Messages in this thread | | | From | Al Boldi <> | Subject | Re: huge improvement with per-device dirty throttling | Date | Wed, 22 Aug 2007 14:31:21 +0300 |
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Jeffrey W. Baker wrote: > I tested 2.6.23-rc2-mm + Peter's per-BDI v9 patches, versus 2.6.20 as > shipped in Ubuntu 7.04. I realize there is a large delta between these > two kernels. > > I load the system with du -hs /bigtree, where bigtree has millions of > files, and dd if=/dev/zero of=bigfile bs=1048576. I test how long it > takes to ls /*, how long it takes to launch gnome-terminal, and how long > it takes to launch firefox. > > 2.6.23-rc2-mm-bdi is better than 2.6.20 by a factor between 50x and > 100x. : : > Yes, you read that correctly. In the presence of a sustained writer and > a competing reader, it takes more than 30 minutes to start firefox. > > 4. > > du -hs /bigtree > > Under 2.6.20, lstat64 has a mean latency of 75ms in the presence of a > sustained writer. Under 2.6.23-rc2-mm+bdi, the mean latency of lstat64 > is only 5ms (15x improvement). The worst case latency I observed was > more than 2.9 seconds for a single lstat64 call. : : > In other words, under 2.6.20, only writing processes make progress. > Readers never make progress. > > 5. > > dd writeout speed > > 2.6.20: 36.3MB/s, 35.3MB/s, 33.9MB/s > 2.6.23: 20.9MB/s, 22.2MB/s > > 2.6.23 is slower when writing out, because other processes make progress > > My system is a Core 2 Duo, 2GB, single SATA disk.
Many thanks for your detailed analysis.
Which io-scheduler did you use, and what numbers do you get with other io-schedulers?
Thanks!
-- Al
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