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linux-next/kernel/time
Thomas Gleixner dce48a84ad sched, timers: move calc_load() to scheduler
Dimitri Sivanich noticed that xtime_lock is held write locked across
calc_load() which iterates over all online CPUs. That can cause long
latencies for xtime_lock readers on large SMP systems. 

The load average calculation is an rough estimate anyway so there is
no real need to protect the readers vs. the update. It's not a problem
when the avenrun array is updated while a reader copies the values.

Instead of iterating over all online CPUs let the scheduler_tick code
update the number of active tasks shortly before the avenrun update
happens. The avenrun update itself is handled by the CPU which calls
do_timer().

[ Impact: reduce xtime_lock write locked section ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
2009-05-15 15:32:45 +02:00
..
clockevents.c clockevents: let set_mode() setup delta information 2009-01-16 12:27:39 +01:00
clocksource.c clocksource: pass clocksource to read() callback 2009-04-21 13:41:47 -07:00
jiffies.c clocksource: pass clocksource to read() callback 2009-04-21 13:41:47 -07:00
Kconfig Kconfig: eliminate "def_bool n" constructs 2008-10-16 11:21:31 -07:00
Makefile timecompare: generic infrastructure to map between two time bases 2009-02-15 22:43:32 -08:00
ntp.c time: ntp: fix bug in ntp_update_offset() & do_adjtimex(), fix 2009-02-26 19:39:47 +01:00
tick-broadcast.c cpumask: replace for_each_cpu_mask_nr with for_each_cpu in kernel/time/ 2009-01-01 10:12:29 +10:30
tick-common.c clockevents: prevent endless loop in tick_handle_periodic() 2009-05-02 10:22:27 +02:00
tick-internal.h NOHZ: restart tick device from irq_enter() 2008-10-17 18:13:38 +02:00
tick-oneshot.c clockevents: remove WARN_ON which was used to gather information 2008-09-09 22:20:01 +02:00
tick-sched.c time-sched.c: tick_nohz_update_jiffies should be static 2009-01-15 12:06:56 +01:00
timecompare.c timecompare: generic infrastructure to map between two time bases 2009-02-15 22:43:32 -08:00
timekeeping.c sched, timers: move calc_load() to scheduler 2009-05-15 15:32:45 +02:00
timer_list.c Merge branch 'timers/range-hrtimers' into v28-range-hrtimers-for-linus-v2 2008-10-22 09:48:06 +02:00
timer_stats.c kernel: use non-racy method for proc entries creation 2008-04-29 08:06:22 -07:00