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| author |   Thomas Gleixner <tglx@linutronix.de> | 2009-04-11 10:43:41 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-05-15 15:32:45 +0200 |
| commit | dce48a84adf1806676319f6f480e30a6daa012f9 (patch) | |
| tree | 79151f5d31d9c3dcdc723ab8877cb943b944890e /kernel/time | |
| parent | sched: Don't export sched_mc_power_savings on multi-socket single core system (diff) | |
| download | linux-dev-dce48a84adf1806676319f6f480e30a6daa012f9.tar.xz linux-dev-dce48a84adf1806676319f6f480e30a6daa012f9.zip | |
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>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/timekeeping.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 687dff49f6e7..52a8bf8931f3 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -22,7 +22,7 @@ /* * This read-write spinlock protects us from races in SMP while - * playing with xtime and avenrun. + * playing with xtime. */ __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); |