Sender: Tejun Heo <htejun@gmail.com>
Date:   Mon, 6 Feb 2023 11:14:30 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Alistair Popple <apopple@nvidia.com>
Cc:     linux-mm@kvack.org, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, jgg@nvidia.com, jhubbard@nvidia.com,
        tjmercier@google.com, hannes@cmpxchg.org, surenb@google.com,
        mkoutny@suse.com, daniel@ffwll.ch,
        "Daniel P . Berrange" <berrange@redhat.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Zefan Li <lizefan.x@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 14/19] mm: Introduce a cgroup for pinned memory
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On Mon, Feb 06, 2023 at 06:47:51PM +1100, Alistair Popple wrote:
> If too much memory in a system is pinned or locked it can lead to
> problems such as performance degradation or in the worst case
> out-of-memory errors as such memory cannot be moved or paged out.
> 
> In order to prevent users without CAP_IPC_LOCK from causing these
> issues the amount of memory that can be pinned is typically limited by
> RLIMIT_MEMLOCK. However this is inflexible as limits can't be shared
> between tasks and the enforcement of these limits is inconsistent
> between in-kernel users of pinned memory such as mlock() and device
> drivers which may also pin pages with pin_user_pages().
> 
> To allow for a single limit to be set introduce a cgroup controller
> which can be used to limit the number of pages being pinned by all
> tasks in the cgroup.

As I wrote before, I think this might fit better as a part of memcg than as
its own controller.

Thanks.

-- 
tejun