diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2009-08-21 11:56:45 +0200 |
|---|---|---|
| committer | Clark Williams <williams@redhat.com> | 2012-03-02 11:52:17 -0600 |
| commit | cdcdd233317e22a1fd623e06d294fe33c9fa8577 (patch) | |
| tree | a44c3902846da9888db4e1cf3b0e73aaefe73329 /kernel | |
| parent | 906e97c64b1957f63a8cb93a4141512a2293d37c (diff) | |
timer: delay waking softirqs from the jiffy tick
People were complaining about broken balancing with the recent -rt
series.
A look at /proc/sched_debug yielded:
cpu#0, 2393.874 MHz
.nr_running : 0
.load : 0
.cpu_load[0] : 177522
.cpu_load[1] : 177522
.cpu_load[2] : 177522
.cpu_load[3] : 177522
.cpu_load[4] : 177522
cpu#1, 2393.874 MHz
.nr_running : 4
.load : 4096
.cpu_load[0] : 181618
.cpu_load[1] : 180850
.cpu_load[2] : 180274
.cpu_load[3] : 179938
.cpu_load[4] : 179758
Which indicated the cpu_load computation was hosed, the 177522 value
indicates that there is one RT task runnable. Initially I thought the
old problem of calculating the cpu_load from a softirq had re-surfaced,
however looking at the code shows its being done from scheduler_tick().
[ we really should fix this RT/cfs interaction some day... ]
A few trace_printk()s later:
sirq-timer/1-19 [001] 174.289744: 19: 50:S ==> [001] 0:140:R <idle>
<idle>-0 [001] 174.290724: enqueue_task_rt: adding task: 19/sirq-timer/1 with load: 177522
<idle>-0 [001] 174.290725: 0:140:R + [001] 19: 50:S sirq-timer/1
<idle>-0 [001] 174.290730: scheduler_tick: current load: 177522
<idle>-0 [001] 174.290732: scheduler_tick: current: 0/swapper
<idle>-0 [001] 174.290736: 0:140:R ==> [001] 19: 50:R sirq-timer/1
sirq-timer/1-19 [001] 174.290741: dequeue_task_rt: removing task: 19/sirq-timer/1 with load: 177522
sirq-timer/1-19 [001] 174.290743: 19: 50:S ==> [001] 0:140:R <idle>
We see that we always raise the timer softirq before doing the load
calculation. Avoid this by re-ordering the scheduler_tick() call in
update_process_times() to occur before we deal with timers.
This lowers the load back to sanity and restores regular load-balancing
behaviour.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/timer.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/timer.c b/kernel/timer.c index 7954334ba238..d1bc5a9c532a 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1334,13 +1334,13 @@ void update_process_times(int user_tick) /* Note: this timer irq context must be accounted for as well. */ account_process_tick(p, user_tick); + scheduler_tick(); run_local_timers(); rcu_check_callbacks(cpu, user_tick); #ifdef CONFIG_IRQ_WORK if (in_irq()) irq_work_run(); #endif - scheduler_tick(); run_posix_cpu_timers(p); } |