From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BAFCC433FE for ; Fri, 30 Sep 2022 16:56:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229644AbiI3Q4M (ORCPT ); Fri, 30 Sep 2022 12:56:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231186AbiI3Q4M (ORCPT ); Fri, 30 Sep 2022 12:56:12 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3DD891A6EA5; Fri, 30 Sep 2022 09:56:10 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E5F9DB82961; Fri, 30 Sep 2022 16:56:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5EC19C433D7; Fri, 30 Sep 2022 16:56:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664556967; bh=fv9rgvbcr2cSVD9DcqU0Y0j86/fEUEzhMuDoX4SSQVk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=IIbUeKfuWrNG8yUB2RKxRAIkZ+ng2fU62fcjYBcBXzNI/BBMh6hUcoyjZJTRIYiHc Xh5LZH+yQDD0sDfx+lCtZTXuDyIfK8HPwcWvm0cmcTZRk8mzrmAqi+hCvKqWh67xEe +sKmmDmH6hDb8JK4q6qBY4Y3l+vJo5yWv7fOviBW+3FWuOETcgBnQ0t4dIoBw+Kdt6 RkQ58zNA27JJBoA1AHrXPpTHr7zC6n2YlaN13SSTjxdwRJ+R5FL+nubtCPuEoEJCK9 D5n+4X60kwaCAlRFRrn0D6G8gAARvxj05Z6uO2HtDhdA8G8rIwj3nsEV5ZDmcGh1Z+ o7JpywQCZaXTQ== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 1EF314062C; Fri, 30 Sep 2022 13:56:05 -0300 (-03) Date: Fri, 30 Sep 2022 13:56:05 -0300 From: Arnaldo Carvalho de Melo To: Namhyung Kim Cc: Adrian Hunter , Ian Rogers , Jiri Olsa , Ingo Molnar , Peter Zijlstra , LKML , linux-perf-users , Kan Liang , Leo Yan Subject: Re: [PATCH 2/5] libperf: Propagate maps only if necessary Message-ID: References: <63905e96-55d5-1aa2-5dbe-167b9aecad8c@intel.com> <37452f10-365d-f496-3cb2-b80481f5f079@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org Em Fri, Sep 30, 2022 at 09:44:49AM -0700, Namhyung Kim escreveu: > On Fri, Sep 30, 2022 at 5:50 AM Adrian Hunter wrote: > > > > On 29/09/22 23:42, Namhyung Kim wrote: > > > On Wed, Sep 28, 2022 at 10:19 PM Adrian Hunter wrote: > > >> > > >> On 29/09/22 08:09, Namhyung Kim wrote: > > >>> On Wed, Sep 28, 2022 at 7:08 PM Ian Rogers wrote: > > >>>> > > >>>> On Wed, Sep 28, 2022 at 4:46 PM Namhyung Kim wrote: > > >>>>> > > >>>>> On Wed, Sep 28, 2022 at 12:54 AM Adrian Hunter wrote: > > >>>>>> > > >>>>>> On 27/09/22 20:28, Namhyung Kim wrote: > > >>>>>>> Hi Adrian, > > >>>>>>> > > >>>>>>> On Tue, Sep 27, 2022 at 12:06 AM Adrian Hunter wrote: > > >>>>>>>> > > >>>>>>>> On 24/09/22 19:57, Namhyung Kim wrote: > > >>>>>>>>> The current code propagate evsel's cpu map settings to evlist when it's > > >>>>>>>>> added to an evlist. But the evlist->all_cpus and each evsel's cpus will > > >>>>>>>>> be updated in perf_evlist__set_maps() later. No need to do it before > > >>>>>>>>> evlist's cpus are set actually. > > >>>>>>>>> > > >>>>>>>>> Actually we discarded this intermediate all_cpus maps at the beginning > > >>>>>>>>> of perf_evlist__set_maps(). Let's not do this. It's only needed when > > >>>>>>>>> an evsel is added after the evlist cpu maps are set. > > >>>>>>>> > > >>>>>>>> That might not be true. Consider evlist__fix_hybrid_cpus() which fiddles > > >>>>>>>> with evsel->core.cpus and evsel->core.own_cpus after the evsel has been > > >>>>>>>> added to the evlist. It can also remove an evsel from the evlist. > > >>>>>>> > > >>>>>>> Thanks for your review. I think it's fine to change evsel cpus or to remove > > >>>>>>> an evsel from evlist before calling evlist__create_maps(). The function > > >>>>>>> will take care of setting evlist's all_cpus from the evsels in the evlist. > > >>>>>>> So previous changes in evsel/cpus wouldn't be any special. > > >>>>>>> > > >>>>>>> After this point, adding a new evsel needs to update evlist all cpus by > > >>>>>>> propagating cpu maps. So I think hybrid cpus should be fine. > > >>>>>>> Did I miss something? > > >>>>>> > > >>>>>> I wondered how it might play out if evlist__fix_hybrid_cpus() reduced the > > >>>>>> cpus from the target->cpu_list (using perf record -C) , since after this > > >>>>>> patch all_cpus always starts with the target->cpu_list instead of an empty > > >>>>>> list. But then, in the hybrid case, it puts a dummy event that uses the > > >>>>>> target cpu list anyway, so the result is the same. > > >>>>>> > > >>>>>> I don't know if there are any cases where all_cpus would actually need to > > >>>>>> exclude some of the cpus from target->cpu_list. > > >>>>> > > >>>>> I'm not aware of other cases to reduce cpu list. I think it'd be fine > > >>>>> if it has a cpu in the evlist->all_cpus even if it's not used. The evsel > > >>>>> should have a correct list anyway and we mostly use the evsel cpus > > >>>>> to do the real work. > > >>>>> > > >>>>> Thanks, > > >>>>> Namhyung > > >>>> > > >>>> The affinity changes made it so that we use all_cpus probably more > > >>>> often than the evsel CPU maps for real work. The reason being we want > > >>>> to avoid IPIs so we do all the work on 1 CPU and then move to the next > > >>>> CPU in evlist all_cpus. evsel CPU maps are used to make sure the > > >>>> indices are kept accurate - for example, if an uncore event is > > >>>> measured with a CPU event: > > >>>> https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/evlist.h?h=perf/core#n366 > > >>>> https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/evlist.c?h=perf/core#n404 > > >>> > > >>> Right, I meant it'd check the evsel cpus eventually even if it iterates > > >>> on the evlist all_cpus. The evlist_cpu_iterator__next() will skip a > > >>> CPU if it's not in the evsel cpus. > > >>> > > >>> Thanks, > > >>> Namhyung > > >> > > >> Perhaps an alternative is to be explicit about deferring map > > >> propagation e.g. > > > > > > Thanks for your patch. Yeah, we can use this. > > > > > > But I still think it'd be better doing it unconditionally > > > since any propagation before perf_evlist__set_maps > > > will be discarded anyway. With this change, other > > > than perf record will collect all cpus before _set_maps > > > and then discard it. It seems like a waste, no? > > > > > > Or else, we can have allow_map_propagation initialized > > > to false and set it to true in perf_evlist__set_maps(). > > > > > > > That sounds fine. > > Thanks! > > Arnaldo, how do you want to handle it? I can send v2 for the > whole series, but I think you already applied it. Then do you > want me to send this change on top? Send v2 for the whole series, I haven't yet published it so I can replace. - Arnaldo