[Mesa-dev] [PATCH 17/20] radeonsi: do not do two full flushes on every compute dispatch

[Bas Nieuwenhuizen]

On Tue, Apr 5, 2016 at 1:18 AM, Marek Olšák <maraeo at gmail.com> wrote:
> On Sat, Apr 2, 2016 at 3:11 PM, Bas Nieuwenhuizen
> <bas at basnieuwenhuizen.nl> wrote:
>> Signed-off-by: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
>> ---
>>  src/gallium/drivers/radeonsi/si_compute.c | 17 ++---------------
>>  src/gallium/drivers/radeonsi/si_state.c   |  6 ++++--
>>  2 files changed, 6 insertions(+), 17 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeonsi/si_compute.c b/src/gallium/drivers/radeonsi/si_compute.c
>> index 6549396..8fe4fe7 100644
>> --- a/src/gallium/drivers/radeonsi/si_compute.c
>> +++ b/src/gallium/drivers/radeonsi/si_compute.c
>> @@ -433,13 +433,8 @@ static void si_launch_grid(
>>         if (!sctx->cs_shader_state.initialized)
>>                 si_initialize_compute(sctx);
>>
>> -       sctx->b.flags |= SI_CONTEXT_INV_VMEM_L1 |
>> -                        SI_CONTEXT_INV_GLOBAL_L2 |
>> -                        SI_CONTEXT_INV_ICACHE |
>> -                        SI_CONTEXT_INV_SMEM_L1 |
>> -                        SI_CONTEXT_FLUSH_WITH_INV_L2 |
>> -                        SI_CONTEXT_FLAG_COMPUTE;
>> -       si_emit_cache_flush(sctx, NULL);
>> +       if(sctx->b.flags)
>
> "if (" please
>
>> +               si_emit_cache_flush(sctx, NULL);
>>
>>         if (!si_switch_compute_shader(sctx, program, &program->shader, info->pc))
>>                 return;
>> @@ -466,14 +461,6 @@ static void si_launch_grid(
>>                 si_setup_tgsi_grid(sctx, info);
>>
>>         si_emit_dispatch_packets(sctx, info);
>> -
>> -       sctx->b.flags |= SI_CONTEXT_CS_PARTIAL_FLUSH |
>> -                        SI_CONTEXT_INV_VMEM_L1 |
>> -                        SI_CONTEXT_INV_GLOBAL_L2 |
>> -                        SI_CONTEXT_INV_ICACHE |
>> -                        SI_CONTEXT_INV_SMEM_L1 |
>> -                        SI_CONTEXT_FLAG_COMPUTE;
>> -       si_emit_cache_flush(sctx, NULL);
>>  }
>>
>>
>> diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
>> index 10d691a..95d2589 100644
>> --- a/src/gallium/drivers/radeonsi/si_state.c
>> +++ b/src/gallium/drivers/radeonsi/si_state.c
>> @@ -3533,7 +3533,8 @@ static void si_memory_barrier(struct pipe_context *ctx, unsigned flags)
>>
>>         /* Subsequent commands must wait for all shader invocations to
>>          * complete. */
>> -       sctx->b.flags |= SI_CONTEXT_PS_PARTIAL_FLUSH;
>> +       sctx->b.flags |= SI_CONTEXT_PS_PARTIAL_FLUSH |
>> +                        SI_CONTEXT_CS_PARTIAL_FLUSH;
>>
>>         if (flags & PIPE_BARRIER_CONSTANT_BUFFER)
>>                 sctx->b.flags |= SI_CONTEXT_INV_SMEM_L1 |
>> @@ -3543,7 +3544,8 @@ static void si_memory_barrier(struct pipe_context *ctx, unsigned flags)
>>                      PIPE_BARRIER_SHADER_BUFFER |
>>                      PIPE_BARRIER_TEXTURE |
>>                      PIPE_BARRIER_IMAGE |
>> -                    PIPE_BARRIER_STREAMOUT_BUFFER)) {
>> +                    PIPE_BARRIER_STREAMOUT_BUFFER |
>> +                    PIPE_BARRIER_GLOBAL_BUFFER)) {
>>                 /* As far as I can tell, L1 contents are written back to L2
>>                  * automatically at end of shader, but the contents of other
>>                  * L1 caches might still be stale. */
>
> Do we have a test that writes to a buffer via a PS and then read from
> it via a CS? And the same with a CS followed by a VS.
>
> I'm not sure if the hardware can execute compute and draw jobs in
> parallel within one IB. (it can certainly do that with draw calls)

Nothing in piglit as far as I know. I tested with a local test with
two compute dispatches that not using CS_PARTIAL_FLUSH the second
dispatch missed writes from the first and using CS_PARTIAL_FLUSH that
synchronization was fixed.

So I think the hardware is able to execute multiple compute dispatches
at the same time in a single IB and that this add proper
synchronization. I have not tried any compute<->graphics interaction.

- Bas