From owner-freebsd-stable@FreeBSD.ORG Sat Mar 25 19:03:50 2006 Return-Path: X-Original-To: stable@freebsd.org Delivered-To: freebsd-stable@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id CC62016A400; Sat, 25 Mar 2006 19:03:50 +0000 (UTC) (envelope-from jmg@hydrogen.funkthat.com) Received: from hydrogen.funkthat.com (gate.funkthat.com [69.17.45.168]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5AA5943D46; Sat, 25 Mar 2006 19:03:50 +0000 (GMT) (envelope-from jmg@hydrogen.funkthat.com) Received: from hydrogen.funkthat.com (3nsbitxdid2wjryk@localhost.funkthat.com [127.0.0.1]) by hydrogen.funkthat.com (8.13.4/8.13.3) with ESMTP id k2PJ3Z4H039610; Sat, 25 Mar 2006 11:03:35 -0800 (PST) (envelope-from jmg@hydrogen.funkthat.com) Received: (from jmg@localhost) by hydrogen.funkthat.com (8.13.4/8.13.3/Submit) id k2PJ3XaQ039607; Sat, 25 Mar 2006 11:03:33 -0800 (PST) (envelope-from jmg) Date: Sat, 25 Mar 2006 11:03:33 -0800 From: John-Mark Gurney To: Mikhail Teterin Message-ID: <20060325190333.GD7001@funkthat.com> Mail-Followup-To: Mikhail Teterin , Peter Jeremy , alc@freebsd.org, Mikhail Teterin , stable@freebsd.org References: <200603232352.k2NNqPS8018729@gate.bitblocks.com> <200603241518.01027.mi+mx@aldan.algebra.com> <20060325103927.GE703@turion.vk2pj.dyndns.org> <200603250920.14208@aldan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200603250920.14208@aldan> User-Agent: Mutt/1.4.2.1i X-Operating-System: FreeBSD 5.4-RELEASE-p6 i386 X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31 96 7A 22 B3 D8 56 36 F4 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html Cc: alc@freebsd.org, Peter Jeremy , Mikhail Teterin , stable@freebsd.org Subject: Re: Reading via mmap stinks (Re: weird bugs with mmap-ing via NFS) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: John-Mark Gurney List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 25 Mar 2006 19:03:50 -0000 Mikhail Teterin wrote this message on Sat, Mar 25, 2006 at 09:20 -0500: > = The downside is that touching an uncached page triggers a trap which may > = not be as efficient as reading a block of data through the filesystem > = interface, and I/O errors are delivered via signals (which may not be as > = easy to handle). > > My point exactly. It does seem to be less efficient *at the moment* and I > am trying to have the kernel support for this cleaner method of reading > *improved*. By convincing someone with a clue to do it, that is... :-) I think the thing is that there isn't an easy way to speed up the faulting of the page, and that is why you are getting such trouble making people believe that there is a problem... To convince people that there is a problem, you need to run benchmarks, and make code modifications to show that yes, something can be done to improve the performance... The other useful/interesting number would be to compare system time between the mmap case and the read case to see how much work the kernel is doing in each case... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."