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| author | Eric Dumazet <dada1@cosmosbay.com> | 2009-04-29 14:44:49 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-04-29 15:02:28 +0200 |
| commit | f5f293a4e3d0a0c52cec31de6762c95050156516 (patch) | |
| tree | b9dad5f4b1e834e414e825345b32fadd1ed6c01a /kernel | |
| parent | 56a50adda49b2020156616c4eb15353e0f9ad7de (diff) | |
| download | linux-stable-f5f293a4e3d0a0c52cec31de6762c95050156516.tar.gz linux-stable-f5f293a4e3d0a0c52cec31de6762c95050156516.tar.bz2 linux-stable-f5f293a4e3d0a0c52cec31de6762c95050156516.zip | |
sched: account system time properly
Andrew Gallatin reported that IRQ and SOFTIRQ times were
sometime not reported correctly on recent kernels, and even
bisected to commit 457533a7d3402d1d91fbc125c8bd1bd16dcd3cd4
([PATCH] fix scaled & unscaled cputime accounting) as the first
bad commit.
Further analysis pointed that commit
79741dd35713ff4f6fd0eafd59fa94e8a4ba922d ([PATCH] idle cputime
accounting) was the real cause of the problem.
account_process_tick() was not taking into account timer IRQ
interrupting the idle task servicing a hard or soft irq.
On mostly idle cpu, irqs were thus not accounted and top or
mpstat could tell user/admin that cpu was 100 % idle, 0.00 %
irq, 0.00 % softirq, while it was not.
[ Impact: fix occasionally incorrect CPU statistics in top/mpstat ]
Reported-by: Andrew Gallatin <gallatin@myri.com>
Re-reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: rick.jones2@hp.com
Cc: brice@myri.com
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <49F84BC1.7080602@cosmosbay.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index b902e587a3a0..26efa475bdc1 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4732,7 +4732,7 @@ void account_process_tick(struct task_struct *p, int user_tick) if (user_tick) account_user_time(p, one_jiffy, one_jiffy_scaled); - else if (p != rq->idle) + else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET)) account_system_time(p, HARDIRQ_OFFSET, one_jiffy, one_jiffy_scaled); else |