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Rene Herman wrote: > Tejun Heo wrote: > >> Everything seems fine in the dmesg. Performance degradation is >> probably some other issue in -rc kernel. I'm suspecting recently >> fixed block layer bug. If it's still the same in the next -rc, >> please report. > > In fact, it's CFQ. The PATA thing was a red herring. 2.6.20-rc2 and 3 > give me ~ 24 MB/s from "hdparm t /dev/hda" while 2.6.20-rc1 and below > give me ~ 50 MB/s. > > Jens: this is due to "[PATCH] cfq-iosched: tighten allow merge > criteria", 719d34027e1a186e46a3952e8a24bf91ecc33837: > > http://www2.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=719d34027e1a186e46a3952e8a24bf91ecc33837 > > > If I revert that one, I have my 50 M/s back. config and dmesg attached > in case they're useful. Wow.. same deal here -- sequential throughput drops from 40MB/sec to 28MB/sec with CFQ -- whereas the anticipatory scheduler maintains the 40MB/sec. Jens.. I wonder if the new merging test is a bit too strict? There are four possible combinations, and the new code allows merging for two of them: sync+sync and async+async. But surely one of (not sure which) sync+async or async+sync may also be okay? Or would it? This is a huge performance hit. Cheers - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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