I thought 'shared_buffers' sets how much memory that is dedicated to PostgreSQL to use for caching data, therefore not available to other applications.
However, as shown in the following screenshots, The server (CentOS 6.6 64bit) has 64GB of RAM, and 'shared_buffer' is set to 32GB, but the free+buffer+cache is 60GB.
Shouldn't the maximum value for free+buffer+cache be 32GB ( 64 - 32)?
Is 'shared_buffers' pre allocated to Postgres, and Postgres only?
While PostgreSQL has reserves the right to use 32GB, as long as PostgreSQL has not actually dirtied that RAM yet, then the kernel is free to keep using it to cache files.