Jason Low c8d75aa47d posix_cpu_timer: Reduce unnecessary sighand lock contention ... It was found while running a database workload on large systems that significant time was spent trying to acquire the sighand lock. The issue was that whenever an itimer expired, many threads ended up simultaneously trying to send the signal. Most of the time, nothing happened after acquiring the sighand lock because another thread had just already sent the signal and updated the "next expire" time. The fastpath_timer_check() didn't help much since the "next expire" time was updated after the threads exit fastpath_timer_check(). This patch addresses this by having the thread_group_cputimer structure maintain a boolean to signify when a thread in the group is already checking for process wide timers, and adds extra logic in the fastpath to check the boolean. Signed-off-by: Jason Low <jason.low2@hp.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: George Spelvin <linux@horizon.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: hideaki.kimura@hpe.com Cc: terry.rudd@hpe.com Cc: scott.norton@hpe.com Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1444849677-29330-5-git-send-email-jason.low2@hp.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>		2015-10-15 11:23:41 +02:00
..
bpf	bpf: fix out of bounds access in verifier log	2015-09-09 14:11:55 -07:00
configs	kconfig: add xenconfig defconfig helper	2015-06-16 11:04:29 +01:00
debug
events	perf: Fix races in computing the header sizes	2015-09-18 09:20:26 +02:00
gcov	gcov: add support for GCC 5.1	2015-06-30 19:44:57 -07:00
irq	genirq: Fix handle_bad_irq kerneldoc comment	2015-10-09 17:17:30 +02:00
livepatch	livepatch: Improve error handling in klp_disable_func()	2015-07-14 22:48:06 +02:00
locking	locking/lockdep: Fix hlock->pin_count reset on lock stack rebuilds	2015-09-23 09:48:53 +02:00
power	Merge branch 'for-4.3/core' of git://git.kernel.dk/linux-block	2015-09-02 13:10:25 -07:00
printk	kexec: split kexec_load syscall from kexec core code	2015-09-10 13:29:01 -07:00
rcu	rcu: Suppress lockdep false positive for rcp->exp_funnel_mutex	2015-09-20 21:01:22 -07:00
sched	sched/core: Fix TASK_DEAD race in finish_task_switch()	2015-10-06 17:05:17 +02:00
time	posix_cpu_timer: Reduce unnecessary sighand lock contention	2015-10-15 11:23:41 +02:00
trace	Mostly this is just clean ups and micro optimizations.	2015-09-08 14:04:14 -07:00
.gitignore
acct.c
async.c
audit_fsnotify.c	audit: clean simple fsnotify implementation	2015-08-06 16:14:53 -04:00
audit_tree.c	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2015-09-08 13:34:59 -07:00
audit_watch.c	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2015-09-08 13:34:59 -07:00
audit.c	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2015-09-08 13:34:59 -07:00
audit.h	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2015-09-08 13:34:59 -07:00
auditfilter.c	audit: implement audit by executable	2015-08-06 16:17:25 -04:00
auditsc.c	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2015-09-08 13:34:59 -07:00
backtracetest.c
bounds.c
capability.c
cgroup_freezer.c	cgroup: allow a cgroup subsystem to reject a fork	2015-07-14 17:29:23 -04:00
cgroup_pids.c	cgroup: pids: fix invalid get/put usage	2015-08-25 14:19:25 -04:00
cgroup.c	Revert "sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem"	2015-09-16 11:51:12 -04:00
compat.c	compat: cleanup coding in compat_get_bitmap() and compat_put_bitmap()	2015-06-04 23:57:18 +02:00
configs.c
context_tracking.c
cpu_pm.c	kernel/cpu_pm: fix cpu_cluster_pm_exit comment	2015-09-03 02:42:20 +02:00
cpu.c	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2015-08-31 20:26:22 -07:00
cpuset.c	cpuset: use trialcs->mems_allowed as a temp variable	2015-08-10 11:18:41 -04:00
crash_dump.c
cred.c	kernel/cred.c: remove unnecessary kdebug atomic reads	2015-09-10 13:29:01 -07:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c	kernel: exit: fix typo in comment	2015-08-07 13:59:49 +02:00
