On Mon, Mar 16, 2009 at 01:03:42PM +0800, Lin, Ming wrote: > On Sun, 2009-03-15 at 08:27 +0800, Linus Torvalds wrote: > > > > On Sat, 14 Mar 2009, Rafael J. Wysocki wrote: > > > > > > The following bug entry is on the current list of known regressions > > > from 2.6.28. Please verify if it still should be listed and let me know > > > (either way). > > > > > > > > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12809 > > > Subject : iozone regression with 2.6.29-rc6 > > > Submitter : Lin Ming <ming.m.lin@xxxxxxxxx> > > > Date : 2009-02-27 9:13 (16 days old) > > > First-Bad-Commit: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1cf6e7d83bf334cc5916137862c920a97aabc018 > > > References : http://marc.info/?l=linux-kernel&m=123572630504360&w=4 > > > Handled-By : Wu Fengguang <fengguang.wu@xxxxxxxxx> > > > > I suspect that I should just raise the default dirty limits. Wu reported > > that it fixed the regression, and while he picked some rather high > > percentages, I think we could certainly raise the rather aggressive > > default ones. > > > > After all, those default percentages were picked (a) with the old dirty > > logic and (b) largely at random and (c) designed to be aggressive. In > > particular, that (a) means that having fixed some of the dirty accounting, > > maybe the real bug is now that it was always too aggressive, just hidden > > by an accounting issue. > > > > If we raised the default ratio from 5/10 to 10/20, what happens to the > > iozone regression? > > echo 10 > /proc/sys/vm/dirty_background_ratio > echo 20 > /proc/sys/vm/dirty_ratio > > It fixed the regression of iozone (filesize 1200M) on 4P dual-core HT > machine(8G mem). A quick&coarse calculation: 8G * 15% = 1200M. This means an iozone process dirtying 1200M data won't be write-blocked. So the thresholds of 10/20 are just about enough for fixing this regression. Thanks, Fengguang -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
