Re: [PATCH] x86/rapl: Do not load in a guest

[Peter Zijlstra]

On Fri, Dec 04, 2015 at 09:51:02AM -0800, Jacob Pan wrote:
> On Fri, 4 Dec 2015 09:22:56 +0100
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > Also, yuck @ powercap/intel_rapl.c for doing rdmsr_on_cpu() +
> > wrmsr_on_cpu() all over the place.
> Can you please be more specific? is the concern related to the
> overhead of IPI? I am doing these calls based on MSR CPU scope and
> consider the fact that access is less frequent.

Yeah, its just offensive to do an IPI to read a value, then twiddle a
few bits on the value and then IPI again to store the value.

I know its low freq, and that MSR access is slow, but *groan*.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/