Messages in this thread | | | Date | Mon, 24 Feb 2003 01:09:38 -0800 | From | Andrew Morton <> | Subject | Re: Minutes from Feb 21 LSE Call |
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Bill Huey (Hui) <billh@gnuppy.monkey.org> wrote: > > On Mon, Feb 24, 2003 at 12:40:05AM -0800, Andrew Morton wrote: > > There is no evidence for any such thing. Nor has any plausible > > theory been put forward as to why such an improvement should occur. > > I find what you're saying a rather unbelievable given some of the > benchmarks I saw when the preempt patch started to floating around. > > If you search linuxdevices.com for articles on preempt, you'll see a > claim about IO performance improvements with the patch. If somethings > changed then I'd like to know. > > The numbers are here: > http://kpreempt.sourceforge.net/ >
That's a 5% difference across five dbench runs. If it is even statistically significant, dbench is notoriously prone to chaotic effects (less so in 2.5) It is a long stretch to say that any increase in dbench numbers can be generalised to "improved IO performance" across the board.
The preempt stuff is all about *worst-case* latency. I doubt if it shifts the average latency (which is in the 50-100 microsecond range) by more that 50 microseconds.
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