The PostgreSQL server failed to start

Maybe transient, but worth tracking:

Saw this fail with devstack.

2014-08-12 18:04:10.694 | + sudo /usr/sbin/service postgresql restart
2014-08-12 18:04:10.703 | * Restarting PostgreSQL 9.1 database server
2014-08-12 18:04:12.270 | * The PostgreSQL server failed to start. Please check the log output:
2014-08-12 18:04:12.270 | 2014-08-12 18:04:12 UTC FATAL: could not create shared memory segment: Invalid argument
2014-08-12 18:04:12.270 | 2014-08-12 18:04:12 UTC DETAIL: Failed system call was shmget(key=5432001, size=36954112, 03600).
2014-08-12 18:04:12.270 | 2014-08-12 18:04:12 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 36954112 bytes), reduce PostgreSQL's shared memory usage, perhaps by reducing shared_buffers or max_connections.
2014-08-12 18:04:12.270 | 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.
2014-08-12 18:04:12.270 | The PostgreSQL documentation contains more information about shared memory configuration.

Full logs @ http://logs.openstack.org/96/103296/11/check/check-tempest-dsvm-postgres-full/3b1e14b/logs/devstacklog.txt.gz