Date:   Wed, 22 Feb 2023 08:57:08 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Alistair Popple <apopple@nvidia.com>
Cc:     Tejun Heo <tj@kernel.org>, Michal Hocko <mhocko@suse.com>,
        Yosry Ahmed <yosryahmed@google.com>, linux-mm@kvack.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
        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 Wed, Feb 22, 2023 at 10:38:25PM +1100, Alistair Popple wrote:
> When a driver unpins a page we scan the pinners list and assign
> ownership to the next driver pinning the page by updating memcg_data and
> removing the vm_account from the list.

I don't see how this works with just the data structure you outlined??
Every unique page needs its own list_head in the vm_account, it is
doable just incredibly costly.

Jason