Messages in this thread | | | Date | Mon, 11 Jan 2010 16:15:39 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH] cfq-iosched: Respect ioprio_class when preempting |
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On Wed, Jan 06 2010, Divyesh Shah wrote: > In cfq_should_preempt(), we currently allow some cases where a non-RT request > can preempt an ongoing RT cfqq timeslice. This should not happen. > Examples include: > > o A sync_noidle wl type non-RT request pre-empting a sync_noidle wl type cfqq > on which we are idling. > o Once we have per-cgroup async queues, a non-RT sync request pre-empting a RT > async cfqq. > > Signed-off-by: Divyesh Shah<dpshah@google.com> > --- > > block/cfq-iosched.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index 7d6cef9..e9e6610 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -3104,6 +3104,12 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, > return true; > > /* > + * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice. > + */ > + if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq)) > + return false;
It would be nice to just be able to do
if (new_cfqq->ioprio_class > cfqq->ioprio_class) return false;
but that doesn't quite work given IOPRIO_CLASS_NONE < _RT. So I think your patch is fine, I've added it. Thanks.
-- Jens Axboe
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