Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH 3/4] nohz: Fix idle/iowait counts going backwards | Date | Thu, 24 Apr 2014 20:45:57 +0200 |
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With this change, "iowait-ness" of every idle period is decided at the moment it starts: if this CPU's run-queue had tasks waiting on I/O, then this idle period's duration will be added to iowait_sleeptime.
This fixes the bug where iowait and/or idle counts could go backwards, but iowait accounting is not precise (it can show more iowait that there really is).
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Cc: Fernando Luis Vazquez Cao <fernando_b1@lab.ntt.co.jp> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Oleg Nesterov <oleg@redhat.com> --- kernel/time/tick-sched.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 8f0f2ee..47ed7cf 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -413,7 +413,7 @@ static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now) /* Updates the per cpu time idle statistics counters */ write_seqcount_begin(&ts->idle_sleeptime_seq); delta = ktime_sub(now, ts->idle_entrytime); - if (nr_iowait_cpu(smp_processor_id()) > 0) + if (ts->idle_active == 2) ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); else ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); @@ -429,7 +429,7 @@ static ktime_t tick_nohz_start_idle(struct tick_sched *ts) write_seqcount_begin(&ts->idle_sleeptime_seq); ts->idle_entrytime = now; - ts->idle_active = 1; + ts->idle_active = nr_iowait_cpu(smp_processor_id()) ? 2 : 1; write_seqcount_end(&ts->idle_sleeptime_seq); sched_clock_idle_sleep_event(); @@ -469,7 +469,7 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) seq = read_seqcount_begin(&ts->idle_sleeptime_seq); idle = ts->idle_sleeptime; - if (ts->idle_active && !nr_iowait_cpu(cpu)) { + if (ts->idle_active == 1) { delta = ktime_sub(now, ts->idle_entrytime); idle = ktime_add(idle, delta); } @@ -511,7 +511,7 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) seq = read_seqcount_begin(&ts->idle_sleeptime_seq); iowait = ts->iowait_sleeptime; - if (ts->idle_active && nr_iowait_cpu(cpu) > 0) { + if (ts->idle_active == 2) { delta = ktime_sub(now, ts->idle_entrytime); iowait = ktime_add(ts->iowait_sleeptime, delta); } -- 1.8.1.4
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