Re: [RFC/HACK] x86: Fast return to kernel

[Ingo Molnar <mingo@kernel.org>]

* Andy Lutomirski <luto@amacapital.net> wrote:

> > That said, regular *device* interrupts do often return to kernel 
> > mode (the idle loop in particular), so if you have any way to 
> > measure that, that might be interesting, and might show some of 
> > the same advantages.
> 
> I can try something awful involving measuring latency of 
> hardware-timed packets on a SolarFlare card, but I'll have 
> calibration issues.  I suppose I could see if 'ping' gets faster.  
> In general, this will speed up interrupts that wake userspace from 
> idle by about 100ns on my box, since it's presumably the same size 
> and the speedup per loop in my silly benchmark.

To simulate high rate device IRQ you can generate very high frequency 
lapic IRQs by using hrtimers, that's generating a ton of per CPU lapic 
IRQs.

Thanks,

	Ingo