[Mesa-dev] [PATCH] intel: Improve teximage perf for Google Chrome paint rects

Chad Versace chad.versace at linux.intel.com
Tue Sep 11 12:04:52 PDT 2012


This patch adds a new fast path for glTexImage2D and glTexSubImage2D,
intel_texsubimage_tiled_memcpy, which is optimized for Google Chrome's
paint rectangles. The fast path is implemented only for 2D GL_BGRA
textures on gen >= 6.

Reduces the time spent in glTexImage and glTexSubImage by roughly 3x on
Sandybridge for the workload described below.

=== Performance Analysis ===

Workload description:

    Personalize your google.com page with a wallpaper.  Start chromium
with flags "--ignore-gpu-blacklist --enable-accelerated-painting
--force-compositing-mode".  Start recording with chrome://tracing. Visit
google.com and wait for page to finish rendering.  Measure the time spent
by process CrGpuMain in GLES2DecoderImpl::HandleTexImage2D and
HandleTexSubImage2D.

System config:

    cpu: Sandybridge Mobile GT2+ (0x0126)
    kernel 3.4.9 x86_64
    chromium 21.0.1180.81 (151980)

Statistics:

           |  N   Median  Avg   Stddev
    -------|--------------------------
    before | 10   184.6  187.4  15.9
    after  | 10   564.2  558.8  24.8

    Difference at 95.0% confidence:
        371.373 +/- 19.533
        198.192% +/- 10.4243%

    Ratio:
        avg:    3.06
        median: 2.99

CC: Stéphane Marchesin <marcheu at chromium.org>
Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
---

Stephane,

This patch applies cleanly to master. Since the patch now occurs at
a significantly different point in history compared to the other patch I sent
you, I reran the workloads and updated the scores.


 src/mesa/drivers/dri/intel/intel_tex.h          |  11 ++
 src/mesa/drivers/dri/intel/intel_tex_image.c    |  12 ++
 src/mesa/drivers/dri/intel/intel_tex_subimage.c | 170 ++++++++++++++++++++++++
 3 files changed, 193 insertions(+)

diff --git a/src/mesa/drivers/dri/intel/intel_tex.h b/src/mesa/drivers/dri/intel/intel_tex.h
index 88a7d55..777574d 100644
--- a/src/mesa/drivers/dri/intel/intel_tex.h
+++ b/src/mesa/drivers/dri/intel/intel_tex.h
@@ -85,4 +85,15 @@ bool intel_copy_texsubimage(struct intel_context *intel,
                             GLint x, GLint y,
                             GLsizei width, GLsizei height);
 
+bool
+intel_texsubimage_tiled_memcpy(struct gl_context *ctx,
+                               GLuint dims,
+                               struct gl_texture_image *texImage,
+                               GLint xoffset, GLint yoffset, GLint zoffset,
+                               GLsizei width, GLsizei height, GLsizei depth,
+                               GLenum format, GLenum type,
+                               const GLvoid *pixels,
+                               const struct gl_pixelstore_attrib *packing,
+                               bool for_glTexImage);
+
 #endif
diff --git a/src/mesa/drivers/dri/intel/intel_tex_image.c b/src/mesa/drivers/dri/intel/intel_tex_image.c
index fe9040c..bbb2fe0 100644
--- a/src/mesa/drivers/dri/intel/intel_tex_image.c
+++ b/src/mesa/drivers/dri/intel/intel_tex_image.c
@@ -206,10 +206,22 @@ intelTexImage(struct gl_context * ctx,
               GLenum format, GLenum type, const void *pixels,
               const struct gl_pixelstore_attrib *unpack)
 {
+   bool ok;
+
    DBG("%s target %s level %d %dx%dx%d\n", __FUNCTION__,
        _mesa_lookup_enum_by_nr(texImage->TexObject->Target),
        texImage->Level, texImage->Width, texImage->Height, texImage->Depth);
 
