From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753333AbdBTQcV (ORCPT ); Mon, 20 Feb 2017 11:32:21 -0500 Received: from mga11.intel.com ([192.55.52.93]:36457 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751538AbdBTQcT (ORCPT ); Mon, 20 Feb 2017 11:32:19 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,187,1484035200"; d="scan'208";a="227563456" From: Alexander Shishkin To: Arnaldo Carvalho de Melo Cc: Adrian Hunter , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Peter Zijlstra , Ingo Molnar Subject: Re: [PATCH 0/4] perf, pt, coresight: AUX flags and VMX update In-Reply-To: <20170220160946.GL4109@kernel.org> References: <20170220133352.17995-1-alexander.shishkin@linux.intel.com> <87ino4j3gr.fsf@ashishki-desk.ger.corp.intel.com> <20170220160946.GL4109@kernel.org> User-Agent: Notmuch/0.23.5 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Mon, 20 Feb 2017 18:31:28 +0200 Message-ID: <87fuj8j02n.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 Arnaldo Carvalho de Melo writes: > Em Mon, Feb 20, 2017 at 05:39:43PM +0200, Adrian Hunter escreveu: >> On 20/02/17 17:18, Alexander Shishkin wrote: >> > Alexander Shishkin writes: >> > >> >> With the vmm_exclusive=0, PT seems to be much more usable on BDW now. This >> >> patchset does three things: >> >> * adds a flag to PERF_RECORD_AUX, signalling that a transaction has gaps >> >> in it (due to VMX root mode kicking in), >> > >> > In the above context, will something like this be fine? > >> Looks fine to me. > >> Acked-by: Adrian Hunter >> >> > From: Alexander Shishkin >> > Subject: [PATCH] perf tools: Handle partial AUX records and print a warning > >> > This patch decodes the 'partial' flag in AUX records and prints >> > a warning to the user, so that they don't have to guess why their >> > PT traces contain gaps (or missing altogether): > >> >> Warning: >> >> AUX data had gaps in it 6 times out of 8! > > The above should be left for a more verbose mode? > >> >> Are you running a KVM guest in the background? > > The warning should be a bit more precise, as you said, tuning > vmm_exclusive is key here, i.e.: > > "Are you running a KVM guest in the background with > kvm_intel.vmm_exclusive=1?" You'll still get gaps with vmm_exclusive=0 if you run perf record -a or if you try to trace the actual kvm. > And that we can even figure out, its just a matter of reading: > > [root@jouet ~]# cat /sys/module/kvm_intel/parameters/vmm_exclusive > Y > > I have tested after setting that using: > > modprobe kvm_intel vmm_exclusive=n > > And I was able to get Intel PT records from a workload. > > So perhaps we can get this patch in, which improves the situation, and > then, on top of it do these extra checks and give proper hints, ok? Sure. Thanks, -- Alex