From owner-freebsd-arch@FreeBSD.ORG Thu Nov 10 01:25:43 2011 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 861FB1065677; Thu, 10 Nov 2011 01:25:43 +0000 (UTC) (envelope-from bright@elvis.mu.org) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id 72CB58FC12; Thu, 10 Nov 2011 01:25:43 +0000 (UTC) Received: by elvis.mu.org (Postfix, from userid 1192) id 2574A1A3C46; Wed, 9 Nov 2011 17:25:43 -0800 (PST) Date: Wed, 9 Nov 2011 17:25:42 -0800 From: Alfred Perlstein To: Paul Saab Message-ID: <20111110012542.GA6110@elvis.mu.org> References: <201110281426.00013.jhb@freebsd.org> <4EB2C9DD.9090606@FreeBSD.org> <20111104160319.GD6110@elvis.mu.org> <201111080800.32717.jhb@freebsd.org> <4EBB104F.5010000@cran.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Cc: Bruce Cran , Ed Schouten , freebsd-arch@freebsd.org, Jilles Tjoelker , arch@freebsd.org Subject: Re: [PATCH] fadvise(2) system call X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Nov 2011 01:25:43 -0000 * Paul Saab [111109 16:32] wrote: > On Wed, Nov 9, 2011 at 3:44 PM, Bruce Cran wrote: > > On 08/11/2011 13:00, John Baldwin wrote: > >> > >> I think it would be fine to add flags to applications like 'tar' to allow > >> users to alter their behavior in specific use cases when it makes sense. > >> However, I think there are more workloads for 'tar' than the ones you are > >> thinking of and we should be hesitant to change applications to use non- > >> default settings. > > > > Someone's done that for GNU tar on Linux, adding a --no-oscache switch: > > http://www.mysqlperformanceblog.com/2010/04/02/fadvise-may-be-not-what-you-expect/ > > So adding this support is good, but not for general purpose. It's > really only good when you're pumping gigs of data through tar. I did > this for libarchive (plus other work for O_DIRECT reading and > creating the archive) for copying large amounts of data without > impacting a running system.. It worked great for this, but then it > absolutely fails when extracting a tar archive with millions of little > files because of all the sync operations. I've thought about this and it almost makes sense to have a secondary LRU that such pages would wind up in that is much smaller than the system one. I'm pretty sure there are a number of papers on this, but I've not looked over them in a long while. > > Anyway, this is a good option to enable and has very practical uses > out there, but it should be turned on with an option and not on by > default. What about the operation of just reading the tar archive itself? -- - Alfred Perlstein .- VMOA #5191, 03 vmax, 92 gs500, 85 ch250, 07 zx10 .- FreeBSD committer