extable.c	kernel/extable.c: remove duplicated include	2015-09-10 13:29:01 -07:00
fork.c	posix_cpu_timer: Convert cputimer->running to bool	2015-10-15 11:23:41 +02:00
freezer.c
futex_compat.c
futex.c	futex: Make should_fail_futex() static	2015-07-20 21:43:54 +02:00
groups.c
hung_task.c
irq_work.c
jump_label.c	locking/static_keys: Add selftest	2015-08-03 11:34:16 +02:00
kallsyms.c
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec_core.c	kexec: export KERNEL_IMAGE_SIZE to vmcoreinfo	2015-09-10 13:29:01 -07:00
kexec_file.c	kexec: split kexec_file syscall code to kexec_file.c	2015-09-10 13:29:01 -07:00
kexec_internal.h	kexec: split kexec_file syscall code to kexec_file.c	2015-09-10 13:29:01 -07:00
kexec.c	kexec: split kexec_load syscall from kexec core code	2015-09-10 13:29:01 -07:00
kmod.c	kmod: handle UMH_WAIT_PROC from system unbound workqueue	2015-09-10 13:29:01 -07:00
kprobes.c	perf/x86/hw_breakpoints: Disallow kernel breakpoints unless kprobe-safe	2015-08-04 10:16:54 +02:00
ksysfs.c	kexec: split kexec_load syscall from kexec core code	2015-09-10 13:29:01 -07:00
kthread.c	kernel/kthread.c:kthread_create_on_node(): clarify documentation	2015-09-04 16:54:41 -07:00
latencytop.c
Makefile	sys_membarrier(): system-wide memory barrier (generic, x86)	2015-09-11 15:21:34 -07:00
membarrier.c	sys_membarrier(): system-wide memory barrier (generic, x86)	2015-09-11 15:21:34 -07:00
memremap.c	add devm_memremap_pages	2015-08-27 19:40:58 -04:00
module_signing.c	PKCS#7: Appropriately restrict authenticated attributes and content type	2015-08-12 17:01:01 +01:00
module-internal.h
module.c	module: weaken locking assertion for oops path.	2015-07-29 06:13:22 +09:30
notifier.c	Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2015-09-01 08:40:25 -07:00
nsproxy.c
padata.c
panic.c	kernel/panic/kexec: fix "crash_kexec_post_notifiers" option issue in oops path	2015-06-30 19:44:57 -07:00
params.c	Minor merge needed, due to function move.	2015-07-01 10:49:25 -07:00
pid_namespace.c
pid.c	rcu: Rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()	2015-07-22 15:27:32 -07:00
profile.c	mm: rename alloc_pages_exact_node() to __alloc_pages_node()	2015-09-08 15:35:28 -07:00
ptrace.c	seccomp: add ptrace options for suspend/resume	2015-07-15 11:52:52 -07:00
range.c
reboot.c	kexec: split kexec_load syscall from kexec core code	2015-09-10 13:29:01 -07:00
relay.c	kernel/relay.c: use kvfree() in relay_free_page_array()	2015-06-30 19:44:59 -07:00
resource.c	mm: enhance region_is_ram() to region_intersects()	2015-08-10 23:07:05 -04:00
seccomp.c	Merge tag 'seccomp-next' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux into next	2015-07-20 17:19:19 +10:00
signal.c	signal: fix information leak in copy_siginfo_to_user	2015-08-07 04:39:40 +03:00
smp.c
smpboot.c	smpboot: allow passing the cpumask on per-cpu thread registration	2015-09-04 16:54:41 -07:00
smpboot.h
softirq.c
stacktrace.c
stop_machine.c	stop_machine: Remove cpu_stop_work's from list in cpu_stop_park()	2015-08-03 12:21:28 +02:00
sys_ni.c	sys_membarrier(): system-wide memory barrier (generic, x86)	2015-09-11 15:21:34 -07:00
sys.c	vfs: Commit to never having exectuables on proc and sysfs.	2015-07-10 10:39:25 -05:00
sysctl_binary.c
sysctl.c	sysctl: fix int -> unsigned long assignments in INT_MIN case	2015-09-10 13:29:01 -07:00
task_work.c	task_work: remove fifo ordering guarantee	2015-09-05 13:46:58 -07:00
taskstats.c
test_kprobes.c
torture.c	rcu: Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE()	2015-05-27 12:56:15 -07:00
tracepoint.c
tsacct.c
uid16.c
up.c
user_namespace.c	capabilities: ambient capabilities	2015-09-04 16:54:41 -07:00
user-return-notifier.c
user.c
utsname_sysctl.c
utsname.c
watchdog.c	watchdog: rename watchdog_suspend() and watchdog_resume()	2015-09-04 16:54:41 -07:00
workqueue_internal.h
workqueue.c	Merge branch 'for-4.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq	2015-09-02 08:02:20 -07:00