On Wed, 14 Jan 2009 18:21:47 -0700 Matthew Wilcox <matthew@xxxxxx> wrote: > On Wed, Jan 14, 2009 at 04:35:57PM -0800, Andrew Morton wrote: > > On Tue, 13 Jan 2009 15:44:17 -0700 > > "Wilcox, Matthew R" <matthew.r.wilcox@xxxxxxxxx> wrote: > > > > > > > (top-posting repaired. That @intel.com address is a bad influence ;)) > > Alas, that email address goes to an Outlook client. Not much to be done > about that. aspirin? > > (cc linux-scsi) > > > > > > This is latest 2.6.29-rc1 kernel OLTP performance result. Compare to > > > > 2.6.24.2 the regression is around 3.5%. > > > > > > > > Linux OLTP Performance summary > > > > Kernel# Speedup(x) Intr/s CtxSw/s us% sys% idle% iowait% > > > > 2.6.24.2 1.000 21969 43425 76 24 0 0 > > > > 2.6.27.2 0.973 30402 43523 74 25 0 1 > > > > 2.6.29-rc1 0.965 30331 41970 74 26 0 0 > > > But the interrupt rate went through the roof. > > Yes. I forget why that was; I'll have to dig through my archives for > that. Oh. I'd have thought that this alone could account for 3.5%. > > A 3.5% slowdown in this workload is considered pretty serious, isn't it? > > Yes. Anything above 0.3% is statistically significant. 1% is a big > deal. The fact that we've lost 3.5% in the last year doesn't make > people happy. There's a few things we've identified that have a big > effect: > > - Per-partition statistics. Putting in a sysctl to stop doing them gets > some of that back, but not as much as taking them out (even when > the sysctl'd variable is in a __read_mostly section). We tried a > patch from Jens to speed up the search for a new partition, but it > had no effect. I find this surprising. > - The RT scheduler changes. They're better for some RT tasks, but not > the database benchmark workload. Chinang has posted about > this before, but the thread didn't really go anywhere. > http://marc.info/?t=122903815000001&r=1&w=2 Well. It's more a case that it wasn't taken anywhere. I appear to have recently been informed that there have never been any CPU-scheduler-caused regressions. Please persist! > SLUB would have had a huge negative effect if we were using it -- on the > order of 7% iirc. SLQB is at least performance-neutral with SLAB. We really need to unblock that problem somehow. I assume that enterprise distros are shipping slab? -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
