cobalt - 有没有办法优化skia::flush时间成本？

Question

我们有两个不同的平台，CPU 频率相同的设置，发现时间成本canvas->flush() rasterizer线程在YT启动时间有很大的差异，快的最多只有1.632ms，慢的最多有7.292ms，那么有没有办法找到差异的根本原因并对其进行优化?

钴版本:Cobalt 11.132145 with ARM-Linux and Opengl

1.

2.canvas代码->flush()

    void HardwareRasterizer::Impl::Submit(
    const scoped_refptr<render_tree::Node>& render_tree,
    const scoped_refptr<backend::RenderTarget>& render_target,
    const Options& options) {
  DCHECK(thread_checker_.CalledOnValidThread());
  scoped_refptr<backend::RenderTargetEGL> render_target_egl(
      base::polymorphic_downcast<backend::RenderTargetEGL*>(
          render_target.get()));
  // Skip rendering if we lost the surface. This can happen just before suspend
  // on Android, so now we're just waiting for the suspend to clean up.
  if (render_target_egl->is_surface_bad()) {
    return;
  }
  backend::GraphicsContextEGL::ScopedMakeCurrent scoped_make_current(
      graphics_context_, render_target_egl);
  // Make sure the render target's framebuffer is bound before continuing.
  // Skia will usually do this, but it is possible for some render trees to
  // have non-skia draw calls only, in which case this needs to be done.
  GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER,
                            render_target_egl->GetPlatformHandle()));
  // First reset the graphics context state for the pending render tree
  // draw calls, in case we have modified state in between.
  gr_context_->resetContext();
  AdvanceFrame();
  // Get a SkCanvas that outputs to our hardware render target.
  SkCanvas* canvas = GetCanvasFromRenderTarget(render_target);
  canvas->save();
  if (options.flags & Rasterizer::kSubmitFlags_Clear) {
    canvas->clear(SkColorSetARGB(0, 0, 0, 0));
  } else if (options.dirty) {
    // Only a portion of the display is dirty. Reuse the previous frame
    // if possible.
    if (render_target_egl->ContentWasPreservedAfterSwap()) {
      canvas->clipRect(CobaltRectFToSkiaRect(*options.dirty));
    }
  }
  // Rasterize the passed in render tree to our hardware render target.
  RasterizeRenderTreeToCanvas(render_tree, canvas, kBottomLeft_GrSurfaceOrigin);
  {
    TRACE_EVENT0("cobalt::renderer", "Skia Flush");
    canvas->flush();
  }
  graphics_context_->SwapBuffers(render_target_egl);
  canvas->restore();
}

Answer 1

Skia flush() 调用是将调用所有 OpenGL 函数的函数(在调用该函数之前，所有绘图函数都被简单地序列化并以内部 Skia 格式排队)。

因此，在这种情况下，我会调查您的 GL 驱动程序实现。可能是您的 CPU 正在等待您的 GPU 使用 GLES 发送给它的一些绘图命令。