Added to TODO: * SMP scalability improvements
http://archives.postgresql.org/pgsql-hackers/2007-07/msg00439.php --------------------------------------------------------------------------- Simon Riggs wrote: > David Strong presented some excellent results of his SMP scalability > testing at Ottawa in May. > http://www.pgcon.org/2007/schedule/events/16.en.html > > There are some easy things we can do to take advantage of those results, > especially the ones that were hardware independent. > > The hardware independent results were these two: > - Avoid contention on WALInsertLock (+28% gain) > - Increase NUM_BUFFER_PARTITIONS (+7.7% gain) > > Scalability begins to slow down at 8 CPUs on 8.2.4 and David was able to > show good gains even at 8 CPUs with these changes. > > Proposals > > 1. For the first result, I suggest that we introduce some padding into > the shmem structure XLogCtlData to alleviate false sharing that may > exist between holders of WALInsertLock, WALWriteLock and info_lck. The > cost of this will be at most about 200 bytes of shmem, with a low risk > change. The benefits are hard to quantify, but we know this is an area > of high contention and we should do all we can to reduce that. > This hasn't been discussed previously, though we have seen good benefit > from avoiding false sharing in other cases, e.g. LWLOCK padding. > > 2. Increase NUM_BUFFER_PARTITIONS from 16 to 256 (or higher). > This has been discussed previously: > http://archives.postgresql.org/pgsql-hackers/2006-09/msg00967.php > > Both of these changes are simple enough to consider for 8.3 > > Comments? > > -- > Simon Riggs > EnterpriseDB http://www.enterprisedb.com > > > ---------------------------(end of broadcast)--------------------------- > TIP 7: You can help support the PostgreSQL project by donating at > > http://www.postgresql.org/about/donate -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://postgres.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + - Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
