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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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