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tools/power turbostat: simplify Bzy_MHz calculation 

Bzy_MHz = TSC_delta*tsc_tweak/APERF_delta/MPERF_delta/measurement_interval

becomes

    Bzy_MHz = base_mhz/APERF_delta/MPERF_delta

on systems which support MSR_NHM_PLATFORM_INFO.

base_mhz is calculated directly from the base_ratio
reported in MSR_NHM_PLATFORM_INFO * bclk,
and bclk is discovered via MSR or cpuid.

This reduces the dependency of Bzy_MHz calculation on the TSC.
Previously, there were 4 TSC readings required in each caculation,
the raw TSC delta combined with the measurement_interval.
This also removes the "tsc_tweak" correction factor used when
TSC runs on a different base clock from the CPU's bclk.

After this change, tsc_tweak is used only for %Busy.

The end-result should be a Bzy_MHz result slightly less prone to jitter.

Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Len Brown 2015-10-19 22:37:40 -04:00
parent 7379047d55
commit 21ed5574d1
1 changed files with 17 additions and 11 deletions
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28
tools/power/x86/turbostat/turbostat.c
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@ -75,6 +75,7 @@ unsigned int aperf_mperf_multiplier = 1;
int do_smi;
double bclk;
double base_hz;
unsigned int has_base_hz;
double tsc_tweak = 1.0;
unsigned int show_pkg;
unsigned int show_core;
@ -96,6 +97,7 @@ unsigned int do_ring_perf_limit_reasons;
unsigned int crystal_hz;
unsigned long long tsc_hz;
int base_cpu;
double discover_bclk(unsigned int family, unsigned int model);
#define RAPL_PKG (1 << 0)
/* 0x610 MSR_PKG_POWER_LIMIT */
@ -511,9 +513,13 @@ int format_counters(struct thread_data *t, struct core_data *c,
}
/* Bzy_MHz */
if (has_aperf)
outp += sprintf(outp, "%8.0f",
1.0 * t->tsc * tsc_tweak / units * t->aperf / t->mperf / interval_float);
if (has_aperf) {
if (has_base_hz)
outp += sprintf(outp, "%8.0f", base_hz / units * t->aperf / t->mperf);
else
outp += sprintf(outp, "%8.0f",
1.0 * t->tsc / units * t->aperf / t->mperf / interval_float);
}
/* TSC_MHz */
outp += sprintf(outp, "%8.0f", 1.0 * t->tsc/units/interval_float);
@ -1158,12 +1164,6 @@ int phi_pkg_cstate_limits[16] = {PCL__0, PCL__2, PCL_6N, PCL_6R, PCLRSV, PCLRSV,
static void
calculate_tsc_tweak()
{
unsigned long long msr;
unsigned int base_ratio;
get_msr(base_cpu, MSR_NHM_PLATFORM_INFO, &msr);
base_ratio = (msr >> 8) & 0xFF;
base_hz = base_ratio * bclk * 1000000;
tsc_tweak = base_hz / tsc_hz;
}
@ -1821,6 +1821,7 @@ void check_permissions()
int probe_nhm_msrs(unsigned int family, unsigned int model)
{
unsigned long long msr;
unsigned int base_ratio;
int *pkg_cstate_limits;
if (!genuine_intel)
@ -1829,6 +1830,8 @@ int probe_nhm_msrs(unsigned int family, unsigned int model)
if (family != 6)
return 0;
bclk = discover_bclk(family, model);
switch (model) {
case 0x1A: /* Core i7, Xeon 5500 series - Bloomfield, Gainstown NHM-EP */
case 0x1E: /* Core i7 and i5 Processor - Clarksfield, Lynnfield, Jasper Forest */
@ -1871,9 +1874,13 @@ int probe_nhm_msrs(unsigned int family, unsigned int model)
return 0;
}
get_msr(base_cpu, MSR_NHM_SNB_PKG_CST_CFG_CTL, &msr);
pkg_cstate_limit = pkg_cstate_limits[msr & 0xF];
get_msr(base_cpu, MSR_NHM_PLATFORM_INFO, &msr);
base_ratio = (msr >> 8) & 0xFF;
base_hz = base_ratio * bclk * 1000000;
has_base_hz = 1;
return 1;
}
int has_nhm_turbo_ratio_limit(unsigned int family, unsigned int model)
@ -2780,7 +2787,6 @@ void process_cpuid()
do_skl_residency = has_skl_msrs(family, model);
do_slm_cstates = is_slm(family, model);
do_knl_cstates = is_knl(family, model);
bclk = discover_bclk(family, model);
rapl_probe(family, model);
perf_limit_reasons_probe(family, model);