Custom Flags

The V8 engine comes with a set of controlling flags that may be useful for fine-grained tuning. You can set these flags in the secondary package.json configuration file. This article contains some of the available flags and short explanation on how you can use them. For a complete list of all V8 flags, see the Flag Definitions header file in GitHub.

Expose Garbage Collector

The --expose_gc flag exposes a global gc() function which can be helpful in advanced memory management scenarios.

{
    ...
    "android": {
        "v8Flags": "--expose_gc"
    }
    ...
}

Marking Mode

The markingMode: none flag instructs NativeScript apps to use a different mode for garbage collection, providing significant performance boost. To enable it:

{
    ...
    "android": {
        "markingMode": "none"
    }
    ...
}

NOTE: Use markingMode: none with caution. Unexpected errors related to premature objects collection may occur. More information on proper memory management using markingMode:none.

Timezone Changes

For improved performance, V8 keeps a cache of various values used for date and time computation. This may lead to a negative side effect for the application because changes made to the current timezone will not be reflected until the application is restarted. While this is not a common requirement for most applications, there are some circumstances where this behavior might be needed. To enable this scenario, you can set the handleTimeZoneChanges flag:

{
    ...
    "android": {
        "handleTimeZoneChanges": true
    }
    ...
}

As a result, the application will register a BroadcastReceiver which will be responsible for the ACTION_TIMEZONE_CHANGED event and automatically invalidate the corresponding cache. Subsequent calls to new Date() will then take into account the new timezone.

Maximum Log Message Size

By default, all messages sent to Logcat are limited to 1024 characters and larger messages are automatically truncated. This value can be controlled with the maxLogcatObjectSize field:

{
    ...
    "android": {
        "maxLogcatObjectSize": 2048
    }
    ...
}

Force Log

When you are using a release build there will be no logs to the console, so if you still want to have your console logs you need to enable the forceLog flag:

{
    ...
    "android": {
        "forceLog": true
    }
    ...
}

Use V8 Symbols

If you want to use V8 API in your application code or you want to have the V8 symbols included in the libNativeScript.so file inside the application when built in release mode, you will need to enable the useB8Symbols flag:

{
    ...
    "android": {
        "useV8Symbols": true
    }
    ...
}

Configuring automatic garbage collection

There are three parameters used for configuring the frequency and conditions of automatic triggerring of garbage collections in the JavaScript world. These are gcThrottleTime, memoryCheckInterval and freeMemoryRatio. For detailed explanation of their behavior please refer to the Syncronizing Garabage Collectors section in Memory Management