Messages in this thread Patch in this message | | | Date | Wed, 11 Nov 2009 08:48:09 +0800 | From | Gui Jianfeng <> | Subject | Re: [PATCH 02/20] blkio: Change CFQ to use CFS like queue time stamps |
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Vivek Goyal wrote: ... > > @@ -1245,10 +1429,10 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd) > struct cfq_queue *cfqq; > int dispatched = 0; > > - while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL) > + while ((cfqq = cfq_get_next_queue(cfqd)) != NULL) > dispatched += __cfq_forced_dispatch_cfqq(cfqq); > > - cfq_slice_expired(cfqd, 0); > + cfq_slice_expired(cfqd); > > BUG_ON(cfqd->busy_queues); > > @@ -1391,7 +1575,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force) > cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || > cfq_class_idle(cfqq))) { > cfqq->slice_end = jiffies + 1; > - cfq_slice_expired(cfqd, 0); > + cfq_slice_expired(cfqd);
Hi Vivek,
I think here you should make sure that when updating cfqq->slice_end, cfqq->slice_end doesn't equal to 0. Because if cfqq->slice_end == 0, cfq_slice_expired() just charge for 1 jiffy, but if cfqq->slice_end is updated when it equals to 0(first request still in the air), at that time cfqq->slice_start == 0, and slice_used is charged as "jiffies - cfqq->slice_start". Following patch fixes this bug.
Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com> --- block/cfq-iosched.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index f23d713..12afc14 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1999,7 +1999,8 @@ static int cfq_dispatch_requests(struct request_queue *q, int force) if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || cfq_class_idle(cfqq))) { - cfqq->slice_end = jiffies + 1; + if (cfqq->slice_end) + cfqq->slice_end = jiffies + 1; cfq_slice_expired(cfqd); } -- 1.5.4.rc3
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