_mutex	2014-05-20 10:59:32 -04:00