Open-Source Raspberry Pi Graphics Drivers Add Double Buffer Mode

Mesa's V3D and V3DV drivers providing open-source OpenGL and Vulkan driver support, respectively, for newer Broadcom VideoCore hardware now has a double buffer mode implemented. This is a win for numerous workloads for these drivers most notably used by modern Raspberry Pi single board computers.

V3D/V3DV has implemented an optional double buffer mode that can help the performance in some areas but not everywhere or even the possibility of regressions, thus isn't enabled by default.

The merge by Igalia's Iago Toral explains, "Double buffer mode splits the tile buffer size in half so we can start processing the next tile while the current one is being stored to memory. This mode is available only if MSAA is not enabled and can, in theory, improve performance by reducing tile store overhead, however, it comes at the cost of reducing the tile size, which also causes some overhead of its own. Testing shows that this helps some cases (i.e the Vulkan Quake ports) but hurts others (i.e. Unreal Engine 4), so for the time being we don't enable this by default but we allow to enable it selectively by using V3D_DEBUG."

The Mesa V3D/V3DV driver development continues to be principally driven for Raspberry Pi usage.

The V3D_DEBUG=db environment variable can be used for activating this double buffering on Mesa 22.0-devel as of today and newer. This support depends upon multi-sample anti-aliasing (MSAA) being disabled.