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| author |   Tim Chen <tim.c.chen@linux.intel.com> | 2014-12-12 15:38:12 -0800 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2015-01-30 19:38:49 +0100 |
| commit | 80e3d87b2c5582db0ab5e39610ce3707d97ba409 (patch) | |
| tree | 26ce03eb8edeebe4eca36d6be4de3c35e7494279 /kernel | |
| parent | Merge branch 'sched/urgent' into sched/core (diff) | |
| download | linux-dev-80e3d87b2c5582db0ab5e39610ce3707d97ba409.tar.xz linux-dev-80e3d87b2c5582db0ab5e39610ce3707d97ba409.zip | |
sched/rt: Reduce rq lock contention by eliminating locking of non-feasible target
This patch adds checks that prevens futile attempts to move rt tasks
to a CPU with active tasks of equal or higher priority.
This reduces run queue lock contention and improves the performance of
a well known OLTP benchmark by 0.7%.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Shawn Bohrer <sbohrer@rgmadvisors.com>
Cc: Suruchi Kadu <suruchi.a.kadu@intel.com>
Cc: Doug Nelson<doug.nelson@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1421430374.2399.27.camel@schen9-desk2.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/rt.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 6725e3c49660..f4d4b077eba0 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1340,7 +1340,12 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags) curr->prio <= p->prio)) { int target = find_lowest_rq(p); - if (target != -1) + /* + * Don't bother moving it if the destination CPU is + * not running a lower priority task. + */ + if (target != -1 && + p->prio < cpu_rq(target)->rt.highest_prio.curr) cpu = target; } rcu_read_unlock(); @@ -1617,6 +1622,16 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq) lowest_rq = cpu_rq(cpu); + if (lowest_rq->rt.highest_prio.curr <= task->prio) { + /* + * Target rq has tasks of equal or higher priority, + * retrying does not release any lock and is unlikely + * to yield a different result. + */ + lowest_rq = NULL; + break; + } + /* if the prio of this runqueue changed, try again */ if (double_lock_balance(rq, lowest_rq)) { /* |