summaryrefslogtreecommitdiff
path: root/tools/power
diff options
context:
space:
mode:
Diffstat (limited to 'tools/power')
-rw-r--r--tools/power/x86/turbostat/turbostat.c51
1 files changed, 50 insertions, 1 deletions
diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 9896619e4382..43a6dda434ef 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -1059,19 +1059,68 @@ int get_counters(struct thread_data *t, struct core_data *c, struct pkg_data *p)
{
int cpu = t->cpu_id;
unsigned long long msr;
+ int aperf_mperf_retry_count = 0;
if (cpu_migrate(cpu)) {
fprintf(outf, "Could not migrate to CPU %d\n", cpu);
return -1;
}
+retry:
t->tsc = rdtsc(); /* we are running on local CPU of interest */
if (has_aperf) {
+ unsigned long long tsc_before, tsc_between, tsc_after, aperf_time, mperf_time;
+
+ /*
+ * The TSC, APERF and MPERF must be read together for
+ * APERF/MPERF and MPERF/TSC to give accurate results.
+ *
+ * Unfortunately, APERF and MPERF are read by
+ * individual system call, so delays may occur
+ * between them. If the time to read them
+ * varies by a large amount, we re-read them.
+ */
+
+ /*
+ * This initial dummy APERF read has been seen to
+ * reduce jitter in the subsequent reads.
+ */
+
+ if (get_msr(cpu, MSR_IA32_APERF, &t->aperf))
+ return -3;
+
+ t->tsc = rdtsc(); /* re-read close to APERF */
+
+ tsc_before = t->tsc;
+
if (get_msr(cpu, MSR_IA32_APERF, &t->aperf))
return -3;
+
+ tsc_between = rdtsc();
+
if (get_msr(cpu, MSR_IA32_MPERF, &t->mperf))
return -4;
+
+ tsc_after = rdtsc();
+
+ aperf_time = tsc_between - tsc_before;
+ mperf_time = tsc_after - tsc_between;
+
+ /*
+ * If the system call latency to read APERF and MPERF
+ * differ by more than 2x, then try again.
+ */
+ if ((aperf_time > (2 * mperf_time)) || (mperf_time > (2 * aperf_time))) {
+ aperf_mperf_retry_count++;
+ if (aperf_mperf_retry_count < 5)
+ goto retry;
+ else
+ warnx("cpu%d jitter %lld %lld",
+ cpu, aperf_time, mperf_time);
+ }
+ aperf_mperf_retry_count = 0;
+
t->aperf = t->aperf * aperf_mperf_multiplier;
t->mperf = t->mperf * aperf_mperf_multiplier;
}
@@ -3554,7 +3603,7 @@ int get_and_dump_counters(void)
}
void print_version() {
- fprintf(outf, "turbostat version 4.10 10 Dec, 2015"
+ fprintf(outf, "turbostat version 4.11 27 Feb 2016"
" - Len Brown <lenb@kernel.org>\n");
}