Performance Tracing

NOTE

• The APIs of this module are no longer maintained since API version 8. It is recommended that you use the APIs of hiTraceMeter instead.
• The initial APIs of this module are supported since API version 7. Newly added APIs will be marked with a superscript to indicate their earliest API version.

Modules to Import

import bytrace from '@ohos.bytrace';

bytrace.startTrace

startTrace(name: string, taskId: number, expectedTime?: number): void

Starts a trace task. expectedTime is an optional parameter, which specifies the expected duration of the trace.

System capability: SystemCapability.Developtools.Bytrace

Parameters

NOTE If multiple trace tasks with the same name need to be performed at the same time or a trace task needs to be performed multiple times concurrently, different task IDs must be specified in startTrace. If the trace tasks with the same name are not performed at the same time, the same taskId can be used. For details, see the bytrace.finishTrace example.

Example

bytrace.startTrace("myTestFunc", 1);
bytrace.startTrace("myTestFunc", 1, 5); // The expected duration of the trace is 5 ms.

bytrace.finishTrace

finishTrace(name: string, taskId: number): void

Stops a trace task.

System capability: SystemCapability.Developtools.Bytrace

Parameters

NOTE To stop a trace task, the values of name and task ID in finishTrace must be the same as those in startTrace.

Example

bytrace.finishTrace("myTestFunc", 1);

// Start track tasks with the same name concurrently.
bytrace.startTrace("myTestFunc", 1);
// Service flow
bytrace.startTrace("myTestFunc", 2); // The second trace task starts while the first task is still running. The first and second tasks have the same name but different task IDs.
// Service flow
bytrace.finishTrace("myTestFunc", 1);
// Service flow
bytrace.finishTrace("myTestFunc", 2);

// Start track tasks with the same name at different times.
bytrace.startTrace("myTestFunc", 1);
// Service flow
bytrace.finishTrace("myTestFunc", 1); // The first trace task ends.
// Service flow
bytrace.startTrace("myTestFunc", 1); // The second trace task starts after the first task ends. The two tasks have the same name and task ID. 
// Service flow
bytrace.finishTrace("myTestFunc", 1);

bytrace.traceByValue

traceByValue(name: string, count: number): void

Traces the value changes of a variable.

System capability: SystemCapability.Developtools.Bytrace

Parameters

Example

let traceCount = 3;
bytrace.traceByValue("myTestCount", traceCount);
traceCount = 4;
bytrace.traceByValue("myTestCount", traceCount);
// Service flow