From owner-freebsd-current@FreeBSD.ORG Wed May 27 11:33:53 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3CB51106566C; Wed, 27 May 2009 11:33:53 +0000 (UTC) (envelope-from snb@freebsd.org) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2001:4f8:fff6::28]) by mx1.freebsd.org (Postfix) with ESMTP id 2ABAA8FC19; Wed, 27 May 2009 11:33:53 +0000 (UTC) (envelope-from snb@freebsd.org) Received: from ebi.local (root@localhost [127.0.0.1]) by freefall.freebsd.org (8.14.3/8.14.3) with ESMTP id n4RBXpoY050769; Wed, 27 May 2009 11:33:52 GMT (envelope-from snb@freebsd.org) Date: Wed, 27 May 2009 13:33:51 +0200 From: Nick Barkas To: Roman Divacky Message-ID: <20090527113351.GA61692@ebi.local> References: <20090527103648.GA61454@ebi.local> <20090527111238.GA2000@freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090527111238.GA2000@freebsd.org> User-Agent: Mutt/1.5.19 (2009-01-05) Cc: "freebsd-current@freebsd.org" Subject: Re: vm_lowmem event handler for dirhash X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 27 May 2009 11:33:53 -0000 On Wed, May 27, 2009 at 01:12:38PM +0200, Roman Divacky wrote: > On Wed, May 27, 2009 at 12:36:49PM +0200, Nick Barkas wrote: > > Some time during the next week or so, I plan on committing the attached > > patch. It adds a vm_lowmem event handler to the dirhash code in UFS2 so > > that dirhashes will be deleted when the system is low on memory. This > > allows one to increase the maximum amount of memory available for > > dirhash on machines that have memory to spare (via the > > vfs.ufs.dirhash_maxmem sysctl), and hopefully just improving behaviour > > in low memory situations. I worked on this last year for the summer of > > code with David Malone as my mentor. > > cool! do you have any performance numbers? graphs? :) what value do you recommend > for the dirhash_maxmem sysctl? Oh yes, I have many graphs: http://wiki.freebsd.org/DirhashDynamicMemory When I ran those tests a few months ago, I used 64MB for dirhash_maxmem on a system with 1GB of memory. I have not tried other amounts of memory besides that, at least that I can recall, so please let me know what you find if you experiment with other values. Performance improvements and sometimes degradations changed depending on the type of work load, and the results on 7.x were also sometimes quite different from -current. I feel that the tests I did were pretty artificial though, so it would be great to hear about any results found with more realistic testing. Nick