Re: [PATCH v2 2/2] powercap/rapl: reduce ipi calls

Jacob Pan
2016-01-13T18:22:01Z

On Wed, 13 Jan 2016 19:04:12 +0100
Borislav Petkov <bp@alien8.de> wrote:

> > Then i was suggested to add a rmw msr api for the common good :), I
> > think it is a good idea since such operation is not limited to RAPL
> > driver.
>
> Others are...?

nothing for the _safe version right now. Quick scan through the code
I see the non safe version has a couple can be converted to rmw.
e.g.

static int cpufreq_p4_setdc(unsigned int cpu, unsigned int newstate)
{
...

rdmsr_on_cpu(cpu, MSR_IA32_THERM_CONTROL, &l, &h);
if (newstate == DC_DISABLE) {
pr_debug("CPU#%d disabling modulation\n", cpu);
wrmsr_on_cpu(cpu, MSR_IA32_THERM_CONTROL, l & ~(1<<4),
h); } else {
pr_debug("CPU#%d setting duty cycle to %d%%\n",
cpu, ((125 * newstate) / 10));
/* bits 63 - 5 : reserved
* bit 4 : enable/disable
* bits 3-1 : duty cycle
* bit 0 : reserved
*/
l = (l & ~14);
l = l | (1<<4) | ((newstate & 0x7)<<1);
wrmsr_on_cpu(cpu, MSR_IA32_THERM_CONTROL, l, h);
}

static int sfi_cpufreq_target(struct cpufreq_policy *policy, unsigned
int index) {
...

rdmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, &lo, &hi);
lo = (lo & ~INTEL_PERF_CTL_MASK) |
((u32) sfi_cpufreq_array[next_perf_state].ctrl_val &
INTEL_PERF_CTL_MASK);
wrmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, lo, hi);