Am 03.12.2011 18:02, schrieb Christoph Zwerschke:
> The difference could be explained by taking credit for the descriptors
> which may not be comprised in the shared_buffers setting, even if the
> shared_buffers value is set in memory units.
Looked a bit more into this - the shared_buffers setting indeed only
determines the memory for he actual shared buffer blocks, even if given
in memory units. It does not include the descriptors and other freelist
related stuff that is also needed to build the shared buffer pool.
When I increased the shared_buffers by 10000, the shared memory usage
increased by 8372.4 Bytes, this is about 2.2% more than 10000 blocks
would use, close to the 2.5% which are documented.
-- Christoph