From patchwork Fri Jul 17 09:17:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Pratik R. Sampat" X-Patchwork-Id: 11669645 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9998013A4 for ; Fri, 17 Jul 2020 09:18:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7E5FA20768 for ; Fri, 17 Jul 2020 09:18:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726686AbgGQJSo (ORCPT ); Fri, 17 Jul 2020 05:18:44 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:53636 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726627AbgGQJSn (ORCPT ); Fri, 17 Jul 2020 05:18:43 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 06H934i2174163; Fri, 17 Jul 2020 05:18:09 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 32b61kcwcf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 17 Jul 2020 05:18:09 -0400 Received: from m0098413.ppops.net (m0098413.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 06H93DjZ174849; Fri, 17 Jul 2020 05:18:08 -0400 Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 32b61kcwbk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 17 Jul 2020 05:18:08 -0400 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 06H99wmV024480; Fri, 17 Jul 2020 09:18:06 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma04ams.nl.ibm.com with ESMTP id 329nmyjr55-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 17 Jul 2020 09:18:06 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 06H9I4n855705760 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 17 Jul 2020 09:18:04 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4B5BB52054; Fri, 17 Jul 2020 09:18:04 +0000 (GMT) Received: from pratiks-thinkpad.ibmuc.com (unknown [9.85.80.176]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id E91DF5204E; Fri, 17 Jul 2020 09:18:01 +0000 (GMT) From: Pratik Rajesh Sampat To: rjw@rjwysocki.net, daniel.lezcano@linaro.org, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, srivatsa@csail.mit.edu, shuah@kernel.org, npiggin@gmail.com, ego@linux.vnet.ibm.com, svaidy@linux.ibm.com, linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v2 0/2] Selftest for cpuidle latency measurement Date: Fri, 17 Jul 2020 14:47:59 +0530 Message-Id: <20200717091801.29289-1-psampat@linux.ibm.com> X-Mailer: git-send-email 2.25.4 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-17_04:2020-07-17,2020-07-17 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 adultscore=0 impostorscore=0 mlxlogscore=999 spamscore=0 clxscore=1015 suspectscore=0 phishscore=0 priorityscore=1501 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007170066 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org v1: https://lkml.org/lkml/2020/7/7/1036 Changelog v1 --> v2 1. Based on Shuah Khan's comment, changed exit code to ksft_skip to indicate the test is being skipped 2. Change the busy workload for baseline measurement from "yes > /dev/null" to "cat /dev/random to /dev/null", based on observed CPU utilization for "yes" consuming ~60% CPU while the latter consumes 100% of CPUs, giving more accurate baseline numbers --- The patch series introduces a mechanism to measure wakeup latency for IPI and timer based interrupts The motivation behind this series is to find significant deviations behind advertised latency and resisdency values To achieve this, we introduce a kernel module and expose its control knobs through the debugfs interface that the selftests can engage with. The kernel module provides the following interfaces within /sys/kernel/debug/latency_test/ for, 1. IPI test: ipi_cpu_dest # Destination CPU for the IPI ipi_cpu_src # Origin of the IPI ipi_latency_ns # Measured latency time in ns 2. Timeout test: timeout_cpu_src # CPU on which the timer to be queued timeout_expected_ns # Timer duration timeout_diff_ns # Difference of actual duration vs expected timer To include the module, check option and include as module kernel hacking -> Cpuidle latency selftests The selftest inserts the module, disables all the idle states and enables them one by one testing the following: 1. Keeping source CPU constant, iterates through all the CPUS measuring IPI latency for baseline (CPU is busy with "cat /dev/random > /dev/null" workload) and the when the CPU is allowed to be at rest 2. Iterating through all the CPUs, sending expected timer durations to be equivalent to the residency of the the deepest idle state enabled and extracting the difference in time between the time of wakeup and the expected timer duration Usage ----- Can be used in conjuction to the rest of the selftests. Default Output location in: tools/testing/cpuidle/cpuidle.log To run this test specifically: $ make -C tools/testing/selftests TARGETS="cpuidle" run_tests There are a few optinal arguments too that the script can take [-h ] [-m ] [-o ] Sample output snippet --------------------- --IPI Latency Test--- --Baseline IPI Latency measurement: CPU Busy-- SRC_CPU DEST_CPU IPI_Latency(ns) ... 0 8 1996 0 9 2125 0 10 1264 0 11 1788 0 12 2045 Baseline Average IPI latency(ns): 1843 ---Enabling state: 5--- SRC_CPU DEST_CPU IPI_Latency(ns) 0 8 621719 0 9 624752 0 10 622218 0 11 623968 0 12 621303 Expected IPI latency(ns): 100000 Observed Average IPI latency(ns): 622792 --Timeout Latency Test-- --Baseline Timeout Latency measurement: CPU Busy-- Wakeup_src Baseline_delay(ns) ... 8 2249 9 2226 10 2211 11 2183 12 2263 Baseline Average timeout diff(ns): 2226 ---Enabling state: 5--- 8 10749 9 10911 10 10912 11 12100 12 73276 Expected timeout(ns): 10000200 Observed Average timeout diff(ns): 23589 Pratik Rajesh Sampat (2): cpuidle: Trace IPI based and timer based wakeup latency from idle states selftest/cpuidle: Add support for cpuidle latency measurement drivers/cpuidle/Makefile | 1 + drivers/cpuidle/test-cpuidle_latency.c | 150 ++++++++++++ lib/Kconfig.debug | 10 + tools/testing/selftests/Makefile | 1 + tools/testing/selftests/cpuidle/Makefile | 6 + tools/testing/selftests/cpuidle/cpuidle.sh | 257 +++++++++++++++++++++ tools/testing/selftests/cpuidle/settings | 1 + 7 files changed, 426 insertions(+) create mode 100644 drivers/cpuidle/test-cpuidle_latency.c create mode 100644 tools/testing/selftests/cpuidle/Makefile create mode 100755 tools/testing/selftests/cpuidle/cpuidle.sh create mode 100644 tools/testing/selftests/cpuidle/settings