From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941192AbcIZM1V (ORCPT ); Mon, 26 Sep 2016 08:27:21 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:47724 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936266AbcIZM1U (ORCPT ); Mon, 26 Sep 2016 08:27:20 -0400 Date: Mon, 26 Sep 2016 14:27:12 +0200 From: Peter Zijlstra To: Julien Desfossez Cc: tglx@linutronix.de, rostedt@goodmis.org, mingo@redhat.com, daolivei@redhat.com, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 0/5] Additional scheduling information in tracepoints Message-ID: <20160926122712.GM5012@twins.programming.kicks-ass.net> References: <1474649375-28056-1-git-send-email-jdesfossez@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1474649375-28056-1-git-send-email-jdesfossez@efficios.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 23, 2016 at 12:49:30PM -0400, Julien Desfossez wrote: > With this macro, we propose new versions of the sched_switch, sched_waking, > sched_process_fork and sched_pi_setprio tracepoint probes that contain more > scheduling information and get rid of the "prio" field. We also add the PI > information to these tracepoints, so if a process is currently boosted, we show > the name and PID of the top waiter. This allows to quickly see the blocking > chain even if some of the trace background is missing. Urgh.. bigger mess than ever :-( So I thought the initial idea was to provide a 'blocked-on' tracepoint, along with with the 'prio-changed' tracepoint, so you can reconstruct the entire PI chain. The only problem with that was initial state; when you start tracing (or miss the start of a trace) its hard (impossible) to know what the current state is. But now you send a patch-set that just adds a metric ton of tracepoints. This doesn't fix the current mess, it makes it worse :-(