linux-kernel - Re: [PATCH] mm:vmscan: shrink skip folios in the exiting task

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Date: Thu, 25 Jan 2024 09:34:53 +0800
From: zhiguojiang <justinjiang@...o.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, opensource.kernel@...o.com
Subject: Re: [PATCH] mm:vmscan: shrink skip folios in the exiting task

在 2024/1/24 21:20, Matthew Wilcox 写道:
> On Wed, Jan 24, 2024 at 08:43:07PM +0800, Zhiguo Jiang wrote:
>> If the shrinking folio is belong to the exiting task, this folio should
>> be freed in the task exit flow rather than being reclaimed in the shrink
>> flow, because the former takes less time.
>>
>> If the folio which is belong to the exiting task is reclaimed in the
>> shrink flow, such as the anon folio, the anon folio needs to be first
>> written to the swap partition by swap-in in shrink flow, and then the
>> corresponding swap folio needs to be released in the task exiting flow.
>> As is well known, releasing a swap folio will task more time than
>> releasing directly an anon folio.
>>
>> In the scenarios of the low memory system and mutil backed-applications,
>> the time-consuming problem caused by shrinking the exiting task's folios
>> will be more severe.
> What testing have you done of this patch?  How often does it happen?
> Are there particular workloads that benefit from this?  (I'm not sure
> what "mutil backed-applications" are?)
1 Yes, this patch has been tested.

2 When the exiting tasks and shrink_inactive_list occur at the same time,
    the folios which shrink_inactive_list reclaims may be the exiting 
tasks's folios
    in lruvecs. And when system is low memory, it more likely to occur, 
because
    more backend applidatuions will be killed.
    The shrink_inactive_list reclaims the exiting tasks's folios in 
lruvecs and
    transforms the exiting tasks's anon folios into swap memory, which leads
    to the increasing load of the current exiting tasks.

3 This patch can alleviate the load of the tasks exiting process. This patch
    can make that the exiting tasks release its anon folios faster 
instead of
    releasing its swap memory from its anon folios swap-in in 
shrink_inactive_list.

4 "mutil backed-applications" means that there are a large number of
     the backend applications in the system.

Thanks
>
> And I do mean specifically of this patch, because to my eyes it
> shouldn't even compile.
Has been tested.