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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 C02DBC433ED for ; Mon, 26 Apr 2021 10:40:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8088661185 for ; Mon, 26 Apr 2021 10:40:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233070AbhDZKlD (ORCPT ); Mon, 26 Apr 2021 06:41:03 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:9146 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233050AbhDZKkz (ORCPT ); Mon, 26 Apr 2021 06:40:55 -0400 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 13QAXB4n032175; Mon, 26 Apr 2021 06:39:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : reply-to : references : mime-version : content-type : in-reply-to; s=pp1; bh=YV33U4MsIKsMOWjMTEzE+UkygN9rxeIPamVaxi8unD0=; b=KmnR2IQ7nBgcEKc+NQP4ZfPVNJC87CuXytLO9SWweSQIyEas/Cn3ehuLFWo5ufhSN5S0 xWpUpY8miACJDxscdqMTH1TOMV5id9rVubQa+o/BqT4QmywAWdXTKj3re2U+Ex0nJuED 8pRJc4twPSaAOyt95ATAz2OPStBulaDJJ0+q3nZx5MFckoDP906EAWb33jdPjAu3e76s iFWI+KhZ5+iVgsjgN3CcnQR6cwhqUvggDNnsiVykuS+UzHunePZYOymAKTS3etuadBNK 3Ri4r+UwyA4MSHMCeoX6WGabNnv3wTWq+Vobf3sJFO5ctknwxK2hA5nTSkNyAVfPixpw dw== Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0a-001b2d01.pphosted.com with ESMTP id 385q8aqw8e-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 26 Apr 2021 06:39:48 -0400 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.0.43/8.16.0.43) with SMTP id 13QAd6O5015852; Mon, 26 Apr 2021 10:39:46 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma06ams.nl.ibm.com with ESMTP id 384akh8r49-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 26 Apr 2021 10:39:45 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 13QAdh0Z11469284 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 26 Apr 2021 10:39:43 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ECE7C4C04E; Mon, 26 Apr 2021 10:39:42 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D1E864C062; Mon, 26 Apr 2021 10:39:40 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by d06av22.portsmouth.uk.ibm.com (Postfix) with SMTP; Mon, 26 Apr 2021 10:39:40 +0000 (GMT) Date: Mon, 26 Apr 2021 16:09:40 +0530 From: Srikar Dronamraju To: Mel Gorman Cc: Ingo Molnar , Peter Zijlstra , LKML , Rik van Riel , Thomas Gleixner , Valentin Schneider , Vincent Guittot , Dietmar Eggemann , Michael Ellerman , Gautham R Shenoy , Parth Shah Subject: Re: [PATCH 00/10] sched/fair: wake_affine improvements Message-ID: <20210426103940.GJ2633526@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20210422102326.35889-1-srikar@linux.vnet.ibm.com> <20210423082532.GA4239@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20210423082532.GA4239@techsingularity.net> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: LRMwzKHVvMJq8A6potO_V-ftjgUOr3MQ X-Proofpoint-ORIG-GUID: LRMwzKHVvMJq8A6potO_V-ftjgUOr3MQ X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-04-26_03:2021-04-26,2021-04-26 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 mlxlogscore=999 adultscore=0 mlxscore=0 phishscore=0 suspectscore=0 impostorscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104260077 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mel Gorman [2021-04-23 09:25:32]: > On Thu, Apr 22, 2021 at 03:53:16PM +0530, Srikar Dronamraju wrote: > > Recently we found that some of the benchmark numbers on Power10 were lesser > > than expected. Some analysis showed that the problem lies in the fact that > > L2-Cache on Power10 is at core level i.e only 4 threads share the L2-cache. > > > > I didn't get the chance to review this properly although I am suspicious > of tracking idle_core and updating that more frequently. It becomes a very > hot cache line that bounces. I did experiement with tracking an idle core > but the data either went stale too quickly or the updates incurred more > overhead than a reduced search saved. > This change does increase the number of times we read the idle-core. There are also more places where we try to update the idle-core. However I feel the number of times, we actually update the idle-core now will be much lesser than previous, because we are mostly doing a conditional update. i.e we are updating the idle-core only if the waking up CPU happens to be part of our core. Also if the system is mostly lightly loaded, we check for available_idle_cpu, so we may not look for an idle-core. If the system is running a CPU intensive task, then the idle-core will most likely to be -1. Its only the cases where the system utilization keeps swinging between lightly loaded to heavy load, that we would end up checking and setting idle-core. Do let me know your thoughts. -- Thanks and Regards Srikar Dronamraju