-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello I am sending this email to ask if anyone has noticed a change in how a server running postgreSQL 9.1 uses and allocates memory compared to older versions. We upgraded all our systems from 8.3 to 9.1 a couple of weeks ago, and we have experienced a radical change in how our servers make use of memory. How memory is allocated has become more unstable and the swap usage has increased dramatically. The pattern that we have started seeing is: * Sudden decrease of swap when running backup/vacuum+analyze jobs * Full use of cached memory when running backup/vacuum+analyze jobs * Sudden increase of swap and unused memory when backup/vacuum+analyze jobs are finnished. * Progressive decrease of swap during the day. Here is a list of things about this upgrade to version 9.1 that can be interesting when analyzing this change of behavior: * The servers are running the samme OS version and linux kernel as with 8.3. * We are running the same values for parameters related to memory allocation as we used in 8.3. * We are running the same backups and maintenance jobs as with version 8.3. These jobs are running at the exactly same time as with 8.3. * Backups (PITR, pg_dumps) and maintenances (vacuum, analyze) jobs are executed between midnight and early morning. * We run several postgreSQL clusters per server, running in different IPs and disks. * We have not seen any significant change in how databases are used/accessed after the upgrade to 9.1. * We upgraded in the first time from 8.3.12 to 9.1.2, but because this bug: http://archives.postgresql.org/pgsql-bugs/2011-12/msg00068.php we had to downgrade to 9.1.1. We thought in the begynning that our memory problems were related to this bug, but everything is the same with 9.1.1. * A couple of days ago we decreased the values of maintenance_work_mem and work_mem over a 50% in relation to values used with 8.3. The only change we have seen is even more unused memory after backup/vacuum +analyze jobs are finnished. Here you have some graphs that can help to get a picture about what we are talking about: * Overview of how memory use changed in one of our servers after the upgrade in the begynning og week 49: http://folk.uio.no/rafael/upgrade_to_9.1/server-1/memory-month.png http://folk.uio.no/rafael/upgrade_to_9.1/server-1/memory-year.png * We could think that all this happens because we are running to much in one server. Here are some graphs from a server with 30GB+ running only one postgres cluster (shared_memory = 6GB, maintenance_work_memory = 512MB, work_mem = 32MB) for a couple of days: http://folk.uio.no/rafael/upgrade_to_9.1/server-2/memory-week.png The memory pattern is the same even when running only one postgres cluster in a server with enough memory. Any ideas about why this dramatic change in memory usage when the only thing apparently changed from our side is the postgres version? Thanks in advance for any help. regards, - -- Rafael Martinez Guerrero Center for Information Technology University of Oslo, Norway PGP Public Key: http://folk.uio.no/rafael/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk7vUpYACgkQBhuKQurGihTvjACff5J08pNJuRDgkegYdtQ5zp52 GeoAnRaaU+F/C/udQ7lMl/TkvRKX2WnP =VcDk -----END PGP SIGNATURE----- -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
