Messages in this thread | | | Date | Thu, 8 Jul 2010 17:15:17 +0200 | Subject | Re: [RFC/RFT PATCH] cfq-iosched: Implement cfq group idling | From | Corrado Zoccolo <> |
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On Thu, Jul 8, 2010 at 4:08 PM, Jeff Moyer <jmoyer@redhat.com> wrote: > Vivek Goyal <vgoyal@redhat.com> writes: > >> On Thu, Jul 08, 2010 at 09:39:45AM -0400, Jeff Moyer wrote: >>> Vivek Goyal <vgoyal@redhat.com> writes: >>> >>> > Currently we idle on sequential queues and allow dispatch from a single >>> > queue and that can become a bottleneck on higher end storage. For example >>> > on my HP EVA, I can run multiple sequential streams and achieve top BW >>> > of around 350 MB/s. But with CFQ, dispatching from single queue does not >>> > keep the array busy (limits to 150-180 MB/s with 4 or 8 processes). >>> > >>> > One approach to solve this issue is simply use slice_idle = 0. But this >>> > also takes away the any service differentiation between groups. >>> >>> That also takes away service differentiation between queues. If you >>> want to maintain that at all, then this is really just pushing the >>> problem to another layer. >>> >> >> Yes it does take away the io priority with-in group. But I think that's >> the trade-off and that's not default. So those who don't require ioprio >> stuff working with-in group and those who know that they have got >> faster storage will set slice_idle=0. For rest of the SATA users default >> is still slice_idle=8. > > [snip] > > Sorry, Vivek, I'm actually hijacking your thread. ;-) I know what the > alternatives are, what I'm looking for is guidance on what Jens wants to > do with CFQ. We can discuss the merits of different approaches once we > agree on a set of requirements. > > Cheers, > Jeff >
Hi Jeff, did you have a look at: http://lkml.indiana.edu/hypermail/linux/kernel/1004.3/00082.html (and following msgs)? We tried to achieve better throughput on multi-spindle disks, by merging queues. I think the idea is promising, but we still need a lot of work to make it concrete. If you want to hack on it, feel free, since I don't have hardware to test it.
Corrado
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dott. Corrado Zoccolo mailto:czoccolo@gmail.com PhD - Department of Computer Science - University of Pisa, Italy -------------------------------------------------------------------------- The self-confidence of a warrior is not the self-confidence of the average man. The average man seeks certainty in the eyes of the onlooker and calls that self-confidence. The warrior seeks impeccability in his own eyes and calls that humbleness. Tales of Power - C. Castaneda -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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