From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756880AbYIYRc0 (ORCPT ); Thu, 25 Sep 2008 13:32:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752407AbYIYRcP (ORCPT ); Thu, 25 Sep 2008 13:32:15 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:59572 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752892AbYIYRcO (ORCPT ); Thu, 25 Sep 2008 13:32:14 -0400 Date: Thu, 25 Sep 2008 10:25:00 -0700 (PDT) From: Linus Torvalds To: Steven Rostedt cc: linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Andrew Morton , prasad@linux.vnet.ibm.com, Mathieu Desnoyers , "Frank Ch. Eigler" , David Wilder , hch@lst.de, Martin Bligh , Christoph Hellwig , Steven Rostedt Subject: Re: [RFC PATCH 1/2 v2] Unified trace buffer In-Reply-To: Message-ID: References: <20080925155807.158539649@goodmis.org> <20080925160048.641420646@goodmis.org> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 25 Sep 2008, Steven Rostedt wrote: > > The problem with this is overwrite mode, which is the only mode ftace > currently offers. What happens when your writer starts overwriting the > ring buffer and there is no reader? Overwrite things on page at a time. Don't you already do that? (I didn't check that closely, I just assumed you would do the _much_ simpler "move the head to the next page" thing rather than trying to mix head and tail on the same page. > What happens is that the start value is gone. You do not have a way to use > all the deltas to catch up to the remaining events. Use the page start date for the first event in a page. But within pages, make everything depend on previous event. Linus