Received: from makus.postgresql.org (makus.postgresql.org [98.129.198.125]) by mail.postgresql.org (Postfix) with ESMTP id 78C6E7D49CF for ; Mon, 23 Apr 2012 20:49:05 -0300 (ADT) Received: from momjian.us ([72.94.173.45]) by makus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1SMT0C-0004QQ-BH for pgsql-docs@postgresql.org; Mon, 23 Apr 2012 23:49:04 +0000 Received: from bruce by momjian.us with local (Exim 4.72) (envelope-from ) id 1SMSzy-0001nn-Rz; Mon, 23 Apr 2012 19:48:50 -0400 Date: Mon, 23 Apr 2012 19:48:50 -0400 From: Bruce Momjian To: Aleksey Tsalolikhin Cc: pgsql-docs@postgresql.org Subject: Re: what is a "working set" ? Message-ID: <20120423234850.GA22081@momjian.us> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) X-Pg-Spam-Score: -1.9 (-) X-Archive-Number: 201204/46 X-Sequence-Number: 7300 On Mon, Apr 23, 2012 at 04:43:25PM -0700, Aleksey Tsalolikhin wrote: > Hi. I'm trying to find a definition of "working set", it seems > important for performance tuning, but I cannot find a PostgreSQL > document defining it. That is a great question, and I plan to write a blog about it soon. Working set is from the mainframe days and tries to represent how much data you "touch" during a specified period of time, e.g. a 5-minute working set is the amount of data you typically access (and maybe write) in a 5-minute period. It is _very_ hard to get that information right now from Postgres, and getting that information for a typical Unix process isn't easy either. -- Bruce Momjian http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +