From owner-svn-src-head@FreeBSD.ORG Fri Aug 16 18:17:38 2013 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 9C2E1D57 for ; Fri, 16 Aug 2013 18:17:38 +0000 (UTC) (envelope-from bounces+73574-9504-svn-src-head=freebsd.org@sendgrid.me) Received: from o3.shared.sendgrid.net (o3.shared.sendgrid.net [208.117.48.85]) by mx1.freebsd.org (Postfix) with SMTP id 228C2288F for ; Fri, 16 Aug 2013 18:17:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sendgrid.info; h=from :mime-version:to:cc:subject:references:in-reply-to:content-type :content-transfer-encoding; s=smtpapi; bh=BfiKIYsCFh5petURArkOE8 5dFjY=; b=TuljUlGAEaiIRKnG48c8S/pWbF5wqp83M5RxX2vnzUS10dRBsd5MCS hpk91PGP/0+zTsmRTt3+PhoSTZxcsusz/rMUTIBzwiocW7u5QH7N4cOCgY9kP3kh 1LgsNE9iqckdix7sGz8Efp9o41RGtTg9PWvHHTKos+/2tk0enLgQc= Received: by with SMTP id filter-138.12338.520E6CB5B Fri, 16 Aug 2013 18:17:25 +0000 (GMT) Received: from mail.tarsnap.com (unknown [10.60.208.15]) by mi17 (SG) with ESMTP id 1408858a505.49f6.777c03 for ; Fri, 16 Aug 2013 18:17:25 +0000 (UTC) Received: (qmail 73696 invoked from network); 16 Aug 2013 18:17:24 -0000 Received: from unknown (HELO clamshell.daemonology.net) (127.0.0.1) by ec2-107-20-205-189.compute-1.amazonaws.com with ESMTP; 16 Aug 2013 18:17:24 -0000 Received: (qmail 62537 invoked from network); 16 Aug 2013 18:17:20 -0000 Received: from unknown (HELO clamshell.daemonology.net) (127.0.0.1) by clamshell.daemonology.net with SMTP; 16 Aug 2013 18:17:20 -0000 Message-ID: <520E6CB0.9000100@freebsd.org> Date: Fri, 16 Aug 2013 11:17:20 -0700 From: Colin Percival User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:17.0) Gecko/20130722 Thunderbird/17.0.7 MIME-Version: 1.0 To: Ivan Voras Subject: Re: svn commit: r254380 - in head/sys: kern sys References: <201308152019.r7FKJI0H095440@svn.freebsd.org> <520D3AD8.4090207@freebsd.org> <520D49EB.9060308@freebsd.org> In-Reply-To: X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SG-EID: EvYvoie/qnEezyq2t4eRKjDm9X7ZKbCMt75WvXA+XNFLOhoeet4uwWdrLLA4PF2CpGKdduVPXqVM2fTTH/4mFakfMr3TTvoNyFRScH5C4dLz6HNehSZ3ic9Pzyqhl05owGoOhGA9VdOSIIje7IxCzg== Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Aug 2013 18:17:38 -0000 On 08/16/13 02:38, Ivan Voras wrote: >> We have a single-writer / multiple-readers lock on *any particular byte* >> of a vnode. The rangelock code is what keeps track of this, and the >> locking contention I was reducing was in the rangelock bookkeeping. > > So, for example, if multiple processes or multiple threads read or > write a file somewhat unintelligently (a small file, operations on the > whole file, like in blogbench), they will effectively content for the > byte 0, right? There can be multiple reads or one write, so yes there would be contention in that case. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid