Re: [Xenomai] x86 Linux with xenomai and i915 graphics stall

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On 01/22/2013 08:32 PM, A User wrote:

> When we run latency, we still get about 10 usec on a quiet system.
> When we run glxgears and make the window size  600x600 pixels, and we
> use the mouse to drag the glxgears window quickly around on the
> desktop, the max latency goes to about 250 usec (with gnome-3
> fallback and compiz).


That is unusual, a typical latency on x86 is under 50us (and this is a
conservative bound). In order to investigate this, enable the I-pipe
tracer in the kernel configuration and run latency -f. Also set the
number of backtrace points to a large value, say 1000 or 10000 and post
the trace here.

> The option CONFIG_PCI_MSI should be disabled
> 
> """
> 
> 
> We will keep CONFIG_PCI_MSI turned on for now, as Gilles suggests.


The danger with CONFIG_PCI_MSI is that you can not mask/disable the
interrupt in a real-time interrupt handler, but as long as you do not do
that, you should be safe.

-- 
                                                                Gilles.