On Sat, Nov 26, 2011 at 6:51 PM, Andres Freund <and...@anarazel.de> wrote:
> On Saturday, November 26, 2011 11:39:23 PM Robert Haas wrote: > > On Sat, Nov 26, 2011 at 5:28 PM, Andres Freund <and...@anarazel.de> > wrote: > > > On Saturday, November 26, 2011 09:52:17 PM Tom Lane wrote: > > >> I'd just as soon keep the fields in a logical order. > > > > > > Btw, I don't think the new order is necessarily worse than the old one. > > > > You forget to attach the benchmark results. > > > > My impression is that cache lines on modern hardware are 64 or 128 > > *bytes*, in which case this wouldn't matter a bit. > > > > But testing is even better than guessing. > Being prodded like that I ran a very quick benchmark on my workstation. > Unfortunately that means I cannot work during the time which is why I kept > it > rather short... > > That machine has 2 E5520@2.27GHz which means 2(sockets) * 4(cores) * > 2(threads) and 24GB of ram. > > Data was initialized with: pgbench -h /tmp/ --unlogged-tables -i -s 20 > pgbench > > > pgbench -h /tmp/ pgbench -S -j 16 -c 16 -T 60 > > origsnap: 92825.743958 93145.110901 93389.915474 93175.482351 > reordersnap: 93560.183272 93613.333494 93495.263012 93523.368489 > > pgbench -h /tmp/ pgbench -S -j 32 -c 32 -T 60 > > origsnap: 81846.743329 81545.175672 81702.755226 81576.576435 > 81228.154119 81546.047708 81421.436262 > reordersnap: 81823.479196 81787.784508 81820.242145 81790.263415 > 81762.421592 81496.333144 81732.088876 > > At that point I noticed I had accidentally run with a nearly stock > config... > An even shorter run with a more approrioate config yielded: > > > pgbench -h /tmp/ pgbench -S -j 32 -c 32 -T 20 > > origsnap: 102234.664020 102003.449741 102119.509053 101722.410387 > 101973.651318 102056.440561 > reordersnap: 103444.877879 103385.888808 103302.318923 103372.659486 > 103330.157612 103313.833821 > > > > Looks like a win to me. Even on this comparatively small machine. > This may not be necessary, but can you please share the modified config you used for the last run. I tabulated your last results to make it more readable, and added columns to show the improvement. origsnap reordersnap diff %age improvement ------------------------------------------------------------------ 102234.66402 103444.877879 1210.213859 1.1837607827 102003.449741 103385.888808 1382.439067 1.3552865815 102119.509053 103302.318923 1182.80987 1.1582604352 101722.410387 103372.659486 1650.249099 1.6223063263 101973.651318 103330.157612 1356.506294 1.3302517626 102056.440561 103313.833821 1257.39326 1.2320567454 That looks like a win to me too. We're getting a little over 1% improvement for free! Maybe submitting this patch to the commitfest might help get some serious consideration from a reviewer. Regards, -- Gurjeet Singh EnterpriseDB Corporation The Enterprise PostgreSQL Company
