From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07F7DC33CB1 for ; Thu, 16 Jan 2020 12:05:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC78720663 for ; Thu, 16 Jan 2020 12:04:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726752AbgAPME7 (ORCPT ); Thu, 16 Jan 2020 07:04:59 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:35418 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726370AbgAPME6 (ORCPT ); Thu, 16 Jan 2020 07:04:58 -0500 Received: from pps.filterd (m0187473.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 00GBvihx023815 for ; Thu, 16 Jan 2020 07:04:57 -0500 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2xfaw2cnka-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 16 Jan 2020 07:04:56 -0500 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 16 Jan 2020 12:04:53 -0000 Received: from b06avi18878370.portsmouth.uk.ibm.com (9.149.26.194) by e06smtp02.uk.ibm.com (192.168.101.132) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 16 Jan 2020 12:04:49 -0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 00GC4mMq44827046 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Jan 2020 12:04:48 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 98BB3A405B; Thu, 16 Jan 2020 12:04:48 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 53105A405C; Thu, 16 Jan 2020 12:04:46 +0000 (GMT) Received: from localhost.localdomain (unknown [9.124.35.120]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 16 Jan 2020 12:04:46 +0000 (GMT) Subject: Re: [PATCH v2 0/3] Introduce per-task latency_tolerance for scheduler hints To: Dhaval Giani Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org, patrick.bellasi@matbug.net, valentin.schneider@arm.com, qais.yousef@arm.com, pavel@ucw.cz, qperret@qperret.net, David.Laight@ACULAB.COM, pjt@google.com, tj@kernel.org, dietmar.eggemann@arm.com, Chris Deon Hyser References: <20191208060410.17814-1-parth@linux.ibm.com> <5a13d54a-7e16-8d6c-8362-bd5f056004db@oracle.com> From: Parth Shah Date: Thu, 16 Jan 2020 17:34:45 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <5a13d54a-7e16-8d6c-8362-bd5f056004db@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20011612-0008-0000-0000-00000349E277 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20011612-0009-0000-0000-00004A6A3C08 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-01-16_03:2020-01-16,2020-01-15 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 spamscore=0 suspectscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 phishscore=0 mlxlogscore=999 bulkscore=0 mlxscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-2001160103 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dhaval, On 1/16/20 2:03 AM, Dhaval Giani wrote: > > > On 12/7/19 10:04 PM, Parth Shah wrote: >> This is the 2nd revision of the patch set to introduce latency_tolerance as >> a per task attribute. >> >> The previous version can be found at: >> v1: https://lkml.org/lkml/2019/11/25/151 >> >> Changes in this revision are: >> v1 -> v2: >> - Addressed comments from Qais Yousef >> - As per suggestion from Dietmar, moved content from newly created >> include/linux/sched/latency_tolerance.h to kernel/sched/sched.h >> - Extend sched_setattr() to support latency_tolerance in tools headers UAPI >> >> >> This patch series introduces a new per-task attribute latency_tolerance to >> provide the scheduler hints about the latency requirements of the task [1]. >> >> Latency_tolerance is a ranged attribute of a task with the value ranging >> from [-20, 19] both inclusive which makes it align with the task nice >> value. >> >> The value should provide scheduler hints about the relative latency >> requirements of tasks, meaning the task with "latency_tolerance = -20" >> should have lower latency than compared to those tasks with higher values. >> Similarly a task with "latency_tolerance = 19" can have higher latency and >> hence such tasks may not care much about latency. >> >> The default value is set to 0. The usecases discussed below can use this >> range of [-20, 19] for latency_tolerance for the specific purpose. This >> patch does not implement any use cases for such attribute so that any >> change in naming or range does not affect much to the other (future) >> patches using this. The actual use of latency_tolerance during task wakeup >> and load-balancing is yet to be coded for each of those usecases. >> >> As per my view, this defined attribute can be used in following ways for a >> some of the usecases: >> 1 Reduce search scan time for select_idle_cpu(): >> - Reduce search scans for finding idle CPU for a waking task with lower >> latency_tolerance values. >> >> 2 TurboSched: >> - Classify the tasks with higher latency_tolerance values as a small >> background task given that its historic utilization is very low, for >> which the scheduler can search for more number of cores to do task >> packing. A task with a latency_tolerance >= some_threshold (e.g, >= +18) >> and util <= 12.5% can be background tasks. >> >> 3 Optimize AVX512 based workload: >> - Bias scheduler to not put a task having (latency_tolerance == -20) on a >> core occupying AVX512 based workload. > > Have you been able to adapt any of these use cases to this new interface? > > Does the interface translate well to them? > > Do you have any code that you can share? Yes, I am able to adapt this patch set for TurboSched and proves useful for classifying low latency requiring tasks and pack those on fewer number of cores. I am able to pack the tasks having latency_tolerance==MAX_LATENCY_TOLERANCE. I will send the RFC v6 of the TurboSched soon on the lkml, which uses the latency_{nice/tolerance}. Thanks, Parth > > Dhaval >