Which makes the implementation independent from cpufreq drivers.
Therefore this would also work on a Xen kernel where the hypervisor
is doing frequency switching and idle entering.
Signed-off-by: Thomas Renninger <trenn@xxxxxxx>
CC: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
CC: cpufreq@xxxxxxxxxxxxxxx
---
tools/power/cpupower/Makefile | 2 +-
.../cpupower/utils/idle_monitor/mperf_monitor.c | 177 ++++++++++++++-----
2 files changed, 131 insertions(+), 48 deletions(-)
diff --git a/tools/power/cpupower/Makefile b/tools/power/cpupower/Makefile
index 94c2cf0..11521d2 100644
--- a/tools/power/cpupower/Makefile
+++ b/tools/power/cpupower/Makefile
@@ -24,7 +24,7 @@
# Set the following to `true' to make a unstripped, unoptimized
# binary. Leave this set to `false' for production use.
-DEBUG ?= false
+DEBUG ?= true
# make the build silent. Set this to something else to make it noisy again.
V ?= false
diff --git a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
index 63ca87a..4f5599e 100644
--- a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
+++ b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
@@ -22,12 +22,15 @@
#define MSR_TSC 0x10
+#define MSR_AMD_HWCR 0xc0010015
+
enum mperf_id { C0 = 0, Cx, AVG_FREQ, MPERF_CSTATE_COUNT };
static int mperf_get_count_percent(unsigned int self_id, double *percent,
unsigned int cpu);
static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
unsigned int cpu);
+static struct timespec time_start, time_end;
static cstate_t mperf_cstates[MPERF_CSTATE_COUNT] = {
{
@@ -54,19 +57,33 @@ static cstate_t mperf_cstates[MPERF_CSTATE_COUNT] = {
},
};
+enum MAX_FREQ_MODE { MAX_FREQ_SYSFS, MAX_FREQ_TSC_REF };
+static int max_freq_mode;
+/*
+ * The max frequency mperf is ticking at (in C0), either retrieved via:
+ * 1) calculated after measurements if we know TSC ticks at mperf/P0 frequency
+ * 2) cpufreq /sys/devices/.../cpu0/cpufreq/cpuinfo_max_freq at init time
+ * 1. Is preferred as it also works without cpufreq subsystem (e.g. on Xen)
+ */
+static unsigned long max_frequency;
+
static unsigned long long tsc_at_measure_start;
static unsigned long long tsc_at_measure_end;
-static unsigned long max_frequency;
static unsigned long long *mperf_previous_count;
static unsigned long long *aperf_previous_count;
static unsigned long long *mperf_current_count;
static unsigned long long *aperf_current_count;
+
/* valid flag for all CPUs. If a MSR read failed it will be zero */
static int *is_valid;
static int mperf_get_tsc(unsigned long long *tsc)
{
- return read_msr(0, MSR_TSC, tsc);
+ int ret;
+ ret = read_msr(0, MSR_TSC, tsc);
+ if (ret)
+ dprint("Reading TSC MSR failed, returning %llu\n", *tsc);
+ return ret;
}
static int mperf_init_stats(unsigned int cpu)
@@ -97,36 +114,11 @@ static int mperf_measure_stats(unsigned int cpu)
return 0;
}
-/*
- * get_average_perf()
- *
- * Returns the average performance (also considers boosted frequencies)
- *
- * Input:
- * aperf_diff: Difference of the aperf register over a time period
- * mperf_diff: Difference of the mperf register over the same time period
- * max_freq: Maximum frequency (P0)
- *
- * Returns:
- * Average performance over the time period
- */
-static unsigned long get_average_perf(unsigned long long aperf_diff,
- unsigned long long mperf_diff)
-{
- unsigned int perf_percent = 0;
- if (((unsigned long)(-1) / 100) < aperf_diff) {
- int shift_count = 7;
- aperf_diff >>= shift_count;
- mperf_diff >>= shift_count;
- }
- perf_percent = (aperf_diff * 100) / mperf_diff;
