On Wed, Mar 4, 2015 at 4:50 AM, Bill Moran <wmoran@xxxxxxxxxxxxxxxxx> wrote: > On Wed, 4 Mar 2015 14:05:09 +0400 > Alexander Shutyaev <shutyaev@xxxxxxxxx> wrote: > >> Thanks for the answer. Now, given this info I've calculated that our >> postgresql should occupy approx. 30,53 GB while the server has 125 GB of >> RAM. However we often see in top that there is very little free memory and >> even swap is used. What could be the reason of postgres using so much >> memory? > > Memory usage is much more dependent on the OS than Postgres than you > might realize. I don't see where you state the OS, but I'll assume > it's Linux for now. > > Linux default NUMA policy seems to be tuned toward applications > that don't use a lot of RAM. If your 128G server has 8 CPUs, then > Linux will allow a single process to use 16G of RAM before deciding > that it has to use swap for that process. This is one of the > advantantages I find with FreeBSD. > > Read up on how NUMA works a bit, and do some research into how to > tune the NUMA policies ... assuming, of course, that you _are_ using > Linux. Or switch to FreeBSD where the default NUMA policy is more > friendly to programs that use a lot of RAM. The single most important step on a NUMA pg machine is to make sure that zone_reclaim_mode = 0. If the kernel detects a largish internode communication cost, it will turn it on at boot time and after you've been running a while it will suddenly slow to a crawl as it tries to move things around in memory. Other important steps are to lower the background dirty bytes so you don't get massive background writes. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
