On Tue, Apr 11, 2000 at 12:21:45PM +0100, Stephen C. Tweedie wrote:
> Hi,
>
> On Tue, Apr 11, 2000 at 02:37:38AM +0200, Andi Kleen wrote:
> >
> > The culprit is probably the elevator code in ll_rw_blk, which uses
> > a single linked list
>
> The elevator doesn't sort buffers, it only sorts requests --- and
> there is a strict limit on how many requests we can have outstanding
> at once. I wouldn't have thought that elevator scalability would
> have had anything to do with performance going downhill above 3000
> buffers.
<Wild speculation>
Still it seems get_request() walks a lot of the 256 element request
array. I could imagine that that will take some time, especially
when you have many wakeups in 2.2 (in 2.3 wait_for_request is a
a wake-one waitqueue so it should work better there, 2.2 probably
has a thundering herd)
Does 2.3 behave better than 2.2 ?
</speculation>
-Andi
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