[Intel-gfx] [PATCH v7 0/3] Dynamic EU configuration of Slice/Sub-slice/EU

[Tvrtko Ursulin]

Hi,

On 13/03/2020 11:12, srinivasan.s at intel.com wrote:
> From: Srinivasan S <srinivasan.s at intel.com>
> 
>        drm/i915: Context aware user agnostic EU/Slice/Sub-slice control within kernel
> 
> This patch sets improves GPU power consumption on Linux kernel based OS such as
> Chromium OS, Ubuntu, etc. Following are the power savings.
> 
> Power savings on GLK-GT1 Bobba platform running on Chrome OS.
> -----------------------------------------------|
> App /KPI                | % Power Benefit (mW) |
> ------------------------|----------------------|
> Hangout Call- 20 minute |	1.8%           |
> Youtube 4K VPB          |       14.13%         |
> WebGL Aquarium          |       13.76%         |
> Unity3D                 |       6.78%          |
> 			|		       |
> ------------------------|----------------------|
> Chrome PLT              | BatteryLife Improves |
> 			| by ~45 minute        |
> -----------------------------------------------|
> 
> Power savings on KBL-GT3 running on  Android and Ubuntu (Linux).
> -----------------------------------------------|
> App /KPI		| % Power Benefit (mW) |
>                          |----------------------|
> 			|  Android |  Ubuntu   |
> ------------------------|----------|-----------|
> 3D Mark (Ice storm)     | 2.30%    | N.A.      |
> TRex On screen          | 2.49%    | 2.97%     |
> Manhattan On screen     | 3.11%    | 4.90%     |
> Carchase On Screen	| N.A.     | 5.06%     |
> AnTuTu 6.1.4            | 3.42%    | N.A.      |
> SynMark2		| N.A.     | 1.7%      |
> -----------------------------------------------|

Have a look at the result Francisco obtained on Icelake with a different 
approach: https://patchwork.freedesktop.org/series/74540/

Not all benchmarks overlap but if you are set up to easily test his 
patches it may be for a mutual benefit.

Regards,

Tvrtko

> We have also observed GPU core residencies improves by 1.035%.
> 
> Technical Insights of the patch:
> Current GPU configuration code for i915 does not allow us to change
> EU/Slice/Sub-slice configuration dynamically. Its done only once while context
> is created.
> 
> While particular graphics application is running, if we examine the command
> requests from user space, we observe that command density is not consistent.
> It means there is scope to change the graphics configuration dynamically even
> while context is running actively. This patch series proposes the solution to
> find the active pending load for all active context at given time and based on
> that, dynamically perform graphics configuration for each context.
> 
> We use a hr (high resolution) timer with i915 driver in kernel to get a
> callback every few milliseconds (this timer value can be configured through
> debugfs, default is '0' indicating timer is in disabled state i.e. original
> system without any intervention).In the timer callback, we examine pending
> commands for a context in the queue, essentially, we intercept them before
> they are executed by GPU and we update context with required number of EUs.
> 
> Two questions, how did we arrive at right timer value? and what's the right
> number of EUs? For the prior one, empirical data to achieve best performance
> in least power was considered. For the later one, we roughly categorized number
> of EUs logically based on platform. Now we compare number of pending commands
> with a particular threshold and then set number of EUs accordingly with update
> context. That threshold is also based on experiments & findings. If GPU is able
> to catch up with CPU, typically there are no pending commands, the EU config
> would remain unchanged there. In case there are more pending commands we
> reprogram context with higher number of EUs. Please note, here we are changing
> EUs even while context is running by examining pending commands every 'x'
> milliseconds.
> 
> Srinivasan S (3):
>    drm/i915: Get active pending request for given context
>    drm/i915: set optimum eu/slice/sub-slice configuration based on load
>      type
>    drm/i915: Predictive governor to control slice/subslice/eu
> 
>   drivers/gpu/drm/i915/Makefile                     |   1 +
>   drivers/gpu/drm/i915/gem/i915_gem_context.c       |  20 +++++
>   drivers/gpu/drm/i915/gem/i915_gem_context.h       |   2 +
>   drivers/gpu/drm/i915/gem/i915_gem_context_types.h |  38 ++++++++
>   drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c    |   1 +
>   drivers/gpu/drm/i915/gt/intel_deu.c               | 104 ++++++++++++++++++++++
>   drivers/gpu/drm/i915/gt/intel_deu.h               |  31 +++++++
>   drivers/gpu/drm/i915/gt/intel_lrc.c               |  44 ++++++++-
>   drivers/gpu/drm/i915/i915_drv.h                   |   6 ++
>   drivers/gpu/drm/i915/i915_gem.c                   |   4 +
>   drivers/gpu/drm/i915/i915_params.c                |   4 +
>   drivers/gpu/drm/i915/i915_params.h                |   1 +
>   drivers/gpu/drm/i915/intel_device_info.c          |  74 ++++++++++++++-
>   13 files changed, 325 insertions(+), 5 deletions(-)
>   create mode 100644 drivers/gpu/drm/i915/gt/intel_deu.c
>   create mode 100644 drivers/gpu/drm/i915/gt/intel_deu.h
>