linux-kernel - Re: [PATCH v2 10/16] mm: multigenerational lru: mm

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Date:   Wed, 14 Apr 2021 15:36:26 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     linux-mm@...ck.org, Alex Shi <alexs@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Benjamin Manes <ben.manes@...il.com>,
        Dave Chinner <david@...morbit.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Hillf Danton <hdanton@...a.com>, Jens Axboe <axboe@...nel.dk>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Mel Gorman <mgorman@...e.de>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Michael Larabel <michael@...haellarabel.com>,
        Michal Hocko <mhocko@...e.com>,
        Michel Lespinasse <michel@...pinasse.org>,
        Rik van Riel <riel@...riel.com>,
        Roman Gushchin <guro@...com>,
        Rong Chen <rong.a.chen@...el.com>,
        SeongJae Park <sjpark@...zon.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Yang Shi <shy828301@...il.com>,
        Ying Huang <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        linux-kernel@...r.kernel.org, lkp@...ts.01.org,
        page-reclaim@...gle.com
Subject: Re: [PATCH v2 10/16] mm: multigenerational lru: mm_struct list

On Tue, Apr 13, 2021 at 12:56:27AM -0600, Yu Zhao wrote:
> In order to scan page tables, we add an infrastructure to maintain
> either a system-wide mm_struct list or per-memcg mm_struct lists.
> Multiple threads can concurrently work on the same mm_struct list, and
> each of them will be given a different mm_struct.
> 
> This infrastructure also tracks whether an mm_struct is being used on
> any CPUs or has been used since the last time a worker looked at it.
> In other words, workers will not be given an mm_struct that belongs to
> a process that has been sleeping.

This seems like a great use for an allocating XArray.  You can use a
search mark to indicate whether it's been used since the last time a
worker looked at it.