@ohos.bytrace (Performance Tracing)

The bytrace module implements performance tracing for processes.

NOTE

• The APIs of this module are no longer maintained since API version 8. You are advised to use @ohos.hiTraceMeter.
• 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

Marks the start of a timeslice trace task.

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 task ID can be used. For details, see the bytrace.finishTrace example.

System capability: SystemCapability.HiviewDFX.HiTrace

Parameters:

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

Marks the end of a timeslice trace task.

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

System capability: SystemCapability.HiviewDFX.HiTrace

Parameters:

Example

bytrace.finishTrace("myTestFunc", 1);

// Start trace 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 trace tasks with the same name in serial mode.
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

Defines a numeric variable that indicates the number of timeslice trace tasks.

System capability: SystemCapability.HiviewDFX.HiTrace

Parameters:

Example

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