On Wed, 2010-03-31 at 18:06 -0400, Greg Freemyer wrote: > On Wed, Mar 31, 2010 at 6:02 PM, Keith Mannthey <kmannth@xxxxxxxxxx> wrote: > > 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 > > I'm curious if your using an internal or external journal? I am unsure. How do I tell? I am using defaults except with the -o nobarrier. I know jdb2 is being used. Thanks, Keith > I'd guess the cost of barriers is much greater with an internal > journal, but I don't recall seeing any benchmarks one way or the > other. > > Greg -- 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
