From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754463AbdBFQGO (ORCPT ); Mon, 6 Feb 2017 11:06:14 -0500 Received: from mga03.intel.com ([134.134.136.65]:4223 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752607AbdBFQGN (ORCPT ); Mon, 6 Feb 2017 11:06:13 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,342,1477983600"; d="scan'208";a="1091459030" From: Alexander Shishkin To: Andi Kleen Cc: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , Borislav Petkov , Thomas Gleixner Subject: Re: [PATCH] perf/x86/intel/pt: Allow disabling branch tracing In-Reply-To: <87efzbjopq.fsf@firstfloor.org> References: <87inosaoi1.fsf@ashishki-desk.ger.corp.intel.com> <20170206144140.14402-1-alexander.shishkin@linux.intel.com> <87efzbjopq.fsf@firstfloor.org> User-Agent: Notmuch/0.23.3 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Mon, 06 Feb 2017 18:05:29 +0200 Message-ID: <87mvdz8fue.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 Andi Kleen writes: > Alexander Shishkin writes: > >> Now that Intel PT supports more types of trace content than just branch >> tracing, it may be useful to allow the user to disable branch tracing >> when it is not needed. >> >> The special case is BDW, where not setting BranchEn is not supported. >> >> This is slightly trickier than necessary, because up to this moment >> the driver has been setting BranchEn automatically and the userspace >> assumes as much. Instead of reversing the semantics of BranchEn, we >> introduce a 'passthrough' bit, which will forego the default and allow >> the user to set BranchEn to their heart's content. > > cpu/passthrough=1,branchen=1/ seems far uglier/more complicanted to me > than the original cpu/nobranch=1/ It's /passthrough=1,branch=0/ or simply /passthrough=1/. Regards, -- Alex