Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752618Ab3JJEsJ (ORCPT ); Thu, 10 Oct 2013 00:48:09 -0400 Received: from mail-pa0-f53.google.com ([209.85.220.53]:35494 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751318Ab3JJEsH (ORCPT ); Thu, 10 Oct 2013 00:48:07 -0400 Message-ID: <52563183.8000508@linaro.org> Date: Wed, 09 Oct 2013 21:48:03 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Ingo Molnar , Dong Zhu CC: Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH RESEND] timer stats: reset entries when disable the timer usage statistics References: <20131010025947.GD2139@zhudong.nay.redhat.com> <20131010043519.GB22519@gmail.com> In-Reply-To: <20131010043519.GB22519@gmail.com> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1580 Lines: 48 On 10/09/2013 09:35 PM, Ingo Molnar wrote: > * Dong Zhu wrote: > >> From f41628c61d8a9172677ba33a55b61e37ce28f7a6 Mon Sep 17 00:00:00 2001 >> From: Dong Zhu >> Date: Thu, 10 Oct 2013 10:38:13 +0800 >> >> When we stop timer statistics collection (via echo 0 > >> /proc/timers_stats), the statistics data is still exported as if it were >> correct, which can cause applicaitons to misuse the statistics. > What misuse do you mean? > >> This patch resets the statistics when we stop collecting them, to avoid >> this problem. > Well, this loses the handy 'snapshot' property of /proc/timer_stats. > Before this change one could do: > > echo 1 > /proc/timers_stats > sleep 60 # run system workload > echo 0 > /proc/timers_stats > > and examine the 1-minute collection result without it changing. Your > change, if I understand it correctly, zeroes it all out. Good point. I misunderstood the patch and thought it was an issue that the statistics are never cleared even if the collection was disabled, but looking closer I see we clear on enable (if we were disabled). So yes, this change doesn't seem right. > Instead of this change I'd suggest adding a 'status' line, with two > outputs: > > Status: collection active > > Status: collection disabled Agreed. thanks -john -- 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/