sched/cputime: Remove extra cost in task_cputime()
There is an extra cost in task_cputime() and task_cputime_scaled() when nohz_full is not activated. When vtime accounting is not enabled, we don't need to get deltas of utime and stime under vtime seqlock. This patch removes that cost with adding a shortcut route if vtime accounting is not enabled. Use context_tracking_is_enabled() to check if vtime is accounting on some cpu, in which case only we need to check the tickless cputime delta. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1447948054-28668-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -853,6 +853,14 @@ void task_cputime(struct task_struct *t, cputime_t *utime, cputime_t *stime)
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{
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cputime_t udelta, sdelta;
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if (!context_tracking_is_enabled()) {
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if (utime)
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*utime = t->utime;
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if (stime)
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*stime = t->stime;
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return;
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}
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fetch_task_cputime(t, utime, stime, &t->utime,
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&t->stime, &udelta, &sdelta);
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if (utime)
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@ -866,6 +874,14 @@ void task_cputime_scaled(struct task_struct *t,
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{
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cputime_t udelta, sdelta;
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if (!context_tracking_is_enabled()) {
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if (utimescaled)
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*utimescaled = t->utimescaled;
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if (stimescaled)
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*stimescaled = t->stimescaled;
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return;
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}
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fetch_task_cputime(t, utimescaled, stimescaled,
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&t->utimescaled, &t->stimescaled, &udelta, &sdelta);
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if (utimescaled)
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