+   ok = intel_texsubimage_tiled_memcpy(ctx, dims, texImage,
+                                       0, 0, 0, /*x,y,z offsets*/
+                                       texImage->Width,
+                                       texImage->Height,
+                                       texImage->Depth,
+                                       format, type, pixels, unpack,
+                                       true /*for_glTexImage*/);
+   if (ok)
+      return;
+
    /* Attempt to use the blitter for PBO image uploads.
     */
    if (dims <= 2 &&
diff --git a/src/mesa/drivers/dri/intel/intel_tex_subimage.c b/src/mesa/drivers/dri/intel/intel_tex_subimage.c
index ae4b3bc..d932f6e 100644
--- a/src/mesa/drivers/dri/intel/intel_tex_subimage.c
+++ b/src/mesa/drivers/dri/intel/intel_tex_subimage.c
@@ -26,6 +26,7 @@
  * 
  **************************************************************************/
 
+#include "main/macros.h"
 #include "main/mtypes.h"
 #include "main/pbo.h"
 #include "main/texobj.h"
@@ -148,6 +149,165 @@ intel_blit_texsubimage(struct gl_context * ctx,
    return true;
 }
 
+/**
+ * \brief A fast path for glTexImage and glTexSubImage.
+ *
+ * \param for_glTexImage Was this called from glTexImage or glTexSubImage?
+ *
+ * This fast path is taken when the hardware natively supports the texture
+ * format (such as GL_BGRA) and when the texture memory is X-tiled. It uploads
+ * the texture data by mapping the texture memory without a GTT fence, thus
+ * acquiring a tiled view of the memory, and then memcpy'ing sucessive
+ * subspans within each tile.
+ *
+ * This is a performance win over the conventional texture upload path because
+ * it avoids the performance penalty of writing throuh the write-combine
+ * buffer. In the conventional texture upload path,
+ * texstore.c:store_texsubimage(), the texture memory is mapped through a GTT
+ * fence, thus acquiring a linear view of the memory, then each row in the
+ * image is memcpy'd. In this fast path, we replace each row's memcpy with
+ * a sequence of memcpy's over each bit6 swizzle span in the row. A large
+ * memcpy through the write-combine buffer has been observed on Sandybridge to
+ * be approximately 3x slower than a memcpy to normal memory.  So, one would
+ * expect this fast path to be approximately 3x faster than the conventional
+ * texture upload path. This expectation has been confirmed on Sandybridge for
+ * 256x256 GL_BGRA textures.
+ *
+ * This fast path's use case is Google Chrome's paint rectangles.  Chrome (as
+ * of version 21) renders each page as a tiling of 256x256 GL_BGRA textures.
+ * Each page's content is initially uploaded with glTexImage2D and damaged
+ * regions are updated with glTexSubImage2D.
+ */
+bool
+intel_texsubimage_tiled_memcpy(struct gl_context * ctx,
+                               GLuint dims,
+                               struct gl_texture_image *texImage,
+                               GLint xoffset, GLint yoffset, GLint zoffset,
+                               GLsizei width, GLsizei height, GLsizei depth,
+                               GLenum format, GLenum type,
+                               const GLvoid *pixels,
+                               const struct gl_pixelstore_attrib *packing,
+                               bool for_glTexImage)
+{
+   struct intel_context *intel = intel_context(ctx);
+   struct intel_texture_image *image = intel_texture_image(texImage);
+
+   /* Offset into the miptree for the texture image. */
+   uint32_t image_offset_x;
+   uint32_t image_offset_y;
+
+   /* The miptree's buffer. */
+   drm_intel_bo *bo;
+
+   int error = 0;
+
+   /* Restrict to gen >= 6 because the performance impact on earlier chipsets
+    * has not been investigated.
+    *
+    * This function could be expanded to accommodate more textures and
+    * chipets, but more performance inverstigation is needed.
+    */
+   if (intel->gen < 6 ||
+       dims != 2 ||
+       depth != 1 ||
+       format != GL_BGRA ||
+       type != GL_UNSIGNED_BYTE ||
+       pixels == NULL ||
+       packing->Alignment > 4)
+      return false;
+
+   if (for_glTexImage)
+      ctx->Driver.AllocTextureImageBuffer(ctx, texImage);
+
+   if (!image->mt ||
+       image->mt->region->tiling != I915_TILING_X) {
