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    SubjectRe: Drastic performance issue in ext2 v ffs

    On Tue, 05 Jan 1999 12:41:59 -0700, Tom Christiansen
    <> said:

    > I believe there is something dramatically wrong here, probably in either
    > the ext2 filesystems or the SCSI driver, or both. Here's the story.

    Are these results from a hot cache, by the way?

    > My first test was du on that directory tree. Here are the timing results
    > of "du -s >/dev/null".

    > linux 0.080u 11.400s 0:11.51
    > bsd 0.030u 0.462s 0:00.49

    On a 75MB tree (the kernel source tree, compiled):
    Linux-2.2.0pre5 0.11u 0.66s 0:08.66 (from cold)
    Subsequent runs: 0.05u 0.09s 0:00.39 (from cache)

    > Here are timings on "find . -ls >/dev/null":

    > linux 1.050u 12.130s 0:13.35
    > bsd 0.739u 0.445s 0:01.18

    Linux-2.2.0pre5 0.76u 0.15s 0:00.91 (again, from cache)

    > So, what might account for this embarrassingly dramatic disparity?

    The fact that you are using such an old Linux kernel? :)

    > Does BSD have an incedibly better inode cache? Is this a known
    > bug? Is it fixed in the next release? :-)

    Not a bug: it is mainly a property of the directory entry caching
    implemented in 2.1/2.2 kernels.


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