[Mesa-dev] glxgears performance higher with software renderer compared to h/w drivers

[Alex Deucher]

On Mon, May 6, 2013 at 10:33 AM, Divick Kishore
<divick.kishore at gmail.com> wrote:
> Hi,
>      I am trying to build s/w only mesa driver. It seems that the
> performance of software only renderer (compiled with
> --with-driver=xlib) is higher than that of h/w drivers. Could someone
> please help me understand what is causing this or if it is expected?
>
> I see that dri based s/w renderer is also slower than xlib/swrast
> driver. So how does dri based s/w rendering work and why is it slower
> than xlib/swrast driver?
>
> I presume that --with-driver=xlib builds s/w only renderer. Please
> correct me if I am wrong.
>
> ./configure -build=x86_64-linux-gnu --with-driver=dri
> --with-dri-drivers="i915 swrast"
> --with-dri-driverdir=/home/divick/work/mesa/mesa-8.0.5/build/dri/x86_64-linux-gnu/
> --with-dri-searchpath='/home/divick/work/mesa/mesa-8.0.5/build/dri/x86_64-linux-gnu/'
> --enable-glx-tls --enable-shared-glapi --enable-texture-float
> --enable-xa --enable-driglx-direct --with-egl-platforms="x11 drm"
> --enable-gallium-llvm --with-gallium-drivers="swrast i915"
> --enable-gles1 --enable-gles2 --enable-openvg --enable-gallium-egl
> --disable-glu CFLAGS="-Wall -g -O2" CXXFLAGS="-Wall -g -O2"
>
> with LIBGL_ALWAYS_SOFTWARE=1
> glxgears reports:
>
> GL_RENDERER   = Software Rasterizer
> GL_VERSION    = 2.1 Mesa 8.0.5
> GL_VENDOR     = Mesa Project
>
> fps: ~ 490 fps
>
> Without LIBGL_ALWAYS_SOFTWARE set:
>
> GL_RENDERER   = Mesa DRI Intel(R) Sandybridge Mobile
> GL_VERSION    = 3.0 Mesa 8.0.5
> GL_VENDOR     = Tungsten Graphics, Inc
>
> fps: ~ 60

The default is to sync to the refresh rate.  Try setting env var
vblank_mode=0 to disable it.

Alex