On Tue, 2010-03-30 at 23:06 -0500, Eric Sandeen wrote: > Keith Mannthey wrote: > > On Mon, 2010-03-29 at 11:10 -0400, Greg Freemyer wrote: > >> On Mon, Mar 29, 2010 at 2:25 AM, Keith Mannthey <kmannth@xxxxxxxxxx> wrote: > >>> > >>> After 2.6.30 I am seeing large performance regressions on a raid setup. > >>> I am working to publish a larger amount of data but I wanted to get some > >>> quick data out about what I am seeing. > >>> > >> Is mdraid involved? > >> > >> They added barrier support for some configs after 2.6.30 I believe. > >> It can cause a drastic perf change, but it increases reliability and > >> is "correct". > > > > lvm and device mapper are is involved. The git bisect just took me to: > > > > 374bf7e7f6cc38b0483351a2029a97910eadde1b is first bad commit > > commit 374bf7e7f6cc38b0483351a2029a97910eadde1b > > Author: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > Date: Mon Jun 22 10:12:22 2009 +0100 > > > > dm: stripe support flush > > > > Flush support for the stripe target. > > > > This sets ti->num_flush_requests to the number of stripes and > > remaps individual flush requests to the appropriate stripe devices. > > > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx> > > > > :040000 040000 542f4b9b442d1371c6534f333b7e00714ef98609 d490479b660139fc1b6b0ecd17bb58c9e00e597e M drivers > > > > > > This may be correct behavior but the performance penalty in this test > > case is pretty high. > > > > I am going to move back to current kernels and starting looking into > > ext4/dm flushing. > > It would probably be interesting to do a mount -o nobarrier to see if > that makes the regression go away. -o nobarrier takes the regression away with 2.6.34-rc3: Default mount: ~27500 -o nobarrier: ~12500 Barriers on this setup cost ALOT during writes. Interestingly as well the "mailserver" workload regression is also removed by mounting with "-o nobarrier". I am going to see what impact is seen on a single disk setup. Thanks, Keith Mannthey LTC FS-Dev -- 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
