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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZUuV9xOZ5k7Ia_V2@tiehlicka>
Date:   Wed, 8 Nov 2023 15:06:47 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Huan Yang <link@...o.com>
Cc:     Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        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>,
        Yosry Ahmed <yosryahmed@...gle.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

On Wed 08-11-23 14:58:11, Huan Yang 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.

Could you explain why? And also why do you need to swap out in that
case?
 
> 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.

Other have already touched on this in other replies but v2 doesn't have
a per-memcg swappiness

> 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)
> 
> Note that when performing unbalanced reclamation, the cgroup swappiness
> will be temporarily adjusted dynamically to the input value. Therefore,
> if the cgroup swappiness is further modified during runtime, there may
> be some errors.

In general this is a bad semantic. The operation shouldn't have side
effect that are potentially visible for another operation.
-- 
Michal Hocko
SUSE Labs