Messages in this thread | | | Date | Tue, 2 Jan 2007 16:14:02 +0100 | From | Jens Axboe <> | Subject | Re: 2.6.20-rc2+: CFQ halving disk throughput. |
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On Tue, Jan 02 2007, Mark Lord wrote: > Jens Axboe wrote: > >On Tue, Jan 02 2007, Jens Axboe wrote: > >>On Tue, Jan 02 2007, Rene Herman wrote: > >>>Jens Axboe wrote: > >>> > >>>>On Mon, Jan 01 2007, Andrew Morton wrote: > >>>>>The patch would appear to need this fix: > >>>>> > >>>>>--- a/block/cfq-iosched.c~a > >>>>>+++ a/block/cfq-iosched.c > >>>>>@@ -592,7 +592,7 @@ static int cfq_allow_merge(request_queue > >>>>> if (cfqq == RQ_CFQQ(rq)) > >>>>> return 1; > >>>>> > >>>>>- return 1; > >>>>>+ return 0; > >>>>>} > >>>>> > >>>>>static inline void > >>>>>_ > >>>>> > >>>>>But that might not fix things... > >>>>Yeah it is, but I don't think it'll fix it (if anything, it'll be more > >>>>conservative). > >>>(to possibly save others from trying -- no, doesn't fix any) > >>As expected. The issue is rq_is_sync(rq) takes the data direction into > >>account as well, while bio_sync() only checks the sync bit. This should > >>fix it. > > > >And here a little more relaxed version, as Mark Lord suggested. We allow > >merge of async bio into a sync request, but not vice versa. > > > >Both patches pending testing, will do so now. > > Performance is right back where it should be now, thanks!
Good, thanks!
> I did have to massage the second patch to get it to apply cleanly > after the first patch. You may want to regenerate it against -rc3.
Hmm odd, I thought I did. Will double check.
-- Jens Axboe
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