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    SubjectRe: QUEUE_FLAG_CLUSTER: not working in 2.6.24 ?
    Mark Lord wrote:
    > 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. 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?
    > ..
    > Because the early 2.6.24 series failed to boot on this machine
    > due to bugs in the block layer -- so the code that caused this regression
    > is probably in the stuff from before the kernels became usable here.

    That sounds more harsh than intended --> the earlier 2.6.24 kernels (up to
    the first couple of -rc* ones failed here because of incompatibilities
    between the block/bio changes and libata.

    That's better, I think!


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