Friendly greetings ! I found something "odd" (something that i can't explain) this weekend. An octocore server with 32GB of ram, running postgresql 8.3.6 Running only postgresql, slony-I and pgbouncer. Just for testing purpose, i tried a setting with 26GB of shared_buffer. I quickly noticed that the performances wasn't very good and the server started to swap slowly but surely. (but still up to 2000query/second as reported by pgfouine) It used all the 2GB of swap. I removed the server from production, added 10GB of swap and left it for the weekend with only slony and postgresql up to keep it in sync with the master database. This morning i found that the whole 12GB of swap were used : Mem: 32892008k total, 32714728k used, 177280k free, 70872k buffers Swap: 12582896k total, 12531812k used, 51084k free, 27047696k cached # cat /proc/meminfo MemTotal: 32892008 kB MemFree: 171140 kB Buffers: 70852 kB Cached: 27065208 kB SwapCached: 4752492 kB Active: 24362168 kB Inactive: 7806884 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 32892008 kB LowFree: 171140 kB SwapTotal: 12582896 kB SwapFree: 53064 kB Dirty: 122636 kB Writeback: 0 kB AnonPages: 280336 kB Mapped: 14118588 kB Slab: 224632 kB PageTables: 235120 kB NFS_Unstable: 0 kB Bounce: 0 kB CommitLimit: 29028900 kB Committed_AS: 28730620 kB VmallocTotal: 34359738367 kB VmallocUsed: 12916 kB VmallocChunk: 34359725307 kB While i understand that a very high shared_buffer wasn't a good idea, i don't understand this behaviour. Any tought ? I tried this setup because having 2 level of data caching doesn't make sense to me. (1 in OS filesystem cache and 1 in shm (shared_buffer)). I'd love to understand what's happening here ! Thank you :) -- F4FQM Kerunix Flan Laurent Laborde -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
