Messages in this thread Patch in this message | | | Date | Thu, 3 Dec 2009 18:51:53 -0500 | From | Vivek Goyal <> | Subject | Re: Block IO Controller V4 |
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On Thu, Dec 03, 2009 at 01:10:03PM -0500, Vivek Goyal wrote:
[..] > Hi Gui, > > Can you please try following patch and see if it helps you. If not, then > we need to figure out why we choose to not idle and delete the group from > service tree. >
Hi Gui,
Please try this version of the patch instead of previous one. During more testing I saw some additional deletions where we should have waited and the reason being that we were hitting boundary condition. At the request completion time slice has not expired but after 4-5 ns, select_queue hits and jiffy has incremented by then and slice expires.
ttime_mean, is not covering this condition because this workload is so sequential that ttime_mean=0.
So I am checking for new condition where if we are into last ms of slice, mark the queue wait_busy.
Thanks Vivek
Signed-off-by: Vivek Goyal <vgoyal@redhat.com> --- block/cfq-iosched.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-)
Index: linux11/block/cfq-iosched.c =================================================================== --- linux11.orig/block/cfq-iosched.c 2009-12-03 15:10:53.000000000 -0500 +++ linux11/block/cfq-iosched.c 2009-12-03 18:37:35.000000000 -0500 @@ -3248,6 +3248,29 @@ static void cfq_update_hw_tag(struct cfq cfqd->hw_tag = 0; } +static inline bool +cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + struct cfq_io_context *cic = cfqd->active_cic; + + /* If there are other queues in the group, don't wait */ + if (cfqq->cfqg->nr_cfqq > 1) + return false; + + if (cfq_slice_used(cfqq)) + return true; + + if (cfqq->slice_end - jiffies == 1) + return true; + + /* if slice left is less than think time, wait busy */ + if (cic && sample_valid(cic->ttime_samples) + && (cfqq->slice_end - jiffies < cic->ttime_mean)) + return true; + + return false; +} + static void cfq_completed_request(struct request_queue *q, struct request *rq) { struct cfq_queue *cfqq = RQ_CFQQ(rq); @@ -3286,11 +3309,10 @@ static void cfq_completed_request(struct } /* - * If this queue consumed its slice and this is last queue - * in the group, wait for next request before we expire - * the queue + * Should we wait for next request to come in before we expire + * the queue. */ - if (cfq_slice_used(cfqq) && cfqq->cfqg->nr_cfqq == 1) { + if (cfq_should_wait_busy(cfqd, cfqq)) { cfqq->slice_end = jiffies + cfqd->cfq_slice_idle; cfq_mark_cfqq_wait_busy(cfqq); }
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