Commit-ID: 7877a0ba5ec63c7b0111b06c773f1696fa17b35a Gitweb: http://git.kernel.org/tip/7877a0ba5ec63c7b0111b06c773f1696fa17b35a Author: Hiroshi Shimamoto <h-shimam...@ct.jp.nec.com> AuthorDate: Thu, 19 Nov 2015 16:47:29 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Fri, 4 Dec 2015 10:34:43 +0100
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-shimam...@ct.jp.nec.com> Signed-off-by: Frederic Weisbecker <fweis...@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Chris Metcalf <cmetc...@ezchip.com> Cc: Christoph Lameter <c...@linux.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Luiz Capitulino <lcapitul...@redhat.com> Cc: Mike Galbraith <efa...@gmx.de> Cc: Paul E . McKenney <paul...@linux.vnet.ibm.com> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Rik van Riel <r...@redhat.com> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/1447948054-28668-3-git-send-email-fweis...@gmail.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
