From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751944AbbG3Ngq (ORCPT ); Thu, 30 Jul 2015 09:36:46 -0400 Received: from mga11.intel.com ([192.55.52.93]:56828 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750877AbbG3Ngp (ORCPT ); Thu, 30 Jul 2015 09:36:45 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,577,1432623600"; d="scan'208";a="758410766" From: Alexander Shishkin To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, adrian.hunter@intel.com, x86@kernel.org, hpa@zytor.com, acme@infradead.org Subject: Re: [PATCH 2/3] perf/x86/intel/pt: Add an option to not force PSB+ on every schedule-in In-Reply-To: <87pp39kdyd.fsf@ashishki-desk.ger.corp.intel.com> References: <1437140050-23363-1-git-send-email-alexander.shishkin@linux.intel.com> <1437140050-23363-3-git-send-email-alexander.shishkin@linux.intel.com> <20150730104310.GW19282@twins.programming.kicks-ass.net> <87y4hxkgj4.fsf@ashishki-desk.ger.corp.intel.com> <20150730121349.GI25159@twins.programming.kicks-ass.net> <87pp39kdyd.fsf@ashishki-desk.ger.corp.intel.com> User-Agent: Notmuch/0.20.2 (http://notmuchmail.org) Emacs/24.4.1 (x86_64-pc-linux-gnu) Date: Thu, 30 Jul 2015 16:36:42 +0300 Message-ID: <87mvydkbrp.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alexander Shishkin writes: > It kinda does make a difference: inside PSB+ you get a TSC packet, which > carries the tsc timestamp as a payload, so, with the current behavior, > since you'll get one of those at every event schedule-in, you'll have > many more time synchronization points with the perf stream, but when the > default changes, suddenly your timestamps way further apart and the > decoder needs to put in additional guesswork to correlate those MMAP > events in the perf stream with the PT trace. I spoke hastily, TSC packets will be generated on every schedule-in (as well as other packets that normally come in PSB+) regardless of the actual PSB, so scratch the above. Let me replace the above with a smaller patch. Regards, -- Alex