From owner-freebsd-hackers Sun Sep 6 04:27:45 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id EAA08630 for freebsd-hackers-outgoing; Sun, 6 Sep 1998 04:27:45 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from indigo.ie (ts05-095.dublin.indigo.ie [194.125.220.105]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id EAA08625 for ; Sun, 6 Sep 1998 04:27:42 -0700 (PDT) (envelope-from rotel@indigo.ie) Received: (from nsmart@localhost) by indigo.ie (8.8.8/8.8.7) id MAA00740; Sun, 6 Sep 1998 12:20:37 +0100 (IST) (envelope-from rotel@indigo.ie) From: Niall Smart Message-Id: <199809061120.MAA00740@indigo.ie> Date: Sun, 6 Sep 1998 12:20:36 +0000 In-Reply-To: <199809031917.VAA12329@labinfo.iet.unipi.it>; Luigi Rizzo Reply-To: rotel@indigo.ie X-Files: The truth is out there X-Mailer: Mail User's Shell (7.2.6 beta(3) 11/17/96) To: Luigi Rizzo , mark@grondar.za (Mark Murray) Subject: Re: Assembler with FreeBSD Cc: dag-erli@ifi.uio.no, ormonde@aker.com.br, hackers@FreeBSD.ORG Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Sep 3, 9:17pm, Luigi Rizzo wrote: } Subject: Re: Assembler with FreeBSD > > It is very CPU and algorithm-dependent, and not always true. > > I did something similar with an FEC code (see my web page for > more) and while i could almost double performance by recoding the core > loop in assembler _on an old Pentium_, things were completely different > on a PentiumII/PentiumPro, were the C code were actually much faster > than my Pentium-optimized assembler, and the obvious asm optimizations > did not gain anything over the C code. As you probably already know the main optimisation technique in the Pentium is to pair instructions so they simultaneously execute in the U and V pipelines, as for optimising on the PII I haven't yet read Intels docs but PII-optimised code will be significantly different to the P-optimised. Do you know if the same potential for performance gain due to hand-coding exists? For anyone interested: the "multimedia" tutorials available at ftp://download.intel.com/design/perftool/cbts/exes/ are good, but require windows. Niall -- Niall Smart, rotel@indigo.ie. Amaze your friends and annoy your enemies: echo '#define if(x) if (!(x))' >> /usr/include/stdio.h To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message