cpupower: Provide -c param for cpupower monitor to schedule process o…

…n all cores

If an MSR based monitor is run in parallel this is not needed. This is the
default case on all/most Intel machines.

But when only sysfs info is read via cpupower monitor -m Idle_Stats (typically
the case for non root users) or when other monitors are PCI based (AMD),
Idle_Stats, read from sysfs can be totally bogus:

cpupower monitor -m Idle_Stats
PKG |CORE|CPU | POLL | C1-N | C3-N | C6-N
   0|   0|   0|  0.00|  0.00|  0.24| 99.81
   0|   0|  32|  0.00|  0.00|  0.00| 100.7
...
   0|  17|  20|  0.00|  0.00|  0.00| 173.1
   0|  17|  52|  0.00|  0.00|  0.07| 173.0
   0|  18|  68|  0.00|  0.00|  0.00|  0.00
   0|  18|  76|  0.00|  0.00|  0.00|  0.00
...

With the -c option all cores are woken up and the kernel
did update cpuidle statistics before reading out sysfs.
This causes some overhead. Therefore avoid if possible, use
if needed:

cpupower monitor -c -m Idle_Stats
PKG |CORE|CPU | POLL | C1-N | C3-N | C6-N
   0|   0|   0|  0.00|  0.00|  0.00| 100.2
   0|   0|  32|  0.00|  0.00|  0.00| 100.2
...
   0|   8|   8|  0.00|  0.00|  0.00| 99.82
   0|   8|  40|  0.00|  0.00|  0.00| 99.81
   0|   9|  24|  0.00|  0.00|  0.00| 100.3
   0|   9|  56|  0.00|  0.00|  0.00| 100.2
   0|  16|   4|  0.00|  0.00|  0.00| 99.75
   0|  16|  36|  0.00|  0.00|  0.00| 99.38
...

Signed-off-by: Thomas Renninger <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>

tools/power/cpupower/man/cpupower-monitor.1

@@ -7,11 +7,11 @@ cpupower\-monitor \- Report processor frequency and idle statistics
 .RB "\-l"
 
 .B cpupower monitor
-.RB [ "\-m <mon1>," [ "<mon2>,..." ] ]
+.RB [ -c ] [ "\-m <mon1>," [ "<mon2>,..." ] ]
 .RB [ "\-i seconds" ]
 .br
 .B cpupower monitor
-.RB [ "\-m <mon1>," [ "<mon2>,..." ] ]
+.RB [ -c ][ "\-m <mon1>," [ "<mon2>,..." ] ]
 .RB command
 .br
 .SH DESCRIPTION
@@ -64,6 +64,17 @@ Only display specific monitors. Use the monitor string(s) provided by \-l option
 Measure intervall.
 .RE
 .PP
+\-c
+.RS 4
+Schedule the process on every core before starting and ending measuring.
+This could be needed for the Idle_Stats monitor when no other MSR based
+monitor (has to be run on the core that is measured) is run in parallel.
+This is to wake up the processors from deeper sleep states and let the
+kernel re
+-account its cpuidle (C-state) information before reading the
+cpuidle timings from sysfs.
+.RE
+.PP
 command
 .RS 4
 Measure idle and frequency characteristics of an arbitrary command/workload.

tools/power/cpupower/utils/helpers/helpers.h

@@ -114,6 +114,7 @@ struct cpupower_topology {
 
 extern int get_cpu_topology(struct cpupower_topology *cpu_top);
 extern void cpu_topology_release(struct cpupower_topology cpu_top);
+
 /* CPU topology/hierarchy parsing ******************/
 
 /* X86 ONLY ****************************************/

tools/power/cpupower/utils/idle_monitor/cpupower-monitor.c

@@ -39,6 +39,7 @@ static int mode;
 static int interval = 1;
 static char *show_monitors_param;
 static struct cpupower_topology cpu_top;
+static unsigned int wake_cpus;
 
 /* ToDo: Document this in the manpage */
 static char range_abbr[RANGE_MAX] = { 'T', 'C', 'P', 'M', };
@@ -314,16 +315,28 @@ int fork_it(char **argv)
 int do_interval_measure(int i)
 {
 	unsigned int num;
+	int cpu;
+
+	if (wake_cpus)
+		for (cpu = 0; cpu < cpu_count; cpu++)
+			bind_cpu(cpu);
 
 	for (num = 0; num < avail_monitors; num++) {
 		dprint("HW C-state residency monitor: %s - States: %d\n",
 		       monitors[num]->name, monitors[num]->hw_states_num);
 		monitors[num]->start();
 	}
+
 	sleep(i);
+
+	if (wake_cpus)
+		for (cpu = 0; cpu < cpu_count; cpu++)
+			bind_cpu(cpu);
+
 	for (num = 0; num < avail_monitors; num++)
 		monitors[num]->stop();
 
+
 	return 0;
 }
 
@@ -332,7 +345,7 @@ static void cmdline(int argc, char *argv[])
 	int opt;
 	progname = basename(argv[0]);
 
-	while ((opt = getopt(argc, argv, "+li:m:")) != -1) {
+	while ((opt = getopt(argc, argv, "+lci:m:")) != -1) {
 		switch (opt) {
 		case 'l':
 			if (mode)
@@ -351,6 +364,9 @@ static void cmdline(int argc, char *argv[])
 			mode = show;
 			show_monitors_param = optarg;
 			break;
+		case 'c':
+			wake_cpus = 1;
+			break;
 		default:
 			print_wrong_arg_exit();
 		}

tools/power/cpupower/utils/idle_monitor/cpupower-monitor.h

@@ -65,4 +65,21 @@ extern long long timespec_diff_us(struct timespec start, struct timespec end);
 				"could be inaccurate\n"), mes, ov);		\
 }
 
+
+/* Taken over from x86info project sources  -> return 0 on success */
+#include <sched.h>
+#include <sys/types.h>
+#include <unistd.h>
+static inline int bind_cpu(int cpu)
+{
+	cpu_set_t set;
+
+	if (sched_getaffinity(getpid(), sizeof(set), &set) == 0) {
+		CPU_ZERO(&set);
+		CPU_SET(cpu, &set);
+		return sched_setaffinity(getpid(), sizeof(set), &set);
+	}
+	return 1;
+}
+
 #endif /* __CPUIDLE_INFO_HW__ */