Re: [Lguest] [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes

[Rusty Russell <rusty@rustcorp.com.au>]

On Sunday 30 November 2008 04:52:41 Avi Kivity wrote:
> Alexander van Heukelum wrote:
> > I now did the benchmarks for the same -rc6 with hpa's 4-byte stubs
> > too. Same machine. It's significantly better than the other two
> > options in terms of speed. It takes about 7% less cpu to handle
> > the interrupts. (0.64% cpu instead of 0.69%.) I have to run now,
> > I'll let interpreting the histogram to someone else ;).
>
> This is noise. 0.05% cpu on a 1GHz machine servicing 1000 interrupt/sec
> boils down to 500 cycles/interrupt.  These changes shouldn't amount to
> so much (and I doubt you have 1000 interrupts/sec with a single disk)..

Sure, but smallest cache wins.  Which is why I thought hpa chose the 3 byte 
option.

> I'm sorry, but the whole effort is misguided, in my opinion.

Respectfully disagree.  I wouldn't do it, but it warms my heart that others 
are.  It's are not subtractive from other optimization efforts.

Cheers,
Rusty.