From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from moutng.kundenserver.de (moutng.kundenserver.de [212.227.126.183]) by ozlabs.org (Postfix) with ESMTP id 83156DDDE7 for ; Sat, 15 Sep 2007 23:34:51 +1000 (EST) From: Arnd Bergmann To: David Woodhouse Subject: Re: [PATCH] add Kconfig option for optimizing for cell Date: Sat, 15 Sep 2007 15:30:15 +0200 References: <200709150221.57825.arnd@arndb.de> <1189862035.3742.5.camel@shinybook.infradead.org> In-Reply-To: <1189862035.3742.5.camel@shinybook.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Message-Id: <200709151530.15441.arnd@arndb.de> Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Saturday 15 September 2007, David Woodhouse wrote: > On Sat, 2007-09-15 at 02:21 +0200, Arnd Bergmann wrote: > > Since the PPE on cell is an in-order core, it suffers significantly > > from wrong instruction scheduling. This adds an Kconfig option that > > enables passing -mtune=cell to gcc in order to generate object > > code that runs well on cell. > > Do we have an option which is useful for a multiplatform kernel (and for > userspace) and which lies between the two extremes? Something which will > improve performance on Cell (and POWER6?) without sucking too hard > elsewhere? No, not really. The impact of -mtune=cell should not be too bad on other out-of-order CPUs, but we don't have any good measurements to back that up, and it may also be really bad for POWER6 and other in-order cores. Arnd <><