- return (max_frequency * perf_percent) / 100;
-}
-
static int mperf_get_count_percent(unsigned int id, double *percent,
unsigned int cpu)
{
unsigned long long aperf_diff, mperf_diff, tsc_diff;
+ unsigned long long timediff;
if (!is_valid[cpu])
return -1;
@@ -136,11 +128,19 @@ static int mperf_get_count_percent(unsigned int id, double *percent,
mperf_diff = mperf_current_count[cpu] - mperf_previous_count[cpu];
aperf_diff = aperf_current_count[cpu] - aperf_previous_count[cpu];
- tsc_diff = tsc_at_measure_end - tsc_at_measure_start;
- *percent = 100.0 * mperf_diff / tsc_diff;
- dprint("%s: mperf_diff: %llu, tsc_diff: %llu\n",
- mperf_cstates[id].name, mperf_diff, tsc_diff);
+ if (max_freq_mode == MAX_FREQ_TSC_REF) {
+ tsc_diff = tsc_at_measure_end - tsc_at_measure_start;
+ *percent = 100.0 * mperf_diff / tsc_diff;
+ dprint("%s: TSC Ref - mperf_diff: %llu, tsc_diff: %llu\n",
+ mperf_cstates[id].name, mperf_diff, tsc_diff);
+ } else if (max_freq_mode == MAX_FREQ_SYSFS) {
+ timediff = timespec_diff_us(time_start, time_end);
+ *percent = 100.0 * mperf_diff / timediff;
+ dprint("%s: MAXFREQ - mperf_diff: %llu, time_diff: %llu\n",
+ mperf_cstates[id].name, mperf_diff, timediff);
+ } else
+ return -1;
if (id == Cx)
*percent = 100.0 - *percent;
@@ -154,7 +154,7 @@ static int mperf_get_count_percent(unsigned int id, double *percent,
static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
unsigned int cpu)
{
- unsigned long long aperf_diff, mperf_diff;
+ unsigned long long aperf_diff, mperf_diff, time_diff, tsc_diff;
if (id != AVG_FREQ)
return 1;
@@ -165,11 +165,21 @@ static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
mperf_diff = mperf_current_count[cpu] - mperf_previous_count[cpu];
aperf_diff = aperf_current_count[cpu] - aperf_previous_count[cpu];
- /* Return MHz for now, might want to return KHz if column width is more
- generic */
- *count = get_average_perf(aperf_diff, mperf_diff) / 1000;
- dprint("%s: %llu\n", mperf_cstates[id].name, *count);
+ if (max_freq_mode == MAX_FREQ_TSC_REF) {
+ /* Calculate max_freq from TSC count */
+ tsc_diff = tsc_at_measure_end - tsc_at_measure_start;
+ time_diff = timespec_diff_us(time_start, time_end);
+ max_frequency = tsc_diff / time_diff;
+ }
+ *count = max_frequency * ((double)aperf_diff / mperf_diff);
+ dprint("%s: Average freq based on %s maximum frequency:\n",
+ mperf_cstates[id].name,
+ (max_freq_mode == MAX_FREQ_TSC_REF) ? "TSC calculated" : "sysfs read");
+ dprint("%max_frequency: %lu", max_frequency);
+ dprint("aperf_diff: %llu\n", aperf_diff);
+ dprint("mperf_diff: %llu\n", mperf_diff);
+ dprint("avg freq: %llu\n", *count);
return 0;
}
@@ -178,6 +188,7 @@ static int mperf_start(void)
int cpu;
unsigned long long dbg;
+ clock_gettime(CLOCK_REALTIME, &time_start);
mperf_get_tsc(&tsc_at_measure_start);
for (cpu = 0; cpu < cpu_count; cpu++)
@@ -193,32 +204,104 @@ static int mperf_stop(void)
unsigned long long dbg;
int cpu;
- mperf_get_tsc(&tsc_at_measure_end);
-
for (cpu = 0; cpu < cpu_count; cpu++)
mperf_measure_stats(cpu);
+ mperf_get_tsc(&tsc_at_measure_end);
+ clock_gettime(CLOCK_REALTIME, &time_end);
+
mperf_get_tsc(&dbg);
dprint("TSC diff: %llu\n", dbg - tsc_at_measure_end);
return 0;
}
-struct cpuidle_monitor mperf_monitor;
-
-struct cpuidle_monitor *mperf_register(void)
+/*
+ * Mperf register is defined to tick at P0 (maximum) frequency
+ *
+ * Instead of reading out P0 which can be tricky to read out from HW,
+ * we use TSC counter if it reliably ticks at P0/mperf frequency.
