Message-ID: <b74b1e28-8479-4b14-9210-5b4334d3ce22@vivo.com>
Date: Wed, 10 Sep 2025 22:14:04 +0800
From: Lei Liu <liulei.rjpt@...o.com>
To: Suren Baghdasaryan <surenb@...gle.com>,
 Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Michal Hocko <mhocko@...e.com>, David Rientjes <rientjes@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Kemeng Shi <shikemeng@...weicloud.com>, Kairui Song <kasong@...cent.com>,
 Nhat Pham <nphamcs@...il.com>, Baoquan He <bhe@...hat.com>,
 Barry Song <baohua@...nel.org>, Chris Li <chrisl@...nel.org>,
 Johannes Weiner <hannes@...xchg.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Muchun Song <muchun.song@...ux.dev>, David Hildenbrand <david@...hat.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Brendan Jackman <jackmanb@...gle.com>, Zi Yan <ziy@...dia.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Chen Yu <yu.c.chen@...el.com>, Hao Jia <jiahao1@...iang.com>,
 "Kirill A. Shutemov" <kas@...nel.org>, Usama Arif <usamaarif642@...il.com>,
 Oleg Nesterov <oleg@...hat.com>, Christian Brauner <brauner@...nel.org>,
 Mateusz Guzik <mjguzik@...il.com>, Steven Rostedt <rostedt@...dmis.org>,
 Andrii Nakryiko <andrii@...nel.org>, Al Viro <viro@...iv.linux.org.uk>,
 Fushuai Wang <wangfushuai@...du.com>,
 "open list:MEMORY MANAGEMENT - OOM KILLER" <linux-mm@...ck.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)"
 <cgroups@...r.kernel.org>
Subject: Re: [PATCH v0 0/2] mm: swap: Gather swap entries and batch async
 release


On 2025/9/10 3:48, Suren Baghdasaryan wrote:
> On Tue, Sep 9, 2025 at 12:21 PM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
>> On Tue, Sep 09, 2025 at 02:53:39PM +0800, Lei Liu wrote:
>>> 1. Problem Scenario
>>> On systems with ZRAM and swap enabled, simultaneous process exits create
>>> contention. The primary bottleneck occurs during swap entry release
>>> operations, causing exiting processes to monopolize CPU resources. This
>>> leads to scheduling delays for high-priority processes.
>>>
>>> 2. Android Use Case
>>> During camera launch, LMKD terminates background processes to free memory.
>> How does LMKD trigger the kills? SIGKILL or cgroup.kill?
> SIGKILL
>
>>> Exiting processes compete for CPU cycles, delaying the camera preview
>>> thread and causing visible stuttering - directly impacting user
>>> experience.
>> Since the exit/kill is due to low memory situation, punting the memory
>> freeing to a low priority async mechanism will help in improving user
>> experience. Most probably the application (camera preview here) will get
>> into global reclaim and will compete for CPU with the async memory
>> freeing.
>>
>> What we really need is faster memory freeing and we should explore all
>> possible ways. As others suggested fix/improve the bottleneck in the
>> memory freeing path. In addition I think we should explore parallelizing
>> this as well.
>>
>> On Android, I suppose most of the memory is associated with single or
>> small set of processes and parallelizing memory freeing would be
>> challenging. BTW is LMKD using process_mrelease() to release the killed
>> process memory?
> Yes, LMKD has a reaper thread which wakes up and calls
> process_mrelease() after the main LMKD thread issued SIGKILL.

Hi Suren

our current issue is that after lmkd kills a process,|exit_mm|takes 
considerable time. The interface you provided might help quickly free 
memory, potentially allowing us to release some memory from processes 
before lmkd kills them. This could be a good idea.

We will take your suggestion into consideration.


Thank you




>

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