Messages in this thread Patch in this message | | | Date | Wed, 06 May 2009 14:46:24 -0700 | From | Greg KH <> | Subject | [patch 56/58] sched: account system time properly |
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2.6.29-stable review patch. If anyone has any objections, please let us know.
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From: Eric Dumazet <dada1@cosmosbay.com>
commit f5f293a4e3d0a0c52cec31de6762c95050156516 upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched.c +++ b/kernel/sched.c @@ -4347,7 +4347,7 @@ void account_process_tick(struct task_st 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
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