On Wed, Mar 26, 2014 at 08:22:01PM +0000, Anand Kumar, Karthik wrote: > Looking a little deeper, I saw signs of memory being heavily fragmented: > > root@site-db01b:/var/log # cat /proc/buddyinfo > Node 0, zone DMA 1 1 2 2 2 1 0 0 1 1 3 > Node 0, zone DMA32 8 7 8 7 10 8 7 11 9 5 92 > Node 0, zone Normal 13069 0 0 0 0 0 0 0 0 0 1 > Node 1, zone Normal 652315 36885 1168 0 1 1 0 1 1 1 0 > > > Node 0 has 13069 4k blocks, and zero 8k blocks available to use > Which is likely what caused the problem, I'd think. > > A little while later though, buddyinfo changed and suddenly there was a > lot more memory in 8k blocks. > > root@site-db01b:/proc # cat /proc/buddyinfo > Node 0, zone DMA 1 1 2 2 2 1 0 > 0 1 1 3 > Node 0, zone DMA32 8 7 8 7 10 8 7 > 11 9 5 92 > Node 0, zone Normal 9645 5495 1115 0 0 0 0 > 0 0 0 1 > Node 1, zone Normal 409734 10953 1 0 1 1 0 > 1 1 1 0 > > (Note the change in the Node 0 line, 8k blocks went up from 0 to 5495) > > Anyone have any idea why memory was so fragmented, and what causes memory > to be defragged? Is it something postgres does? Are there any kernel > specific settings that control it? If I had to take a guess, it is zone_reclaim; see: http://frosty-postgres.blogspot.com/2012/08/postgresql-numa-and-zone-reclaim-mode.html The fix is this sysctl: vm.zone_reclaim_mode = 0 -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
