EXT: Re: [PATCH weston 0/4] Optimize pixman renderer

[Ray, Ian (GE Healthcare)]

> On 21 May 2018, at 16.29, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> 
> Hi,
> 
> this series was originally written by me as you can see, and Fabien
> lifted the patches, reviewed, tested and submitted them. If no-one
> objects, I would like to land these on Thursday.

Reviewed-by: Ian Ray <ian.ray at ge.com>

(Nit: patch 3, typo “shadoe”.)


> 
> 
> Thanks,
> pq
> 
> 
> On Mon, 23 Apr 2018 11:44:55 +0200
> Fabien Lahoudere <fabien.lahoudere at collabora.com> wrote:
> 
>> Optimizes pixman renderer by:
>> - optimizing compositing damage in DRM/pixman
>> 
>>  Reduce Weston's CPU usage by avoiding unnecessary compositing when updating 
>>  the shadow buffer in pixman-renderer, under the DRM backend. The test was a 
>>  proprietary graphical X11 application in demo mode. The effect is a drop of
>>  total system CPU usage from 0.41 to 0.33.
>> 
>> - optimizing shadow buffer usage
>> 
>>  The shadow framebuffer is an intermediate buffer where the scene is composited
>>  and then copied from the shadow to the actual hardware buffer. This extra step
>>  costs memory bandwidth compared to compositing directly into a hardware buffer.
>> 
>>  Weston's DRM-backend with the Pixman-renderer uses a shadow framebuffer by
>>  default. Especially on systems with dedicated VRAM, read-modify-write cycles
>>  (a.k.a blending) into the scanout-capable buffer can be very slow. Also the
>>  scanout pixel format may not be optimal for compositing. Therefore Weston takes
>>  the safe default to always use a shadow framebuffer.
>> 
>>  However, in our use case, the hardware does not have dedicated VRAM behind a
>>  relatively slow bus, and the graphical load has practically no blending. We 
>>  can reduce Weston's CPU usage quite a lot by not using the shadow frambuffer.
>> 
>>  We test on proprietary graphical X11 application in demo mode. Using perf we
>>  measure that this change improve weston CPU usage by 13% with dual display and
>>  11% with clone mode.
>> 
>> Pekka Paalanen (4):
>>  pixman,drm: do not composite previous damage
>>  pixman: make shadow buffer optional
>>  compositor-drm: expose global shadow flag for pixman
>>  main: add setting for DRM/pixman shadow framebuffer
>> 
>> compositor/main.c               |  3 ++
>> libweston/compositor-drm.c      | 30 +++++++------
>> libweston/compositor-drm.h      |  3 ++
>> libweston/compositor-fbdev.c    |  3 +-
>> libweston/compositor-headless.c |  3 +-
>> libweston/compositor-rdp.c      |  5 ++-
>> libweston/compositor-wayland.c  |  3 +-
>> libweston/compositor-x11.c      |  6 ++-
>> libweston/pixman-renderer.c     | 99 ++++++++++++++++++++++++++++-------------
>> libweston/pixman-renderer.h     | 13 +++++-
>> man/weston-drm.man              |  4 ++
>> 11 files changed, 118 insertions(+), 54 deletions(-)
>> 
> 
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