Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 2/7] cputime: Remove extra cost in task_cputime | Date | Thu, 19 Nov 2015 16:47:29 +0100 |
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From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
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> Cc: stable@vger.kernel.org Cc: Christoph Lameter <cl@linux.com> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> --- kernel/sched/cputime.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 05de80b..1128d4b 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -853,6 +853,14 @@ void task_cputime(struct task_struct *t, cputime_t *utime, cputime_t *stime) { cputime_t udelta, sdelta; + if (!context_tracking_is_enabled()) { + if (utime) + *utime = t->utime; + if (stime) + *stime = t->stime; + return; + } + fetch_task_cputime(t, utime, stime, &t->utime, &t->stime, &udelta, &sdelta); if (utime) @@ -866,6 +874,14 @@ void task_cputime_scaled(struct task_struct *t, { cputime_t udelta, sdelta; + if (!context_tracking_is_enabled()) { + if (utimescaled) + *utimescaled = t->utimescaled; + if (stimescaled) + *stimescaled = t->stimescaled; + return; + } + fetch_task_cputime(t, utimescaled, stimescaled, &t->utimescaled, &t->stimescaled, &udelta, &sdelta); if (utimescaled) -- 2.5.3
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