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    SubjectRe: A quick fio test (was Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3)

    * Suparna Bhattacharya <suparna@in.ibm.com> wrote:

    > > syslet still on top. Measuring O_DIRECT reads (of 4kb size) on ramfs
    > > with 100 processes each with a depth of 200, reading a per-process
    > > private file of 10mb (need to fit in my ram...) 10 times each. IOW,
    > > doing 10,000MiB of IO in total:
    >
    > But, why ramfs ? Don't we want to exercise the case where O_DIRECT
    > actually blocks ? Or am I missing something here ?

    ramfs is just the easiest way to measure the pure CPU overhead of a
    workload without real IO delays (and resulting idle time) getting in the
    way. It's certainly not the same thing, but still it's pretty useful
    most of the time. I used a different method, loopback block device, and
    got similar results. [ Real IO shows similar results as well, but is a
    lot more noisy and hence harder to interpret (and thus easier to get
    wrong). ]

    Ingo
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