Kenneth Graunke <kenn...@whitecape.org> writes: > On 02/27/2014 02:52 PM, Eric Anholt wrote: >> One thing I noticed while working on this was that we only reallocate buffer >> storage for INVALIDATE_BUFFER_BIT when UNSYNCHRONIZED_BIT is unset. The >> ARB_mbr spec says that the contents "may be discarded", not "must be >> discarded". However, while writing the glamor code I happened to type this >> for the wraparound case: >> >> glamor_priv->vb = glMapBufferRange(GL_ARRAY_BUFFER, >> 0, size, >> GL_MAP_WRITE_BIT | >> GL_MAP_INVALIDATE_BUFFER_BIT | >> GL_MAP_UNSYNCHRONIZED_BIT | >> GL_MAP_PERSISTENT_BIT | >> GL_MAP_COHERENT_BIT); >> >> intending that the buffer storage get reallocated, and that we not worry >> about >> any synchronization after that. My code would have been broken on the i965 >> driver. I'm wondering if this is the intended behavior of the spec, or if we >> want to treat the "may" as a "must". > > I don't understand. Your code here sets GL_MAP_INVALIDATE_BUFFER_BIT > and GL_MAP_UNSYNCHRONIZED_BIT, which would have reallocated the storage, > as you intended. Was this a mispaste - you originally lacked the > GL_MAP_UNSYNCHRONIZED_BIT, were surprised, and eventually added it?
Here's the only i965 code referencing MAP_INVALIDATE_BUFFER_BIT:
if (!(access & GL_MAP_UNSYNCHRONIZED_BIT)) {
if (drm_intel_bo_references(brw->batch.bo, intel_obj->buffer)) {
if (access & GL_MAP_INVALIDATE_BUFFER_BIT) {
drm_intel_bo_unreference(intel_obj->buffer);
intel_bufferobj_alloc_buffer(brw, intel_obj);
} else {
perf_debug("Stalling on the GPU for mapping a busy buffer "
"object\n");
intel_batchbuffer_flush(brw);
}
} else if (drm_intel_bo_busy(intel_obj->buffer) &&
(access & GL_MAP_INVALIDATE_BUFFER_BIT)) {
drm_intel_bo_unreference(intel_obj->buffer);
intel_bufferobj_alloc_buffer(brw, intel_obj);
}
}
so for that glamor call we wouldn't have thrown out the storage, even
though it was referenced by the batch or the GPU. I think we should
pull the INVALIDATE_BUFFER test out and just always invalidate when it's
set.
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