From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757956AbcAPBNB (ORCPT ); Fri, 15 Jan 2016 20:13:01 -0500 Received: from mga09.intel.com ([134.134.136.24]:41968 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755176AbcAPBM4 (ORCPT ); Fri, 15 Jan 2016 20:12:56 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,302,1449561600"; d="scan'208";a="891483704" From: Andi Kleen To: acme@kernel.org Cc: peterz@infradead.org, jolsa@kernel.org, eranian@google.com, linux-kernel@vger.kernel.org, mingo@kernel.org Subject: Add top down metrics to perf stat Date: Fri, 15 Jan 2016 17:12:42 -0800 Message-Id: <1452906773-7581-1-git-send-email-andi@firstfloor.org> X-Mailer: git-send-email 2.4.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [v2: Address review feedback. Metrics are now always printed, but colored when crossing threshold. --topdown implies --metric-only. Various smaller fixes, see individual patches] Note to reviewers: includes both tools and kernel patches. The kernel patches are at the end. This patchkit adds support for TopDown measurements to perf stat It applies on top of my earlier metrics patchkit, posted separately. TopDown is intended to replace the frontend cycles idle/ backend cycles idle metrics in standard perf stat output. These metrics are not reliable in many workloads, due to out of order effects. This implements a new --topdown mode in perf stat (similar to --transaction) that measures the pipe line bottlenecks using standardized formulas. The measurement can be all done with 5 counters (one fixed counter) The result are four metrics: FrontendBound, BackendBound, BadSpeculation, Retiring that describe the CPU pipeline behavior on a high level. FrontendBound and BackendBound BadSpeculation is a higher The full top down methology has many hierarchical metrics. This implementation only supports level 1 which can be collected without multiplexing. A full implementation of top down on top of perf is available in pmu-tools toplev. (http://github.com/andikleen/pmu-tools) The current version works on Intel Core CPUs starting with Sandy Bridge, and Atom CPUs starting with Silvermont. In principle the generic metrics should be also implementable on other out of order CPUs. TopDown level 1 uses a set of abstracted metrics which are generic to out of order CPU cores (although some CPUs may not implement all of them): topdown-total-slots Available slots in the pipeline topdown-slots-issued Slots issued into the pipeline topdown-slots-retired Slots successfully retired topdown-fetch-bubbles Pipeline gaps in the frontend topdown-recovery-bubbles Pipeline gaps during recovery from misspeculation These metrics then allow to compute four useful metrics: FrontendBound, BackendBound, Retiring, BadSpeculation. The formulas to compute the metrics are generic, they only change based on the availability on the abstracted input values. The kernel declares the events supported by the current CPU and perf stat then computes the formulas based on the available metrics. Example output: $ perf stat --topdown -I 100 ./BC1s 0.100576098 frontend bound retiring bad speculation backend bound 0.100576098 8.83% 48.93% 35.24% 7.00% 0.200800845 8.84% 48.49% 35.53% 7.13% 0.300905983 8.73% 48.64% 35.58% 7.05% ... On Hyper Threaded CPUs Top Down computes metrics per core instead of per logical CPU. In this case perf stat automatically enables --per-core mode and also requires global mode (-a) and avoiding other filters (no cgroup mode) One side effect is that this may require root rights or a kernel.perf_event_paranoid=-1 setting. On systems without Hyper Threading it can be used per process. Full tree available in git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc perf/top-down-11