From patchwork Tue Jul 7 15:29:16 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: 11648949 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 38FF26C1 for ; Tue, 7 Jul 2020 15:30:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2331F2078D for ; Tue, 7 Jul 2020 15:30:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730141AbgGGPaB (ORCPT ); Tue, 7 Jul 2020 11:30:01 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:25992 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729527AbgGGPaA (ORCPT ); Tue, 7 Jul 2020 11:30:00 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 067F1mUA098873; Tue, 7 Jul 2020 11:29:27 -0400 Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0b-001b2d01.pphosted.com with ESMTP id 324pr1swbs-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 07 Jul 2020 11:29:26 -0400 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 067F6lWN013952; Tue, 7 Jul 2020 15:29:25 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma06ams.nl.ibm.com with ESMTP id 322h1h3gw5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 07 Jul 2020 15:29:24 +0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 067FTMpk30670966 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 7 Jul 2020 15:29:22 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B894AAE055; Tue, 7 Jul 2020 15:29:22 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A31D1AE045; Tue, 7 Jul 2020 15:29:20 +0000 (GMT) Received: from pratiks-thinkpad.ibmuc.com (unknown [9.85.70.197]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 7 Jul 2020 15:29:20 +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, 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 1/2] cpuidle: Trace IPI based and timer based wakeup latency from idle states Date: Tue, 7 Jul 2020 20:59:16 +0530 Message-Id: <20200707152917.10652-2-psampat@linux.ibm.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: <20200707152917.10652-1-psampat@linux.ibm.com> References: <20200707152917.10652-1-psampat@linux.ibm.com> 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=2020-07-07_08:2020-07-07,2020-07-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 priorityscore=1501 malwarescore=0 phishscore=0 mlxlogscore=999 mlxscore=0 cotscore=-2147483648 lowpriorityscore=0 bulkscore=0 adultscore=0 suspectscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007070109 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Fire directed smp_call_function_single IPIs from a specified source CPU to the specified target CPU to reduce the noise we have to wade through in the trace log. The module is based on the idea written by Srivatsa Bhat and maintained by Vaidyanathan Srinivasan internally. Queue HR timer and measure jitter. Wakeup latency measurement for idle states using hrtimer. Echo a value in ns to timer_test_function and watch trace. A HRtimer will be queued and when it fires the expected wakeup vs actual wakeup is computes and delay printed in ns. Implemented as a module which utilizes debugfs so that it can be integrated with selftests. To include the module, check option and include as module kernel hacking -> Cpuidle latency selftests [srivatsa.bhat@linux.vnet.ibm.com: Initial implementation in cpidle/sysfs] [svaidy@linux.vnet.ibm.com: wakeup latency measurements using hrtimer and fix some of the time calculation] [ego@linux.vnet.ibm.com: Fix some whitespace and tab errors and increase the resolution of IPI wakeup] Signed-off-by: Pratik Rajesh Sampat --- drivers/cpuidle/Makefile | 1 + drivers/cpuidle/test-cpuidle_latency.c | 150 +++++++++++++++++++++++++ lib/Kconfig.debug | 10 ++ 3 files changed, 161 insertions(+) create mode 100644 drivers/cpuidle/test-cpuidle_latency.c diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile index f07800cbb43f..2ae05968078c 100644 --- a/drivers/cpuidle/Makefile +++ b/drivers/cpuidle/Makefile @@ -8,6 +8,7 @@ obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o obj-$(CONFIG_DT_IDLE_STATES) += dt_idle_states.o obj-$(CONFIG_ARCH_HAS_CPU_RELAX) += poll_state.o obj-$(CONFIG_HALTPOLL_CPUIDLE) += cpuidle-haltpoll.o +obj-$(CONFIG_IDLE_LATENCY_SELFTEST) += test-cpuidle_latency.o ################################################################################## # ARM SoC drivers diff --git a/drivers/cpuidle/test-cpuidle_latency.c b/drivers/cpuidle/test-cpuidle_latency.c new file mode 100644 index 000000000000..61574665e972 --- /dev/null +++ b/drivers/cpuidle/test-cpuidle_latency.c @@ -0,0 +1,150 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Module-based API test facility for cpuidle latency using IPIs and timers + */ + +#include +#include +#include + +/* IPI based wakeup latencies */ +struct latency { + unsigned int src_cpu; + unsigned int dest_cpu; + ktime_t time_start; + ktime_t time_end; + u64 latency_ns; +} ipi_wakeup; + +static void measure_latency(void *info) +{ + struct latency *v; + ktime_t time_diff; + + v = (struct latency *)info; + v->time_end = ktime_get(); + time_diff = ktime_sub(v->time_end, v->time_start); + v->latency_ns = ktime_to_ns(time_diff); +} + +void run_smp_call_function_test(unsigned int cpu) +{ + ipi_wakeup.src_cpu = smp_processor_id(); + ipi_wakeup.dest_cpu = cpu; + ipi_wakeup.time_start = ktime_get(); + smp_call_function_single(cpu, measure_latency, &ipi_wakeup, 1); +} + +/* Timer based wakeup latencies */ +struct timer_data { + unsigned int src_cpu; + u64 timeout; + ktime_t time_start; + ktime_t time_end; + struct hrtimer timer; + u64 timeout_diff_ns; +} timer_wakeup; + +static enum hrtimer_restart timer_called(struct hrtimer *hrtimer) +{ + struct timer_data *w; + ktime_t time_diff; + + w = container_of(hrtimer, struct timer_data, timer); + w->time_end = ktime_get(); + + time_diff = ktime_sub(w->time_end, w->time_start); + time_diff = ktime_sub(time_diff, ns_to_ktime(w->timeout)); + w->timeout_diff_ns = ktime_to_ns(time_diff); + return HRTIMER_NORESTART; +} + +static void run_timer_test(unsigned int ns) +{ + hrtimer_init(&timer_wakeup.timer, CLOCK_MONOTONIC, + HRTIMER_MODE_REL); + timer_wakeup.timer.function = timer_called; + timer_wakeup.time_start = ktime_get(); + timer_wakeup.src_cpu = smp_processor_id(); + timer_wakeup.timeout = ns; + + hrtimer_start(&timer_wakeup.timer, ns_to_ktime(ns), + HRTIMER_MODE_REL_PINNED); +} + +static struct dentry *dir; + +static int cpu_read_op(void *data, u64 *value) +{ + *value = ipi_wakeup.dest_cpu; + return 0; +} + +static int cpu_write_op(void *data, u64 value) +{ + run_smp_call_function_test(value); + return 0; +} +DEFINE_SIMPLE_ATTRIBUTE(ipi_ops, cpu_read_op, cpu_write_op, "%llu\n"); + +static int timeout_read_op(void *data, u64 *value) +{ + *value = timer_wakeup.timeout; + return 0; +} + +static int timeout_write_op(void *data, u64 value) +{ + run_timer_test(value); + return 0; +} +DEFINE_SIMPLE_ATTRIBUTE(timeout_ops, timeout_read_op, timeout_write_op, "%llu\n"); + +static int __init latency_init(void) +{ + struct dentry *temp; + + dir = debugfs_create_dir("latency_test", 0); + if (!dir) { + pr_alert("latency_test: failed to create /sys/kernel/debug/latency_test\n"); + return -1; + } + temp = debugfs_create_file("ipi_cpu_dest", + 0666, + dir, + NULL, + &ipi_ops); + if (!temp) { + pr_alert("latency_test: failed to create /sys/kernel/debug/ipi_cpu_dest\n"); + return -1; + } + debugfs_create_u64("ipi_latency_ns", 0444, dir, &ipi_wakeup.latency_ns); + debugfs_create_u32("ipi_cpu_src", 0444, dir, &ipi_wakeup.src_cpu); + + temp = debugfs_create_file("timeout_expected_ns", + 0666, + dir, + NULL, + &timeout_ops); + if (!temp) { + pr_alert("latency_test: failed to create /sys/kernel/debug/timeout_expected_ns\n"); + return -1; + } + debugfs_create_u64("timeout_diff_ns", 0444, dir, &timer_wakeup.timeout_diff_ns); + debugfs_create_u32("timeout_cpu_src", 0444, dir, &timer_wakeup.src_cpu); + pr_info("Latency Test module loaded\n"); + return 0; +} + +static void __exit latency_cleanup(void) +{ + pr_info("Cleaning up Latency Test module.\n"); + debugfs_remove_recursive(dir); +} + +module_init(latency_init); +module_exit(latency_cleanup); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("IBM Corporation"); +MODULE_DESCRIPTION("Measuring idle latency for IPIs and Timers"); diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index d74ac0fd6b2d..e2283790245a 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1375,6 +1375,16 @@ config DEBUG_KOBJECT If you say Y here, some extra kobject debugging messages will be sent to the syslog. +config IDLE_LATENCY_SELFTEST + tristate "Cpuidle latency selftests" + depends on CPU_IDLE + help + This option provides a kernel module that runs tests using the IPI and + timers to measure latency. + + Say M if you want these self tests to build as a module. + Say N if you are unsure. + config DEBUG_KOBJECT_RELEASE bool "kobject release debugging" depends on DEBUG_OBJECTS_TIMERS