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    SubjectRe: clearing filesystem cache for I/O benchmarks
    On Mon, Jul 26, 2004 at 11:40:05PM -0700, Andrew Morton wrote:
    > ...
    > However... If you write any amount of data to a file with O_DIRECT, that
    > will, as a side-effect, remove _all_ of that file's pagecache. In 2.4 as
    > well as 2.6. So you could scrub the pagecache by reading the first 4k then
    > writing it back with O_DIRECT.
    >
    > However O_DIRECT is supported on very few filesystems in 2.4. ext2 and
    > reiserfs have it.
    >
    > XFS in 2.4 has O_DIRECT, I think, but I don't know if the invalidation
    > side-effect works on XFS.

    Yep, it does.

    cheers.

    --
    Nathan
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