From patchwork Fri Sep 8 22:49:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Elliot Berman X-Patchwork-Id: 13377882 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 D592AEEB572 for ; Fri, 8 Sep 2023 22:50:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344354AbjIHWu7 (ORCPT ); Fri, 8 Sep 2023 18:50:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243165AbjIHWu6 (ORCPT ); Fri, 8 Sep 2023 18:50:58 -0400 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 075C71FED; Fri, 8 Sep 2023 15:50:55 -0700 (PDT) Received: from pps.filterd (m0279863.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 388K0e4L016695; Fri, 8 Sep 2023 22:50:43 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h=from : subject : date : message-id : mime-version : content-type : content-transfer-encoding : to : cc; s=qcppdkim1; bh=F3k7KeTvDFRHY2FyLaq52d7ups1kR425uouE6mppmeU=; b=jjUfAeVkAtSZlNvvbQuGfrFOksmvF/p6eWwRdR1hh7bFoLMtbggRYSlU8ZrxeF6UoEdN Iq7t4p+WZ7/VgMOXv5LUSvXwq2vbfbacPRvZuj6FzSqQ0ts/scaONQeCog1YTwzGtJJj 0504JCrDSGclIuJaQdKAtWWLNGq9at972EFEYTpAoDhFWluy0Z+dY4yQZNhXDR4pQur0 yFQ7XzxkW9GGaxRK7LQY9s7xV11AMZOsRTf6QRCuihAJdjWVLHSHsXSEEcvfi+OI/2ho 8bKqtUUfFMMsZCtp84GVIJmQ6xXAemvORCsAowIbjfB17G3DiwE/dtJ2jozStuHgUPuP 4Q== Received: from nasanppmta02.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3syu012ek5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 08 Sep 2023 22:50:42 +0000 Received: from nasanex01b.na.qualcomm.com (nasanex01b.na.qualcomm.com [10.46.141.250]) by NASANPPMTA02.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 388MofIT010603 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 8 Sep 2023 22:50:42 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.36; Fri, 8 Sep 2023 15:50:38 -0700 From: Elliot Berman Subject: [PATCH v4 0/2] Avoid spurious freezer wakeups Date: Fri, 8 Sep 2023 15:49:14 -0700 Message-ID: <20230908-avoid-spurious-freezer-wakeups-v4-0-6155aa3dafae@quicinc.com> MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAOqk+2QC/4XOy07EIBgF4FeZsBbDpRbqyvcws+DyY/84QoUBL 5O+u3RiosZFl+csvnMupEBGKOT+cCEZGhZMsYfh5kDcbOITUPQ9E8GEZJoralpCT8tSM6ZaaMg An5Dpm3mGuhQ6BT3yadTMSkM6Yk0BarOJbu5MrKdTL5cMAd+vq4/Hnmcs55Q/rica39rvPaH39 hqnnGoL2gU18kGJh9eKDqO7demFbHgTv0DJdkGxgVopMdw5b737D8ofcGL7D2UH/TBpwYM3bPB /wXVdvwDIFuUyhQEAAA== To: Ingo Molnar , Peter Zijlstra , "Rafael J. Wysocki" , Pavel Machek CC: Thomas Gleixner , , , , , Elliot Berman , "Prakash Viswalingam" X-Mailer: b4 0.13-dev X-Originating-IP: [10.49.16.6] X-ClientProxiedBy: nalasex01c.na.qualcomm.com (10.47.97.35) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: kV7UEk9X3XJ8DieBq9vYArLkT9TCIxrM X-Proofpoint-GUID: kV7UEk9X3XJ8DieBq9vYArLkT9TCIxrM X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-09-08_18,2023-09-05_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=1 mlxscore=0 suspectscore=0 adultscore=0 bulkscore=1 phishscore=0 impostorscore=0 clxscore=1011 spamscore=0 malwarescore=0 mlxlogscore=912 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2308100000 definitions=main-2309080209 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org After commit f5d39b020809 ("freezer,sched: Rewrite core freezer logic"), tasks that transition directly from TASK_FREEZABLE to TASK_FROZEN are always woken up on the thaw path. Prior to that commit, tasks could ask freezer to consider them "frozen enough" via freezer_do_not_count(). The commit replaced freezer_do_not_count() with a TASK_FREEZABLE state which allows freezer to immediately mark the task as TASK_FROZEN without waking up the task. This is efficient for the suspend path, but on the thaw path, the task is always woken up even if the task didn't need to wake up and goes back to its TASK_(UN)INTERRUPTIBLE state. Although these tasks are capable of handling of the wakeup, we can observe a power/perf impact from the extra wakeup. We observed on Android many tasks wait in the TASK_FREEZABLE state (particularly due to many of them being binder clients). We observed nearly 4x the number of tasks and a corresponding linear increase in latency and power consumption when thawing the system. The latency increased from ~15ms to ~50ms. Avoid the spurious wakeups by saving the state of TASK_FREEZABLE tasks. If the task was running before entering TASK_FROZEN state (__refrigerator()) or if the task received a wake up for the saved state, then the task is woken on thaw. saved_state from PREEMPT_RT locks can be re-used because freezer would not stomp on the rtlock wait flow: TASK_RTLOCK_WAIT isn't considered freezable. For testing purposes, I use these commands can help see how many tasks were woken during thawing: 1. Setup: mkdir /sys/kernel/tracing/instances/freezer cd /sys/kernel/tracing/instances/freezer echo 0 > tracing_on ; echo > trace echo power:suspend_resume > set_event echo 'enable_event:sched:sched_wakeup if action == "thaw_processes" && start == 1' > events/power/suspend_resume/trigger echo 'traceoff if action == "thaw_processes" && start == 0' > events/power/suspend_resume/trigger echo 1 > tracing_on 2. Let kernel go to suspend 3. After kernel's back up: cat /sys/kernel/tracing/instances/freezer/trace | grep sched_wakeup | grep -o "pid=[0-9]*" | sort -u | wc -l Signed-off-by: Elliot Berman --- Changes in v4: - Split into 2 commits - Link to v3: https://lore.kernel.org/r/20230908-avoid-spurious-freezer-wakeups-v3-1-d49821fda04d@quicinc.com Changes in v3: - Remove #ifdeferry for saved_state in kernel/sched/core.c - Link to v2: https://lore.kernel.org/r/20230830-avoid-spurious-freezer-wakeups-v2-1-8877245cdbdc@quicinc.com Changes in v2: - Rebase to v6.5 which includes commit 1c06918788e8 ("sched: Consider task_struct::saved_state in wait_task_inactive()") This allows us to remove the special jobctl handling on thaw. - Link to v1: https://lore.kernel.org/r/20230828-avoid-spurious-freezer-wakeups-v1-1-8be8cf761472@quicinc.com --- Elliot Berman (2): sched/core: Remove ifdeffery for saved_state freezer,sched: Use saved_state to reduce some spurious wakeups include/linux/sched.h | 2 -- kernel/freezer.c | 41 +++++++++++++++++++---------------------- kernel/sched/core.c | 40 +++++++++++++++++----------------------- 3 files changed, 36 insertions(+), 47 deletions(-) --- base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c change-id: 20230817-avoid-spurious-freezer-wakeups-9f8619680b3a Best regards,