[Mesa-dev] [PATCH] nvc0: don't make use of push hint if there are no non-const user vbos

[Samuel Pitoiset]

On 06/19/2016 04:09 PM, Ilia Mirkin wrote:
> On Sun, Jun 19, 2016 at 9:56 AM, Samuel Pitoiset
> <samuel.pitoiset at gmail.com> wrote:
>> I don't know if you remember, but I suggested exactly the same patch few
>> days ago when I was looking at the Talos issue, but I was not really sure if
>> this was the "correct" fix.
>
> Sorry, I had no recollection of that - I only remember the patch that
> you sent to the list, which effectively set vbo_push_hint to 0 for
> everything.

No worries. :-)

>
>>
>> Anyways, this patch looks fine to me (even if we don't exactly know why it
>> works this way).
>>
>> This will also improve performance in Talos because the manual push path is
>> sometimes slow and that arbitrary limit should be improved.
>
> Well, it's especially slow when it's used when it shouldn't be - like
> when there are no user buffers. Which is 99% of modern applications,
> since user buffers were nixed in core contexts as I recall.
>
>>
>> We still need to fix the remaining issue (ie. the green wall thing) but this
>> one is most likely totally unrelated to the push path.
>>
>> Reviewed-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>
> Thanks!
>
>>
>>
>> On 06/19/2016 06:34 AM, Ilia Mirkin wrote:
>>>
>>> This makes the check match up what we do on nv50 as well - there's no
>>> point in switching over the push path if everything's in managed
>>> buffers. This can happen when a shader uses a vertex without an enabled
>>> array - we end up passing it a constant attribute.
>>>
>>> This also has the effect of "fixing" some flickering in Talos. I have no
>>> idea why. I've stared at the push logic forwards, backwards, and
>>> sideways. By always forcing the push path (which is slow), the
>>> flickering also goes away, but other rendering is still wrong
>>> (specifically draw 383068 as identified in the bug). However by not
>>> switching over to the push path, draw 383068 is correct.
>>>
>>> Note that other flickering remains in Talos, like the red/green
>>> walls/floors. This takes care of the shadow flickering though.
>>>
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90513
>>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>>> Cc: "12.0" <mesa-stable at lists.freedesktop.org>
>>> ---
>>>  src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> b/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> index 7662bdd..cae621c 100644
>>> --- a/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> +++ b/src/gallium/drivers/nouveau/nvc0/nvc0_vbo.c
>>> @@ -441,8 +441,10 @@ nvc0_vertex_arrays_validate(struct nvc0_context
>>> *nvc0)
>>>     if (unlikely(vertex->need_conversion) ||
>>>         unlikely(nvc0->vertprog->vp.edgeflag < PIPE_MAX_ATTRIBS)) {
>>>        vbo_mode = 3;
>>> +   } else if (nvc0->vbo_user & ~nvc0->constant_vbos) {
>>> +      vbo_mode = nvc0->vbo_push_hint ? 1 : 0;
>>>     } else {
>>> -      vbo_mode = (nvc0->vbo_user && nvc0->vbo_push_hint) ? 1 : 0;
>>> +      vbo_mode = 0;
>>>     }
>>>     const_vbos = vbo_mode ? 0 : nvc0->constant_vbos;
>>>
>>>
>>