From owner-freebsd-stable@FreeBSD.ORG Fri Oct 29 15:05:35 2010 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 8C7BE106566B for ; Fri, 29 Oct 2010 15:05:35 +0000 (UTC) (envelope-from avg@icyb.net.ua) Received: from citadel.icyb.net.ua (citadel.icyb.net.ua [212.40.38.140]) by mx1.freebsd.org (Postfix) with ESMTP id D4E718FC19 for ; Fri, 29 Oct 2010 15:05:32 +0000 (UTC) Received: from odyssey.starpoint.kiev.ua (alpha-e.starpoint.kiev.ua [212.40.38.101]) by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id SAA07363; Fri, 29 Oct 2010 18:05:28 +0300 (EEST) (envelope-from avg@icyb.net.ua) Message-ID: <4CCAE2B6.1050906@icyb.net.ua> Date: Fri, 29 Oct 2010 18:05:26 +0300 From: Andriy Gapon User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.9.2.11) Gecko/20101021 Lightning/1.0b2 Thunderbird/3.1.5 MIME-Version: 1.0 To: Kostik Belousov References: <4CCACDC0.7050802@icyb.net.ua> <1BDB4D1B02274CC8AA2DD5E68190CB5D@vosz.local> <20101029145349.GX2392@deviant.kiev.zoral.com.ua> In-Reply-To: <20101029145349.GX2392@deviant.kiev.zoral.com.ua> X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=KOI8-U Content-Transfer-Encoding: 7bit Cc: freebsd-stable@freebsd.org, Alexander Zagrebin Subject: Re: 8.1-STABLE: zfs and sendfile: problem still exists 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: Fri, 29 Oct 2010 15:05:35 -0000 on 29/10/2010 17:53 Kostik Belousov said the following: > Could it be the priming of the vm object pages content ? Sorry, not familiar with this term. Do you mean prepopulation of vm object with valid pages? > Due to double-buffering, and (possibly false) optimization to only What optimization? > perform double-buffering when vm object already has some data cached, > reads can prime vm object page list before file is mmapped or > sendfile-ed. > No double-buffering is done to optimize anything. Double-buffering is a consequence of having page cache and ARC. The special "double-buffering code" is to just handle that fact - e.g. making sure that VOP_READ reads data from page cache instead of ARC if it's possible that the data in them differs (i.e. page cache has more recent data). So, if I understood the term 'priming' correctly, no priming should ever occur. -- Andriy Gapon