I increased PostgreSQL's shared buffer (among other settings) to 4096M and now PostgreSQL fails to start, giving the error message below.
Should I change the kernel's
SHMMAX parameter to 4096M? The system has 16GB of RAM. How should this be done? What should I change
SHMALL to? I want the changes to be permanent and persists after reboots.
* Starting PostgreSQL 9.1 database server * The PostgreSQL server failed to start. Please check the log output:
2013-04-15 06:15:53 UTC FATAL: could not create shared memory segment: Invalid argument
2013-04-15 06:15:53 UTC DETAIL: Failed system call was shmget(key=5432001, size=4418322432, 03600).
2013-04-15 06:15:53 UTC HINT: This error usually means that PostgreSQL's request for a shared memory segment exceeded your kernel's SHMMAX parameter. You can either reduce the request size or reconfigure the kernel with larger SHMMAX. To reduce the request size (currently 4418322432 bytes), reduce PostgreSQL's shared memory usage, perhaps by reducing shared_buffers or max_connections.
If the request size is already small, it's possible that it is less than your kernel's SHMMIN parameter, in which case raising the request size or reconfiguring SHMMIN is called for.
The PostgreSQL documentation contains more information about shared memory configuration.
total used free shared buffers cached Mem: 24744200 1244936 23499264 0 77480 670240 -/+ buffers/cache: 497216 24246984 Swap: 16775160 0 16775160