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 X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00695C43219 for ; Fri, 26 Apr 2019 12:45:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF089206C1 for ; Fri, 26 Apr 2019 12:45:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726206AbfDZMpS (ORCPT ); Fri, 26 Apr 2019 08:45:18 -0400 Received: from mga11.intel.com ([192.55.52.93]:27479 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726039AbfDZMpS (ORCPT ); Fri, 26 Apr 2019 08:45:18 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Apr 2019 05:45:17 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,397,1549958400"; d="scan'208";a="137680155" Received: from otc-lr-04.jf.intel.com ([10.54.39.156]) by orsmga008.jf.intel.com with ESMTP; 26 Apr 2019 05:45:17 -0700 From: kan.liang@linux.intel.com To: acme@redhat.com, mingo@redhat.com, linux-kernel@vger.kernel.org Cc: jolsa@redhat.com, namhyung@gmail.com, lgoncalv@redhat.com, ak@linux.intel.com, Kan Liang Subject: [PATCH V2] perf stat: Add hint for SMI cost measurement Date: Fri, 26 Apr 2019 05:45:03 -0700 Message-Id: <1556282703-120695-1-git-send-email-kan.liang@linux.intel.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kan Liang Entering/exiting a C-state deeper than C0 may cause slight difference in counts between aperf and unhalted core cycles, which may impact the SMI cost. Add smi_env_check() to check if C-state is completely disabled during the measurement. If not, give a hint to user. Update the document as well. Suggested-by: Arnaldo Carvalho de Melo Signed-off-by: Kan Liang --- Changes since V1: - Update changelog, document, and user-visible message tools/perf/Documentation/perf-stat.txt | 5 +++++ tools/perf/builtin-stat.c | 25 +++++++++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt index 39c05f8..19b7267 100644 --- a/tools/perf/Documentation/perf-stat.txt +++ b/tools/perf/Documentation/perf-stat.txt @@ -309,6 +309,11 @@ The output is SMI cycles%, equals to (aperf - unhalted core cycles) / aperf Users who wants to get the actual value can apply --no-metric-only. +Entering/exiting a C-state deeper than C0 may cause slight difference in counts +between aperf and unhalted core cycles, which may impact the SMI cost. +Please completely disable C-state during the measurement, +e.g. set idle=poll in grub. + EXAMPLES -------- diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index c3625ec..e437788 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -87,6 +87,7 @@ #define DEFAULT_SEPARATOR " " #define FREEZE_ON_SMI_PATH "devices/cpu/freeze_on_smi" +#define CPUIDLE_CUR_DRV "devices/system/cpu/cpuidle/current_driver" static void print_counters(struct timespec *ts, int argc, const char **argv); @@ -1024,6 +1025,27 @@ __weak void arch_topdown_group_warn(void) { } +static void smi_env_check(void) +{ + char *name; + size_t len; + int err; + + err = sysfs__read_str(CPUIDLE_CUR_DRV, &name, &len); + if (err) { + pr_warning("Failed to read %s, err %d. Ignoring C-state status check.\n", + CPUIDLE_CUR_DRV, err); + return; + } + + if (strncmp(name, "none", 4)) { + pr_warning("Entering/exiting a C-state deeper than C0 may result inaccurate SMI cost.\n" + "Please completely disable C-state, e.g. set idle=poll in grub.\n"); + } + + free(name); +} + /* * Add default attributes, if there were no attributes specified or * if -d/--detailed, -d -d or -d -d -d is used: @@ -1196,6 +1218,9 @@ static int add_default_attributes(void) if (pmu_have_event("msr", "aperf") && pmu_have_event("msr", "smi")) { + + smi_env_check(); + if (!force_metric_only) stat_config.metric_only = true; err = parse_events(evsel_list, smi_cost_attrs, &errinfo); -- 2.7.4