On 2015-03-03 15:06:54 +0400, Alexander Shutyaev wrote: > Recently we've been having problems with swap on our postgresql server. It > has 125GB of RAM. We've decided to calculate it's memory consumption. To do > this we've used the formulas from the official docs [1]. Note that I think those formulas have been removed from the docs for a while now (9.2?). > However there is > one parameter that seems strange - Shared disk buffers. According to the > formula it occupies the following space: > > (block_size + 208) * shared_buffers > Our values are > > block_size=8192 > shared_buffers=30GB > The block_size has the default value and shared_buffers was calculated by > pgtune. According to the formula the product will be around 252 000 GB > which doesn't make any sense. The problem with your calculation is that the shared_buffers referenced in the formula is the number of buffers - whereas when you specify it using a size unit (like MB, GB,...) that amount of memory is divided by the size of a page. So you're off by a factor of 8192. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
