Den 30/11/2012 kl. 17.06 skrev Shaun Thomas <sthomas@xxxxxxxxxxxxxxxx>: > On 11/30/2012 09:44 AM, Niels Kristian Schjødt wrote: > > Just a note on your iostat numbers. The first reading is actually just a summary. You want the subsequent readings. > >> The pgsql_tmp dir is not changing at all it's constantly empty (a size >> of 4.0K). > > Good. > >> Filesystem 1K-blocks Used Available Use% Mounted on >> /dev/md3 230619228 5483796 213420620 3% /ssd > > Good. > > You could just be seeing lots of genuine activity. But going back on the thread, I remember seeing this in your postgresql.conf: > > shared_buffers = 7680MB > > Change this to: > > shared_buffers = 4GB > > I say that because you mentioned you're using Ubuntu 12.04, and we were having some problems with PG on that platform. With shared_buffers over 4GB, it starts doing really weird things to the memory subsystem. Whatever it does causes the kernel to purge cache rather aggressively. We saw a 60% reduction in read IO by reducing shared_buffers to 4GB. Without as many reads, your writes should be much less disruptive. > > You'll need to restart PG to adopt that change. > > But I encourage you to keep iostat running in a terminal window so you can watch it for a while. It's very revealing. > > -- > Shaun Thomas > OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604 > 312-444-8534 > sthomas@xxxxxxxxxxxxxxxx > > ______________________________________________ > > See http://www.peak6.com/email_disclaimer/ for terms and conditions related to this email Couldn't this be if you haven't changed these: http://www.postgresql.org/docs/9.2/static/kernel-resources.html ? I have changed the following in my configuration: kernel.shmmax = 8589934592 #(8GB) kernel.shmall = 17179869184 #(16GB) -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
