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    SubjectRe: ext3 performance inconsistencies, 2.4/2.6

    On Tue, 4 Nov 2003, Paul Venezia wrote:
    >
    > I've been running bonnie++ filesystems testing on an IBM x335 server
    > recently. This box uses the MPT RAID controller, but I've disabled the
    > RAID and am addressing the disks individually. I'm getting wildly
    > different results between 2.4.20-20-9 (RedHat mod), 2.4.22 (stock), and
    > 2.6.0-test9.

    Interesting. The 2.4.22 sequential "per char" results are totally out of
    line with anything else.

    The thing is, the overhead for the per-char stuff really should be almost
    all in user space unless I'm mistaken. It's just using getch/putch, no?

    Which makes me suspect that either the libc does something different
    depending on kernel version, _or_ 2.4.22 returns a different st_blksize
    thing, causing stdio to use a different blocking size.

    Have you tried stracing the "per char" parts of the benchmark to see what
    the system call patterns are? That should show both effects.

    Linus

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