Le 19 décembre 2011 16:04, Rafael Martinez <r.m.guerrero@xxxxxxxxxxx> a écrit : > -----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. Can you report what is filling the cache and the swap ? -- Cédric Villemain +33 (0)6 20 30 22 52 http://2ndQuadrant.fr/ PostgreSQL: Support 24x7 - Développement, Expertise et Formation -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
