(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Mon, 22 Aug 2011 15:20:41 GMT bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=41552 > > Summary: Performance of writing and reading from multiple > drives decreases by 40% when going from Linux Kernel > 2.6.36.4 to 2.6.37 (and beyond) > Product: IO/Storage > Version: 2.5 > Kernel Version: 2.6.37 > Platform: All > OS/Version: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: SCSI > AssignedTo: linux-scsi@xxxxxxxxxxxxxxx > ReportedBy: mpete_06@xxxxxxxxxxx > Regression: No > > > We have an application that will write and read from every sector on a drive. > The application can perform these tasks on multiple drives at the same time. > It is designed to run on top of the Linux Kernel, which we periodically update > so that we can get the latest device drivers. When performing the last update > from 2.6.33.2 to 2.6.37, we found that the performance of a set of drives > decreased by some 40% (took 3 hours and 11 minutes to write and read from 5 > drives on 2.6.37 versus 2 hours and 12 minutes on 2.6.33.3). I was able to > determine that the issue was in the 2.6.37 Kernel as I was able to run it with > the 2.6.36.4 kernel, and it had the better performance. After seeing that I/O > throttling was introduced in the 2.6.37 Kernel, I naturally suspected that. > However, by default, all the throttling was turned off (I attached the actual > .config that was used to build the kernel). I then tried to turn on the > throttling and set it to a high number to see what would happen. When I did > that, I was able to reduce the time from 3 hours and 11 minutes to 2 hours and > 50 minutes. There seems to be something there that changed that is impacting > performance on multiple drives. When we do this same test with only one drive, > the performance is identical between the systems. This issue still occurs on > Kernel 3.0.2. > Are you able to determine whether this regression is due to slower reading, to slower writing or to both? Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>