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    SubjectRe: disk statistics issue in 2.6.27
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    On Wed, 2008-10-22 at 19:17 +0200, Jens Axboe wrote:
    > On Wed, Oct 22 2008, Miquel van Smoorenburg wrote:
    > > On Mon, 2008-10-20 at 19:12 +0200, Jens Axboe wrote:
    > > > On Sun, Oct 19 2008, Miquel van Smoorenburg wrote:
    >
    > > > > I noticed that the "iostat -k -x 2" output does't make any sense.
    > > > > The number of reads/sec and number of writes/sec are about what I
    > > > > would expect, and so are the other fields, but rkB/sec and wkB/sec
    > > > > are completely off-scale: gigabytes read/written per second.
    > > >
    > >
    > > > Are the reported values in iostat any sort of multiple of the real
    > > > throughtput, or is is just insanely large?
    > >
    > > It looks like it's a multiple, but it appears to vary between 128 and
    > > 512, and is different for reads and writes, so I do not know what to
    > > make of it.
    > >

    I added some debug statements to block/blk-core.c, and it appears that
    blk_end_io() is always called with nr_bytes == 16320 Kbytes (16711680).

    Ofcourse I should have noticed earlier that iostat -x 2 always prints
    32640 as "average request size" (in sectors).

    Mike.



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