diff options
| -rw-r--r-- | tools/power/x86/turbostat/turbostat.c | 51 |
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"); } |