[Mesa-dev] [PATCH] i965: Ask the VBO module to actually use VBOs.

[Matt Turner]

On Tue, May 20, 2014 at 11:00 AM, Eric Anholt <eric at anholt.net> wrote:
> Note that this covers the Begin/End rendering path, but not user vertex
> arrays (so we can't drop copy_array_to_vbo_array() code).  Improves
> performance of isosurf GLVERTEX|TRIANGLES by 16.7506% +/- 4.98934%
> (n=20). No difference on openarena (n=10), which was why this was reverted
> back in cbde2765804a4fc62bcf092230a01376aedbf2cd.
> ---
>  src/mesa/drivers/dri/i965/brw_context.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
> index 17ae685..39dd582 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.c
> +++ b/src/mesa/drivers/dri/i965/brw_context.c
> @@ -781,6 +781,9 @@ brwCreateContext(gl_api api,
>        brw_init_performance_monitors(brw);
>     }
>
> +   vbo_use_buffer_objects(ctx);
> +   vbo_always_unmap_buffers(ctx);
> +

Just for my own understanding:

This is opting-in to using a VBO to back immediate-mode data?

How is immediate-mode data sent to the GPU before this?

In case it's not obvious from the answer to the previous question, why
is putting the data in a VBO such an improvement?