intel: Add a comment explaining why we early return on matching BO names.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

diff --git a/src/mesa/drivers/dri/intel/intel_context.c b/src/mesa/drivers/dri/intel/intel_context.c
index 2494ac7..378859c 100644 (file)
--- a/src/mesa/drivers/dri/intel/intel_context.c
+++ b/src/mesa/drivers/dri/intel/intel_context.c
@@ -893,6 +893,10 @@ intel_process_dri2_buffer(struct intel_context *intel,
    if (!rb)
       return;
 
+   /* We try to avoid closing and reopening the same BO name, because the first
+    * use of a mapping of the buffer involves a bunch of page faulting which is
+    * moderately expensive.
+    */
    if (rb->mt &&
        rb->mt->region &&
        rb->mt->region->name == buffer->name)