Simon Riggs <simon@xxxxxxxxxxxxxxx> writes: > On Mon, 2009-03-16 at 16:26 +0000, Matthew Wakeling wrote: >> One possibility would be for the locks to alternate between exclusive >> and >> shared - that is: >> >> 1. Take a snapshot of all shared waits, and grant them all - >> thundering >> herd style. >> 2. Wait until ALL of them have finished, granting no more. >> 3. Take a snapshot of all exclusive waits, and grant them all, one by >> one. >> 4. Wait until all of them have been finished, granting no more. >> 5. Back to (1) > I agree with that, apart from the "granting no more" bit. > Currently we queue up exclusive locks, but there is no need to since for > ProcArrayLock commits are all changing different data. > The most useful behaviour is just to have two modes: > * exclusive-lock held - all other x locks welcome, s locks queue > * shared-lock held - all other s locks welcome, x locks queue My goodness, it seems people have forgotten about the "lightweight" part of the LWLock design. regards, tom lane - Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
