From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752474AbdIAQ6E (ORCPT ); Fri, 1 Sep 2017 12:58:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54070 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752441AbdIAQ6D (ORCPT ); Fri, 1 Sep 2017 12:58:03 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 02324C04D288 Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=jolsa@redhat.com Date: Fri, 1 Sep 2017 18:57:59 +0200 From: Jiri Olsa To: Andi Kleen Cc: acme@kernel.org, jolsa@kernel.org, linux-kernel@vger.kernel.org, Andi Kleen Subject: Re: [PATCH v3 01/11] perf, tools: Support weak groups Message-ID: <20170901165759.GA32113@krava> References: <20170831194036.30146-1-andi@firstfloor.org> <20170831194036.30146-2-andi@firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170831194036.30146-2-andi@firstfloor.org> User-Agent: Mutt/1.8.3 (2017-05-23) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 01 Sep 2017 16:58:03 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 31, 2017 at 12:40:26PM -0700, Andi Kleen wrote: > From: Andi Kleen > > Setting up groups can be complicated due to the > complicated scheduling restrictions of different PMUs. > User tools usually don't understand all these restrictions. > Still in many cases it is useful to set up groups and > they work most of the time. However if the group > is set up wrong some members will not reported any values > because they never get scheduled. > > Add a concept of a 'weak group': try to set up a group, > but if it's not schedulable fallback to not using > a group. That gives us the best of both worlds: > groups if they work, but still a usable fallback if they don't. > > In theory it would be possible to have more complex fallback > strategies (e.g. try to split the group in half), but > the simple fallback of not using a group seems to work for now. > > So far the weak group is only implemented for perf stat, > not for record. > > Here's an unschedulable group (on IvyBridge with SMT on) > > % perf stat -e '{branches,branch-misses,l1d.replacement,l2_lines_in.all,l2_rqsts.all_code_rd}' -a sleep 1 > > 73,806,067 branches > 4,848,144 branch-misses # 6.57% of all branches > 14,754,458 l1d.replacement > 24,905,558 l2_lines_in.all > l2_rqsts.all_code_rd <------- will never report anything > > With the weak group: > > % perf stat -e '{branches,branch-misses,l1d.replacement,l2_lines_in.all,l2_rqsts.all_code_rd}:W' -a sleep 1 > > 125,366,055 branches (80.02%) > 9,208,402 branch-misses # 7.35% of all branches (80.01%) > 24,560,249 l1d.replacement (80.00%) > 43,174,971 l2_lines_in.all (80.05%) > 31,891,457 l2_rqsts.all_code_rd (79.92%) > > The extra event scheduled with some extra multiplexing > > v2: Move fallback code to separate function. > Add comment on for_each_group_member > Adjust to new perf_evsel__close interface > v3: > Fix debug print out. > Signed-off-by: Andi Kleen Acked-by: Jiri Olsa thanks, jirka