linux-kernel - Re: [PATCH v1 09/14] mm: multigenerational lru: mm

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Message-ID: <87pmzzsvfb.fsf@yhuang6-desk1.ccr.corp.intel.com>
Date:   Tue, 16 Mar 2021 10:07:36 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Rik van Riel <riel@...riel.com>
Cc:     Yu Zhao <yuzhao@...gle.com>, <linux-mm@...ck.org>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Hillf Danton <hdanton@...a.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.com>,
        Roman Gushchin <guro@...com>, Vlastimil Babka <vbabka@...e.cz>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Yang Shi <shy828301@...il.com>, <linux-kernel@...r.kernel.org>,
        <page-reclaim@...gle.com>
Subject: Re: [PATCH v1 09/14] mm: multigenerational lru: mm_struct list

Rik van Riel <riel@...riel.com> writes:

> On Sat, 2021-03-13 at 00:57 -0700, Yu Zhao wrote:
>
>> +/*
>> + * After pages are faulted in, they become the youngest generation.
>> They must
>> + * go through aging process twice before they can be evicted. After
>> first scan,
>> + * their accessed bit set during initial faults are cleared and they
>> become the
>> + * second youngest generation. And second scan makes sure they
>> haven't been used
>> + * since the first.
>> + */
>
> I have to wonder if the reductions in OOM kills and 
> low-memory tab discards is due to this aging policy
> change, rather than from the switch to virtual scanning.

If my understanding were correct, the temperature of the processes is
considered in addition to that of the individual pages.  That is, the
pages of the processes that haven't been scheduled after the previous
scanning will not be scanned.  I guess that this helps OOM kills?

If so, how about just take advantage of that information for OOM killing
and page reclaiming?  For example, if a process hasn't been scheduled
for long time, just reclaim its private pages.

Best Regards,
Huang, Ying