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Date: Tue, 24 Nov 2009 09:37:05 -0500 From: Vivek Goyal <vgoyal@...hat.com> To: Corrado Zoccolo <czoccolo@...il.com> Cc: Linux-Kernel <linux-kernel@...r.kernel.org>, Jens Axboe <jens.axboe@...cle.com>, Jeff Moyer <jmoyer@...hat.com> Subject: Re: [PATCH 2/4] cfq-iosched: fix no-idle preemption logic On Tue, Nov 24, 2009 at 02:49:02PM +0100, Corrado Zoccolo wrote: > An incoming no-idle queue should preempt the active no-idle queue > only if the active queue is idling due to service tree empty. > Previous code was buggy in two ways: > * it relied on service_tree field to be set on the active queue, while > it is not set when the code is idling for a new request > * it didn't check for the service tree empty condition, so could lead to > LIFO behaviour if multiple queues with depth > 1 were preempting each > other on an non-NCQ device. > > Reported-by: Vivek Goyal <vgoyal@...hat.com> > Signed-off-by: Corrado Zoccolo <czoccolo@...il.com> > --- > block/cfq-iosched.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index 6925ab9..2a304f4 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -2401,8 +2401,9 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, > if (cfq_class_idle(cfqq)) > return true; > > - if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD > - && new_cfqq->service_tree == cfqq->service_tree) > + if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD && > + cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD && > + new_cfqq->service_tree->count == 1) > return true; > Looks good to me. Acked-by: Vivek Goyal <vgoyal@...hat.com> Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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