linux-kernel - Re: [PATCH 14/19] mm: Introduce a cgroup for pinned memory

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Message-ID: <Y/YRJNwwvqp7nKKt@nvidia.com>
Date:   Wed, 22 Feb 2023 08:57:08 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Alistair Popple <apopple@...dia.com>
Cc:     Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...e.com>,
        Yosry Ahmed <yosryahmed@...gle.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        jhubbard@...dia.com, tjmercier@...gle.com, hannes@...xchg.org,
        surenb@...gle.com, mkoutny@...e.com, daniel@...ll.ch,
        "Daniel P . Berrange" <berrange@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Zefan Li <lizefan.x@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 14/19] mm: Introduce a cgroup for pinned memory

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