Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936193AbZDCSFn (ORCPT ); Fri, 3 Apr 2009 14:05:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934992AbZDCSFV (ORCPT ); Fri, 3 Apr 2009 14:05:21 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:42953 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754816AbZDCSFT (ORCPT ); Fri, 3 Apr 2009 14:05:19 -0400 Date: Fri, 3 Apr 2009 11:05:16 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Ingo Molnar , Tom Zanussi , linux-kernel , fweisbec@gmail.com Subject: Re: [PATCH] tracing/filters: allow event filters to be set only when not tracing Message-ID: <20090403180516.GC6968@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1238390546.6368.65.camel@bookworm> <20090401122408.GG12966@elte.hu> <1238653371.6655.48.camel@bookworm> <20090403135956.GD8875@elte.hu> <20090403162642.GB6968@linux.vnet.ibm.com> <20090403163755.GA3047@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1353 Lines: 33 On Fri, Apr 03, 2009 at 12:43:15PM -0400, Steven Rostedt wrote: > > On Fri, 3 Apr 2009, Ingo Molnar wrote: > > > > > > My kneejerk reaction is "why would anyone want to trace the idle > > > loop?" > > > > heh :-) > > > > Idle enter/exit events are useful to tune power use for example. The > > more events we have there, the more we prevent the CPU from slowly > > going into deep sleep mode. But we could in principle trace idle enter/exit from the scheduler, correct? That said, it would be possible to allow much of the idle loop to contain RCU read-side critical sections, but this requires putting rcu_qsctr_inc() in each and every idle loop, plus catching the cases where idle loops shut down the CPU. Note that this applies to synchronize_sched() as well as synchronize_rcu(). > I can say I use it a lot. I'm still needing a way to set the function pid > recorder to 0 since the conversion to the pid structure. There are times > I only want to trace the interrupts that happen in the idle loop. It would be OK to trace the interrupts, just not the idle loop itself. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/