From owner-freebsd-current Sun Feb 9 7:17:10 2003 Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8A25537B406 for ; Sun, 9 Feb 2003 07:17:09 -0800 (PST) Received: from mail.gmx.net (mail.gmx.net [213.165.65.60]) by mx1.FreeBSD.org (Postfix) with SMTP id D454143FA3 for ; Sun, 9 Feb 2003 07:17:07 -0800 (PST) (envelope-from mdcki@gmx.net) Received: (qmail 8925 invoked by uid 0); 9 Feb 2003 15:17:06 -0000 Received: from cvpn017.gwdg.de (HELO gmx.net) (134.76.22.17) by mail.gmx.net (mp008-rz3) with SMTP; 9 Feb 2003 15:17:06 -0000 Message-ID: <3E4671E6.8090000@gmx.net> Date: Sun, 09 Feb 2003 16:21:10 +0100 From: Marcin Dalecki User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021230 X-Accept-Language: en-us, en MIME-Version: 1.0 To: David Schultz Cc: Adrian Chadd , Terry Lambert , Ray Kohler , freebsd-current@freebsd.org Subject: Re: Compiling with high optimization? References: <20030208173756.GA56030@arkadia.nv.cox.net> <20030208232724.GA20435@HAL9000.homeunix.com> <3E459BF3.BB3FC381@mindspring.com> <20030209002542.GA20812@HAL9000.homeunix.com> <20030209141006.GB33928@skywalker.creative.net.au> <20030209150120.GA2263@HAL9000.homeunix.com> In-Reply-To: <20030209150120.GA2263@HAL9000.homeunix.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG David Schultz wrote: > Strangely, gcc in FreeBSD 5.0 actually generates *slower* code > when compiling for more recent architectures than when compiling > for a 386. I don't know whether that is a bug in gcc or whether > gcc is using some fancy feature like SSE that the kernel handles > poorly on context switches. I think there was some discussion on > the lists about it earlier. The reason is that the optimization done by GCC are ill balanced. All the scheduling of instractions and what a not - which would be fine on a micro scope level is causing so much higher pressure on the CPUs caches that the code is actually loosing. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message