-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Em 13-05-2013 09:50, Heikki Linnakangas escreveu: > I've been working on-and-off on the WAL-insert scaling patch. It's > in pretty good shape now, and I'll post it shortly, but one thing I > noticed is that it benefits a lot from using an atomic > compare-and-swap instruction for the contention-critical part. > > I realized that we could also use compare-and-swap to make LWLocks > scale better. The LWLock struct is too large to compare-and-swap > atomically, but we can still use CAS to increment/decrement the > shared/exclusive counters, when there's no need to manipulate the > wait queue. That would help with workloads where you have a lot of > CPUs, and a lot of backends need to acquire the same lwlock in > shared mode, but there's no real contention (ie. few exclusive > lockers). > > pgbench -S is such a workload. With 9.3beta1, I'm seeing this > profile, when I run "pgbench -S -c64 -j64 -T60 -M prepared" on a > 32-core Linux machine: > > - 64.09% postgres postgres [.] tas - tas - 99.83% > s_lock - 53.22% LWLockAcquire + 99.87% GetSnapshotData - 46.78% > LWLockRelease GetSnapshotData + GetTransactionSnapshot + 2.97% > postgres postgres [.] tas + 1.53% postgres > libc-2.13.so [.] 0x119873 + 1.44% postgres postgres > [.] GetSnapshotData + 1.29% postgres [kernel.kallsyms] [k] > arch_local_irq_enable + 1.18% postgres postgres [.] > AllocSetAlloc ...
I'd like to test this here but I couldn't reproduce that perf output here in a 64-core or 24-core machines, could you post the changes to postgresql.conf and the perf arguments that you used? Thanks! []s - -- Dickson S. Guedes mail/xmpp: gue...@guedesoft.net - skype: guediz http://guedesoft.net - http://www.postgresql.org.br http://github.net/guedes - twitter: @guediz -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJRltDJAAoJEBa5zL7BI5C7UQkH/Au8p90pTMl1qvbft3q1Gtxp a4PV8fjOrzQou2I+9Sxu5W1ql3qyVmfFare+bJVKg5L3LmvACjZ6bbw9oKBEnPGB vzE9nB6+3F3eyo464Niq19cTVgmyRQBcuOT/Ye88Uh2mrrgUYB+lGfk9M2Af7on1 nUZI5YsWWXt/bm9wf6rRCzDs76fS7ity943V0aSg2AHryjfcB8o4oBhJBnrRfnm7 v+SxLg0xDEWQPo8VOCQlIw5IhoxNokHjMAt8Ho7o0dXJRR91vSerdulK4Uxkz13Q E9GlDBDBzZsHmqHCGECNSglqVegXRA5g2i/o3tmQ/lEKzCF9OiX7GBSkXN+gEsc= =nGJ5 -----END PGP SIGNATURE----- -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
