linux-kernel - Re: [RFC 0/4] Introduce unbalance proactive reclaim

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Message-ID: <f952117e-cc7f-41b9-9571-1d32b157cc82@vivo.com>
Date:   Wed, 8 Nov 2023 17:12:19 +0800
From:   Huan Yang <link@...o.com>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Wei Xu <weixugc@...gle.com>, David Rientjes <rientjes@...gle.com>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Huang Ying <ying.huang@...el.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Peter Xu <peterx@...hat.com>,
        "Vishal Moola (Oracle)" <vishal.moola@...il.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Hugh Dickins <hughd@...gle.com>, cgroups@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, opensource.kernel@...o.com
Subject: Re: [RFC 0/4] Introduce unbalance proactive reclaim


在 2023/11/8 16:59, Yosry Ahmed 写道:
> On Wed, Nov 8, 2023 at 12:26 AM Huan Yang <link@...o.com> wrote:
>>
>> 在 2023/11/8 16:00, Yosry Ahmed 写道:
>>> +Wei Xu +David Rientjes
>>>
>>> On Tue, Nov 7, 2023 at 10:59 PM Huan Yang <link@...o.com> wrote:
>>>> In some cases, we need to selectively reclaim file pages or anonymous
>>>> pages in an unbalanced manner.
>>>>
>>>> For example, when an application is pushed to the background and frozen,
>>>> it may not be opened for a long time, and we can safely reclaim the
>>>> application's anonymous pages, but we do not want to touch the file pages.
>>>>
>>>> This patchset extends the proactive reclaim interface to achieve
>>>> unbalanced reclamation. Users can control the reclamation tendency by
>>>> inputting swappiness under the original interface. Specifically, users
>>>> can input special values to extremely reclaim specific pages.
>>> I proposed this a while back:
>>>
>>> https://lore.kernel.org/linux-mm/CAJD7tkbDpyoODveCsnaqBBMZEkDvshXJmNdbk51yKSNgD7aGdg@mail.gmail.com/
>> Well to know this, proactive reclaim single type is usefull in our
>> production too.
>>> The takeaway from the discussion was that swappiness is not the right
>>> way to do this. We can add separate arguments to specify types of
>>> memory to reclaim, as Roman suggested in that thread. I had some
>>> patches lying around to do that at some point, I can dig them up if
>>> that's helpful, but they are probably based on a very old kernel now,
>>> and before MGLRU landed. IIRC it wasn't very difficult, I think I
>>> added anon/file/shrinkers bits to struct scan_control and then plumbed
>>> them through to memory.reclaim.
>>>
>>>> Example:
>>>>           echo "1G" 200 > memory.reclaim (only reclaim anon)
>>>>             echo "1G" 0  > memory.reclaim (only reclaim file)
>>>>             echo "1G" 1  > memory.reclaim (only reclaim file)
>>> The type of interface here is nested-keyed, so if we add arguments
>>> they need to be in key=value format. Example:
>>>
>>> echo 1G swappiness=200 > memory.reclaim
>> Yes, this is better.
>>> As I mentioned above though, I don't think swappiness is the right way
>>> of doing this. Also, without swappiness, I don't think there's a v1 vs
>>> v2 dilemma here. memory.reclaim can work as-is in cgroup v1, it just
>>> needs to be exposed there.
>> Cgroupv1 can't use memory.reclaim, so, how to exposed it? Reclaim this by
>> pass memcg's ID?
> That was mainly about the idea that cgroup v2 does not have per-memcg
> swappiness, so this proposal seems to be inclined towards v1, at least
I seem current comments of mem_cgroup_swappiness it is believed that
per-memcg swappiness can be added.

But, we first need to explain that using swappiness is a very useful way.
And in the discussions of your patchset, end that not use it.
> conceptually. Either way, we need to add memory.reclaim to the v1
> files to get it to work on v1. Whether this is acceptable or not is up
> to the maintainers. I personally don't think it's a problem, it should
Yes, but, I understand that cgroup v2 is a trend, so it is 
understandable that no
new interfaces are added to v1. :)
Maybe you can promoting the use of cgroupv2 on Android?
> work as-is for v1.