From owner-freebsd-hackers@FreeBSD.ORG Mon Dec 29 23:25:07 2008 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EE6EB1065700 for ; Mon, 29 Dec 2008 23:25:07 +0000 (UTC) (envelope-from neldredge@math.ucsd.edu) Received: from euclid.ucsd.edu (euclid.ucsd.edu [132.239.145.52]) by mx1.freebsd.org (Postfix) with ESMTP id B5EBE8FC0C for ; Mon, 29 Dec 2008 23:25:07 +0000 (UTC) (envelope-from neldredge@math.ucsd.edu) Received: from zeno.ucsd.edu (zeno.ucsd.edu [132.239.145.22]) by euclid.ucsd.edu (8.11.7p3+Sun/8.11.7) with ESMTP id mBTNP7Z00019; Mon, 29 Dec 2008 15:25:07 -0800 (PST) Received: from localhost (neldredg@localhost) by zeno.ucsd.edu (8.11.7p3+Sun/8.11.7) with ESMTP id mBTNP3b08065; Mon, 29 Dec 2008 15:25:07 -0800 (PST) X-Authentication-Warning: zeno.ucsd.edu: neldredg owned process doing -bs Date: Mon, 29 Dec 2008 15:25:03 -0800 (PST) From: Nate Eldredge X-X-Sender: neldredg@zeno.ucsd.edu To: Christian Weisgerber In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-hackers@freebsd.org Subject: Re: lzo2 shows insane speed gap X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 29 Dec 2008 23:25:08 -0000 On Mon, 29 Dec 2008, Christian Weisgerber wrote: > The archivers/lzo2 port runs a series of regression tests after the > actual build. These tests show extremely divergent behavior on > different machines. There are two types of machines: > > Type #1: > Running the tests takes roughly the same time as configure and > compile did, whether it's 30 seconds on a fast machine or 10 > minutes on an old slow one. > > Type #2: > Running the tests takes much, much, MUCH longer. > > I've tried this across alpha, amd64, i386, and sparc64, partially > on FreeBSD, partially on OpenBSD. The operating system doesn't > matter and there is no pattern related to endianness or 32/64 bits. > > You can find machines that are the same architecture (e.g. amd64) > and are of similar overall speed (e.g. an Intel Xeon Xeon E5405 and > an AMD Phenom 9350e) and one of these machines will be type #1 and > the other will be #2 and take _a hundred_ times longer to run the > tests. A hundred times. > > I have never seen anything like this before. It might be good first to rule out compiler / library differences. First, can you isolate a single lzo command / input combination whose time differs dramatically? This would simplify tests compared to running the whole test suite. (It should be easy because it looks like the test suite prints the time for each test.) It might also simplify things to work on one "fast" and one "slow" machine. Then try copying the lzo binary from the "fast" machine to the "slow" machine (and vice versa) and see if the same test speeds up with the copied binary. If not, try again with the binary statically linked. If still not, it would be good to have a copy of the binary made available, along with more information about the "fast" and "slow" machines (CPU, amount of memory, load on the machine, kernel version, disk, etc). If the copied binary isn't faster than the natively produced one, then it would be good to have information about the compiler options, versions, etc. -- Nate Eldredge neldredge@math.ucsd.edu