Commit 2dfc818b authored by Thomas Renninger's avatar Thomas Renninger Committed by Dominik Brodowski
Browse files

cpupower: mperf monitor - Use TSC to calculate max frequency if possible



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: default avatarThomas Renninger <trenn@suse.de>
Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 75f25bd3
......@@ -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
......
......@@ -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));
......
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