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>

diff --git a/tools/power/x86/turbostat/turbostat.8 b/tools/power/x86/turbostat/turbostat.8
index 56bfb52..9b95069 100644 (file)
--- 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,
 .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
 .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
  ...
 .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
 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.
 .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.
 
 .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.
 
 .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,
 
 \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.
 
 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
 
 The APERF, MPERF MSRs are defined to count non-halted cycles.
 Although it is not guaranteed by the architecture, turbostat assumes

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index b654b64..a02c02f 100644 (file)
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -673,24 +673,26 @@ delta_thread(struct thread_data *new, struct thread_data *old,
 
        old->c1 = new->c1 - old->c1;
 
 
        old->c1 = new->c1 - old->c1;
 

-       if ((new->aperf > old->aperf) && (new->mperf > old->mperf)) {
-               old->aperf = new->aperf - old->aperf;
-               old->mperf = new->mperf - old->mperf;
-       } else {
+       if (has_aperf) {
+               if ((new->aperf > old->aperf) && (new->mperf > old->mperf)) {
+                       old->aperf = new->aperf - old->aperf;
+                       old->mperf = new->mperf - old->mperf;
+               } else {

 
 

-               if (!aperf_mperf_unstable) {
-                       fprintf(stderr, "%s: APERF or MPERF went backwards *\n", progname);
-                       fprintf(stderr, "* Frequency results do not cover entire interval *\n");
-                       fprintf(stderr, "* fix this by running Linux-2.6.30 or later *\n");
+                       if (!aperf_mperf_unstable) {
+                               fprintf(stderr, "%s: APERF or MPERF went backwards *\n", progname);
+                               fprintf(stderr, "* Frequency results do not cover entire interval *\n");
+                               fprintf(stderr, "* fix this by running Linux-2.6.30 or later *\n");

 
 

-                       aperf_mperf_unstable = 1;
+                               aperf_mperf_unstable = 1;
+                       }
+                       /*
+                        * mperf delta is likely a huge "positive" number
+                        * can not use it for calculating c0 time
+                        */
+                       skip_c0 = 1;
+                       skip_c1 = 1;

                }
                }

-               /*
-                * mperf delta is likely a huge "positive" number
-                * can not use it for calculating c0 time
-                */
-               skip_c0 = 1;
-               skip_c1 = 1;

        }
 
 
        }
 
 


@@ -2244,14 +2246,11 @@ void check_cpuid()
        has_epb = ecx & (1 << 3);
 
        if (verbose)
        has_epb = ecx & (1 << 3);
 
        if (verbose)

-               fprintf(stderr, "CPUID(6): %s%s%s%s\n",
-                       has_aperf ? "APERF" : "No APERF!",
-                       do_dts ? ", DTS" : "",
-                       do_ptm ? ", PTM": "",
-                       has_epb ? ", EPB": "");
-
-       if (!has_aperf)
-               errx(-1, "No APERF");
+               fprintf(stderr, "CPUID(6): %sAPERF, %sDTS, %sPTM, %sEPB\n",
+                       has_aperf ? "" : "No ",
+                       do_dts ? "" : "No ",
+                       do_ptm ? "" : "No ",
+                       has_epb ? "" : "No ");

 
        do_nhm_platform_info = do_nhm_cstates = do_smi = has_nhm_msrs(family, model);
        do_snb_cstates = has_snb_msrs(family, model);
 
        do_nhm_platform_info = do_nhm_cstates = do_smi = has_nhm_msrs(family, model);
        do_snb_cstates = has_snb_msrs(family, model);


@@ -2632,7 +2631,7 @@ int main(int argc, char **argv)
        cmdline(argc, argv);
 
        if (verbose)
        cmdline(argc, argv);
 
        if (verbose)

-               fprintf(stderr, "turbostat v3.8 14-Aug 2014"
+               fprintf(stderr, "turbostat v3.9 23-Jan, 2015"

                        " - Len Brown <lenb@kernel.org>\n");
 
        turbostat_init();
                        " - Len Brown <lenb@kernel.org>\n");
 
        turbostat_init();