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[1/2] pm: cpupower: Fix the snapshot-order of tsc,mperf, clock in mperf_stop()

Message ID 20250612122355.19629-2-gautham.shenoy@amd.com
State New
Headers show
Series pm: cpupower: Couple of fixes to the cpupower monitor | expand

Commit Message

Gautham R. Shenoy June 12, 2025, 12:23 p.m. UTC 
In the function mperf_start(), mperf_monitor snapshots the time, tsc
and finally the aperf,mperf MSRs. However, this order of snapshotting
in is reversed in mperf_stop(). As a result, the C0 residency (which
is computed as delta_mperf * 100 / delta_tsc) is under-reported on
CPUs that is 100% busy.

Fix this by snapshotting time, tsc and then aperf,mperf in
mperf_stop() in the same order as in mperf_start().

Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
---
 tools/power/cpupower/utils/idle_monitor/mperf_monitor.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
index 73b6b10cbdd2..5ae02c3d5b64 100644
--- a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
+++ b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
@@ -240,9 +240,9 @@  static int mperf_stop(void)
 	int cpu;
 
 	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]);
+		mperf_get_tsc(&tsc_at_measure_end[cpu]);
+		mperf_measure_stats(cpu);
 	}
 
 	return 0;