com.facebook.battery.metrics.cpu

Class CpuFrequencyMetricsCollector

java.lang.Object

com.facebook.battery.metrics.api.SystemMetricsCollector<CpuFrequencyMetrics>

com.facebook.battery.metrics.cpu.CpuFrequencyMetricsCollector

public class CpuFrequencyMetricsCollector
extends SystemMetricsCollector<CpuFrequencyMetrics>

Capture CPU frequency statistics.

Note that cpu frequencies are device wide and not specific to a process: this will be more accurate the more frequently it's sampled, but there are times when it will mis-attribute different frequencies while the instrumented app is inactive. The net cpu time of this app at those times should also be very low, so the net energy impact should not be too affected.

The available statistics are well documented on kernel.org at https://www.kernel.org/doc/Documentation/cpu-freq/cpufreq-stats.txt.

Constructor Summary

Constructors

Constructor and Description
CpuFrequencyMetricsCollector()

Method Summary

Modifier and Type	Method and Description
CpuFrequencyMetrics	createMetrics() Creates an empty instance of the corresponding system metrics.
protected java.lang.String	getPath(int core)
boolean	getSnapshot(CpuFrequencyMetrics snapshot) Note that access to snapshot instances is not synchronized and must be taken care of by the caller requesting getSnapshot.
static int	getTotalCores() Returns total cores available on the system: note that this is different from Runtime.availableProcessors() which will exclude currently offline processors.
static void	overrideCores() Override cores: this only works /before/ the first call to getTotalCores.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CpuFrequencyMetricsCollector

public CpuFrequencyMetricsCollector()

Method Detail

getSnapshot

public boolean getSnapshot(CpuFrequencyMetrics snapshot)

Description copied from class: SystemMetricsCollector

Note that access to snapshot instances is not synchronized and must be taken care of by the caller requesting getSnapshot.

Specified by:

getSnapshot in class SystemMetricsCollector<CpuFrequencyMetrics>

Parameters:

snapshot - snapshot on which the data will be written

Returns:

true if the snapshot has been updated with valid data.

getPath

protected java.lang.String getPath(int core)

createMetrics

public CpuFrequencyMetrics createMetrics()

Description copied from class: SystemMetricsCollector

Creates an empty instance of the corresponding system metrics.

Explicitly having this function available reduces a significant amount of boilerplate

Specified by:

createMetrics in class SystemMetricsCollector<CpuFrequencyMetrics>

Returns:

New System Metrics object

getTotalCores

public static int getTotalCores()

Returns total cores available on the system: note that this is different from Runtime.availableProcessors() which will exclude currently offline processors.

overrideCores

public static void overrideCores()

Override cores: this only works /before/ the first call to getTotalCores.