Messages in this thread | | | Subject | Re: iozone write 50% regression in kernel 2.6.24-rc1 | From | "Zhang, Yanmin" <> | Date | Mon, 12 Nov 2007 10:14:00 +0800 |
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On Fri, 2007-11-09 at 10:54 +0100, Peter Zijlstra wrote: > On Fri, 2007-11-09 at 17:47 +0800, Zhang, Yanmin wrote: > > Comparing with 2.6.23, iozone sequential write/rewrite (512M) has 50% regression > > in kernel 2.6.24-rc1. 2.6.24-rc2 has the same regression. > > > > My machine has 8 processor cores and 8GB memory. > > > > By bisect, I located patch > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=04fbfdc14e5f48463820d6b9807daa5e9c92c51f. > > > > > > Another behavior: with kernel 2.6.23, if I run iozone for many times after rebooting machine, > > the result looks stable. But with 2.6.24-rc1, the first run of iozone got a very small result and > > following run has 4Xorig_result. > > So the second run is 4x as fast as the first run? Pls. see below comments.
> > > What I reported is the regression of 2nd/3rd run, because first run has bigger regression. > > So the 2nd and 3rd run are stable at 50% slower than .23? Almostly. I did more testing today. Pls. see below result list.
> > > I also tried to change /proc/sys/vm/dirty_ratio,dirty_backgroud_ratio and didn't get improvement. > > Could you try: > > --- > Subject: mm: speed up writeback ramp-up on clean systems I tested kernel 2.6.23, 2,6,24-rc2, 2.6.24-rc2_peter(2.6.24-rc2+this patch).
1) Compare among first/second/following running 2.6.23: second run of iozone will get about 28% improvement than first run. Following run is very stable like 2nd run. 2.6.24-rc2: second run of iozone will get about 170% improvement than first run. 3rd run will get about 80% improvement than 2nd. Following run is very stable like 3rd run. 2.6.24-rc2_peter: second run of iozone will get about 14% improvement than first run. Following run is mostly stable like 2nd run. So the new patch really improves the first run result. Comparing wiht 2.6.24-rc2, 2.6.24-rc2_peter has 330% improvement on the first run.
2) Compare among different kernels(based on the stable highest result): 2.6.24-rc2 has about 50% regression than 2.6.23. 2.6.24-rc2_peter has the same result like 2.6.24-rc2. >From this point of view, above patch has no improvement. :)
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