[Mesa-dev] [PATCH] intel: Don't spam "intelReadPixels: fallback to swrast" in non-PBO case.

[Kenneth Graunke]

When an application is using PBOs, we attempt to use the BLT engine to
perform ReadPixels.  If that fails due to some restrictions, it's useful
to raise a performance warning.

In the non-PBO case, we always use a CPU mapping since getting the data
into client memory requires a CPU-side copy.  This is a very common case,
so raising a performance warning is annoying.  In particular, apitrace's
image dumping code hits this path, causing it to print hundreds of
thousands of performance warnings via ARB_debug_output.  This tends to
obscure actual errors or other important messages.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/intel/intel_pixel_read.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/mesa/drivers/dri/intel/intel_pixel_read.c b/src/mesa/drivers/dri/intel/intel_pixel_read.c
index 6b715d0..ebdc528 100644
--- a/src/mesa/drivers/dri/intel/intel_pixel_read.c
+++ b/src/mesa/drivers/dri/intel/intel_pixel_read.c
@@ -89,12 +89,7 @@ do_blit_readpixels(struct gl_context * ctx,
    if (!src)
       return false;
 
-   if (!_mesa_is_bufferobj(pack->BufferObj)) {
-      /* PBO only for now:
-       */
-      DBG("%s - not PBO\n", __FUNCTION__);
-      return false;
-   }
+   assert(_mesa_is_bufferobj(pack->BufferObj));
 
    struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
    struct intel_renderbuffer *irb = intel_renderbuffer(rb);
@@ -178,9 +173,15 @@ intelReadPixels(struct gl_context * ctx,
 
    DBG("%s\n", __FUNCTION__);
 
-   if (do_blit_readpixels
-       (ctx, x, y, width, height, format, type, pack, pixels))
-      return;
+   if (_mesa_is_bufferobj(pack->BufferObj)) {
+      /* Using PBOs, so try the BLT based path. */
+      if (do_blit_readpixels(ctx, x, y, width, height, format, type, pack,
+                             pixels)) {
+         return;
+      }
+
+      perf_debug("%s: fallback to CPU mapping in PBO case\n", __FUNCTION__);
+   }
 
    /* glReadPixels() wont dirty the front buffer, so reset the dirty
     * flag after calling intel_prepare_render(). */
@@ -188,8 +189,6 @@ intelReadPixels(struct gl_context * ctx,
    intel_prepare_render(intel);
    intel->front_buffer_dirty = dirty;
 
-   perf_debug("%s: fallback to swrast\n", __FUNCTION__);
-
    /* Update Mesa state before calling _mesa_readpixels().
     * XXX this may not be needed since ReadPixels no longer uses the
     * span code.
-- 
1.8.2.3