diff options
Diffstat (limited to 'tools/power/x86/turbostat/turbostat.8')
| -rw-r--r-- | tools/power/x86/turbostat/turbostat.8 | 66 |
1 files changed, 45 insertions, 21 deletions
diff --git a/tools/power/x86/turbostat/turbostat.8 b/tools/power/x86/turbostat/turbostat.8 index 56bfb523c5bb..9b950699e63d 100644 --- a/tools/power/x86/turbostat/turbostat.8 +++ b/tools/power/x86/turbostat/turbostat.8 @@ -12,16 +12,16 @@ turbostat \- Report processor frequency and idle statistics .RB [ "\-i interval_sec" ] .SH DESCRIPTION \fBturbostat \fP reports processor topology, frequency, -idle power-state statistics, temperature and power on modern X86 processors. -Either \fBcommand\fP is forked and statistics are printed -upon its completion, or statistics are printed periodically. - -\fBturbostat \fP -must be run on root, and -minimally requires that the processor -supports an "invariant" TSC, plus the APERF and MPERF MSRs. -Additional information is reported depending on hardware counter support. - +idle power-state statistics, temperature and power on X86 processors. +There are two ways to invoke turbostat. +The first method is to supply a +\fBcommand\fP, which is forked and statistics are printed +upon its completion. +The second method is to omit the command, +and turbodstat will print statistics every 5 seconds. +The 5-second interval can changed using the -i option. + +Some information is not availalbe on older processors. .SS Options The \fB-p\fP option limits output to the 1st thread in 1st core of each package. .PP @@ -130,12 +130,13 @@ cpu3: MSR_IA32_THERM_STATUS: 0x884e0000 (27 C +/- 1) ... .fi The \fBmax efficiency\fP frequency, a.k.a. Low Frequency Mode, is the frequency -available at the minimum package voltage. The \fBTSC frequency\fP is the nominal -maximum frequency of the processor if turbo-mode were not available. This frequency +available at the minimum package voltage. The \fBTSC frequency\fP is the base +frequency of the processor -- this should match the brand string +in /proc/cpuinfo. This base frequency should be sustainable on all CPUs indefinitely, given nominal power and cooling. The remaining rows show what maximum turbo frequency is possible -depending on the number of idle cores. Note that this information is -not available on all processors. +depending on the number of idle cores. Note that not all information is +available on all processors. .SH FORK EXAMPLE If turbostat is invoked with a command, it will fork that command and output the statistics gathered when the command exits. @@ -176,6 +177,11 @@ not including any non-busy idle time. .B "turbostat " must be run as root. +Alternatively, non-root users can be enabled to run turbostat this way: + +# setcap cap_sys_rawio=ep ./turbostat + +# chmod +r /dev/cpu/*/msr .B "turbostat " reads hardware counters, but doesn't write them. @@ -184,15 +190,33 @@ multiple invocations of itself. \fBturbostat \fP may work poorly on Linux-2.6.20 through 2.6.29, -as \fBacpi-cpufreq \fPperiodically cleared the APERF and MPERF +as \fBacpi-cpufreq \fPperiodically cleared the APERF and MPERF MSRs in those kernels. -If the TSC column does not make sense, then -the other numbers will also make no sense. -Turbostat is lightweight, and its data collection is not atomic. -These issues are usually caused by an extremely short measurement -interval (much less than 1 second), or system activity that prevents -turbostat from being able to run on all CPUS to quickly collect data. +AVG_MHz = APERF_delta/measurement_interval. This is the actual +number of elapsed cycles divided by the entire sample interval -- +including idle time. Note that this calculation is resiliant +to systems lacking a non-stop TSC. + +TSC_MHz = TSC_delta/measurement_interval. +On a system with an invariant TSC, this value will be constant +and will closely match the base frequency value shown +in the brand string in /proc/cpuinfo. On a system where +the TSC stops in idle, TSC_MHz will drop +below the processor's base frequency. + +%Busy = MPERF_delta/TSC_delta + +Bzy_MHz = TSC_delta/APERF_delta/MPERF_delta/measurement_interval + +Note that these calculations depend on TSC_delta, so they +are not reliable during intervals when TSC_MHz is not running at the base frequency. + +Turbostat data collection is not atomic. +Extremely short measurement intervals (much less than 1 second), +or system activity that prevents turbostat from being able +to run on all CPUS to quickly collect data, will result in +inconsistent results. The APERF, MPERF MSRs are defined to count non-halted cycles. Although it is not guaranteed by the architecture, turbostat assumes |