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

Daniel Vetter daniel at ffwll.ch
Tue Sep 11 12:40:42 PDT 2012


Only quick read-through but I'd have expected a has_llc check in there
- if vlv is anything like the previous platforms wc gtt will be much
faster there.
-Daniel

On Tue, Sep 11, 2012 at 9:04 PM, Chad Versace
<chad.versace at linux.intel.com> wrote:
> 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
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev



-- 
Daniel Vetter
daniel.vetter at ffwll.ch - +41 (0) 79 364 57 48 - http://blog.ffwll.ch


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