From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751360AbcBKO5I (ORCPT ); Thu, 11 Feb 2016 09:57:08 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:57008 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750777AbcBKO5H (ORCPT ); Thu, 11 Feb 2016 09:57:07 -0500 Date: Thu, 11 Feb 2016 15:57:02 +0100 From: Peter Zijlstra To: Tong Zhang Cc: Ingo Molnar , Arnaldo Carvalho de Melo , LKML Subject: Re: [PATCH 1/1] Perf: fix overwritten of free running PEBSv3 timestamp Message-ID: <20160211145702.GK6357@twins.programming.kicks-ass.net> References: <1455143882-3899-1-git-send-email-ztong@vt.edu> <1455143882-3899-2-git-send-email-ztong@vt.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1455143882-3899-2-git-send-email-ztong@vt.edu> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 10, 2016 at 05:38:02PM -0500, Tong Zhang wrote: > commit a7b58d211ba18c9175b139e18b68c86a6bcc3c3f introduced feature of > timestamp on free running PEBSv3, however, the timestamp is later > overwritten, which makes the effort in vain. > > This patch fixed this problem by detecting whether timestamp is provided. > > Signed-off-by: Tong Zhang > --- > include/linux/perf_event.h | 1 + > kernel/events/core.c | 45 +++++++++++++++++++++++++++++++++------------ > kernel/events/ring_buffer.c | 4 +++- > 3 files changed, 37 insertions(+), 13 deletions(-) > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index f9828a4..12d7b95 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -815,6 +815,7 @@ static inline void perf_sample_data_init(struct perf_sample_data *data, > data->weight = 0; > data->data_src.val = PERF_MEM_NA; > data->txn = 0; > + data->time = 0; > } Argh, you just touched a new cacheline and made _every_ single event slower.