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. > (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. > 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. - 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 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. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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
