linux-kernel - Re: [PATCH v3 0/7] Support fdinfo runtime and memory stats on Panthor

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Date: Thu, 13 Jun 2024 16:28:08 +0100
From: Steven Price <steven.price@....com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>,
 Boris Brezillon <boris.brezillon@...labora.com>,
 Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/7] Support fdinfo runtime and memory stats on Panthor

On 06/06/2024 01:49, Adrián Larumbe wrote:
> This patch series enables userspace utilities like gputop and nvtop to
> query a render context's fdinfo file and figure out rates of engine
> and memory utilisation.
> 
> Previous discussion can be found at
> https://lore.kernel.org/dri-devel/20240423213240.91412-1-adrian.larumbe@collabora.com/
> 
> Changelog:
> v3:
>  - Fixed some nits and removed useless bounds check in panthor_sched.c
>  - Added support for sysfs profiling knob and optional job accounting
>  - Added new patches for calculating size of internal BO's
> v2:
>  - Split original first patch in two, one for FW CS cycle and timestamp
>  calculations and job accounting memory management, and a second one
>  that enables fdinfo.
>  - Moved NUM_INSTRS_PER_SLOT to the file prelude
>  - Removed nelem variable from the group's struct definition.
>  - Precompute size of group's syncobj BO to avoid code duplication.
>  - Some minor nits.
> 
> 
> Adrián Larumbe (7):
>   drm/panthor: introduce job cycle and timestamp accounting
>   drm/panthor: add DRM fdinfo support
>   drm/panthor: enable fdinfo for memory stats
>   drm/panthor: add sysfs knob for enabling job profiling
>   drm/panthor: support job accounting
>   drm/drm_file: add display of driver's internal memory size
>   drm/panthor: register size of internal objects through fdinfo

The general shape of what you end up with looks correct, but these
patches are now in a bit of a mess. It's confusing to review when the
accounting is added unconditionally and then a sysfs knob is added which
changes it all to be conditional. Equally that last patch (register size
of internal objects through fdinfo) includes a massive amount of churn
moving everything into an 'fdinfo' struct which really should be in a
separate patch.

Ideally this needs to be reworked into a logical series of patches with
knowledge of what's coming next. E.g. the first patch could introduce
the code for cycle/timestamp accounting but leave it disabled to be then
enabled by the sysfs knob patch.

One thing I did notice though is that I wasn't seeing the GPU frequency
change, looking more closely at this it seems like there's something
dodgy going on with the devfreq code. From what I can make out I often
end up in a situation where all contexts are idle every time tick_work()
is called - I think this is simply because tick_work() is scheduled with
a delay and by the time the delay has hit the work is complete. Nothing
to do with this series, but something that needs looking into. I'm on
holiday for a week but I'll try to look at this when I'm back.

Steve

>  Documentation/gpu/drm-usage-stats.rst     |   4 +
>  drivers/gpu/drm/drm_file.c                |   9 +-
>  drivers/gpu/drm/msm/msm_drv.c             |   2 +-
>  drivers/gpu/drm/panfrost/panfrost_drv.c   |   2 +-
>  drivers/gpu/drm/panthor/panthor_devfreq.c |  10 +
>  drivers/gpu/drm/panthor/panthor_device.c  |   2 +
>  drivers/gpu/drm/panthor/panthor_device.h  |  21 ++
>  drivers/gpu/drm/panthor/panthor_drv.c     |  83 +++++-
>  drivers/gpu/drm/panthor/panthor_fw.c      |  16 +-
>  drivers/gpu/drm/panthor/panthor_fw.h      |   5 +-
>  drivers/gpu/drm/panthor/panthor_gem.c     |  67 ++++-
>  drivers/gpu/drm/panthor/panthor_gem.h     |  16 +-
>  drivers/gpu/drm/panthor/panthor_heap.c    |  23 +-
>  drivers/gpu/drm/panthor/panthor_heap.h    |   6 +-
>  drivers/gpu/drm/panthor/panthor_mmu.c     |   8 +-
>  drivers/gpu/drm/panthor/panthor_mmu.h     |   3 +-
>  drivers/gpu/drm/panthor/panthor_sched.c   | 304 +++++++++++++++++++---
>  include/drm/drm_file.h                    |   7 +-
>  18 files changed, 522 insertions(+), 66 deletions(-)
> 
> 
> base-commit: 310ec03841a36e3f45fb528f0dfdfe5b9e84b037