On December 4, 2015 2:14:46 PM PST, Peter Zijlstra <[email protected]> wrote: >On Fri, Dec 04, 2015 at 09:51:02AM -0800, Jacob Pan wrote: >> On Fri, 4 Dec 2015 09:22:56 +0100 >> Peter Zijlstra <[email protected]> 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*.
Yes, for that it would be better to invoke a common routine to do all the accesses on the target CPU. MSR accesses may be slow, but IPIs are way slower. -- Sent from my Android device with K-9 Mail. Please excuse brevity and formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