+      /* The algorithm below is written only for X-tiled memory.
+       *
+       * Memcpy'ing to Y-tiled memory is likely faster when done the
+       * conventional way: that is, map the memory through a fence in order to
+       * acquire a linear view of the memory, then memcpy one row at a time.
+       * Due to the arrangement of Y-tiled memory, if we were to upload
+       * a Y-tiled buffer using the algorithm below, then we could only copy
+       * one byte at a time.
+       */
+      return false;
+   }
+
+   intel_miptree_get_image_offset(image->mt,
+                                  texImage->Level,
+                                  texImage->Face,
+                                  0 /*layer*/,
+                                  &image_offset_x,
+                                  &image_offset_y);
+
+   bo = image->mt->region->bo;
+   error = drm_intel_bo_map(image->mt->region->bo, true /*write_enable*/);
+   if (error || bo->virtual == NULL) {
+      DBG("%s: failed to map bo\n", __FUNCTION__);
+      return false;
+   }
+
+   /* We postponed printing this message until having committed to executing
+    * the function.
+    */
+   DBG("%s: level=%d offset=(%d,%d) (w,h)=(%d,%d)\n",
+       __FUNCTION__, texImage->Level, xoffset, yoffset, width, height);
+
+   /* In the tiling algorithm below, some variables are in units of pixels,
+    * others are in units of bytes, and others (such as height) are unitless.
+    * Each variable name is either prefixed or suffixed with its units.
+    */
+
+   const uint32_t pixel_max_x = xoffset + width;
+   const uint32_t pixel_max_y = yoffset + height;
+
+   const uint32_t tile_size_bytes = 4096;
+
+   const uint32_t tile_width_bytes = 512;
+   const uint32_t tile_width_pixels = 128;
+
+   const uint32_t tile_height = 8;
+
+   const uint32_t cpp = 4; /* chars per pixel of GL_BGRA */
+   const uint32_t swizzle_width_pixels = 16;
+
+   const uint32_t stride_bytes = image->mt->region->pitch * cpp;
+   const uint32_t width_tiles = stride_bytes / tile_width_bytes;
+
+   uint8_t *map = bo->virtual
+		+ image_offset_y * stride_bytes
+		+ image_offset_x * cpp;
+
+   for (uint32_t pixel_y = yoffset; pixel_y < pixel_max_y; ++pixel_y) {
+      const uint32_t byte_offset_y = (pixel_y / tile_height) * width_tiles * tile_size_bytes
+                                   + (pixel_y % tile_height) * tile_width_bytes;
+
+      for (uint32_t pixel_x = xoffset; pixel_x < pixel_max_x; pixel_x += swizzle_width_pixels) {
+         const uint32_t byte_offset_x = (pixel_x / tile_width_pixels) * tile_size_bytes
+                                      + (pixel_x % tile_width_pixels) * cpp;
+         intptr_t byte_offset = byte_offset_y + byte_offset_x;
+         if (intel->has_swizzling) {
+            bool bit6 = (byte_offset >> 6) & 1;
+            bool bit9 = (byte_offset >> 9) & 1;
+            bool bit10 = (byte_offset >> 10) & 1;
+
+            byte_offset += 64 * (bit9 ^ bit10) * (1 - 2 * bit6);
+         }
+
+         const uint32_t swizzle_bound_pixels = ALIGN(pixel_x + 1, swizzle_width_pixels);
+         const uint32_t memcpy_bound_pixels = MIN2(pixel_max_x, swizzle_bound_pixels);
+         const uint32_t copy_size = cpp * (memcpy_bound_pixels - pixel_x);
+
+         memcpy(map + byte_offset, pixels, copy_size);
+         pixels += copy_size;
+         pixel_x -= (pixel_x % swizzle_width_pixels);
+      }
+   }
+
+   drm_intel_bo_unmap(bo);
+   return true;
+}
+
 static void
 intelTexSubImage(struct gl_context * ctx,
                  GLuint dims,
@@ -158,6 +318,16 @@ intelTexSubImage(struct gl_context * ctx,
                  const GLvoid * pixels,
                  const struct gl_pixelstore_attrib *packing)
 {
+   bool ok;
+
+   ok = intel_texsubimage_tiled_memcpy(ctx, dims, texImage,
+                                       xoffset, yoffset, zoffset,
+                                       width, height, depth,
+                                       format, type, pixels, packing,
+                                       false /*for_glTexImage*/);
+   if (ok)
+     return;
+
    /* The intel_blit_texsubimage() function only handles 2D images */
    if (dims != 2 || !intel_blit_texsubimage(ctx, texImage,
 			       xoffset, yoffset,
-- 
1.7.12



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