From owner-freebsd-stable@FreeBSD.ORG Thu Aug 29 19:42:40 2013 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id E79728E1 for ; Thu, 29 Aug 2013 19:42:40 +0000 (UTC) (envelope-from robert.burmeister@utoledo.edu) Received: from sam.nabble.com (sam.nabble.com [216.139.236.26]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id C9F372404 for ; Thu, 29 Aug 2013 19:42:40 +0000 (UTC) Received: from [192.168.236.26] (helo=sam.nabble.com) by sam.nabble.com with esmtp (Exim 4.72) (envelope-from ) id 1VF875-00083y-Tv for freebsd-stable@freebsd.org; Thu, 29 Aug 2013 12:42:39 -0700 Date: Thu, 29 Aug 2013 12:42:39 -0700 (PDT) From: Robert_Burmeister To: freebsd-stable@freebsd.org Message-ID: <1377805359915-5840115.post@n5.nabble.com> In-Reply-To: <521C9E85.4060801@UToledo.edu> References: <521C9E85.4060801@UToledo.edu> Subject: Re: Suggest changing dirhash defaults for FreeBSD 9.2. MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 29 Aug 2013 19:42:41 -0000 After scouring the internet, it seems that no one else has done a great deal of testing of UFS2 dirhash defaults lately. As the dirhash feature has effectively been tested for regressions, I would like to propose setting the default dirhash values to my original recommendation: vfs.ufs.dirhash_maxmem: 20971520 vfs.ufs.dirhash_reclaimage: 60 The last benchmarks from 2008 only tested dirhash_maxmem at 2 and 64 megs. I found in my testing that setting maxmem much over 32 megs makes the UFS dirhash dysfunctional, as scavenging 10% of maxmem on each vm_lowmem event becomes too aggressive. While autotuning defaults is highly desirable, autotuning dirhash_maxmem opens the can of worms of also tuning the hard coded 10% scavenging. It may be better to hard code the maxmem default. It may be appropriate to set the reclaimage to 5 minutes rather than 5 seconds; I consider 60 seconds to still be a very conservative value, but at least an effective one. -- View this message in context: http://freebsd.1045724.n5.nabble.com/Suggest-changing-dirhash-defaults-for-FreeBSD-9-2-tp5839351p5840115.html Sent from the freebsd-stable mailing list archive at Nabble.com.