Messages in this thread |  | | | Date | Sun, 8 Nov 2009 18:01:50 +0100 | | Subject | Re: Performance regression in IO scheduler still there | | From | Corrado Zoccolo <> |
On Fri, Nov 6, 2009 at 7:56 PM, Jeff Moyer <jmoyer@redhat.com> wrote: > Jeff Moyer <jmoyer@redhat.com> writes: > rlat | rrlat | wlat | rwlat > kernel | Thr | read | randr | write | randw | avg, max | avg, max | avg, max | avg,max > ------------------------------------------------------------------------------------------------------------------------ > 2.6.29 | 8 | 66.43 | 20.52 | 296.32 | 214.17 | 22.330, 3106.47 | 70.026, 2804.02 | 4.817, 2406.65 | 1.420, 349.44 > | 16 | 63.28 | 20.45 | 322.65 | 212.77 | 46.457, 5779.14 |137.455, 4982.75 | 8.378, 5408.60 | 2.764, 425.79 > ------------------------------------------------------------------------------------------------------------------------ > 2.6.32-rc6 | 8 | 87.66 | 115.22 | 324.19 | 222.18 | 16.677, 3065.81 | 11.834, 194.18 | 4.261, 1212.86 | 1.577, 103.20 > low_lat=0 | 16 | 94.06 | 49.65 | 327.06 | 214.74 | 30.318, 5468.20 | 50.947, 1725.15 | 8.271, 1522.95 | 3.064, 89.16 > ------------------------------------------------------------------------------------------------------------------------ >
Jeff, Jens, do you think we should try to do more auto-tuning of cfq parameters? Looking at those numbers for SANs, I think we are being suboptimal in some cases. E.g. sequential read throughput is lower than random read. In those cases, converting all sync queues in sync-noidle (as defined in for-2.6.33) should allow a better aggregate throughput when there are multiple sequential readers, as in those tiobench tests. I also think that current slice_idle and slice_sync values are good for devices with 8ms seek time, but they are too high for non-NCQ flash devices, where "seek" penalty is under 1ms, and we still prefer idling. If we agree on this, should the measurement part (I'm thinking to measure things like seek time, throughput, etc...) be added to the common elevator code, or done inside cfq? If we want to put it in the common code, maybe we can also remove the duplication of NCQ detection, by publishing the NCQ flag from elevator to the io-schedulers.
Thanks, Corrado
> > Cheers, > Jeff > -- -- 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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