[Mesa-dev] [PATCH] i965: Add a driconf option to disable flush throttling.

[Paul Berry]

Normally when submitting the first batch buffer after a flush, we
check whether the GPU has completed processing of the first batch
buffer of the previous frame.  If it hasn't, we wait for it to finish
before submitting any more batches.  This prevents GPU-heavy and
CPU-light applications from racing too far ahead of the current frame,
but at the expense of possibly lower frame rates.  Sometimes when
benchmarking we want to disable this mechanism.

This patch adds the driconf option "disable_throttling" to disable the
throttling mechanism.
---
 src/mesa/drivers/dri/common/xmlpool/t_options.h | 5 +++++
 src/mesa/drivers/dri/intel/intel_context.c      | 8 +++++++-
 src/mesa/drivers/dri/intel/intel_context.h      | 1 +
 src/mesa/drivers/dri/intel/intel_screen.c       | 3 ++-
 4 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/common/xmlpool/t_options.h b/src/mesa/drivers/dri/common/xmlpool/t_options.h
index 1e7eced..7b441c6 100644
--- a/src/mesa/drivers/dri/common/xmlpool/t_options.h
+++ b/src/mesa/drivers/dri/common/xmlpool/t_options.h
@@ -75,6 +75,11 @@ DRI_CONF_OPT_BEGIN(always_flush_cache,bool,def) \
         DRI_CONF_DESC(en,gettext("Enable flushing GPU caches with each draw call")) \
 DRI_CONF_OPT_END
 
+#define DRI_CONF_DISABLE_THROTTLING(def) \
+DRI_CONF_OPT_BEGIN(disable_throttling,bool,def) \
+	DRI_CONF_DESC(en,gettext("Disable throttling on first batch after flush")) \
+DRI_CONF_OPT_END
+
 #define DRI_CONF_FORCE_GLSL_EXTENSIONS_WARN(def) \
 DRI_CONF_OPT_BEGIN(force_glsl_extensions_warn,bool,def) \
         DRI_CONF_DESC(en,gettext("Force GLSL extension default behavior to 'warn'")) \
diff --git a/src/mesa/drivers/dri/intel/intel_context.c b/src/mesa/drivers/dri/intel/intel_context.c
index 2df70b7..bf4045e 100644
--- a/src/mesa/drivers/dri/intel/intel_context.c
+++ b/src/mesa/drivers/dri/intel/intel_context.c
@@ -440,7 +440,8 @@ intel_prepare_render(struct intel_context *intel)
     * so we just us the first batch we emitted after the last swap.
     */
    if (intel->need_throttle && intel->first_post_swapbuffers_batch) {
-      drm_intel_bo_wait_rendering(intel->first_post_swapbuffers_batch);
+      if (!intel->disable_throttling)
+         drm_intel_bo_wait_rendering(intel->first_post_swapbuffers_batch);
       drm_intel_bo_unreference(intel->first_post_swapbuffers_batch);
       intel->first_post_swapbuffers_batch = NULL;
       intel->need_throttle = false;
@@ -841,6 +842,11 @@ intelInitContext(struct intel_context *intel,
       intel->always_flush_cache = 1;
    }
 
+   if (driQueryOptionb(&intel->optionCache, "disable_throttling")) {
+      fprintf(stderr, "disabling flush throttling\n");
+      intel->disable_throttling = 1;
+   }
+
    return true;
 }
 
diff --git a/src/mesa/drivers/dri/intel/intel_context.h b/src/mesa/drivers/dri/intel/intel_context.h
index 2df15d4..59cf197 100644
--- a/src/mesa/drivers/dri/intel/intel_context.h
+++ b/src/mesa/drivers/dri/intel/intel_context.h
@@ -285,6 +285,7 @@ struct intel_context
    bool no_rast;
    bool always_flush_batch;
    bool always_flush_cache;
+   bool disable_throttling;
 
    /* State for intelvb.c and inteltris.c.
     */
diff --git a/src/mesa/drivers/dri/intel/intel_screen.c b/src/mesa/drivers/dri/intel/intel_screen.c
index 32e9259..3ca10c8 100644
--- a/src/mesa/drivers/dri/intel/intel_screen.c
+++ b/src/mesa/drivers/dri/intel/intel_screen.c
@@ -80,6 +80,7 @@ PUBLIC const char __driConfigOptions[] =
      DRI_CONF_NO_RAST(false)
      DRI_CONF_ALWAYS_FLUSH_BATCH(false)
      DRI_CONF_ALWAYS_FLUSH_CACHE(false)
+     DRI_CONF_DISABLE_THROTTLING(false)
      DRI_CONF_FORCE_GLSL_EXTENSIONS_WARN(false)
      DRI_CONF_DISABLE_GLSL_LINE_CONTINUATIONS(false)
      DRI_CONF_DISABLE_BLEND_FUNC_EXTENDED(false)
@@ -94,7 +95,7 @@ PUBLIC const char __driConfigOptions[] =
    DRI_CONF_SECTION_END
 DRI_CONF_END;
 
-const GLuint __driNConfigOptions = 16;
+const GLuint __driNConfigOptions = 17;
 
 #include "intel_batchbuffer.h"
 #include "intel_buffers.h"
-- 
1.8.2