Messages in this thread | | | Date | Wed, 14 Jan 2009 18:21:47 -0700 | From | Matthew Wilcox <> | Subject | Re: Mainline kernel OLTP performance update |
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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@intel.com> 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."
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