> On Wed, 18 Apr 2007 15:54:00 +0200 Valerie Clement <valerie.clement@xxxxxxxx> wrote: > > Running benchmark tests (FFSB) on an ext4 filesystem, I noticed a > performance degradation (about 15-20 percent) in sequential write tests > between 2.6.19-rc6 and 2.6.21-rc4 kernels. > > I ran the same tests on ext3 and XFS filesystems and I saw the same > performance difference between the two kernel versions for these two > filesystems. > > I have also reproduced it between 2.6.20.7 and 2.6.21-rc7. > The FFSB tests run 16 threads, each creating 1GB files. The tests were > done on the same x86_64 system, with the same kernel configuration and > on the same scsi device. Below are the throughput values given by FFSB. > > kernel XFS ext3 > ---------- > 2.6.20.7 48 MB/sec 44 MB/sec > > 2.6.21-rc7 38 MB/sec 37 MB/sec > > Did anyone else run across the problem? > Is there a known issue? > That's a new discovery, thanks. It could be due to I/O scheduler changes. Which one are you using? CFQ? Or it could be that there has been some changed behaviour at the VFS/pagecache layer: the VFS might be submitting little hunks of lots of files, rather than large hunks of few files. Or it could be a block-layer thing: perhaps some driver change has caused us to be placing less data into the queue. Which device driver is that machine using? Being a simple soul, the first thing I'll try when I get near a test box will be for i in $(seq 1 16) do time dd if=/dev/zero of=$i bs=1M count=1024 & done - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
