[Mesa-dev] [PATCH 1/7] nvc0: reduce the number of PUSH_SPACE in draw path

[Ilia Mirkin]

On Wed, Oct 26, 2016 at 4:14 AM, Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
>
>
> On 10/25/2016 09:49 PM, Ilia Mirkin wrote:
>>
>> What if instance_count = 1M? (It can happen.)
>
>
> We allocate a giant space in the pushbuf in one shot. Well, anyways this is
> not the optimization of the year, so I can drop it. :-)

There are limits to pushbuf sizes. Either drop it, or batch the
instance draws. There's really very limited advantage to doing it this
way though, since PUSH_SPACE is a no-op unless the pushbuf is full.

>
>
>>
>> On Tue, Oct 25, 2016 at 3:41 PM, Samuel Pitoiset
>> <samuel.pitoiset at gmail.com> wrote:
>>>
>>> This might help CPU-bounds applications but should not have
>>> any real effects for GPU-bounds ones.
>>>
>>> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>>> ---
>>>  src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c | 8 +++-----
>>>  1 file changed, 3 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> b/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> index 69ca091..bc4ab9e 100644
>>> --- a/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> +++ b/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> @@ -598,8 +598,8 @@ nvc0_draw_arrays(struct nvc0_context *nvc0,
>>>
>>>     prim = nvc0_prim_gl(mode);
>>>
>>> +   PUSH_SPACE(push, 6 * instance_count);
>>>     while (instance_count--) {
>>> -      PUSH_SPACE(push, 6);
>>>        BEGIN_NVC0(push, NVC0_3D(VERTEX_BEGIN_GL), 1);
>>>        PUSH_DATA (push, prim);
>>>        BEGIN_NVC0(push, NVC0_3D(VERTEX_BUFFER_FIRST), 2);
>>> @@ -730,10 +730,9 @@ nvc0_draw_elements(struct nvc0_context *nvc0, bool
>>> shorten,
>>>     }
>>>
>>>     if (nvc0->idxbuf.buffer) {
>>> -      PUSH_SPACE(push, 1);
>>> +      PUSH_SPACE(push, 1 + 7 * instance_count);
>>>        IMMED_NVC0(push, NVC0_3D(VERTEX_BEGIN_GL), prim);
>>>        do {
>>> -         PUSH_SPACE(push, 7);
>>>           BEGIN_NVC0(push, NVC0_3D(INDEX_BATCH_FIRST), 2);
>>>           PUSH_DATA (push, start);
>>>           PUSH_DATA (push, count);
>>> @@ -747,8 +746,8 @@ nvc0_draw_elements(struct nvc0_context *nvc0, bool
>>> shorten,
>>>     } else {
>>>        const void *data = nvc0->idxbuf.user_buffer;
>>>
>>> +      PUSH_SPACE(push, 3 * instance_count);
>>>        while (instance_count--) {
>>> -         PUSH_SPACE(push, 2);
>>>           BEGIN_NVC0(push, NVC0_3D(VERTEX_BEGIN_GL), 1);
>>>           PUSH_DATA (push, prim);
>>>           switch (index_size) {
>>> @@ -768,7 +767,6 @@ nvc0_draw_elements(struct nvc0_context *nvc0, bool
>>> shorten,
>>>              assert(0);
>>>              return;
>>>           }
>>> -         PUSH_SPACE(push, 1);
>>>           IMMED_NVC0(push, NVC0_3D(VERTEX_END_GL), 0);
>>>
>>>           prim |= NVC0_3D_VERTEX_BEGIN_GL_INSTANCE_NEXT;
>>> --
>>> 2.10.1
>>>
>>> _______________________________________________
>>> mesa-dev mailing list
>>> mesa-dev at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
>
> --
> -Samuel