From owner-freebsd-stable@FreeBSD.ORG Sat Mar 21 00:47:26 2015 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id A4269F58; Sat, 21 Mar 2015 00:47:26 +0000 (UTC) Received: from smarthost1.sentex.ca (smarthost1.sentex.ca [IPv6:2607:f3e0:0:1::12]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "smarthost.sentex.ca", Issuer "smarthost.sentex.ca" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 632556D6; Sat, 21 Mar 2015 00:47:26 +0000 (UTC) Received: from [IPv6:2607:f3e0:0:4:f025:8813:7603:7e4a] (saphire3.sentex.ca [IPv6:2607:f3e0:0:4:f025:8813:7603:7e4a]) by smarthost1.sentex.ca (8.14.9/8.14.9) with ESMTP id t2L0lIEw053988; Fri, 20 Mar 2015 20:47:18 -0400 (EDT) (envelope-from mike@sentex.net) Message-ID: <550CBF80.6030809@sentex.net> Date: Fri, 20 Mar 2015 20:46:56 -0400 From: Mike Tancsa Organization: Sentex Communications User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Konstantin Belousov , d@delphij.net Subject: Re: RELENG_10 performance regression (was Re: 35-40% performance drop releng9 vs releng10 openvpn References: <5506250A.2000506@sentex.net> <20150316132055.GQ32288@funkthat.com> <5509D6C6.4050204@sentex.net> <20150318211457.GL51048@funkthat.com> <550B6950.8060806@sentex.net> <550C5AAF.9060502@sentex.net> <550C8AEE.4090408@sentex.net> <550CB306.7030405@delphij.net> <20150321001559.GB2379@kib.kiev.ua> In-Reply-To: <20150321001559.GB2379@kib.kiev.ua> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.75 Cc: John-Mark Gurney , FreeBSD-STABLE Mailing List , John Baldwin X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 21 Mar 2015 00:47:26 -0000 On 3/20/2015 8:15 PM, Konstantin Belousov wrote: >> >> For the purpose of devfs, does it make sense to bump timestamps like >> normal filesystems for each read/write operation? Looks like Mac OS X >> will bump timestamps for each operation but Debian don't. > > First question is, what timecounter hardware is used. I would accept > some slowdown from hardware like HPET, but it is indeed surprising > if caused by TSC. > > David Wolfskill suggested trying the problem commit with vfs.timestamp_precision=0 and it does indeed restore performance to what it was. The raw dtrace files are available and FlameGraphs can all be found at http://tancsa.com/time/ ---Mike -- ------------------- Mike Tancsa, tel +1 519 651 3400 Sentex Communications, mike@sentex.net Providing Internet services since 1994 www.sentex.net Cambridge, Ontario Canada http://www.tancsa.com/