Messages in this thread |  | | Date | Sun, 04 Nov 2001 23:14:27 -0800 | From | Andrew Morton <> | Subject | Re: [Ext2-devel] disk throughput |
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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.
Right, thanks. With the ialloc.c one-liner I didn't touch elvtune. Defaults seem fine.
It should the number of requests which are allowed to pass a request, not the number of sectors!
Well, you know what I mean: Make it
1 + nr_sectors_in_request / 1000
> > 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.
OK.
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