Use mapped memory for uploading large textures.

gpu/command_buffer/client/gles2_implementation.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // A class to emulate GLES2 over command buffers.
 
 #include "gpu/command_buffer/client/gles2_implementation.h"
 
 #include <GLES2/gl2ext.h>
 #include <GLES2/gl2extchromium.h>
@@ skipping 2185 matching lines @@
     CopyRectToBuffer(
         pixels, height, unpadded_row_size, src_padded_row_size, unpack_flip_y_,
         buffer.address(), padded_row_size);
     helper_->TexImage2D(
         target, level, internalformat, width, height, format, type,
         buffer.shm_id(), buffer.offset());
     CheckGLError();
     return;
   }
 
+  // Check if we can allocate shared memory to send it.
+  int32 mapped_shm_id = 0;
+  unsigned int mapped_shm_offset = 0;
+  void* mem = mapped_memory_->Alloc(size, &mapped_shm_id, &mapped_shm_offset);
+  if (mem) {
+    CopyRectToBuffer(
+        pixels, height, unpadded_row_size, src_padded_row_size, unpack_flip_y_,
+        mem, padded_row_size);
+    helper_->TexImage2D(
+        target, level, internalformat, width, height, format, type,
+        mapped_shm_id, mapped_shm_offset);
+    CheckGLError();
+    mapped_memory_->FreePendingToken(mem, helper_->InsertToken());

[piman, 2015/06/08 21:12:35]

Can you force a shallow flush here? Without it, the risk is that if the context
is never flushed (e.g. offscreen rasterization), we'll grow the mapped memory
unbounded (and then run out of address space or memory or file descriptors).

If we get here, that means we have to upload a large texture and the relative
cost of the flush will be minimal.

[David Yen, 2015/06/08 21:34:06]

Done. Although in order to do this in my new version I had to set a flag to do
the flush after releases in the scoped mapped memory class.

+    return;
+  }
+
   // No, so send it using TexSubImage2D.
   helper_->TexImage2D(
      target, level, internalformat, width, height, format, type,
      0, 0);
   TexSubImage2DImpl(
       target, level, 0, 0, width, height, format, type, unpadded_row_size,
       pixels, src_padded_row_size, GL_TRUE, &buffer, padded_row_size);
   CheckGLError();
 }
 
@@ skipping 3514 matching lines @@
   CheckGLError();
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "gpu/command_buffer/client/gles2_implementation_impl_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu