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| author | Srivatsa Vaddagiri <vatsa@codeaurora.org> | 2016-09-16 18:28:51 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-09-22 15:20:18 +0200 |
| commit | 8bf46a39be910937d4c9e8d999a7438a7ae1a75b (patch) | |
| tree | c5f4794c74ad0b2147f5a0a300c64d4dee9cdd50 /kernel/sched | |
| parent | 35a773a07926a22bf19d77ee00024522279c4e68 (diff) | |
| download | linux-8bf46a39be910937d4c9e8d999a7438a7ae1a75b.tar.gz linux-8bf46a39be910937d4c9e8d999a7438a7ae1a75b.tar.bz2 linux-8bf46a39be910937d4c9e8d999a7438a7ae1a75b.zip | |
sched/fair: Fix SCHED_HRTICK bug leading to late preemption of tasks
SCHED_HRTICK feature is useful to preempt SCHED_FAIR tasks on-the-dot
(just when they would have exceeded their ideal_runtime).
It makes use of a per-CPU hrtimer resource and hence arming that
hrtimer should be based on total SCHED_FAIR tasks a CPU has across its
various cfs_rqs, rather than being based on number of tasks in a
particular cfs_rq (as implemented currently).
As a result, with current code, its possible for a running task (which
is the sole task in its cfs_rq) to be preempted much after its
ideal_runtime has elapsed, resulting in increased latency for tasks in
other cfs_rq on same CPU.
Fix this by arming sched hrtimer based on total number of SCHED_FAIR
tasks a CPU has across its various cfs_rqs.
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1474075731-11550-1-git-send-email-joonwoop@codeaurora.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/fair.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 986c10c25176..8fb4d1942c14 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4469,7 +4469,7 @@ static void hrtick_start_fair(struct rq *rq, struct task_struct *p) WARN_ON(task_rq(p) != rq); - if (cfs_rq->nr_running > 1) { + if (rq->cfs.h_nr_running > 1) { u64 slice = sched_slice(cfs_rq, se); u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; s64 delta = slice - ran; |