unimore/kernel-hacking-2024-linux-steffo
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sched_clock: fix NOHZ interaction

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If HLT stops the TSC, we'll fail to account idle time, thereby inflating the
actual process times. Fix this by re-calibrating the clock against GTOD when
leaving nohz mode.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-09-01 16:44:23 +02:00 committed by Ingo Molnar
parent b380b0d4f7
commit 56c7426b39
1 changed files with 3 additions and 0 deletions
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3
kernel/time/tick-sched.c
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@ -162,6 +162,8 @@ void tick_nohz_stop_idle(int cpu)
ts->idle_lastupdate = now;
ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
ts->idle_active = 0;
sched_clock_idle_wakeup_event(0);
}
}
@ -177,6 +179,7 @@ static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
}
ts->idle_entrytime = now;
ts->idle_active = 1;
sched_clock_idle_sleep_event();
return now;
}