linux-kernel - Re: [RFC][PATCH v6 3/7] drm: ttm_pool: Rework ttm_pool_free_page to allow us to use it as a function pointer

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Date:   Tue, 9 Feb 2021 09:39:33 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Christian König <christian.koenig@....com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Chris Goldsworthy <cgoldswo@...eaurora.org>,
        Laura Abbott <labbott@...nel.org>,
        Brian Starkey <Brian.Starkey@....com>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Daniel Mentz <danielmentz@...gle.com>,
        Ørjan Eide <orjan.eide@....com>,
        Robin Murphy <robin.murphy@....com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Simon Ser <contact@...rsion.fr>,
        James Jones <jajones@...dia.com>,
        linux-media <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [RFC][PATCH v6 3/7] drm: ttm_pool: Rework ttm_pool_free_page to
 allow us to use it as a function pointer

On Tue, Feb 9, 2021 at 4:14 AM Christian König <christian.koenig@....com> wrote:
> Am 05.02.21 um 20:47 schrieb John Stultz:
> > On Fri, Feb 5, 2021 at 12:28 AM Christian König
> > <christian.koenig@....com> wrote:
> >> Adding this to all pages would increase the memory footprint drastically.
> > Yea, that's a good point!  Hrm... bummer. I'll have to see if there's
> > some other way I can get the needed context for the free from the
> > generic page-pool side.
>
> What exactly is the problem here?

Me, usually. :)

> As far as I can see we just have the
> lru entry (list_head) and the pool.

Yea, I reworked it to an embedded drm_page_pool struct, but that is
mostly a list_head.

> How the lru is cast to the page can be completely pool implementation
> specific.

Yea, I had it do container_of(), just haven't gotten around to sending
it out yet.

Thanks so much for the feedback and ideas!

thanks
-john