Re: drm/i915/bdw: Enable resource streamer on Broadwell

[Abdiel Janulgue <abdiel.janulgue@linux.intel.com>]

On 11.06.2014 11:10, Jesse Barnes wrote:
> On Tue,  6 May 2014 22:25:04 +0300
> Abdiel Janulgue <abdiel.janulgue@linux.intel.com> wrote:
>
>> From: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
>>
>> This is a re-spin of my resource streamer patchset from October
>> adapted to enable the feature on Broadwell instead.
>>
>> The resource streamer is a hw-feature that helps in reducing commands
>> being submitted by the CPU. Haswell initially has this feature.
>> Unfortunately, HSW seems to have problems switching between non-RS
>> and RS-enabled commands[1]. On BDW however it works seamlessly
>> as expected.
>>
>> The i-g-t test comes next on a separate patch-series.
>>
>> --
>> [1] http://lists.freedesktop.org/archives/intel-gfx/2014-May/044577.html
>>
>> Abdiel Janulgue (2):
>>        drm/i915/bdw: Enable resource streamer bits on MI_BATCH_BUFFER_START
>>        drm/i915/bdw: Expose I915_EXEC_RESOURCE_STREAMER flag
>>
>>   drivers/gpu/drm/i915/i915_gem_execbuffer.c |    8 ++++++++
>>   drivers/gpu/drm/i915/i915_reg.h            |    1 +
>>   drivers/gpu/drm/i915/intel_ringbuffer.c    |    3 ++-
>>   drivers/gpu/drm/i915/intel_ringbuffer.h    |    1 +
>>   include/uapi/drm/i915_drm.h                |    7 ++++++-
>>   5 files changed, 18 insertions(+), 2 deletions(-)
> These seem trivial enough... have you seen cases where you'd like to
> enable it in Mesa?  If so, it probably makes sense to merge this patch
> so you can do your tuning and enabling on the Mesa side...

I've had some Mesa patches since last year. Unfortunately, the changes 
didn't
give any dramatic performance improvements. On the other hand, I admit: 
1. I've
only run it against GLBenchmark and Unigine benchmarks. Discussion with 
Portland
folks seem to suggest that we need to have a comprehensive run with more
benchmarks. 2. I only did the benchmarks in Haswell. Would be nice to see
how it does on Broadwell.

I agree though that further tuning of the performance needs to be done on
the Mesa side.