From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nmxmail.nanometrics.ca (mail.nanometrics.ca [206.191.47.130]) by ozlabs.org (Postfix) with ESMTP id 77978DDF09 for ; Thu, 15 May 2008 06:16:54 +1000 (EST) Message-ID: <482B48DA.5080300@nanometrics.ca> Date: Wed, 14 May 2008 16:17:30 -0400 From: Ben Gardiner MIME-Version: 1.0 To: Dan Malek Subject: Re: 8xx: Work around CPU15 erratum. References: <482AFCC5.2070907@nanometrics.ca> <07769C41-66EB-48C5-9494-3BBE34447BBD@embeddedalley.com> In-Reply-To: <07769C41-66EB-48C5-9494-3BBE34447BBD@embeddedalley.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Dan Malek wrote: > > On May 14, 2008, at 10:52 AM, Ben Gardiner wrote: > >> So there likely are reasons why the following is not possible: > > That's way too much code for a tlb exception handler. > From a system resource perspective, you are much better > off with a small and efficient piece of tlb loading code, > always invalidating pages on both ends and taking the > tlb exception fault. Unfortunately, this could cause some > thrashing edge cases, so a little intelligence would be > needed. Exception processing isn't free, and it quickly > destroys the cache footprint of your application, further > slowing down the entire system. The tlb reload handler > goal should be maximum of 8 instructions and 4 memory > accesses, not 4K of elaborate conditional testing. :-) > > Thanks. > > -- Dan > Hi Dan, Thanks for the rapid reply :) I really appreciate you giving me an answer "from the horse's mouth." I would still like to experiment a little and I'm not really sure it is safe to use any bits in a PTE. Assuming I was crazy enough to ruin my cache footprint; are there any three bits in the PTE that are safe to use for some page status information? Best Regards, Ben