Messages in this thread | | | Date | Tue, 25 Feb 2003 07:59:42 -0500 | Subject | Re: IO scheduler benchmarking | From | rwhron@earthlin ... |
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>> Why does 2.5.62-mm2 have higher sequential >> write latency than 2.5.61-mm1?
> And there are various odd interactions in, at least, ext3. You did not > specify which filesystem was used.
ext2
>> Thr MB/sec CPU% avg lat max latency >> 2.5.62-mm2-as 8 14.76 52.04% 6.14 4.5 >> 2.5.62-mm2-dline 8 9.91 13.90% 9.41 .8 >> 2.5.62-mm2 8 9.83 15.62% 7.38 408.9
> Fishiness. 2.5.62-mm2 _is_ 2.5.62-mm2-as. Why the 100x difference?
Bad EXTRAVERSION naming on my part. 2.5.62-mm2 _was_ booted with elevator=cfq.
How it happened: 2.5.61-mm1 tested 2.5.61-mm1-cfq tested and elevator=cfq added to boot flags 2.5.62-mm1 tested (elevator=cfq still in lilo boot boot flags) Then to test the other two schedulers I changed extraversion and boot flags.
> That 408 seconds looks suspect.
AFAICT, that's the one request in over 500,000 that took the longest. The numbers are fairly consistent. How relevant they are is debatable.
> If you want to test write latency, do this:
Your approach is more realistic than tiobench.
> There is a place in VFS where one writing task could accidentally hammer a > different one. I cannot trigger that, but I'll fix it up in next -mm.
2.5.62-mm3 or 2.5.63-mm1? (-mm3 is running now)
-- Randy Hron http://home.earthlink.net/~rwhron/kernel/bigbox.html
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