Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754977Ab3JJGMt (ORCPT ); Thu, 10 Oct 2013 02:12:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:24783 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754309Ab3JJGMs (ORCPT ); Thu, 10 Oct 2013 02:12:48 -0400 Date: Thu, 10 Oct 2013 14:14:08 +0800 From: Dong Zhu To: Ingo Molnar , John Stultz Cc: Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] timer stats: add a 'status' line to timer usage statistics Message-ID: <20131010061408.GF2139@zhudong.nay.redhat.com> References: <20131010025947.GD2139@zhudong.nay.redhat.com> <20131010043519.GB22519@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131010043519.GB22519@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2596 Lines: 84 Hi Ingo and John, On Thu, Oct 10, 2013 at 06:35:19AM +0200, 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. Yes, I am wrong about it. Thanks for pointing this out and pretty sorry for confusing you John. > > Instead of this change I'd suggest adding a 'status' line, with two > outputs: > > Status: collection active > > Status: collection disabled > Agree, I modified this patch and resubmited it again, Could you help reviewing it again ? Thanks ! >From 263c40abea8011c82582b2d671ae783b26f44bd5 Mon Sep 17 00:00:00 2001 From: Dong Zhu Date: Thu, 10 Oct 2013 13:46:08 +0800 We can enable|disable timer statistics collection (via echo [1|0] > /proc/timers_stats), this patch adds a 'status' line to display the current timer collection status. Signed-off-by: Dong Zhu --- kernel/time/timer_stats.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/time/timer_stats.c b/kernel/time/timer_stats.c index 0b537f2..bac5e91 100644 --- a/kernel/time/timer_stats.c +++ b/kernel/time/timer_stats.c @@ -303,6 +303,10 @@ static int tstats_show(struct seq_file *m, void *v) if (atomic_read(&overflow_count)) seq_printf(m, "Overflow: %d entries\n", atomic_read(&overflow_count)); + if (timer_stats_active) + seq_puts(m, "Status: collection active\n"); + else + seq_puts(m, "Status: collection disabled\n"); for (i = 0; i < nr_entries; i++) { entry = entries + i; -- 1.7.11.7 -- Best Regards, Dong Zhu -- 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/