tools/power turbostat: relax dependency on APERF_MSR
While turbostat is significantly less useful on systems with no APERF_MSR, it seems more friendly to run on such systems and report what we can, rather than refusing to run. Update man page to reflect recent changes. Signed-off-by: Len Brown <len.brown@intel.com>hifive-unleashed-5.1
Len Brown
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d789944753
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a729617c58
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@ -12,16 +12,16 @@ turbostat \- Report processor frequency and idle statistics
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.RB [ "\-i interval_sec" ]
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.SH DESCRIPTION
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\fBturbostat \fP reports processor topology, frequency,
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idle power-state statistics, temperature and power on modern X86 processors.
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Either \fBcommand\fP is forked and statistics are printed
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upon its completion, or statistics are printed periodically.
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\fBturbostat \fP
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must be run on root, and
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minimally requires that the processor
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supports an "invariant" TSC, plus the APERF and MPERF MSRs.
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Additional information is reported depending on hardware counter support.
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idle power-state statistics, temperature and power on X86 processors.
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There are two ways to invoke turbostat.
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The first method is to supply a
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\fBcommand\fP, which is forked and statistics are printed
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upon its completion.
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The second method is to omit the command,
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and turbodstat will print statistics every 5 seconds.
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The 5-second interval can changed using the -i option.
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Some information is not availalbe on older processors.
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.SS Options
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The \fB-p\fP option limits output to the 1st thread in 1st core of each package.
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.PP
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@ -130,12 +130,13 @@ cpu3: MSR_IA32_THERM_STATUS: 0x884e0000 (27 C +/- 1)
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...
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.fi
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The \fBmax efficiency\fP frequency, a.k.a. Low Frequency Mode, is the frequency
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available at the minimum package voltage. The \fBTSC frequency\fP is the nominal
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maximum frequency of the processor if turbo-mode were not available. This frequency
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available at the minimum package voltage. The \fBTSC frequency\fP is the base
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frequency of the processor -- this should match the brand string
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in /proc/cpuinfo. This base frequency
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should be sustainable on all CPUs indefinitely, given nominal power and cooling.
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The remaining rows show what maximum turbo frequency is possible
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depending on the number of idle cores. Note that this information is
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not available on all processors.
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depending on the number of idle cores. Note that not all information is
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available on all processors.
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.SH FORK EXAMPLE
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If turbostat is invoked with a command, it will fork that command
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and output the statistics gathered when the command exits.
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@ -176,6 +177,11 @@ not including any non-busy idle time.
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.B "turbostat "
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must be run as root.
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Alternatively, non-root users can be enabled to run turbostat this way:
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# setcap cap_sys_rawio=ep ./turbostat
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# chmod +r /dev/cpu/*/msr
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.B "turbostat "
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reads hardware counters, but doesn't write them.
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@ -184,15 +190,33 @@ multiple invocations of itself.
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\fBturbostat \fP
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may work poorly on Linux-2.6.20 through 2.6.29,
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as \fBacpi-cpufreq \fPperiodically cleared the APERF and MPERF
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as \fBacpi-cpufreq \fPperiodically cleared the APERF and MPERF MSRs
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in those kernels.
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If the TSC column does not make sense, then
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the other numbers will also make no sense.
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Turbostat is lightweight, and its data collection is not atomic.
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These issues are usually caused by an extremely short measurement
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interval (much less than 1 second), or system activity that prevents
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turbostat from being able to run on all CPUS to quickly collect data.
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AVG_MHz = APERF_delta/measurement_interval. This is the actual
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number of elapsed cycles divided by the entire sample interval --
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including idle time. Note that this calculation is resiliant
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to systems lacking a non-stop TSC.
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TSC_MHz = TSC_delta/measurement_interval.
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On a system with an invariant TSC, this value will be constant
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and will closely match the base frequency value shown
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in the brand string in /proc/cpuinfo. On a system where
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the TSC stops in idle, TSC_MHz will drop
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below the processor's base frequency.
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%Busy = MPERF_delta/TSC_delta
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Bzy_MHz = TSC_delta/APERF_delta/MPERF_delta/measurement_interval
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Note that these calculations depend on TSC_delta, so they
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are not reliable during intervals when TSC_MHz is not running at the base frequency.
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Turbostat data collection is not atomic.
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Extremely short measurement intervals (much less than 1 second),
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or system activity that prevents turbostat from being able
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to run on all CPUS to quickly collect data, will result in
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inconsistent results.
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The APERF, MPERF MSRs are defined to count non-halted cycles.
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Although it is not guaranteed by the architecture, turbostat assumes
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@ -673,24 +673,26 @@ delta_thread(struct thread_data *new, struct thread_data *old,
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old->c1 = new->c1 - old->c1;
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if ((new->aperf > old->aperf) && (new->mperf > old->mperf)) {
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old->aperf = new->aperf - old->aperf;
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old->mperf = new->mperf - old->mperf;
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} else {
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if (has_aperf) {
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if ((new->aperf > old->aperf) && (new->mperf > old->mperf)) {
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old->aperf = new->aperf - old->aperf;
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old->mperf = new->mperf - old->mperf;
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} else {
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if (!aperf_mperf_unstable) {
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fprintf(stderr, "%s: APERF or MPERF went backwards *\n", progname);
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fprintf(stderr, "* Frequency results do not cover entire interval *\n");
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fprintf(stderr, "* fix this by running Linux-2.6.30 or later *\n");
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if (!aperf_mperf_unstable) {
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fprintf(stderr, "%s: APERF or MPERF went backwards *\n", progname);
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fprintf(stderr, "* Frequency results do not cover entire interval *\n");
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fprintf(stderr, "* fix this by running Linux-2.6.30 or later *\n");
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aperf_mperf_unstable = 1;
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aperf_mperf_unstable = 1;
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}
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/*
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* mperf delta is likely a huge "positive" number
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* can not use it for calculating c0 time
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*/
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skip_c0 = 1;
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skip_c1 = 1;
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}
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/*
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* mperf delta is likely a huge "positive" number
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* can not use it for calculating c0 time
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*/
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skip_c0 = 1;
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skip_c1 = 1;
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}
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@ -2244,14 +2246,11 @@ void check_cpuid()
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has_epb = ecx & (1 << 3);
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if (verbose)
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fprintf(stderr, "CPUID(6): %s%s%s%s\n",
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has_aperf ? "APERF" : "No APERF!",
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do_dts ? ", DTS" : "",
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do_ptm ? ", PTM": "",
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has_epb ? ", EPB": "");
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if (!has_aperf)
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errx(-1, "No APERF");
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fprintf(stderr, "CPUID(6): %sAPERF, %sDTS, %sPTM, %sEPB\n",
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has_aperf ? "" : "No ",
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do_dts ? "" : "No ",
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do_ptm ? "" : "No ",
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has_epb ? "" : "No ");
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do_nhm_platform_info = do_nhm_cstates = do_smi = has_nhm_msrs(family, model);
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do_snb_cstates = has_snb_msrs(family, model);
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@ -2632,7 +2631,7 @@ int main(int argc, char **argv)
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cmdline(argc, argv);
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if (verbose)
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fprintf(stderr, "turbostat v3.8 14-Aug 2014"
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fprintf(stderr, "turbostat v3.9 23-Jan, 2015"
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" - Len Brown <lenb@kernel.org>\n");
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turbostat_init();
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