From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755113AbaE1RPL (ORCPT ); Wed, 28 May 2014 13:15:11 -0400 Received: from mga02.intel.com ([134.134.136.20]:42489 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751756AbaE1RPI (ORCPT ); Wed, 28 May 2014 13:15:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.98,929,1392192000"; d="scan'208";a="547899475" Date: Wed, 28 May 2014 10:12:43 -0700 From: Andi Kleen To: Stephane Eranian Cc: Peter Zijlstra , "Yan, Zheng" , LKML , "mingo@elte.hu" Subject: Re: [RFC PATCH 6/7] perf, x86: large PEBS interrupt threshold Message-ID: <20140528171243.GL29957@tassilo.jf.intel.com> References: <1401257890-30535-1-git-send-email-zheng.z.yan@intel.com> <1401257890-30535-7-git-send-email-zheng.z.yan@intel.com> <20140528081053.GP11096@twins.programming.kicks-ass.net> <20140528145831.GH29957@tassilo.jf.intel.com> <20140528165144.GK29957@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > So, you're telling me this is a sanity check. That p->status can > only have one bit set. Somehow that's not how I recall it working. It can have multiple bits set. We don't know for sure for which it is, but we should only deliver it for one anyways. > The point is that a single PEBS record is enough for multiple > events when the overflows occur simultaneously because they > all get the same machine state which is correct. A single entry > also saves space in the buffer. The CPU will generate multiple PEBS records in this case. So if we delivered it for all you would overcount by factor 4x [Again this is a very unlikely situation. Normally counters are not in lock step] -Andi -- ak@linux.intel.com -- Speaking for myself only