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 08:10:10 +0100 Message-ID: <52B93352.2030909@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f170.google.com ([209.85.212.170]:42180 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751284Ab3LXHKO (ORCPT ); Tue, 24 Dec 2013 02:10:14 -0500 Received: by mail-wi0-f170.google.com with SMTP id hq4so11189098wib.1 for ; Mon, 23 Dec 2013 23:10:12 -0800 (PST) In-Reply-To: <20131224021822.GH20765@two.firstfloor.org> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Andi Kleen Cc: linux-perf-users@vger.kernel.org Thanks, "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. I am thus going to look a offcore request to sample remote memory accesses with correct IPs values. Manu On 12/24/2013 03:18 AM, Andi Kleen wrote: >> In my experiments I get LFB samples with weight equal or greater than >> local RAM samples, I should I interpret these values ? > > The measured latency can include the pipeline latency. > >> Moreover, because I am more interested in identifying remote memory >> accesses sources than in effective load latency weight, I am wondering >> if using the perf mem tool (using the >> MEM_INST_RETIRED.LATENCY_ABOVE_THRESHOLD event) is the best solution. >> Couldn't I use sampling on other events such as UNCORE ones more >> easily and efficiently ? > > You cannot use uncore events to sample on IPs. > > -Andi >