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 1618EEE49A6 for ; Mon, 21 Aug 2023 13:17:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232694AbjHUNRc (ORCPT ); Mon, 21 Aug 2023 09:17:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232651AbjHUNRb (ORCPT ); Mon, 21 Aug 2023 09:17:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62441102; Mon, 21 Aug 2023 06:17:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E64D5616C0; Mon, 21 Aug 2023 13:16:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 18D6DC433C7; Mon, 21 Aug 2023 13:16:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692623805; bh=KPa/AwkosoOhlmZaq4JF40z1lU8eMUi0EpScWLPvrao=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oQGcvU4wKYUz0g3IFUpnVo7fmvXH7c9xTWmCvN5nKublD+oTZFbwrvB3/fwz8vUXJ 9Nl6MsOfLIliTwSVVUKXvzsDRSq8wj1kmRmUkPv+xrfgUbT+uC7GSD1sgeCJk3CThJ vpTdTDw3Tcn/dygVBsT2eM5u9/5AjyG5Qt1TXzW76qYiF78o2j7ALb78FbMI7YtxyN p0dUhg52o9EIbf4VbRmGelqxpVrit3dcUW4kstNvfH+1ZxYa54rN2HYQKQwoNeeaTJ w35WMwpMqKX1LySH82BEguEDeP9cepX6bYCiGi5zAFyLmFmTcoK1+gAoWKMLA7Y+B3 17Yhm6PEzfOnQ== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 648F340722; Mon, 21 Aug 2023 10:16:42 -0300 (-03) Date: Mon, 21 Aug 2023 10:16:42 -0300 From: Arnaldo Carvalho de Melo To: "liwei (GF)" Cc: Ian Rogers , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Adrian Hunter , Kan Liang , Sean Christopherson , K Prateek Nayak , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] perf header: Fix missing PMU caps Message-ID: References: <20230818171952.3719251-1-irogers@google.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 Sat, Aug 19, 2023 at 12:16:09PM +0800, liwei (GF) escreveu: > Hi Ian: > > On 2023/8/19 1:19, Ian Rogers wrote: > > PMU caps are written as HEADER_PMU_CAPS or for the special case of the > > PMU "cpu" as HEADER_CPU_PMU_CAPS. As the PMU "cpu" is special, and not > > any "core" PMU, the logic had become broken and core PMUs not called > > "cpu" were not having their caps written. This affects ARM and s390 > > non-hybrid PMUs. > > > > Simplify the PMU caps writing logic to scan one fewer time and to be > > more explicit in its behavior. > > > > Reported-by: Wei Li > > Fixes: 178ddf3bad98 ("perf header: Avoid hybrid PMU list in write_pmu_caps") > > Signed-off-by: Ian Rogers > > --- > > tools/perf/util/header.c | 31 ++++++++++++++++--------------- > > 1 file changed, 16 insertions(+), 15 deletions(-) > > > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > > index 52fbf526fe74..13c71d28e0eb 100644 > > --- a/tools/perf/util/header.c > > +++ b/tools/perf/util/header.c > > @@ -1605,8 +1605,15 @@ static int write_pmu_caps(struct feat_fd *ff, > > int ret; > > > > while ((pmu = perf_pmus__scan(pmu))) { > > - if (!pmu->name || !strcmp(pmu->name, "cpu") || > > - perf_pmu__caps_parse(pmu) <= 0) > > + if (!strcmp(pmu->name, "cpu")) { > > So you removed the check of 'pmu->name', does this check really redundant? since > we can find such checks in many places in the perf code. If not, i think it is > necessary for strcmp(). Indeed, when sorting in tools/perf/util/pmus.c in cmp_sevent() we have: /* Order by PMU name. */ if (as->pmu != bs->pmu) { a_pmu_name = a_pmu_name ?: (as->pmu->name ?: ""); b_pmu_name = b_pmu_name ?: (bs->pmu->name ?: ""); ret = strcmp(a_pmu_name, b_pmu_name); if (ret) return ret; } And even if in this specific case, for some reason, we could guarantee that pmu->name isn't NULL, then removing that check should be best left for a separate patch with an explanation as to why that is safe. Having it as: while ((pmu = perf_pmus__scan(pmu))) { - if (!pmu->name || !strcmp(pmu->name, "cpu") || - perf_pmu__caps_parse(pmu) <= 0) + if (!pmu->name || !strcmp(pmu->name, "cpu")) { even eases a bit reviewing, as we see we're just removing that perf_pmu__caps_parse(pmu) line. Ian? - Arnaldo > > + /* > > + * The "cpu" PMU is special and covered by > > + * HEADER_CPU_PMU_CAPS. Note, core PMUs are > > + * counted/written here for ARM, s390 and Intel hybrid. > > + */ > > + continue; > > + } > > + if (perf_pmu__caps_parse(pmu) <= 0) > > continue; > > nr_pmu++; > > } > > @@ -1619,23 +1626,17 @@ static int write_pmu_caps(struct feat_fd *ff, > > return 0; > > > > /* > > - * Write hybrid pmu caps first to maintain compatibility with > > - * older perf tool. > > + * Note older perf tools assume core PMUs come first, this is a property > > + * of perf_pmus__scan. > > */ > > - if (perf_pmus__num_core_pmus() > 1) { > > - pmu = NULL; > > - while ((pmu = perf_pmus__scan_core(pmu))) { > > - ret = __write_pmu_caps(ff, pmu, true); > > - if (ret < 0) > > - return ret; > > - } > > - } > > - > > pmu = NULL; > > while ((pmu = perf_pmus__scan(pmu))) { > > - if (pmu->is_core || !pmu->nr_caps) > > + if (!strcmp(pmu->name, "cpu")) { > > same here > > Thanks, > Wei > > > + /* Skip as above. */ > > + continue; > > + } > > + if (perf_pmu__caps_parse(pmu) <= 0) > > continue; > > - > > ret = __write_pmu_caps(ff, pmu, true); > > if (ret < 0) > > return ret; -- - Arnaldo