Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 21 Dec 2006 21:18:18 +0100 | From | Jens Axboe <> | Subject | Re: performance regression from block merge |
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On Thu, Dec 21 2006, Andrew Morton wrote: > On Thu, 21 Dec 2006 20:47:41 +0100 > Jens Axboe <jens.axboe@oracle.com> wrote: > > > On Thu, Dec 21 2006, Jens Axboe wrote: > > > On Thu, Dec 21 2006, Andrew Morton wrote: > > > > > > > > Jens, elapsed time for `mke2fs /dev/hdc5' with the anticipatory scheduler > > > > (at least) has gone from nine seconds to sixty as a result of the recent > > > > block merge. > > > > > > About when? I'll double check and test here, I'm assuming you mean since > > > 2.6.19? > > In yesterday's merge. I double-checked by testing yesterday's-Linus versus > yesterday's-Linus-plus-yesterday's-git-block. The latter was slow. > > > Auch, brown paper bag time, I spotted an obvious typo in the recent > > merge. Does this fix it? It should be safe to kill the ->special check, > > but lets leave that for another time. > > > > diff --git a/block/elevator.c b/block/elevator.c > > index 62c7a30..536be74 100644 > > --- a/block/elevator.c > > +++ b/block/elevator.c > > @@ -82,7 +82,7 @@ inline int elv_rq_merge_ok(struct reques > > /* > > * must be same device and not a special request > > */ > > - if (rq->rq_disk != bio->bi_bdev->bd_disk || !rq->special) > > + if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special) > > return 0; > > > > if (!elv_iosched_allow_merge(rq, bio)) > > > > I shan't be near that machine for eight hours or so; shall test then.
I already verified it, that was the bug! I'll send it upstream.
-- Jens Axboe
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