On Mon, Jul 25, 2011 at 4:07 PM, Robert Haas <robertmh...@gmail.com> wrote: > As to what that something might be, I reran this last test with > LWLOCK_STATS enabled and here are the top things that are blocking: > > lwlock 310: shacq 96846 exacq 108433 blk 16275 > lwlock 3: shacq 64 exacq 2628381 blk 36027 > lwlock 7: shacq 0 exacq 2628615 blk 85220 > lwlock 11: shacq 84913908 exacq 4539551 blk 2119423 > lwlock 4: shacq 28667307 exacq 2628524 blk 3356651 > > During this 5-minute test run, an LWLock acquisition blocked 6180335 > times. As you can see from the above results, ProcArrayLock accounts > for 54% of that blocking, and CLogControlLock accounts for another > 34%. lwlock 7 is WALInsertLock, which manages to account for more > than 1% of the blocking despite the fact that WAL has been largely > eliminated in this test...
I reran this test on master with permanent (not unlogged) tables, and got the following stats for blocking: lwlock 11: shacq 58376164 exacq 2122076 blk 1130974 lwlock 4: shacq 15168924 exacq 1367303 blk 1555799 lwlock 7: shacq 0 exacq 8440615 blk 1726896 grand total: shacq 144563929 exacq 41618873 blk 4886107 So that's 35% WALInsertLock, 32% ProcArrayLock, and 23% CLogControlLock. No other single lock accounted for more than 1% of the blocking. It's a good guess we're going to have to fix more than one thing to really make this zippy. Also note that CLogControlLock accounts for better than 40% of the shared-lock acquisitions across all LWLocks. The next-most-frequently share-locked LWLock is ProcArrayLock, with 10% of the total shared-lock acquisitions, followed by SInvalReadLock, at 9%. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
