linux-kernel - Re: [PATCH v4 2/2] Documentation/gpu: Add fdinfo meanings of drm-*-internal memory tags

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Message-ID: <Z2A4RjVe8gPWpRua@e110455-lin.cambridge.arm.com>
Date: Mon, 16 Dec 2024 14:25:10 +0000
From: Liviu Dudau <liviu.dudau@....com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Boris Brezillon <boris.brezillon@...labora.com>,
	Steven Price <steven.price@....com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	kernel@...labora.com, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] Documentation/gpu: Add fdinfo meanings of
 drm-*-internal memory tags

On Wed, Dec 11, 2024 at 04:34:32PM +0000, Adrián Larumbe wrote:
> A previous commit enabled display of driver-internal kernel BO sizes
> through the device file's fdinfo interface.
> 
> Expand the description of the relevant driver-specific key:value pairs
> with the definitions of the new drm-*-internal ones.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
> ---
>  Documentation/gpu/panthor.rst | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/Documentation/gpu/panthor.rst b/Documentation/gpu/panthor.rst
> index 3f8979fa2b86..c6d8236e3665 100644
> --- a/Documentation/gpu/panthor.rst
> +++ b/Documentation/gpu/panthor.rst
> @@ -26,6 +26,10 @@ the currently possible format options:
>       drm-cycles-panthor:     94439687187
>       drm-maxfreq-panthor:    1000000000 Hz
>       drm-curfreq-panthor:    1000000000 Hz
> +     drm-total-internal:     10396 KiB
> +     drm-shared-internal:    0
> +     drm-active-internal:    10396 KiB
> +     drm-resident-internal:  10396 KiB
>       drm-total-memory:       16480 KiB
>       drm-shared-memory:      0
>       drm-active-memory:      16200 KiB
> @@ -44,3 +48,13 @@ driver by writing into the appropriate sysfs node::
>  
>  Where `N` is a bit mask where cycle and timestamp sampling are respectively
>  enabled by the first and second bits.
> +
> +Possible `drm-*-internal` key names are: `total`, `active` and `resident`.

I think Mihail's comment stands. There is no harm in being thorough, so either
we list `shared` as a possible key name, or we remove it from the example and
re-introduce it later with a patch.

> +These values convey the sizes of the internal driver-owned shmem BO's that
> +aren't exposed to user-space through a DRM handle, like queue ring buffers,
> +sync object arrays and heap chunks. Because they are all allocated and pinned
> +at creation time, `drm-resident-internal` and `drm-total-internal` should always
> +be equal. `drm-active-internal` shows the size of kernel BO's associated with
> +VM's and groups currently being scheduled for execution by the GPU.
> +`drm-shared-memory` is unused at present, but in the future it might stand for
> +the size of the Firmware regions, since they do not belong to an open file context.

But there are firmware regions that are per context, like the save/restore buffers.
Also, I think we are creating confusion there between drm-shared-memory and
drm-shared-internal. I'm fine with having a note here regarding `drm-shared-memory`
as long as `drm-shared-internal` also gets a note to explain the difference with its
cousin.

Best regards,
Liviu

> -- 
> 2.47.0
> 

-- 
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