From f5f293a4e3d0a0c52cec31de6762c95050156516 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 29 Apr 2009 14:44:49 +0200 Subject: 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 Re-reported-by: Andrew Morton Signed-off-by: Eric Dumazet Acked-by: Martin Schwidefsky Cc: rick.jones2@hp.com Cc: brice@myri.com Cc: Paul Mackerras Cc: Benjamin Herrenschmidt LKML-Reference: <49F84BC1.7080602@cosmosbay.com> Signed-off-by: Ingo Molnar --- kernel/sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') 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 -- cgit v1.2.3