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    SubjectRe: [PATCH] updated reiser4 - reduced cpu usage for writes by writing more than 4k at a time (has implications for generic write code and eventually for the IO layer)
    On Wed, May 24 2006, Hans Reiser wrote:
    > Tom Vier wrote:
    >
    > >On Tue, May 23, 2006 at 01:14:54PM -0700, Hans Reiser wrote:
    > >
    > >
    > >>underlying FS can be improved. Performance results show that the new
    > >>code consumes 40% less CPU when doing "dd bs=1MB ....." (your hardware,
    > >>and whether the data is in cache, may vary this result). Note that this
    > >>has only a small effect on elapsed time for most hardware.
    > >>
    > >>
    > >
    > >Write requests in linux are restricted to one page?
    > >
    > >
    > >
    > It may go to the kernel as a 64MB write, but VFS sends it to the FS as
    > 64MB/4k separate 4k writes.

    Nonsense, there are ways to get > PAGE_CACHE_SIZE writes in one chunk.
    Other file systems have been doing it for years.

    --
    Jens Axboe

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