Messages in this thread |  | | Date | Mon, 5 Nov 2001 10:20:36 +0100 | From | Jens Axboe <> | Subject | Re: [Ext2-devel] disk throughput |
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On Mon, Nov 05 2001, Mike Fedyk wrote: > On Mon, Nov 05, 2001 at 08:18:36AM +0100, Jens Axboe wrote: > > On Mon, Nov 05 2001, Jens Axboe wrote: > > > 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 here it is. It's not as efficient as the 2.5 version since it > > proceeds to scan the entire queue for a merge, but it should suffice for > > your testing. > > > > Does the elevator still favor blocks that are on the outside of the platter > over all others? If so, I think this should be removed in favor of a > timeout just like the other seek requests...
It doesn't quite favor outside LBA's (lower numbers), it's a combination of sector and device. It's hard to do this right in 2.4 because request sectors are not absolute but a combination of partion + offset. 2.5 will have this fixed, generic_make_request remaps buffer heads (well actually bio's, but same deal) before submitting so the I/O scheduler can be a bit smarter.
> I've been able to put a swap partition on the outside of my drive, and get > utterly abizmal performance, while on another similar system, with swap on > the inside of the drive performance was much better during a swap storm...
That sounds very odd, swap should be much faster on the outside.
-- Jens Axboe
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