From owner-freebsd-hackers@FreeBSD.ORG Tue Aug 15 08:04:08 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id EC86516A4DD for ; Tue, 15 Aug 2006 08:04:08 +0000 (UTC) (envelope-from admin@intron.ac) Received: from intron.ac (unknown [210.51.165.237]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8D62243D46 for ; Tue, 15 Aug 2006 08:04:07 +0000 (GMT) (envelope-from admin@intron.ac) Received: from localhost (localhost [127.0.0.1]) (uid 1003) by intron.ac with local; Tue, 15 Aug 2006 16:04:00 +0800 id 00102C04.44E17FF0.00006B85 References: <20060814231504.GB69362@lor.one-eyed-alien.net> In-Reply-To: <20060814231504.GB69362@lor.one-eyed-alien.net> From: "Intron" To: Brooks Davis Date: Tue, 15 Aug 2006 16:04:00 +0800 Mime-Version: 1.0 Content-Type: text/plain; charset="gb2312"; format=flowed Content-Transfer-Encoding: 7bit Message-ID: Cc: freebsd-hackers@freebsd.org Subject: Re: The optimization of malloc(3): FreeBSD vs GNU libc 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: Tue, 15 Aug 2006 08:04:09 -0000 Brooks Davis wrote: > On Tue, Aug 15, 2006 at 07:10:47AM +0800, Intron wrote: >> One day, a friend told me that his program was 3 times slower under >> FreeBSD 6.1 than under GNU/Linux (from Redhat 7.2 to Fedora Core 5). >> I was astonished by the real repeatable performance difference on >> AMD Athlon XP 2500+ (1.8GHz, 512KB L2 Cache). >> >> After hacking, I found that the problem is nested in malloc(3) of >> FreeBSD libc. >> >> Download the testing program: http://ftp.intron.ac/tmp/fdtd.tar.bz2 >> >> You may try to compile the program WITHOUT the macro "MY_MALLOC" >> defined (in Makefile) to use malloc(3) provided by FreeBSD 6.1. >> Then, time the running of the binary (on Athlon XP 2500+): >> >> #/usr/bin/time ./fdtd.FreeBSD 500 500 1000 >> ... >> 165.24 real 164.19 user 0.02 sys >> >> Please try to recompile the program (Remember to "make clean") >> WITH the macro "MY_MALLOC" defined (in Makefile) to use my own >> simple implementation of malloc(3) (i.e. my_malloc() in cal.c). >> And time the running again: >> >> #/usr/bin/time ./fdtd.FreeBSD 500 500 1000 >> ... >> 50.41 real 49.95 user 0.04 sys >> >> You may repeat this testing again and again. >> >> I guess this kind of performance difference comes from: >> >> 1. His program uses malloc(3) to obtain so many small memory blocks. >> >> 2. In this case, FreeBSD malloc(3) obtains small memory blocks from >> kernel and pass them to application. >> >> But malloc(3) of GNU libc obtains large memory blocks from kernel >> and splits & reallocates them in small blocks to application. >> >> You may verify my judgement with truss(1). >> >> 3. The way of FreeBSD malloc(3) makes VM page mapping too chaotic, which >> reduces the efficiency of CPU L2 Cache. In contrast, my my_malloc() >> simulates the behavior of GNU libc malloc(3) partially and avoids >> the over-chaos. >> >> Callgrind is broken under FreeBSD, or I will verify my guess with it. >> >> I have also verified the program on Intel Pentium 4 511 (2.8GHz, 1MB >> L2 cache, running FreeBSD 6.1 i386 though this CPU supports EM64T) >> >> >/usr/bin/time ./fdtd.FreeBSD 500 500 1000 >> ... >> 185.30 real 184.28 user 0.02 sys >> >> >/usr/bin/time ./fdtd.FreeBSD 500 500 1000 >> ... >> 36.31 real 35.94 user 0.03 sys >> >> NOTE: you probably cannot see the performance difference on CPU with >> small L2 cache such as Intel Celeron 1.7GHz with 128 KB L2 Cache. > > In CURRENT we've replaced phkmalloc with jemalloc. It would be useful > to see how this benchmark performs with that. I believe it does similar > things. > > -- Brooke You're right. Now with truss(1) I can see that malloc(3) on 7.0-CURRENT (4 days ago) calls brk(2) to obtain 2MB each time. I will continue my testing. ------------------------------------------------------------------------ From Beijing, China