Mesa (master): intel: Only do frame throttling at glFlush time when using frontbuffer.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: b01b73c482474609aceb6bb13b083e96c06ba353
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b01b73c482474609aceb6bb13b083e96c06ba353

Author: Eric Anholt <eric at anholt.net>
Date:   Sat Dec 25 08:57:22 2010 -0800

intel: Only do frame throttling at glFlush time when using frontbuffer.

This is the hack for input interactivity of frontbuffer rendering
(like we do for backbuffer at intelDRI2Flush()) by waiting for the n-2
frame to complete before starting a new one.  However, for an
application doing multiple contexts or regular rebinding of a single
context, this would end up lockstepping the CPU to the GPU because
every unbind was considered the end of a frame.

Improves WOW performance on my Ironlake by 48.8% (+/- 2.3%, n=5)

---

 src/mesa/drivers/dri/intel/intel_context.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/mesa/drivers/dri/intel/intel_context.c b/src/mesa/drivers/dri/intel/intel_context.c
index 9c222c7..d183d27 100644
--- a/src/mesa/drivers/dri/intel/intel_context.c
+++ b/src/mesa/drivers/dri/intel/intel_context.c
@@ -565,7 +565,8 @@ intel_glFlush(struct gl_context *ctx)
 
    intel_flush(ctx);
    intel_flush_front(ctx);
-   intel->need_throttle = GL_TRUE;
+   if (intel->is_front_buffer_rendering)
+      intel->need_throttle = GL_TRUE;
 }
 
 void