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    SubjectRe: ll_rw_blk.c fails to merge requests. Help!
    Jens Axboe wrote:
    >
    > Okay, here's a new version. The pending list always contains requests
    > from the write list, so we can use list_splice. We batch a quarter
    > the size freelist, i.e. half the size of the write list -- whether
    > that is a good number, I don't know. I suspect it should be less
    > than that.

    To preface this, I don't really know what I'm talking about so ignore me
    if this is stupid.

    I understand you are coalescing the freed requests to add them back to
    the freelist in a batch, but this is done only for 'write' requests, so
    it makes sense that the wake_up is postponed until the list_splice of
    the pending_list into the write_list.

    But, it looks like with your patch, if the req->free_list is the 'read'
    freelist the wake_up will *never* happen (unlike in the original
    version). Is this missing wake_up intended?

    (you mentioned in an earlier post that read requests can be stolen from
    the write free_list, I suppose if your code is correct it has something
    to do with this fact :-) as I said, I know next to nothing here, just
    learning)

    David Mansfield
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