From owner-freebsd-performance@FreeBSD.ORG Tue Apr 10 04:48:02 2007 Return-Path: X-Original-To: freebsd-performance@freebsd.org Delivered-To: freebsd-performance@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 45F0616A404 for ; Tue, 10 Apr 2007 04:48:02 +0000 (UTC) (envelope-from kevin@insidesystems.net) Received: from imap.insidesystems.net (imap.insidesystems.net [206.216.149.56]) by mx1.freebsd.org (Postfix) with ESMTP id 22C3413C4B7 for ; Tue, 10 Apr 2007 04:48:02 +0000 (UTC) (envelope-from kevin@insidesystems.net) Received: from [68.32.227.193] (helo=[127.0.0.1]) by imap.insidesystems.net with esmtpa (Exim 4.66 (FreeBSD)) (envelope-from ) id 1Hb7bA-0006iS-F6 for freebsd-performance@freebsd.org; Tue, 10 Apr 2007 04:04:52 +0000 Message-ID: <461B0CD0.8090404@insidesystems.net> Date: Tue, 10 Apr 2007 00:04:32 -0400 From: Kevin Way Organization: Inside Systems, Inc. User-Agent: Thunderbird 2.0b2 (Windows/20070116) MIME-Version: 1.0 To: freebsd-performance@freebsd.org Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg=sha1; boundary="------------ms090905020204060708080506" Subject: Re: Anyone interested in improving postgresql scaling? X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Apr 2007 04:48:02 -0000 This is a cryptographically signed message in MIME format. --------------ms090905020204060708080506 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Kris Kennaway wrote: > If so, then your task is the following: > > Make SYSV semaphores less dumb about process wakeups. Currently > whenever the semaphore state changes, all processes sleeping on the > semaphore are woken, even if we only have released enough resources > for one waiting process to claim. i.e. there is a thundering herd > wakeup situation which destroys performance at high loads. Fixing > this will involve replacing the wakeup() calls with appropriate > amounts of wakeup_one(). Could this cause problem cause a situation where an 8-Core system was 50-75% slower than an otherwise equivalent 2-Core system? I have a graph of my sysbench/pgsql results here: http://blog.insidesystems.net/files/sysctl-pgsq-amd64-wtf.png As the graph shows, the 8-core system is about half the speed of the 2-core system at 2 simultaneous threads, and it decays down to approximately 1/4 the speed of the 2-core system as the # of threads hits 5. All other (non-pgsql, non-sysv) tests came back approximately as expected, but I'm left wondering if I did something wrong, or if 8 cpus are slower than 2, when it comes to Postgres on currently available FreeBSD. Kevin Way Inside Systems, Inc. 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