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    SubjectRe: [RFC] IO scheduler based io controller (V5)
    On Mon, Jun 22, 2009 at 11:40:42AM -0400, Jeff Moyer wrote:
    > Vivek Goyal <vgoyal@redhat.com> writes:
    >
    > > On Sun, Jun 21, 2009 at 08:51:16PM +0530, Balbir Singh wrote:
    > >> * Vivek Goyal <vgoyal@redhat.com> [2009-06-19 16:37:18]:
    > >>
    > >> >
    > >> > Hi All,
    > >> >
    > >> > Here is the V5 of the IO controller patches generated on top of 2.6.30.
    > >> [snip]
    > >>
    > >> > Testing
    > >> > =======
    > >> >
    > >>
    > >> [snip]
    > >>
    > >> I've not been reading through the discussions in complete detail, but
    > >> I see no reference to async reads or aio. In the case of aio, aio
    > >> presumes the context of the user space process. Could you elaborate on
    > >> any testing you've done with these cases?
    > >>
    > >
    > > Hi Balbir,
    > >
    > > So far I had not done any testing with AIO. I have done some just now.
    > > Here are the results.
    > >
    > > Test1 (AIO reads)
    > > ================
    > > Set up two fio, AIO read jobs in two cgroup with weight 1000 and 500
    > > respectively. I am using cfq scheduler. Following are some lines from my test
    > > script.
    > >
    > > ===================================================================
    > > fio_args="--ioengine=libaio --rw=read --size=512M"
    >
    > AIO doesn't make sense without O_DIRECT.
    >

    Ok, here are the read results with --direct=1 for reads. In previous posting,
    writes were already direct.

    test1 statistics: time=8 16 20796 sectors=8 16 1049648
    test2 statistics: time=8 16 10551 sectors=8 16 581160


    Not sure why reads are so slow with --direct=1? In the previous test
    (no direct IO), I had cleared the caches using
    (echo 3 > /proc/sys/vm/drop_caches) so reads could not have come from page
    cache?

    Thanks
    Vivek


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