[PATCH v3] cpupower: fix TSC MHz calculation

[PATCH v3] cpupower: fix TSC MHz calculation

[He Rongguang]

Commit 'cpupower: Make TSC read per CPU for Mperf monitor' (c2adb1877b7)
changes TSC counter reads per cpu, but left time diff global (from start
of all cpus to end of all cpus), thus diff(time) is too large for a
cpu's tsc counting, resulting in far less than acutal TSC_Mhz and thus
`cpupower monitor` showing far less than actual cpu realtime frequency.

/proc/cpuinfo shows frequency:
cat /proc/cpuinfo | egrep -e 'processor' -e 'MHz'
...
processor : 171
cpu MHz   : 4108.498
...

before fix (System 100% busy):
    | Mperf              || Idle_Stats
 CPU| C0   | Cx   | Freq  || POLL | C1   | C2
 171|  0.77| 99.23|  2279||  0.00|  0.00|  0.00

after fix (System 100% busy):
    | Mperf              || Idle_Stats
 CPU| C0   | Cx   | Freq  || POLL | C1   | C2
 171|  0.46| 99.54|  4095||  0.00|  0.00|  0.00

Fixes: c2adb1877b76 ("cpupower: Make TSC read per CPU for Mperf monitor")
Signed-off-by: He Rongguang <herongguang@linux.alibaba.com>
---
Changes in v3:
- disable thunderbird sending mail auto wrap.
- Link to v2: https://lore.kernel.org/linux-pm/60562222-6186-4eec-9c20-08b1cebb1311@linux.alibaba.com/T/#u

Changes in v2:
- Fix scripts/checkpatch.pl style warnings.
- Link to v1: https://lore.kernel.org/linux-pm/269b8bb2-85b5-4cc9-9354-a1270f2eed35@linux.alibaba.com/T/#u
---
 .../cpupower/utils/idle_monitor/mperf_monitor.c   | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
index ae6af354a81d..08a399b0be28 100644
--- a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
+++ b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
@@ -33,7 +33,7 @@ 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 struct timespec *time_start, *time_end;
 
 static cstate_t mperf_cstates[MPERF_CSTATE_COUNT] = {
 	{
@@ -174,7 +174,7 @@ static int mperf_get_count_percent(unsigned int id, double *percent,
 		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 = max_frequency * timespec_diff_us(time_start, time_end);
+		timediff = max_frequency * timespec_diff_us(time_start[cpu], time_end[cpu]);
 		*percent = 100.0 * mperf_diff / timediff;
 		dprint("%s: MAXFREQ - mperf_diff: %llu, time_diff: %llu\n",
 		       mperf_cstates[id].name, mperf_diff, timediff);
@@ -207,7 +207,7 @@ static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
 	if (max_freq_mode == MAX_FREQ_TSC_REF) {
 		/* Calculate max_freq from TSC count */
 		tsc_diff = tsc_at_measure_end[cpu] - tsc_at_measure_start[cpu];
-		time_diff = timespec_diff_us(time_start, time_end);
+		time_diff = timespec_diff_us(time_start[cpu], time_end[cpu]);
 		max_frequency = tsc_diff / time_diff;
 	}
 
@@ -226,9 +226,8 @@ static int mperf_start(void)
 {
 	int cpu;
 
-	clock_gettime(CLOCK_REALTIME, &time_start);
-
 	for (cpu = 0; cpu < cpu_count; cpu++) {
+		clock_gettime(CLOCK_REALTIME, &time_start[cpu]);
 		mperf_get_tsc(&tsc_at_measure_start[cpu]);
 		mperf_init_stats(cpu);
 	}
@@ -243,9 +242,9 @@ static int mperf_stop(void)
 	for (cpu = 0; cpu < cpu_count; cpu++) {
 		mperf_measure_stats(cpu);
 		mperf_get_tsc(&tsc_at_measure_end[cpu]);
+		clock_gettime(CLOCK_REALTIME, &time_end[cpu]);
 	}
 
-	clock_gettime(CLOCK_REALTIME, &time_end);
 	return 0;
 }
 
@@ -349,6 +348,8 @@ struct cpuidle_monitor *mperf_register(void)
 	aperf_current_count = calloc(cpu_count, sizeof(unsigned long long));
 	tsc_at_measure_start = calloc(cpu_count, sizeof(unsigned long long));
 	tsc_at_measure_end = calloc(cpu_count, sizeof(unsigned long long));
+	time_start = calloc(cpu_count, sizeof(struct timespec));
+	time_end = calloc(cpu_count, sizeof(struct timespec));
 	mperf_monitor.name_len = strlen(mperf_monitor.name);
 	return &mperf_monitor;
 }
@@ -361,6 +362,8 @@ void mperf_unregister(void)
 	free(aperf_current_count);
 	free(tsc_at_measure_start);
 	free(tsc_at_measure_end);
+	free(time_start);
+	free(time_end);
 	free(is_valid);
 }
 
-- 
2.43.0

Re: [PATCH v3] cpupower: fix TSC MHz calculation

[Shuah]

On 12/11/24 19:14, He Rongguang wrote:
> Commit 'cpupower: Make TSC read per CPU for Mperf monitor' (c2adb1877b7)
> changes TSC counter reads per cpu, but left time diff global (from start
> of all cpus to end of all cpus), thus diff(time) is too large for a
> cpu's tsc counting, resulting in far less than acutal TSC_Mhz and thus
> `cpupower monitor` showing far less than actual cpu realtime frequency.
> 
> /proc/cpuinfo shows frequency:
> cat /proc/cpuinfo | egrep -e 'processor' -e 'MHz'
> ...
> processor : 171
> cpu MHz   : 4108.498
> ...
> 
> before fix (System 100% busy):
>      | Mperf              || Idle_Stats
>   CPU| C0   | Cx   | Freq  || POLL | C1   | C2
>   171|  0.77| 99.23|  2279||  0.00|  0.00|  0.00
> 
> after fix (System 100% busy):
>      | Mperf              || Idle_Stats
>   CPU| C0   | Cx   | Freq  || POLL | C1   | C2
>   171|  0.46| 99.54|  4095||  0.00|  0.00|  0.00
> 
> Fixes: c2adb1877b76 ("cpupower: Make TSC read per CPU for Mperf monitor")
> Signed-off-by: He Rongguang <herongguang@linux.alibaba.com>
> ---

Applied to
https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux.git/log/?h=cpupower
to be included in my next pull request to Rafael.

thanks,
-- Shuah