linux-kernel - Re: [PATCH] media: mediatek: vcodec: Reduce msg queue trans buffer size

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Message-ID: <CAC=S1njnqrdrQqJZYQ7mffgmAUUxtoO7utZumED0dmX=Fa9+Qw@mail.gmail.com>
Date: Fri, 7 Jun 2024 19:20:04 +0800
From: Fei Shao <fshao@...omium.org>
To: Nicolas Dufresne <nicolas.dufresne@...labora.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Hans Verkuil <hverkuil-cisco@...all.nl>, Yunfei Dong <yunfei.dong@...iatek.com>, 
	Andrew-CT Chen <andrew-ct.chen@...iatek.com>, Dan Carpenter <dan.carpenter@...aro.org>, 
	Matthias Brugger <matthias.bgg@...il.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Tiffany Lin <tiffany.lin@...iatek.com>, Xiaoyong Lu <xiaoyong.lu@...iatek.com>, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-media@...r.kernel.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] media: mediatek: vcodec: Reduce msg queue trans buffer size

On Fri, May 31, 2024 at 8:47 PM Nicolas Dufresne
<nicolas.dufresne@...labora.com> wrote:
>
> Le mardi 21 mai 2024 à 17:54 +0800, Fei Shao a écrit :
> > In the MediaTek HW vcodec pipeline, the `trans` buffer is used to
> > transfer the data decoded by the lat decoder to the core decoder.
> >
> > In the beginning, 6MB and 30MB were allocated for the trans buffer to
> > handle FHD and higher-resolution contents respectively, but it turns out
> > that's more than enough in practice and there's room for improvement.
> >
> > The buffer sizes were reduced to 5MB / 8MB respectively and the decoders
> > have been validated to work normally on the MediaTek Android products.
> > It's time to adopt that change in the upstream MediaTek vcodec driver.
> >
> > Reduce the msg queue trans buffer size to 5MB / 8MB respectively to
> > optimize the memory usage per decoder instance and improve the overall
> > system performance.
>
> I don't disagree with the change, but it feels like this is has hack over a
> hack. We have an entropy decoder (LAT) metadata buffer, which of course is
> resolution dependent, for which we hardcore two sizes.
>
> Any chance Mediatek can document this blob, or at least document the proper
> relation between the size and the resolution ? This way we could dynamically
> size the buffer for the chosen resolution and trust it to remain big enough for
> a long time. Removing the non scientific claim of "have been validated", which
> is producible for anyone hitting issue with that change in the future.
>
> Nicolas
>

Sorry for the delayed reply. I totally agree with your point, but last
time I was told these are what they are using internally so I guess
it's not there... or it could be me that didn't ask the right question
(we want to do this with finer granularity or dynamically).
If we don't get an answer here, I can also bring this up to MediaTek
next time and see if they can provide more details.

Regards,
Fei