From owner-freebsd-performance@FreeBSD.ORG Thu Aug 4 19:13:12 2005 Return-Path: X-Original-To: freebsd-performance@freebsd.org Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 724F716A41F for ; Thu, 4 Aug 2005 19:13:12 +0000 (GMT) (envelope-from sean@noc-phone.gigave.com) Received: from mailhost.gigave.com (mailhost.gigave.com [38.113.228.14]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4ABB643D49 for ; Thu, 4 Aug 2005 19:13:12 +0000 (GMT) (envelope-from sean@noc-phone.gigave.com) Date: Thu, 4 Aug 2005 12:13:12 -0700 From: Sean Chittenden To: Bruce Walker Message-ID: <20050804191312.GF70123@sean.gigave.com> References: <20050804174508.GA70123@sean.gigave.com> <42F25526.5030002@borderware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42F25526.5030002@borderware.com> Cc: freebsd-performance@freebsd.org Subject: Re: changing max_connections in postgresql on FreeBSD 5.4 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: Thu, 04 Aug 2005 19:13:12 -0000 > >>Will more RAM become available to postgresql if I change the > >>kernel-values mentioned above to half the size? > > > >Yes, it will raise the in-kernel limits so that PostgreSQL can > >allocate more RAM for its user-land cache. > > > >You will probably have a better ROI in terms of performance by > >increasing the kernel's caching parameters as opposed to > >PostgreSQL's cache. You need both, don't get me wrong, but there > >is lots of performance to be gained by increasing the amount of > >caching the kernel does. -sc > > Any generally good rules of thumb you could share? Which kernel > caching are you referring to (ie disk, ...) ? Hrm... I'll suggest one tunable: options KSTACK_MAX_PAGES=32 # Maximum pages to give the kernel stack Don't crank it up too far, but 64 seems to be a decent number in my experience. I'd pimp more settings, but given that tuning is still closer to an art than a science (it wouldn't be if someone catalogued settings for various applications and hardware combinations, but I digress), I'll suggest having you take a peak at the various NOTES files and some of the headers, such as: src/sys/amd64/include/param.h. I've divulged more in the archives, too. -sc -- Sean Chittenden