[Mesa-dev] [PATCH 1/2] i965: Massively simplify the intel_upload implementation.

[Eric Anholt]

Kenneth Graunke <kenneth at whitecape.org> writes:

> On 03/25/2014 11:27 AM, Eric Anholt wrote:
>> The implementation kept a page-sized area for uploading data, and
>> uploaded chunks from that to a 64kb-sized streamed buffer.  This wasted
>> cache footprint (and extra state tracking to do so) when we want to just
>> write our data into the buffer immediately.
>> 
>> Instead, build it around an interface like brw_state_batch() that just
>> gets you a pointer to BO memory to upload your stuff immediately.
>> 
>> Improves OpenArena on HSW by 1.62209% +/- 0.355299% (n=61) and on BYT by
>> 1.7916% +/- 0.415743% (n=31).
>> 
>> v2: Rebase on Mesa master, drop old prototypes.  Re-do performance
>>     comparison on a kernel that doesn't punish CPU efficiency
>>     improvements.
>> ---
>>  src/mesa/drivers/dri/i965/brw_context.h          |   5 +-
>>  src/mesa/drivers/dri/i965/brw_draw_upload.c      |  10 +-
>>  src/mesa/drivers/dri/i965/intel_buffer_objects.h |  21 +--
>>  src/mesa/drivers/dri/i965/intel_upload.c         | 167 +++++++++--------------
>>  4 files changed, 77 insertions(+), 126 deletions(-)
>> 
>> diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
>> index 04af5d0..e119682 100644
>> --- a/src/mesa/drivers/dri/i965/brw_context.h
>> +++ b/src/mesa/drivers/dri/i965/brw_context.h
>> @@ -1041,10 +1041,7 @@ struct brw_context
>>  
>>     struct {
>>        drm_intel_bo *bo;
>> -      GLuint offset;
>> -      uint32_t buffer_len;
>> -      uint32_t buffer_offset;
>> -      char buffer[4096];
>> +      uint32_t next_offset;
>>     } upload;
>>  
>>     /**
>> diff --git a/src/mesa/drivers/dri/i965/brw_draw_upload.c b/src/mesa/drivers/dri/i965/brw_draw_upload.c
>> index e261163..a579025 100644
>> --- a/src/mesa/drivers/dri/i965/brw_draw_upload.c
>> +++ b/src/mesa/drivers/dri/i965/brw_draw_upload.c
>> @@ -381,21 +381,17 @@ copy_array_to_vbo_array(struct brw_context *brw,
>>     const unsigned char *src = element->glarray->Ptr + min * src_stride;
>>     int count = max - min + 1;
>>     GLuint size = count * dst_stride;
>> +   uint8_t *dst = intel_upload_space(brw, size, dst_stride,
>> +                                     &buffer->bo, &buffer->offset);
>>  
>
> It sure seems like these references will exist across batchbuffers,
> meaning we may hold on to the upload buffer containing our vertex data
> until we do copy_array_to_vbo_array on it again.  That seems
> unfortunate.  (Or, maybe I'm wrong?)

copy_array_to_vbo_array() happens per draw call, so it won't persist
across batchbuffers.
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