On Tue, Apr 28, 2009 at 5:41 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Merlin Moncure <mmoncure@xxxxxxxxx> writes: >> I have a unloaded development server running 8.4b1 that is returning >> from a 'select * from pg_locks' in around 5 ms. While the time itself >> is not a big deal, I was curious and tested querying locks on a fairly >> busy (200-500 tps sustained) running 8.2 on inferior hardware. This >> returned (after an initial slower time) in well under 1 ms most of the >> time. Is this noteworthy? What factors slow down best case >> pg_lock_status() performance? > >> edit: I bet it's the max_locks_per_transaction parameter. I really >> cranked it on the dev box during an experiment, to 16384. >> testing...yup that's it. Are there any negative performance >> side-effects that could result from (perhaps overly) cranked >> max_locks_per_transaction? > > [squint...] AFAICS the only *direct* cost component in pg_lock_status > is the number of locks actually held or awaited. If there's a > noticeable component that depends on max_locks_per_transaction, it must > be from hash_seq_search() iterating over empty hash buckets. Which is > a mighty tight loop. What did you have max_connections set to? 16384 :D (I was playing with a function that created a large number of tables/schemas) merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
