From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932517AbcARW2g (ORCPT ); Mon, 18 Jan 2016 17:28:36 -0500 Received: from one.firstfloor.org ([193.170.194.197]:35964 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932372AbcARW2e (ORCPT ); Mon, 18 Jan 2016 17:28:34 -0500 Date: Mon, 18 Jan 2016 23:28:32 +0100 From: Andi Kleen To: Peter Zijlstra Cc: Andi Kleen , acme@kernel.org, jolsa@kernel.org, eranian@google.com, linux-kernel@vger.kernel.org, mingo@kernel.org, Andi Kleen Subject: Re: [PATCH 09/11] x86, perf: Support sysfs files depending on SMT status Message-ID: <20160118222832.GK4698@two.firstfloor.org> References: <1452906773-7581-1-git-send-email-andi@firstfloor.org> <1452906773-7581-10-git-send-email-andi@firstfloor.org> <20160118180614.GV6357@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160118180614.GV6357@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > So one obvious problem with this is that a concurrent hotplug operation > can toggle ht_on resulting in bogus measurements. > > I'm not sure there's anything we can do about that, other than WARN in > the tool if it finds inconsistent results; does it? Right. Supporting a good interface for user programs to be informed of CPU hotplug would be useful for a lot of things, but currently it doesn't exist and it's definitely outside the scope of this patchkit. If such an interface existed perf stat could use it to reconfigure itself. It's hard to do a good sanity check unfortunately. -Andi -- ak@linux.intel.com -- Speaking for myself only.