I am trying to figure out why ~30 idle postgres processes take up so much process-specific memory after normal usage. I am using Postgres 9.3.1 and CentOS release 6.3 (Final).
Using top, I can see that many of the postgres connections are using up to 300mb (average ~200mb) of non-shared (RES - SHR) memory:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3534 postgres 20 0 2330m 1.4g 1.1g S 0.0 20.4 1:06.99 postgres: deploy mtalcott 10.222.154.172(53495) idle
9143 postgres 20 0 2221m 1.1g 983m S 0.0 16.9 0:14.75 postgres: deploy mtalcott 10.222.154.167(35811) idle
6026 postgres 20 0 2341m 1.1g 864m S 0.0 16.4 0:46.56 postgres: deploy mtalcott 10.222.154.167(37110) idle
18538 postgres 20 0 2327m 1.1g 865m S 0.0 16.1 2:06.59 postgres: deploy mtalcott 10.222.154.172(47796) idle
1575 postgres 20 0 2358m 1.1g 858m S 0.0 15.9 1:41.76 postgres: deploy mtalcott 10.222.154.172(52560) idle
There are about 29 total idle connections. These idle connections keep growing in memory until the machine starts using swap, then performance grinds to a halt. As expected, resetting the connection clears the process-specific memory. The same number of connections on the same machine only use 20% of memory (with 0 swap) when I periodically reconnect. What kind of information are these processes holding on to? I would expect long-running, idle postgres processes to have similar memory usage to brand new, idle ones.
Worth noting: I am heavily using schemas. On every request to my app, I am setting and resetting search_path.