On Mon, 2010-02-01 at 09:40 +0200, Heikki Linnakangas wrote: > Simon Riggs wrote: > > The way this would work is if Startup waits on a buffer pin we > > immediately send out a request to all backends to cancel themselves if > > they are holding the buffer pin required && waiting on a lock. We then > > sleep until max_standby_delay. When max_standby_delay = -1 we only sleep > > until deadlock timeout and then check (on the Startup process). > > Should wake up to check for deadlocks after deadlock_timeout also when > max_standby_delay > deadlock_timeout. max_standby_delay could be hours - > we want to detect a deadlock sooner than that.
The patch does detect deadlocks sooner that that - "immediately", as described above. The simplified logic is if (MaxStandbyDelay == 0) immediate time out any buffer pin holders else if (MaxStandbyDelay == -1) wait for deadlock_timeout then check for deadlockers else if (standby_delay > MaxStandbyDelay) immediate time out on buffer pin else { immediate(*) check for deadlockers wait for remainder of time then time out any buffer pin holders } (*) Doing it this way makes the logic sigalarm handler code easier/more bug free. The only difference is a potential performance gain from not running deadlock detection early. -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers