Messages in this thread | | | Subject | Re: [PATCH 1/2] sched: allow SCHED_BATCH to preempt SCHED_IDLE tasks | From | Mike Galbraith <> | Date | Wed, 23 Feb 2011 05:20:54 +0100 |
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On Tue, 2011-02-22 at 13:04 -0800, Darren Hart wrote: > Perform the test for SCHED_IDLE before testing for SCHED_BATCH (and ensure idle > tasks don't preempt idle tasks) so the non-interactive, but still important, > SCHED_BATCH tasks will run in favor of the very low priority SCHED_IDLE tasks.
Yeah, that could be construed as a fairness fix for light SCHED_BATCH vs a heavy SCHED_IDLE. It should lower latencies for both when mixed.
Acked-by: Mike Galbraith <efault@gmx.de>
Nit below.
> Signed-off-by: Darren Hart <dvhart@linux.intel.com> > CC: Peter Zijlstra <peterz@infradead.org> > CC: Ingo Molnar <mingo@elte.hu> > CC: Richard Purdie <richard.purdie@linuxfoundation.org> > --- > kernel/sched_fair.c | 12 +++++++----- > 1 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 0c26e2d..ff04bbd 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -1857,16 +1857,18 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ > if (test_tsk_need_resched(curr)) > return; > > + /* Idle tasks are by definition preempted by non-idle tasks. */ > + if (unlikely(curr->policy == SCHED_IDLE) && > + likely(p->policy != SCHED_IDLE)) > + goto preempt; > +
if (unlikely(curr->policy == SCHED_IDLE && p->policy != curr->policy)) goto preempt;
Looks better to me.
-Mike
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