On Thu, Sep 14, 2000 at 04:00:31PM +0200, Andrea Arcangeli wrote:
> On Wed, 13 Sep 2000, Andi Kleen wrote:
>
> >I guess it boils down to that the plugging (run_task(&tq_disc)) is overloaded
> >in Linux. It does merging of requests which are the same anyways (=from the
> >same operation in upper layers) and merging of requests that are unrelated.
>
> &tq_disk doesn't merge anything. It only tells the driver to start eating
> the requests in the queue. The driver will just blindy process them and if
> they're big with many bh on them it will do scatter gather with lots of
> I/O in one scsi command. If they're small, the driver will produce 4k/1k
> sized scsi commands as worse (same for IDE).
Sorry, i've been imprecise in my wording. I really meant "controls the end of
merging" with "does the merging"
-Andi
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