From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 25 Jun 2001 21:53:33 -0300 (BRT) From: Marcelo Tosatti Subject: Re: VM tuning through fault trace gathering [with actual code] In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: John Fremlin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On 25 Jun 2001, John Fremlin wrote: > > Last year I had the idea of tracing the memory accesses of the system > to improve the VM - the traces could be used to test algorithms in > userspace. The difficulty is of course making all memory accesses > fault without destroying system performance. > > The following patch (i386 only) will dump all page faults to > /dev/biglog (you need devfs for this node to appear). If you echo 1 > > /proc/sys/vm/trace then *almost all* userspace memory accesses will > take a soft fault. Note that this is a bit suicidal at the moment > because of the staggeringly inefficient way its implemented, on my box > (K6-2 300MHz) only processes which do very little (e.g. /usr/bin/yes) > running at highest priority are able to print anything to the console. > > I think the best way would be to have only one valid l2 pte per > process. I'll have a go at doing that in a day or two unless someone > has a better idea? Linux Trace Toolkit (http://www.opersys.com/LTT) does that. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/