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    SubjectRe: QUEUE_FLAG_CLUSTER: not working in 2.6.24 ?
    Jens Axboe wrote:
    > On Thu, Dec 13 2007, Mark Lord wrote:
    >> Matthew Wilcox wrote:
    >>> On Thu, Dec 13, 2007 at 01:48:18PM -0500, Mark Lord wrote:
    >>>> Problem confirmed. 2.6.23.8 regularly generates segments up to 64KB for
    >>>> libata,
    >>>> but 2.6.24 uses only 4KB segments and a *few* 8KB segments.
    >>> Just a suspicion ... could this be slab vs slub? ie check your configs
    >>> are the same / similar between the two kernels.
    >> ..
    >>
    >> Mmmm.. a good thought, that one.
    >> But I just rechecked, and both have CONFIG_SLAB=y
    >>
    >> My guess is that something got changed around when Jens
    >> reworked the block layer for 2.6.24.
    >> I'm going to dig around in there now.
    >
    > I didn't rework the block layer for 2.6.24 :-). The core block layer
    > changes since 2.6.23 are:
    >
    > - Support for empty barriers. Not a likely candidate.
    > - Shared tag queue fixes. Totally unlikely.
    > - sg chaining support. Not likely.
    > - The bio changes from Neil. Of the bunch, the most likely suspects in
    > this area, since it changes some of the code involved with merges and
    > blk_rq_map_sg().
    > - Lots of simple stuff, again very unlikely.
    >
    > Anyway, it sounds odd for this to be a block layer problem if you do see
    > occasional segments being merged. So it sounds more like the input data
    > having changed.
    >
    > Why not just bisect it?
    ..

    CC'ing Neil Brown.



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