loader/dri3: Always use at least two back buffers

This can make a significant difference for performance with some extreme
test cases such as vblank_mode=0 glxgears.

Fixes: 1e3218bc5ba2 ("loader/dri3: Overhaul dri3_update_num_back")
Cc: "12.0 11.2" <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97549
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>

diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
index 86ae5ae..3ce0352 100644 (file)
--- a/src/loader/loader_dri3_helper.c
+++ b/src/loader/loader_dri3_helper.c
@@ -70,10 +70,8 @@ dri3_update_num_back(struct loader_dri3_drawable *draw)
 {
    if (draw->flipping)
       draw->num_back = 3;
-   else if (draw->vtable->get_swap_interval(draw) != 0)
-      draw->num_back = 2;
    else
-      draw->num_back = 1;
+      draw->num_back = 2;
 }
 
 void