From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-f72.google.com (mail-ot1-f72.google.com [209.85.210.72]) by kanga.kvack.org (Postfix) with ESMTP id 05DD76B000D for ; Wed, 3 Oct 2018 09:16:01 -0400 (EDT) Received: by mail-ot1-f72.google.com with SMTP id s68so3657426ota.11 for ; Wed, 03 Oct 2018 06:16:01 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id f12si633712oti.282.2018.10.03.06.15.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 Oct 2018 06:15:59 -0700 (PDT) Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w93DDvfn162167 for ; Wed, 3 Oct 2018 09:15:59 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0b-001b2d01.pphosted.com with ESMTP id 2mvw29v0qg-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 03 Oct 2018 09:15:59 -0400 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 3 Oct 2018 14:15:57 +0100 Date: Wed, 3 Oct 2018 18:45:49 +0530 From: Srikar Dronamraju Subject: Re: [PATCH 2/2] mm, numa: Migrate pages to local nodes quicker early in the lifetime of a task Reply-To: Srikar Dronamraju References: <20181001100525.29789-1-mgorman@techsingularity.net> <20181001100525.29789-3-mgorman@techsingularity.net> <20181002124149.GB4593@linux.vnet.ibm.com> <20181002135459.GA7003@techsingularity.net> <20181002173005.GD4593@linux.vnet.ibm.com> <20181002182248.GB7003@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20181002182248.GB7003@techsingularity.net> Message-Id: <20181003131549.GB4488@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Peter Zijlstra , Ingo Molnar , Jirka Hladky , Rik van Riel , LKML , Linux-MM > > if we want to prioritize STREAM like workloads (i.e private faults) one simpler > > fix could be to change the quadtraic equation > > > > from: > > if (!cpupid_pid_unset(last_cpupid) && > > cpupid_to_nid(last_cpupid) != dst_nid) > > return false; > > to: > > if (!cpupid_pid_unset(last_cpupid) && > > cpupid_to_nid(last_cpupid) == dst_nid) > > return true; > > > > i.e to say if the group tasks likely consolidated to a node or the task was > > moved to a different node but access were private, just move the memory. > > > > The drawback though is we keep pulling memory everytime the task moves > > across nodes. (which is probably restricted for long running tasks to some > > extent by your fix) > > > > This has way more consequences as it changes the behaviour for the entire > lifetime of the workload. It could cause excessive migrations in the case > where a machine is almost fully utilised and getting load balanced or in > cases where tasks are pulled frequently cross-node (e.g. worker thread > model or a pipelined computation). > > I'm only looking to address the case where the load balancer spreads a > workload early and the memory should move to the new node quickly. If it > turns out there are cases where that decision is wrong, it gets remedied > quickly but if your proposal is ever wrong, the system doesn't recover. > Agree. -- Thanks and Regards Srikar Dronamraju