From owner-freebsd-stable@FreeBSD.ORG Mon Nov 30 17:52:32 2009 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2051F1065679 for ; Mon, 30 Nov 2009 17:52:32 +0000 (UTC) (envelope-from se@freebsd.org) Received: from smtp110.mail.ukl.yahoo.com (smtp110.mail.ukl.yahoo.com [77.238.184.48]) by mx1.freebsd.org (Postfix) with SMTP id 8BA6B8FC12 for ; Mon, 30 Nov 2009 17:52:31 +0000 (UTC) Received: (qmail 69219 invoked from network); 30 Nov 2009 17:52:30 -0000 Received: from (se@88.128.83.247 with plain) by smtp110.mail.ukl.yahoo.com with SMTP; 30 Nov 2009 17:52:29 +0000 GMT X-Yahoo-SMTP: iDf2N9.swBDAhYEh7VHfpgq0lnq. X-YMail-OSG: IkJsw7sVM1ksM6N5suoaBc.wvyVvTno2cNxCX9t9.48ojA_ZoAGP49sOIYiG8EyE5Az0XQR4C3y41ay2qKWUrmaX7Z9qOCVY9PxBAva7Hz51sFELnepvlbqZzFHHmA7qMIHKB5_dqPahc5xdDihoFHCuwlYMFenLN.dNJF6ywgMJclBYKPMDgc6ZngJeZCOwp.bbMDPIxpWXTJ.vcFeoayiO93HytAEQJ.DoducV_1pXyI_MX5W3O9xr8d.GW2by X-Yahoo-Newman-Property: ymail-3 Message-ID: <4B14065B.1020209@freebsd.org> Date: Mon, 30 Nov 2009 18:52:27 +0100 From: Stefan Esser User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.5) Gecko/20091121 Lightning/1.0pre Thunderbird/3.0 MIME-Version: 1.0 To: freebsd-stable@freebsd.org References: <4B13869D.1080907@zedat.fu-berlin.de> <0D3A9408-84A8-4C74-A318-F580B41FC1A6@exscape.org> <20091130084704.2893cc85.wmoran@potentialtech.com> <19219.55350.599595.807654@jerusalem.litteratus.org> In-Reply-To: X-Enigmail-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: Phoronix Benchmarks: Waht's wrong with FreeBSD 8.0? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 30 Nov 2009 17:52:32 -0000 Am 30.11.2009 15:46, schrieb Ivan Voras: > Robert Huff wrote: >> Bill Moran writes: >> >>> It's common knowledge that the default value for vfs.read_max is >>> non- optimal for most hardware and that significant performance >>> improvements can be made in most cases by raising it. >> >> Documentation/discussion where? > > There is no documentation except for the sysctl documentation itself: > "vfs.read_max: Cluster read-ahead max block count" but it depends on the > load - it helps sequential reads, will probably do nothing for other > kinds of loads. It is also UFS-only. I tested different values some time ago. vfs.read_max can be raised to about twice its default value and I set it to 15, when I had UFS+SU file systems (switched over to ZFS, long ago.) Tests included operations on large files (multi-GB) that were processed and written back to the same drive. But even in these tests, there was an upper limit beyond that system responsiveness declined massively (IIRC, at about 25). The best value (without impact on randoim I/O) seems to be in the range 12 to 16. (FreeBSD used to apply a heuristic on read-ahead, and only incremented the read amount to the limit set by the sysctl as long as the accesses were purely sequential.) Regards, STefan