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001474491f
linux/kernel
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Woodruff, Richard 001474491f nohz: suppress needless timer reprogramming 
In my device I get many interrupts from a high speed USB device in a very
short period of time.  The system spends a lot of time reprogramming the
hardware timer which is in a slower timing domain as compared to the CPU. 
This results in the CPU spending a huge amount of time waiting for the
timer posting to be done.  All of this reprogramming is useless as the
wake up time has not changed.

As measured using ETM trace this drops my reprogramming penalty from
almost 60% CPU load down to 15% during high interrupt rate.  I can send
traces to show this.

Suppress setting of duplicate timer event when timer already stopped. 
Timer programming can be very costly and can result in long cpu stall/wait
times.

[akpm@linux-foundation.org: coding-style fixes]
[tglx@linutronix.de: move the check to the right place and avoid raising
		     the softirq for nothing]

Signed-off-by: Richard Woodruff <r-woodruff2@ti.com>
Cc: johnstul@us.ibm.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-12-12 16:55:31 +01:00
..
irq genirq: __irq_set_trigger: change pr_warning to pr_debug 2008-11-13 11:59:48 +01:00
power [PATCH] kill obsolete temporary comment in swsusp_close() 2008-12-04 04:22:54 -05:00
time nohz: suppress needless timer reprogramming 2008-12-12 16:55:31 +01:00
trace ftrace: prevent recursion 2008-11-27 10:11:53 +01:00
.gitignore
acct.c
audit_tree.c Fix inotify watch removal/umount races 2008-11-15 12:26:44 -08:00
audit.c [PATCH] fix broken timestamps in AVC generated by kernel threads 2008-12-09 02:27:41 -05:00
audit.h
auditfilter.c Fix inotify watch removal/umount races 2008-11-15 12:26:44 -08:00
auditsc.c [PATCH] fix broken timestamps in AVC generated by kernel threads 2008-12-09 02:27:41 -05:00
backtracetest.c
bounds.c
capability.c
cgroup_debug.c cgroups: fix probable race with put_css_set[_taskexit] and find_css_set 2008-10-20 08:52:38 -07:00
cgroup_freezer.c freezer_cg: disable writing freezer.state of root cgroup 2008-11-12 17:17:16 -08:00
cgroup.c cgroups: fix a serious bug in cgroupstats 2008-11-19 18:50:00 -08:00
compat.c Merge branches 'timers/clocksource', 'timers/hrtimers', 'timers/nohz', 'timers/ntp', 'timers/posixtimers' and 'timers/debug' into v28-timers-for-linus 2008-10-20 13:14:06 +02:00
configs.c kernel/configs.c: remove useless comments 2008-10-20 08:52:34 -07:00
cpu.c cpuinit fixes in kernel/* 2008-11-30 10:03:37 -08:00
cpuset.c sched, cpusets: fix warning in kernel/cpuset.c 2008-11-29 20:39:29 +01:00
delayacct.c
dma-coherent.c
dma.c kernel/dma.c: remove a CVS keyword 2008-10-16 11:21:30 -07:00
exec_domain.c proc: move /proc/execdomains to kernel/exec_domain.c 2008-10-23 14:30:41 +04:00
exit.c Move "exit_robust_list" into mm_release() 2008-11-15 10:20:36 -08:00
extable.c
fork.c fix mapping_writably_mapped() 2008-12-10 14:40:45 -08:00
freezer.c freezer_cg: use thaw_process() in unfreeze_cgroup() 2008-10-30 11:38:45 -07:00
futex_compat.c
futex.c
hrtimer.c hrtimer: clean up unused callback modes 2008-11-12 09:54:40 +01:00
itimer.c
kallsyms.c sprint_symbol(): use less stack 2008-11-19 18:49:58 -08:00
Kconfig.freezer container freezer: implement freezer cgroup subsystem 2008-10-20 08:52:34 -07:00
Kconfig.hz
Kconfig.preempt
kexec.c kexec: fix crash_save_vmcoreinfo_init build problem 2008-10-20 15:28:50 -07:00
kfifo.c
kgdb.c
kmod.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus 2008-10-16 12:38:34 -07:00
kprobes.c kernel/kprobes.c: don't pad kretprobe_table_locks[] on uniprocessor builds 2008-11-12 17:17:17 -08:00
ksysfs.c profiling: dynamically enable readprofile at runtime 2008-10-16 11:21:31 -07:00
