From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH] PERF(kernel): Cleanup power events V2 Date: Tue, 26 Oct 2010 22:38:42 +0200 Message-ID: <201010262238.42536.rjw@sisk.pl> References: <1287488171-25303-3-git-send-email-trenn@suse.de> <201010262108.23537.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-2" Content-Transfer-Encoding: 7bit Return-path: Received: from ogre.sisk.pl ([217.79.144.158]:55746 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754539Ab0JZUkZ (ORCPT ); Tue, 26 Oct 2010 16:40:25 -0400 In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Pierre Tardy Cc: Peter Zijlstra , Arjan van de Ven , Ingo Molnar , Thomas Renninger , Linus Torvalds , Andrew Morton , Thomas Gleixner , Masami Hiramatsu , Frank Eigler , Steven Rostedt , Kevin Hilman , linux-omap@vger.kernel.org, linux-pm@lists.linux-foundation.org, linux-trace-users@vger.kernel.org, Jean Pihet , Frederic Weisbecker , Tejun Heo , Mathieu Desnoyers On Tuesday, October 26, 2010, Pierre Tardy wrote: > On Tue, Oct 26, 2010 at 2:08 PM, Rafael J. Wysocki wrote: > > On Tuesday, October 26, 2010, Pierre Tardy wrote: > >> On Tue, Oct 26, 2010 at 12:58 PM, Peter Zijlstra wrote: > >> > On Tue, 2010-10-26 at 11:56 -0500, Pierre Tardy wrote: > >> >> > >> >> + trace_runtime_pm_usage(dev, atomic_read(&dev->power.usage_count)+1); > >> >> atomic_inc(&dev->power.usage_count); > >> > > >> > That's terribly racy.. > >> > > >> I know. I'm not proud of this.. As I said, this is preliminary patch. > >> We dont really need to have this prev_usage. This is just for debug. > >> It mayprobably endup with something like: > >> > >> atomic_inc(&dev->power.usage_count); > >> + trace_power_device_usage(dev); > > > > Well, please tell me what you're trying to achieve. > > Please see attached the kind of pytimechart output I'm trying to > achieve (yes, this chart is not coherent, seems I'm still missing some > traces) > > We basically want to have a trace point eachtime the usage_counter > changes, so that I can display nice timecharts, and Arjan can have the > comm of the process that eventually generated the rpm_get, in order to > pinpoint it in powertop. > > What you dont see in the above two lines is that > trace_power_device_usage(dev); actually reads the usage_count, as well > as the driver and device name. I'm afraid that for this to really work you'd need to put usage_count under a spinlock along with your trace point, which I'm not really sure I like. Besides, I'm not really sure the manipulations of usage_count are worth tracing. Thanks, Rafael