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    SubjectRe: SSD and IO schedulers
    From
    Well, that's not an usual workload for netbooks, where most SSDs are
    currently deployed.
    For usual workloads, that are mostly read, cfq has lower performance
    both in throughput and in latency than deadline.

    Corrado

    2009/4/8 Heinz Diehl <htd@fancy-poultry.org>:
    > On 08.04.2009, Corrado Zoccolo wrote:
    >
    >> I found that elevator=deadline performs much better than noop for
    >> writes, and almost as well for reads
    > [....]
    >
    > The DL elevator has slightly more throughput than cfq and anticipatory,
    > but is almost unusuable under load.
    >
    > Running Theodore Ts'os "fsync-tester" while doing Linus' torture test
    > "while : ; do time sh -c "dd if=/dev/zero of=bigfile bs=8M count=256 ; sync; rm bigfile"; done"
    > shows it clearly:
    >
    > mount: /dev/sda4 on /home type xfs (rw,noatime,logbsize=256k,logbufs=2,nobarrier)
    > Kernel 2.6.29.1 (vanilla)
    >
    > with cfq:
    >
    > htd@liesel:~/!> ./fsync-tester
    > fsync time: 0.7640
    > fsync time: 0.6166
    > fsync time: 1.2830
    > fsync time: 0.4273
    > fsync time: 1.1693
    > fsync time: 1.7466
    > fsync time: 1.2477
    > fsync time: 1.9411
    > fsync time: 1.9636
    > fsync time: 1.9065
    > fsync time: 1.1561
    > fsync time: 1.8267
    > fsync time: 0.2431
    > fsync time: 0.2898
    > fsync time: 0.2394
    > fsync time: 0.4309
    > fsync time: 1.5699
    > fsync time: 0.3742
    > fsync time: 1.3194
    > fsync time: 1.9442
    > fsync time: 1.0899
    > fsync time: 1.9443
    > fsync time: 1.0062
    >
    > with dl:
    >
    > fsync time: 10.5853
    > fsync time: 10.3339
    > fsync time: 5.3374
    > fsync time: 6.5707
    > fsync time: 10.6095
    > fsync time: 4.1154
    > fsync time: 4.9604
    > fsync time: 10.5325
    > fsync time: 10.4543
    > fsync time: 10.4970
    > fsync time: 10.5570
    > fsync time: 5.2717
    > fsync time: 10.5619
    > fsync time: 5.3058
    > fsync time: 3.1019
    > fsync time: 5.1504
    > fsync time: 5.7564
    > fsync time: 10.5998
    > fsync time: 4.0895
    >
    >
    > Regards, Heinz.
    >
    >



    --
    __________________________________________________________________________

    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


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