diff options
| author | Srivatsa Vaddagiri <vatsa@codeaurora.org> | 2013-04-18 11:42:22 -0700 |
|---|---|---|
| committer | David Keitel <dkeitel@codeaurora.org> | 2016-03-23 19:58:32 -0700 |
| commit | 82f6fb4f5c85f3842a65b15142ecd8378893dac4 (patch) | |
| tree | ea49e644b3806cd9a4211b001a7efd7927bc120a | |
| parent | 2c04026b1799a0b89f0259df66b4a66923671bfc (diff) | |
sched: 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 a per-cpu hrtimer resource and hence alarming 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 alarming sched hrtimer based on total number of SCHED_FAIR
tasks a CPU has across its various cfs_rqs.
Change-Id: I1f23680a64872f8ce0f451ac4bcae28e8967918f
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>
[rameezmustafa@codeaurora.org]: Squash "c24fb502 sched: fix reference to
wrong cfs_rq" into this patch]
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>
| -rw-r--r-- | kernel/sched/fair.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6d05808faff2..38d1e32d19f9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4095,7 +4095,7 @@ 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; @@ -4111,8 +4111,7 @@ static void hrtick_start_fair(struct rq *rq, struct task_struct *p) /* * called from enqueue/dequeue and updates the hrtick when the - * current task is from our class and nr_running is low enough - * to matter. + * current task is from our class. */ static void hrtick_update(struct rq *rq) { @@ -4121,8 +4120,7 @@ static void hrtick_update(struct rq *rq) if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) return; - if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) - hrtick_start_fair(rq, curr); + hrtick_start_fair(rq, curr); } #else /* !CONFIG_SCHED_HRTICK */ static inline void |