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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 E62F1C10DCE for ; Fri, 6 Mar 2020 16:37:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE63A2072A for ; Fri, 6 Mar 2020 16:37:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Zkvbz5AZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726368AbgCFQhw (ORCPT ); Fri, 6 Mar 2020 11:37:52 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:54922 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726166AbgCFQhw (ORCPT ); Fri, 6 Mar 2020 11:37:52 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 026GO3jm057857; Fri, 6 Mar 2020 16:36:23 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=9ZCQRPE4NdnV5SiDVz+scsYqRIMTLEQ9Pcsn2lnmDDI=; b=Zkvbz5AZq/9hJV58lqyFWgxGe8nW2hHrkmgqgTq8AcuycF7ItnWv40QCKM2BeOVIdzik tHmpzGDGbzUKomAD01t9OIpmeMMfGyMKHoSgbjZthSX5CoE6cdE5EEXel7tqFgVxobUz TefJK2rS4mDKWxAhq0TZ9nKKkWoqoiZBOAMS0fHqQDp6HMymEFVYwgblwo/ff/bDqeMe it5vo6zeb76/zU0cJJ0qcvvGGUTrYqaVfDd/xDmGOH0WMkjrKNfehkOXX5l+00PRjmgS sY0uEnlgq9RTq2asNHXIQWTB2h3TfBUb5RLsReH+KW8+qFLnfY0TBY//t7CtUd7L4i3k ig== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by userp2130.oracle.com with ESMTP id 2ykgys2vyd-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 06 Mar 2020 16:36:23 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 026GDOLN155623; Fri, 6 Mar 2020 16:36:22 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 2yg1h655wp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 06 Mar 2020 16:36:22 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 026GaD9C014797; Fri, 6 Mar 2020 16:36:14 GMT Received: from [192.168.0.195] (/69.207.174.138) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 06 Mar 2020 08:36:13 -0800 Subject: Re: [PATCH v5 0/4] Introduce per-task latency_nice for scheduler hints To: Parth Shah , linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, qais.yousef@arm.com, pkondeti@codeaurora.org, patrick.bellasi@matbug.net, valentin.schneider@arm.com, David.Laight@ACULAB.COM, pjt@google.com, pavel@ucw.cz, tj@kernel.org, dhaval.giani@oracle.com, qperret@google.com, tim.c.chen@linux.intel.com References: <20200228090755.22829-1-parth@linux.ibm.com> From: chris hyser Message-ID: <2bf111d3-bc0a-80ef-29e4-b8487701e428@oracle.com> Date: Fri, 6 Mar 2020 11:36:10 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20200228090755.22829-1-parth@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9552 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 phishscore=0 suspectscore=0 malwarescore=0 mlxlogscore=999 mlxscore=0 spamscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003060110 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9552 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 lowpriorityscore=0 mlxscore=0 mlxlogscore=999 bulkscore=0 impostorscore=0 phishscore=0 adultscore=0 priorityscore=1501 spamscore=0 clxscore=1011 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003060110 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/28/20 4:07 AM, Parth Shah wrote: > This is the 5th revision of the patch set to introduce latency_nice as a > per task attribute. > > The previous version can be found at: > v1: https://lkml.org/lkml/2019/11/25/151 > v2: https://lkml.org/lkml/2019/12/8/10 > v3: https://lkml.org/lkml/2020/1/16/319 > v4: https://lkml.org/lkml/2020/2/24/216 > > Changes in this revision are: > v4->v5: > - Added debugging prints in /proc//sched for latency_nice ( based on > suggestion from Pavan Kondeti ) > - Initialized init_task with latency_nice = 0 > - Collected review tag and added few minor fixes. > v3->v4: > - Based on Chris's comment, added security check to refrain non-root user > set lower value than the current latency_nice values. > v2 -> v3: > - This series changes the longer attribute name to "latency_nice" as per > the comment from Dietmar Eggemann https://lkml.org/lkml/2019/12/5/394 > 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 > > > Introduction: > ============== > This patch series introduces a new per-task attribute latency_nice to > provide the scheduler hints about the latency requirements of the task [1]. > > Latency_nice 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_nice = -20" > should have lower latency requirements than compared to those tasks with > higher values. Similarly a task with "latency_nice = 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_nice 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_nice 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_nice values. > > 2 TurboSched: > - Classify the tasks with higher latency_nice 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_nice >= some_threshold (e.g, == 19) > and util <= 12.5% can be background tasks. > > 3 Optimize AVX512 based workload: > - Bias scheduler to not put a task having (latency_nice == -20) on a > core occupying AVX512 based workload. > > > Series Organization: > ==================== > - Patch 1-3: Add support for latency_nice attr in the task struct using > sched_{set,get}attr syscall > - Patch 4 : Add permission checks for setting the value. > > > The patch series can be applied on tip/sched/core at the > commit a0f03b617c3b ("sched/numa: Stop an exhastive search if a reasonable swap candidate or idle CPU is found") > > > References: > ============ > [1]. Usecases for the per-task latency-nice attribute, > https://lkml.org/lkml/2019/9/30/215 > [2]. Task Latency-nice, "Subhra Mazumdar", > https://lkml.org/lkml/2019/8/30/829 > [3]. Introduce per-task latency_tolerance for scheduler hints, > https://lkml.org/lkml/2019/12/8/10 > > > > Parth Shah (4): > sched: Introduce latency-nice as a per-task attribute > sched/core: Propagate parent task's latency requirements to the child > task > sched: Allow sched_{get,set}attr to change latency_nice of the task > sched/core: Add permission checks for setting the latency_nice value > > include/linux/sched.h | 1 + > include/uapi/linux/sched.h | 4 +++- > include/uapi/linux/sched/types.h | 19 +++++++++++++++++++ > init/init_task.c | 1 + > kernel/sched/core.c | 26 ++++++++++++++++++++++++++ > kernel/sched/debug.c | 1 + > kernel/sched/sched.h | 18 ++++++++++++++++++ > tools/include/uapi/linux/sched.h | 4 +++- > 8 files changed, 72 insertions(+), 2 deletions(-) I've now had a chance to test and play with this a fair amount. It looks good, meets the need. Thanks Parth. -chrish