+ *
+ * Still try to fall back to:
+ * /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
+ * on older Intel HW without invariant TSC feature.
+ * Or on AMD machines where TSC does not tick at P0 (do not exist yet, but
+ * it's still double checked (MSR_AMD_HWCR)).
+ *
+ * On these machines the user would still get useful mperf
+ * stats when acpi-cpufreq driver is loaded.
+ */
+static int init_maxfreq_mode(void)
{
+ int ret;
+ unsigned long long hwcr;
unsigned long min;
- if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_APERF))
- return NULL;
-
- /* Assume min/max all the same on all cores */
+ if (!cpupower_cpu_info.caps & CPUPOWER_CAP_INV_TSC)
+ goto use_sysfs;
+
+ if (cpupower_cpu_info.vendor == X86_VENDOR_AMD) {
+ /* MSR_AMD_HWCR tells us whether TSC runs at P0/mperf
+ * freq.
+ * A test whether hwcr is accessable/available would be:
+ * (cpupower_cpu_info.family > 0x10 ||
+ * cpupower_cpu_info.family == 0x10 &&
+ * cpupower_cpu_info.model >= 0x2))
+ * This should be the case for all aperf/mperf
+ * capable AMD machines and is therefore safe to test here.
+ * Compare with Linus kernel git commit: acf01734b1747b1ec4
+ */
+ ret = read_msr(0, MSR_AMD_HWCR, &hwcr);
+ /*
+ * If the MSR read failed, assume a Xen system that did
+ * not explicitly provide access to it and assume TSC works
+ */
+ if (ret != 0) {
+ dprint("TSC read 0x%x failed - assume TSC working\n",
+ MSR_AMD_HWCR);
+ return 0;
+ } else if (1 & (hwcr >> 24)) {
+ max_freq_mode = MAX_FREQ_TSC_REF;
+ return 0;
+ } else { /* Use sysfs max frequency if available */ }
+ } else if (cpupower_cpu_info.vendor == X86_VENDOR_INTEL) {
+ /*
+ * On Intel we assume mperf (in C0) is ticking at same
+ * rate than TSC
+ */
+ max_freq_mode = MAX_FREQ_TSC_REF;
+ return 0;
+ }
+use_sysfs:
if (cpufreq_get_hardware_limits(0, &min, &max_frequency)) {
dprint("Cannot retrieve max freq from cpufreq kernel "
"subsystem\n");
- return NULL;
+ return -1;
}
+ max_freq_mode = MAX_FREQ_SYSFS;
+ return 0;
+}
+
+/*
+ * This monitor provides:
+ *
+ * 1) Average frequency a CPU resided in
+ * This always works if the CPU has aperf/mperf capabilities
+ *
+ * 2) C0 and Cx (any sleep state) time a CPU resided in
+ * Works if mperf timer stops ticking in sleep states which
+ * seem to be the case on all current HW.
+ * Both is directly retrieved from HW registers and is independent
+ * from kernel statistics.
+ */
+struct cpuidle_monitor mperf_monitor;
+struct cpuidle_monitor *mperf_register(void)
+{
+ if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_APERF))
+ return NULL;
+
+ if (init_maxfreq_mode())
+ return NULL;
/* Free this at program termination */
is_valid = calloc(cpu_count, sizeof(int));
--
1.7.3.4
--
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