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. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
