From patchwork Mon Feb 14 11:09:14 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adrian Hunter X-Patchwork-Id: 12745464 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 09029C433F5 for ; Mon, 14 Feb 2022 11:30:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351621AbiBNLaW (ORCPT ); Mon, 14 Feb 2022 06:30:22 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:57478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351608AbiBNLaF (ORCPT ); Mon, 14 Feb 2022 06:30:05 -0500 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF534403CD; Mon, 14 Feb 2022 03:10:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644837036; x=1676373036; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=LMcqPNXnMe4ZfRX2pvOSR54SRmRLNEnmPESpB5J91po=; b=iaCW/6D1BVgoXIxxfl0YnafhWCEGR4dzpRErpcfNNsKCkSrt0QXFO/BX etIp04lnHoSeWjZ1FZo7hU1r9HebFZC6rAZH5L5nVldPKsmWggl2UrciA vRcgx0dViooz70P3Eye79jxR44hHEyh2lwLp1FYYmvJ8qj3yitOE7WVnG eQzmxUlHZVXw58pO8nWOTB4kXTMOh1nhTrzsLQcW0GSlPwfSRfgE80Ddt 69Ly4B8VMn2tQF2a2yGcZzaQqNvYwwX4RpgiSJyQO3Ch/uqvMMQtAHgMC ZQjpUhlCD6YmTejPXn+9daV67RDaBJx/yjygi6HjauX1HNJDX8rSzNdKt g==; X-IronPort-AV: E=McAfee;i="6200,9189,10257"; a="233616257" X-IronPort-AV: E=Sophos;i="5.88,367,1635231600"; d="scan'208";a="233616257" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Feb 2022 03:10:36 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,367,1635231600"; d="scan'208";a="635103897" Received: from ahunter-desktop.fi.intel.com ([10.237.72.92]) by orsmga004.jf.intel.com with ESMTP; 14 Feb 2022 03:10:30 -0800 From: Adrian Hunter To: Peter Zijlstra Cc: Alexander Shishkin , Arnaldo Carvalho de Melo , Jiri Olsa , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, kvm@vger.kernel.org, H Peter Anvin , Mathieu Poirier , Suzuki K Poulose , Leo Yan Subject: [PATCH V2 11/11] perf intel-pt: Add documentation for new clock IDs Date: Mon, 14 Feb 2022 13:09:14 +0200 Message-Id: <20220214110914.268126-12-adrian.hunter@intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220214110914.268126-1-adrian.hunter@intel.com> References: <20220214110914.268126-1-adrian.hunter@intel.com> MIME-Version: 1.0 Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Add brief documentation for new clock IDs CLOCK_PERF_HW_CLOCK and CLOCK_PERF_HW_CLOCK_NS, as well as new config variables intel-pt.max_nonturbo_ratio and intel-pt.tsc_art_ratio. Signed-off-by: Adrian Hunter --- tools/perf/Documentation/perf-intel-pt.txt | 47 ++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt index ff58bd4c381b..45f750024e3d 100644 --- a/tools/perf/Documentation/perf-intel-pt.txt +++ b/tools/perf/Documentation/perf-intel-pt.txt @@ -509,6 +509,31 @@ notnt Disable TNT packets. Without TNT packets, it is not possible to walk "0" otherwise. +perf event clock +~~~~~~~~~~~~~~~~ + +Newer kernel and tools support 2 special clocks: CLOCK_PERF_HW_CLOCK which is +TSC and CLOCK_PERF_HW_CLOCK_NS which is TSC converted to nanoseconds. +CLOCK_PERF_HW_CLOCK_NS is the same as the default perf event clock, but it is +not subject to paravirtualization, so it still works with Intel PT in a VM +guest. CLOCK_PERF_HW_CLOCK_NS is used by default if it is supported. + +To use TSC instead of nanoseconds, use the option: + + --clockid CLOCK_PERF_HW_CLOCK + +Beware forgetting that the time stamp of events will show TSC ticks +(divided by 1,000,000,000) not seconds. + +To use the default perf event clock instead of CLOCK_PERF_HW_CLOCK_NS when +CLOCK_PERF_HW_CLOCK_NS is supported, use the option: + + --no-clockid + +Other clocks are not supported for use with Intel PT because they cannot be +converted to/from TSC. + + AUX area sampling option ~~~~~~~~~~~~~~~~~~~~~~~~ @@ -1398,6 +1423,28 @@ There were none. :17006 17006 [001] 11500.262869216: ffffffff8220116e error_entry+0xe ([guest.kernel.kallsyms]) pushq %rax +Tracing within a Virtual Machine +-------------------------------- + +When supported, using Intel PT within a virtual machine does not support TSC +because the perf event clock is subject to paravirtualization. That is +overcome by the new CLOCK_PERF_HW_CLOCK_NS clock - refer 'perf event clock' +above. In addition, in a VM, the following might be zero: + + /sys/bus/event_source/devices/intel_pt/max_nonturbo_ratio + /sys/bus/event_source/devices/intel_pt/tsc_art_ratio + +The decoder needs this information to correctly interpret timing packets, +so the values can be provided by config variables in that case. Note in +the absence of VMCS TSC Scaling, this is probably the same as the host values. +The config variables are: + + intel-pt.max_nonturbo_ratio + intel-pt.tsc_art_ratio + +For more information about perf config variables, refer linkperf:perf-config[1] + + Event Trace -----------