From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2402 invoked by alias); 30 May 2006 10:37:53 -0000 Received: (qmail 2392 invoked by uid 22791); 30 May 2006 10:37:52 -0000 X-Spam-Check-By: sourceware.org Received: from nz-out-0102.google.com (HELO nz-out-0102.google.com) (64.233.162.200) by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 30 May 2006 10:37:51 +0000 Received: by nz-out-0102.google.com with SMTP id n29so726611nzf for ; Tue, 30 May 2006 03:37:49 -0700 (PDT) Received: by 10.64.48.20 with SMTP id v20mr3758111qbv; Tue, 30 May 2006 03:37:49 -0700 (PDT) Received: by 10.64.199.17 with HTTP; Tue, 30 May 2006 03:37:49 -0700 (PDT) Message-ID: <69dd805e0605300337i9fbbcfet525dda57c821256c@mail.gmail.com> Date: Tue, 30 May 2006 10:37:00 -0000 From: "Fabian Scheler" To: "Nils Labugt" Cc: ecos-discuss@ecos.sourceware.org In-Reply-To: <200605301133.45160.elabu@online.no> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <69dd805e0605300109k5dcf7986of596c0b5f796c6b4@mail.gmail.com> <20060530081637.GH2876@lunn.ch> <200605301133.45160.elabu@online.no> X-IsSubscribed: yes Mailing-List: contact ecos-discuss-help@ecos.sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: ecos-discuss-owner@ecos.sourceware.org Subject: Re: [ECOS] Hard-Realtime behaviour X-SW-Source: 2006-05/txt/msg00243.txt.bz2 > > So you at least need to disable caches when you determine what the > > worst case is, assuming the cache is actually helping you. > > What about invalidating the caches instead of disabling them before measuring > the worst case execution time? (I am assuming sufficient cache size to fit > both the system call and any interrupt handlers.) Especially if there are > loops, that will make a big difference. This is only an option, when you can ensure, that your code will not be preempted. That also might be a reason why it is clever to switch off caches within the running system (regardless what I mentioned in my foregoing post ;-)): In a loop, for instance, you can be preempted after every iteration, so you would have to invalidate the caches after every iteration, otherwise, you determine some execution time but not the worst case execution time. Ciao, Fabian -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss