linux-kernel - Re: [PATCH v3 0/2] sched/numa: Skip VMA scanning on memory pinned

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Message-ID: <66884086-39fc-4f65-b207-08758c0756b8@oracle.com>
Date: Thu, 17 Apr 2025 14:07:00 -0700
From: Libo Chen <libo.chen@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: peterz@...radead.org, mgorman@...e.de, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org, tj@...nel.org,
        rostedt@...dmis.org, llong@...hat.com, kprateek.nayak@....com,
        raghavendra.kt@....com, yu.c.chen@...el.com, tim.c.chen@...el.com,
        vineethr@...ux.ibm.com, chris.hyser@...cle.com,
        daniel.m.jordan@...cle.com, lorenzo.stoakes@...cle.com,
        mkoutny@...e.com, Dhaval.Giani@....com, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/2] sched/numa: Skip VMA scanning on memory pinned



On 4/17/25 13:12, Andrew Morton wrote:
> On Thu, 17 Apr 2025 12:15:41 -0700 Libo Chen <libo.chen@...cle.com> wrote:
> 
>> v1->v2:
>> 1. add perf improvment numbers in commit log. Yet to find perf diff on
>> will-it-scale, so not included here. Plan to run more workloads.
>> 2. add tracepoint.
>> 3. To peterz's comment, this will make it impossible to attract tasks to
>> those memory just like other VMA skippings. This is the current
>> implementation, I think we can improve that in the future, but at the
>> moment it's probabaly better to keep it consistent.
>>
>> v2->v3:
>> 1. add enable_cpuset() based on Mel's suggestion but again I think it's
>> redundant
>> 2. print out nodemask with %*p.. format in the tracepoint
> 
> I do agree with Mel - bitmap_weight() is somewhat expensive and
> cpusets_enabled() is super fast.  So the benefit to
> cpusets_enabled()=false kernels will exceed to cost to
> cpusets_enabled()=true kernels.
> 
Ah yes, that's right. Thanks for grabbing it~

Libo

> This isn't traditionally mm.git material, but it's close.  I'll grab
> the patchset for some testing.  and shall drop it again if it turns up
> via another tree.
>