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authorWanpeng Li <wanpeng.li@hotmail.com>2016-08-11 13:36:35 +0800
committerIngo Molnar <mingo@kernel.org>2016-08-11 11:02:14 +0200
commitf9bcf1e0e0145323ba2cf72ecad5264ff3883eb1 (patch)
treea91de94c46cb85a38fb8198ee2c65e37e4bb8347 /kernel/sched/cputime.c
parentc0c8c9fa210c9a042060435f17e40ba4a76d6d6f (diff)
sched/cputime: Fix steal time accounting
Commit: 57430218317 ("sched/cputime: Count actually elapsed irq & softirq time") ... didn't take steal time into consideration with passing the noirqtime kernel parameter. As Paolo pointed out before: | Why not? If idle=poll, for example, any time the guest is suspended (and | thus cannot poll) does count as stolen time. This patch fixes it by reducing steal time from idle time accounting when the noirqtime parameter is true. The average idle time drops from 56.8% to 54.75% for nohz idle kvm guest(noirqtime, idle=poll, four vCPUs running on one pCPU). Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Radim <rkrcmar@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1470893795-3527-1-git-send-email-wanpeng.li@hotmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/cputime.c')
-rw-r--r--kernel/sched/cputime.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 1934f658c036..8b9bcc5a58fa 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -508,13 +508,20 @@ void account_process_tick(struct task_struct *p, int user_tick)
*/
void account_idle_ticks(unsigned long ticks)
{
-
+ cputime_t cputime, steal;
if (sched_clock_irqtime) {
irqtime_account_idle_ticks(ticks);
return;
}
- account_idle_time(jiffies_to_cputime(ticks));
+ cputime = cputime_one_jiffy;
+ steal = steal_account_process_time(cputime);
+
+ if (steal >= cputime)
+ return;
+
+ cputime -= steal;
+ account_idle_time(cputime);
}
/*