From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 78275679F5 for ; Fri, 14 Apr 2006 08:38:48 +1000 (EST) Subject: Re: [PATCH] [2/2] POWERPC: Lower threshold for DART enablement to 1GB, V2 From: Benjamin Herrenschmidt To: Olof Johansson In-Reply-To: <20060413222721.GN24769@pb15.lixom.net> References: <20060413020559.GC24769@pb15.lixom.net> <20060413022809.GD24769@pb15.lixom.net> <20060413025233.GE24769@pb15.lixom.net> <20060413064027.GH10412@granada.merseine.nu> <1144925149.4935.14.camel@localhost.localdomain> <20060413160712.GG24769@pb15.lixom.net> <1144961515.4935.22.camel@localhost.localdomain> <20060413222721.GN24769@pb15.lixom.net> Content-Type: text/plain Date: Fri, 14 Apr 2006 08:38:31 +1000 Message-Id: <1144967911.4935.35.camel@localhost.localdomain> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, paulus@samba.org, linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2006-04-13 at 17:27 -0500, Olof Johansson wrote: > On Fri, Apr 14, 2006 at 06:51:55AM +1000, Benjamin Herrenschmidt wrote: > > > an improvement with the DART thanks to virtual merging. Currently, we > > pay a cost due to our stupid invalidate mecanism that we should really > > fix by shooting the TLB directly. > > What was keeping me from implementing this before was the lack of public > documentation on how to do it. Has that changed? I'd be happy to do the > implementation. Darwin has the macros to access the TLB though it doesn't use them... I suppose I can get the necessary doco bit from the microelectronics folks for the CPC925, that should apply to U3 as well, though U4 has a different format afaik. I'll dig and will come back to you. > > Also have you made sure all your > > additions for handling crappy hardware are nicely wrapped in unlikely() > > statements ? :) > > I would expect the dynamic predictor to work quite well on this. I'm not > worried about the overhead of the tests as much as the overhead of > having to enable the DART for smaller configs. If benchmark profiling > shows different down the road then we can add them. Ok. Ben.