kthread.c Merge branch 'tracing-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-10-20 13:35:07 -07:00
latencytop.c KSYM_SYMBOL_LEN fixes 2008-12-10 08:01:54 -08:00
lockdep_internals.h
lockdep_proc.c
lockdep.c lockdep: consistent alignement for lockdep info 2008-11-21 08:59:40 +01:00
Makefile Remove -mno-spe flags as they dont belong 2008-11-17 13:24:35 -08:00
marker.c markers: bit-field is not thread-safe nor smp-safe 2008-10-14 10:38:45 +02:00
module.c Merge branch 'proc' of git://git.kernel.org/pub/scm/linux/kernel/git/adobriyan/proc 2008-10-23 12:04:37 -07:00
mutex-debug.c
mutex-debug.h
mutex.c
mutex.h
notifier.c
ns_cgroup.c
nsproxy.c
panic.c taint: add missing comment 2008-12-01 19:55:24 -08:00
params.c Fix compile warning in kernel/params.c 2008-10-23 12:09:00 -07:00
pid_namespace.c
pid.c
pm_qos_params.c
posix-cpu-timers.c posix-cpu-timers: fix clock_gettime with CLOCK_PROCESS_CPUTIME_ID 2008-11-24 16:41:40 +01:00
posix-timers.c Merge branch 'timers/range-hrtimers' into v28-range-hrtimers-for-linus-v2 2008-10-22 09:48:06 +02:00
printk.c printk: remove unused code from kernel/printk.c 2008-10-23 21:54:29 +02:00
profile.c cpuinit fixes in kernel/* 2008-11-30 10:03:37 -08:00
ptrace.c remove __ARCH_WANT_COMPAT_SYS_PTRACE 2008-11-30 11:00:15 -08:00
rcuclassic.c
rcupdate.c rcupdate: fix bug of rcu_barrier*() 2008-10-21 15:59:53 +02:00
rcupreempt_trace.c
rcupreempt.c byteorder: remove direct includes of linux/byteorder/swab[b].h 2008-10-20 08:52:40 -07:00
rcutorture.c byteorder: remove direct includes of linux/byteorder/swab[b].h 2008-10-20 12:51:53 -07:00
relay.c relayfs: fix infinite loop with splice() 2008-12-10 08:01:52 -08:00
res_counter.c
resource.c reserve_region_with_split: Fix GFP_KERNEL usage under spinlock 2008-11-01 09:53:58 -07:00
rtmutex_common.h
rtmutex-debug.c
rtmutex-debug.h
rtmutex-tester.c
rtmutex.c
rtmutex.h
rwsem.c
sched_clock.c
sched_cpupri.c
sched_cpupri.h
sched_debug.c sched: fix kernel warning on /proc/sched_debug access 2008-11-16 08:07:15 +01:00
sched_fair.c sched: release buddies on yield 2008-11-11 11:57:22 +01:00
sched_features.h sched: backward looking buddy 2008-11-05 10:30:14 +01:00
sched_idletask.c sched: add CONFIG_SMP consistency 2008-10-22 10:01:52 +02:00
sched_rt.c Merge commit 'v2.6.28-rc1' into sched/urgent 2008-10-24 12:48:46 +02:00
sched_stats.h sched, signals: fix the racy usage of ->signal in account_group_xxx/run_posix_cpu_timers 2008-11-17 16:49:35 +01:00
sched.c sched: CPU remove deadlock fix 2008-12-09 19:27:03 +01:00
seccomp.c
semaphore.c
signal.c 'kill sig -1' must only apply to caller's namespace 2008-10-30 11:38:46 -07:00
smp.c generic-ipi: fix the smp_mb() placement 2008-11-06 08:41:56 +01:00
softirq.c irq: call __irq_enter() before calling the tick_idle_check 2008-11-10 22:36:39 +01:00
softlockup.c check_hung_task(): unsigned sysctl_hung_task_warnings cannot be less than 0 2008-12-03 10:11:51 +01:00
spinlock.c
srcu.c
stacktrace.c
stop_machine.c stop_machine: fix race with return value (fixes Bug #11989) 2008-11-16 15:09:52 -08:00
sys_ni.c reintroduce accept4 2008-11-19 18:49:57 -08:00
sys.c Merge branch 'timers/range-hrtimers' into v28-range-hrtimers-for-linus-v2 2008-10-22 09:48:06 +02:00
sysctl_check.c
sysctl.c epoll: introduce resource usage limits 2008-12-01 19:55:24 -08:00
taskstats.c
test_kprobes.c
time.c
timeconst.pl
timer.c Add round_jiffies_up and related routines 2008-11-06 08:42:48 +01:00
tracepoint.c tracepoint: check if the probe has been registered 2008-10-27 16:45:46 +01:00
tsacct.c
uid16.c
user_namespace.c
user.c
utsname_sysctl.c sysctl: simplify ->strategy 2008-10-16 11:21:47 -07:00
utsname.c
wait.c wait: kill is_sync_wait() 2008-10-16 11:21:31 -07:00
workqueue.c cpumask: introduce new API, without changing anything 2008-11-06 09:05:33 +01:00