[Mesa-dev] [PATCH 2/2] radeonsi: drop few partial flushes when uploading bindless descriptors

[Nicolai Hähnle]

On 03.07.2017 18:03, Nicolai Hähnle wrote:
> On 29.06.2017 21:59, Samuel Pitoiset wrote:
>> Only emit partial flushes when the underlying shader stages
>> are using bindless samplers or images.
>>
>> This gets rid of 4% of partial flushes in the DOW3 benchmark.
> 
> Do those flushes still trigger during play?
> 
> I'd think it should be possible to eliminate these partial flushes 
> entirely. The logic is that you only ever need the wait in the first 
> place when you're overriding a previously used descriptor.
> 
> So what you could do is add a counter (per context, I think?) which is 
> incremented whenever a flush happens, and then release descriptors 
> lazily based on that.
> 
> Alternatively (maybe easier, not sure): all shaders are guaranteed to 
> have finished when the fence of a submit fires, so use that as the guard 
> for lazily releasing descriptors.

Looking at the other patch, it seems the flushes are triggered for 
descriptor changes for buffer invalidations? In that case, forget what I 
wrote.

Cheers,
Nicolai


> 
> Anyway, this patch is a nice first step.
> 
> Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
> 
> 
>> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>> ---
>>   src/gallium/drivers/radeonsi/si_descriptors.c | 18 ++++++++++++++++--
>>   1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeonsi/si_descriptors.c 
>> b/src/gallium/drivers/radeonsi/si_descriptors.c
>> index 88f7dcee959..7d8b3670887 100644
>> --- a/src/gallium/drivers/radeonsi/si_descriptors.c
>> +++ b/src/gallium/drivers/radeonsi/si_descriptors.c
>> @@ -1934,14 +1934,28 @@ static void 
>> si_upload_bindless_descriptor(struct si_context *sctx,
>>   static void si_upload_bindless_descriptors(struct si_context *sctx)
>>   {
>> +    unsigned shader_uses_bindless_mask;
>> +
>>       if (!sctx->bindless_descriptors_dirty)
>>           return;
>>       /* Wait for graphics/compute to be idle before updating the 
>> resident
>>        * descriptors directly in memory, in case the GPU is using them.
>>        */
>> -    sctx->b.flags |= SI_CONTEXT_PS_PARTIAL_FLUSH |
>> -             SI_CONTEXT_CS_PARTIAL_FLUSH;
>> +    sctx->b.flags |= SI_CONTEXT_CS_PARTIAL_FLUSH;
>> +
>> +    /* To avoid unnecessary partial flushes, check which shader 
>> stages are
>> +     * using bindless samplers or images.
>> +     */
>> +    shader_uses_bindless_mask = 
>> sctx->shader_uses_bindless_samplers_mask |
>> +                    sctx->shader_uses_bindless_images_mask;
>> +
>> +    if (shader_uses_bindless_mask & (1 << PIPE_SHADER_FRAGMENT)) {
>> +        sctx->b.flags |= SI_CONTEXT_PS_PARTIAL_FLUSH;
>> +    } else if (shader_uses_bindless_mask) {
>> +        sctx->b.flags |= SI_CONTEXT_VS_PARTIAL_FLUSH;
>> +    }
>> +
>>       si_emit_cache_flush(sctx);
>>       util_dynarray_foreach(&sctx->resident_tex_handles,
>>
> 
> 


-- 
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Aber vergiss niemals, wie sie sein sollte.