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    SubjectRe: [Ext2-devel] disk throughput
    On Mon, Nov 05 2001, Mike Fedyk wrote:
    > On Mon, Nov 05, 2001 at 08:18:36AM +0100, Jens Axboe wrote:
    > > On Mon, Nov 05 2001, Jens Axboe wrote:
    > > > Interesting, the 2.5 design prevents this since it doesn't account
    > > > merges as a penalty (like a seek). I can do something like that for 2.4
    > > > too, I'll do a patch for you to test.
    > >
    > > Ok here it is. It's not as efficient as the 2.5 version since it
    > > proceeds to scan the entire queue for a merge, but it should suffice for
    > > your testing.
    > >
    > Does the elevator still favor blocks that are on the outside of the platter
    > over all others? If so, I think this should be removed in favor of a
    > timeout just like the other seek requests...

    It doesn't quite favor outside LBA's (lower numbers), it's a combination
    of sector and device. It's hard to do this right in 2.4 because request
    sectors are not absolute but a combination of partion + offset. 2.5 will
    have this fixed, generic_make_request remaps buffer heads (well actually
    bio's, but same deal) before submitting so the I/O scheduler can be a
    bit smarter.

    > I've been able to put a swap partition on the outside of my drive, and get
    > utterly abizmal performance, while on another similar system, with swap on
    > the inside of the drive performance was much better during a swap storm...

    That sounds very odd, swap should be much faster on the outside.

    Jens Axboe

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