Messages in this thread | | | Date | Tue, 20 Jan 2009 23:54:47 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [ltt-dev] [RFC PATCH] block: Fix bio merge induced high I/O latency |
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* Ben Gamari (bgamari@gmail.com) wrote: > On Tue, Jan 20, 2009 at 7:25 PM, Mathieu Desnoyers > <mathieu.desnoyers@polymtl.ca> wrote: > > * Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) wrote: > > > > As a side-note : I'd like to have my results confirmed by others. > > Well, I think the (fixed) patch did help to some degree (I haven't > done fio benchmarks to compare against yet). Unfortunately, the I/O > wait time problem still remains. I have been waiting 3 minutes now for > evolution to start with 88% I/O wait time yet no visible signs of > progress. I've confirmed I'm using the CFQ scheduler, so that's not > the problem. >
Did you also
echo 1 > /sys/block/sd{a,b}/device/queue_depth echo 1 > /sys/block/sd{a,b}/queue/iosched/slice_async_rq echo 1 > /sys/block/sd{a,b}/queue/iosched/quantum
(replacing sd{a,b} with your actual drives) ?
It seems to have been part of the factors that helped (along with the patch).
And hopefully you don't have a recent Seagate hard drive like me ? :-)
So you test case is : - start a large dd with 1M block size - time evolution
?
Mathieu
> Also, Jens, I'd just like to point out that the problem is > reproducible across all schedulers. Does your patch seek to tackle a > problem specific to the CFQ scheduler, leaving the I/O wait issue for > later? Just wondering. > > I'll post some benchmarks numbers once I have them. Thanks, > > - Ben > > _______________________________________________ > ltt-dev mailing list > ltt-dev@lists.casi.polymtl.ca > http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev >
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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