From mboxrd@z Thu Jan 1 00:00:00 1970 From: Manuel Selva Subject: Re: Understanding perf mem -t load results Date: Tue, 24 Dec 2013 08:42:57 +0100 Message-ID: <52B93B01.4020305@gmail.com> References: <1776760155.10395562.1386857164818.JavaMail.root@insa-lyon.fr> <877gb5vmmn.fsf@tassilo.jf.intel.com> <52AE2721.8020501@insa-lyon.fr> <20131215234548.GP21717@two.firstfloor.org> <20131224021822.GH20765@two.firstfloor.org> <52B93352.2030909@gmail.com> <20131224072813.GI20765@two.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-wi0-f172.google.com ([209.85.212.172]:34373 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751067Ab3LXHnC (ORCPT ); Tue, 24 Dec 2013 02:43:02 -0500 Received: by mail-wi0-f172.google.com with SMTP id en1so11723527wid.17 for ; Mon, 23 Dec 2013 23:42:58 -0800 (PST) In-Reply-To: <20131224072813.GI20765@two.firstfloor.org> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Andi Kleen Cc: linux-perf-users@vger.kernel.org On 12/24/2013 08:28 AM, Andi Kleen wrote: > On Tue, Dec 24, 2013 at 08:10:10AM +0100, Manuel Selva wrote: >> "You cannot use uncore events to sample IPs" means that the values >> corresponding to PERF_SAMPLE_IP are not correct ? Some benchmarks I >> did by sampling ME_INST_RETIRED with PERF_SAMPLE_IP let me think >> that I was able to get the source of th event. The IP value was >> coherent. Maybe this is not always the case. > > It's the IP of a random core on the socket that happens to read the u= ncore > registers. > Ok. Where should I have read this information, in the Intel Software=20 Developer=92s Manual volume 3B (I guess this is a hardware limitation) = ? I checked what can be measured with the offcore facility. I can ask to=20 count remote memory accesses, but now I am not sure PEBS is enable for=20 these events. If the answer is no, I can't accurately identify remote=20 memory accesses with offcore events ? As a consequence I am wondering i= f=20 there is a way to do such thing ? Manu