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    SubjectRe: Higher than expected disk write(2) latency

    > I thought you were doing I/O to the underlying block device. If so,
    > there's no need to open with O_SYNC. You do, however, need to open the
    > device with O_DIRECT and align your buffers (and buffer lengths)
    > properly.

    Yes, we are using O_DIRECT + aligning the buffers. However, usign O_SYNC
    vs. O_ASYNC seems to matter (different latency). Maybe this is because
    we are using librt?

    > Which AIO interface are you using, libaio or librt? How many I/Os are
    > you queueing to the device? You may want to take a look at aio-stress.c
    > as a way to test your device (this uses libaio, the in-kernel AIO
    > interface).

    We are using librt, queueing 10240 writes, 512 bytes each.

    We'll retry with libaio. Thanks for advice.


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