Received: from localhost (maia-3.hub.org [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id 4592C9FB550 for ; Thu, 19 Jul 2007 13:21:35 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-maia, port 10024) with ESMTP id 03548-09 for ; Thu, 19 Jul 2007 13:21:31 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from davinci.ethosmedia.com (server227.ethosmedia.com [209.128.84.227]) by postgresql.org (Postfix) with ESMTP id 04A0D9FB52F for ; Thu, 19 Jul 2007 13:21:31 -0300 (ADT) X-EthosMedia-Virus-Scanned: no infections found Received: from [63.195.55.98] (account josh@agliodbs.com HELO [192.168.2.3]) by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 12696270; Thu, 19 Jul 2007 09:25:41 -0700 From: Josh Berkus Organization: PostgreSQL @ Sun To: Alvaro Herrera Subject: Re: User concurrency thresholding: where do I look? Date: Thu, 19 Jul 2007 09:22:24 -0700 User-Agent: KMail/1.8.2 Cc: pgsql-performance@postgresql.org References: <200707190828.59088.josh@agliodbs.com> <20070719154912.GG6538@alvh.no-ip.org> In-Reply-To: <20070719154912.GG6538@alvh.no-ip.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707190922.24497.josh@agliodbs.com> X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200707/241 X-Sequence-Number: 25925 Alvaro, > Have you messed with max_connections and/or max_locks_per_transaction > while testing this? The lock table is sized to max_locks_per_xact times > max_connections, and shared memory hash tables get slower when they are > full. Of course, the saturation point would depend on the avg number of > locks acquired per user, which would explain why you are seeing a lower > number for some users and higher for others (simpler/more complex > queries). That's an interesting thought. Let me check lock counts and see if this is possibly the case. -- Josh Berkus PostgreSQL @ Sun San Francisco