Keeping the Screen Turned off While Getting Inputs

[Dave Howorth]

On Sat, 26 Aug 2023 13:43:21 -0400 (EDT), Vladimir Dergachev wrote:

> On Sat, 26 Aug 2023, Ahmad Nouralizadeh wrote:
> 
> > >> Those accesses might not stop with just the display off - some
> > >> applications may keep redrawing.  
> > Will these accesses cause iGPU or dedicated GPU accesses to the
> > DRAM? I think that those redrawings originate from the processor. 
> > >I'm not sure a graphical benchmark will run without a graphical
> > >system running?  
> > Yes, VLC is one of the benchmarks and will not run without GUI.  
> 
> You can start system with plain X and twm for window manager - this
> would produce minimal load on the GPU.
> 
> However, I would have expected that VLC would produce a lot GPU/iGPU 
> accesses even without drawing anything, because it would try to use
> GPU decoder.
> 
> Displaying video is also often done using GL or Xvideo - plain X is
> too slow for this.
> 
> >   
> > >Maybe do the reverse of what I suggested. Run the benchmark but
> > >send the output to a remote display.  
> > Will it avoid screen activation in the local machine?  
> 
> There should be a rather drastic difference in speed between VLC 
> displaying locally and in a remote X using network.

Indeed but speed doesn't seem to matter. Some count of particular RAM
accesses is what seems to be important. I'm not clear exactly what RAM
accesses nor why the count is important, nor what disturbance to the
normal operation is permitted. Maybe instrumenting a gdb trace of the
benchmarks would be more accurate?

> best
> 
> Vladimir Dergachev