[Mesa-dev] Mesa (master): st/mesa: use buffer usage history to set dirty flags for revalidation

[Ilia Mirkin]

On Wed, Jun 8, 2016 at 5:48 PM, Fredrik Höglund <fredrik at kde.org> wrote:
> On Wednesday 08 June 2016, Ilia Mirkin wrote:
>> Glancing at the code (I don't even have a piglit checkout here):
>>
>> static void
>> set_ubo_binding(struct gl_context *ctx, ...)
>> ...
>>    /* If this is a real buffer object, mark it has having been used
>>     * at some point as a UBO.
>>     */
>>    if (size >= 0)
>>       bufObj->UsageHistory |= USAGE_UNIFORM_BUFFER;
>>
>> That seems bogus - what if the current size is 0 (unallocated), the
>> buffer object gets bound to a UBO endpoint, and then someone goes in
>> and does glBufferData()? Same for set_ssbo_binding.
>>
>>   -ilia
>
> The test is greater than or equal to zero, so the UsageHistory should
> be set even when the buffer is unallocated.

Right, duh.

>
> But the piglit test doesn't bind the buffer as a uniform buffer before
> it allocates it.  It allocates the buffer first with glNamedBufferData(),
> and then binds it.  The UsageHistory is still set to the default value in
> the glNamedBufferData() call, since the buffer has never been bound
> at that point.  But the uniform buffer state should still be marked as
> dirty in the glBindBufferRange() call.  I think this failure suggests
> that that doesn't happen for some reason.

I haven't looked in GREAT detail, but the test does pass on nv50,
nvc0, and softpipe. It only fails on llvmpipe.

Brian, this might be out of my comfort area to figure out... Given
that it's working on the other drivers, that seems more likely to be a
failing of llvmpipe somehow.

  -ilia