[lkml]   [2010]   [Jul]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [RFC/RFT PATCH] cfq-iosched: Implement cfq group idling
    Vivek Goyal <> 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.

    This is the crux of my issues with CFQ. It works really well for SATA
    disks. Once you try running it on enterprise storage, it falls flat.
    Is it a design goal of CFQ to get it to run well on enterprise storage?



     \ /
      Last update: 2010-07-08 15:43    [W:0.021 / U:68.112 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site