Messages in this thread | | | Date | Mon, 5 Nov 2001 08:18:55 +0100 | From | Jens Axboe <> | Subject | Re: [Ext2-devel] disk throughput |
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On Sun, Nov 04 2001, Mike Fedyk wrote: > On Mon, Nov 05, 2001 at 08:06:35AM +0100, Jens Axboe wrote: > > On Sun, Nov 04 2001, Andrew Morton wrote: > > > The meaning of the parameter to elvtune is a complete mystery, and the > > > code is uncommented crud (tautology). So I just used -r20000 -w20000. > > > > It's the number of sectors that are allowed to pass a request on the > > queue, because of merges or inserts before that particular request. So > > you want lower than that probably, and you want READ latency to be > > smaller than WRITE latency too. The default I set is 8192/16384 iirc, so > > go lower than this -- -r512 -w1024 or even lower just to check the > > results. > > > > Does the elevator do better with powers of two?
No, that doesn't matter.
> > > This was based on observing the request queue dynamics. We frequently > > > fail to merge requests which really should be merged regardless of > > > latency. Bumping the elvtune settings fixed it all. But once the > > > fs starts writing data out contiguously it's all academic. > > > > Interesting, the 2.5 design prevents this since it doesn't account > > merges as a penalty (like a seek). I can do something like that for 2.4 > > too, I'll do a patch for you to test. > > > > I'd be very interested in this patch. Can you post it pubically?
Just posted :-)
-- Jens Axboe
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