On May 14, 2012, at 9:06 AM, Bruce Momjian <br...@momjian.us> wrote: > So the new release item wording will be: > > Add group commit capability for sessions that commit at the same > time > > This is the git commit message: > > Make group commit more effective. > > When a backend needs to flush the WAL, and someone else is already flushing > the WAL, wait until it releases the WALInsertLock and check if we still > need > to do the flush or if the other backend already did the work for us, before > acquiring WALInsertLock. This helps group commit, because when the WAL > flush > finishes, all the backends that were waiting for it can be woken up in one > go, and the can all concurrently observe that they're done, rather than > waking them up one by one in a cascading fashion. > > This is based on a new LWLock function, LWLockWaitUntilFree(), which has > peculiar semantics. If the lock is immediately free, it grabs the lock and > returns true. If it's not free, it waits until it is released, but then > returns false without grabbing the lock. This is used in XLogFlush(), so > that when the lock is acquired, the backend flushes the WAL, but if it's > not, the backend first checks the current flush location before retrying. > > Original patch and benchmarking by Peter Geoghegan and Simon Riggs, > although > this patch as committed ended up being very different from that. > > (Heikki Linnakangas) > > Is that commit message inaccurate?
No, I think it's actually more accurate than the proposed release note wording. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
