From owner-freebsd-current@FreeBSD.ORG Sat Sep 15 23:42:34 2012 Return-Path: Delivered-To: freebsd-current@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 87153106566C; Sat, 15 Sep 2012 23:42:34 +0000 (UTC) (envelope-from dimitry@andric.com) Received: from tensor.andric.com (cl-327.ede-01.nl.sixxs.net [IPv6:2001:7b8:2ff:146::2]) by mx1.freebsd.org (Postfix) with ESMTP id 423778FC08; Sat, 15 Sep 2012 23:42:34 +0000 (UTC) Received: from [IPv6:2001:7b8:3a7:0:244e:b47c:3b46:43d5] (unknown [IPv6:2001:7b8:3a7:0:244e:b47c:3b46:43d5]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by tensor.andric.com (Postfix) with ESMTPSA id 981045C37; Sun, 16 Sep 2012 01:42:32 +0200 (CEST) Message-ID: <50551266.3000704@andric.com> Date: Sun, 16 Sep 2012 01:42:30 +0200 From: Dimitry Andric User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20120905 Thunderbird/16.0 MIME-Version: 1.0 To: Luigi Rizzo References: <50550285.4040203@andric.com> <20120915232220.GA50519@onelab2.iet.unipi.it> In-Reply-To: <20120915232220.GA50519@onelab2.iet.unipi.it> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-current@FreeBSD.org, freebsd-toolchain@FreeBSD.org Subject: Re: Compiler performance tests on FreeBSD 10.0-CURRENT X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 15 Sep 2012 23:42:34 -0000 On 2012-09-16 01:22, Luigi Rizzo wrote: ... > the fact that the difference is so small is interesting, > and it might almost suggests that the test is dominated by > other factors than the compiler. Yes, this result was more or less what I expected: runtime performance is probably related more to hardware speed, and the efficiency of the chosen algorithms in the kernel, than to the optimizations any current compiler can produce. Apparently our kernel hackers already produce quite efficient code. :) > By chance do you have a > way to produce other data points with different optimization > levels in the compiler ? I could re-run the tests with e.g. -O1 instead of -O2, or maybe even -O0, though I am not sure if the kernel will compile correctly without any optimization. This will take a while though, and I am not sure if I can borrow Gavin's machine long enough. :) -Dimitry