>-----Original Message----- >From: Matthew Wilcox [mailto:matthew@xxxxxx] >Sent: Wednesday, January 14, 2009 5:22 PM >To: Andrew Morton >Cc: Wilcox, Matthew R; Ma, Chinang; linux-kernel@xxxxxxxxxxxxxxx; Tripathi, >Sharad C; arjan@xxxxxxxxxxxxxxx; Kleen, Andi; Siddha, Suresh B; Chilukuri, >Harita; Styner, Douglas W; Wang, Peter Xihong; Nueckel, Hubert; >chris.mason@xxxxxxxxxx; srostedt@xxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; >Andrew Vasquez; Anirban Chakraborty >Subject: Re: Mainline kernel OLTP performance update > >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. I took a quick look at the interrupts figure between 2.6.24 and 2.6.27. i/o interuputs is slightly down in 2.6.27 (due to reduce throughput). But both NMI and reschedule interrupt increased. Reschedule interrupts is 2x of 2.6.24. > >> 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." -Chinang -- 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
