Package Exports

gc-stats
gc-stats/binding

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (gc-stats) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

GCStats

Exposes stats about V8 GC after it has been executed.

Usage

Create a new instance of the module and subscribe to stats-events from that:

var gc = (require('gc-stats'))();

gc.on('stats', function (stats) {
    console.log('GC happened', stats);
});

This will print blobs like this whenever a GC happened:

GC happened {
    pause: 433034,
    pauseMS: 0,
    gctype: 1,
    before: {
        totalHeapSize: 18635008,
        totalHeapExecutableSize: 4194304,
        usedHeapSize: 12222496,
        heapSizeLimit: 1535115264
    }, after: {
        totalHeapSize: 18635008,
        totalHeapExecutableSize: 4194304,
        usedHeapSize: 8116600,
        heapSizeLimit: 1535115264
    }, diff: {
        totalHeapSize: 0,
        totalHeapExecutableSize: 0,
         usedHeapSize: -4105896,
        heapSizeLimit: 0
    }
}

Property insights

totalHeapSize: Number of bytes V8 has allocated for the heap. This can grow if usedHeap needs more.
usedHeapSize: Number of bytes in use by application data
total HeapExecutableSize: Number of bytes for compiled bytecode and JITed code
heapSizeLimit: The absolute limit the heap cannot exceed
totalPhysicalSize: Commited size (node 0.11+)
pause: Nanoseconds from start to end of GC using hrtime()
pause: Nanoseconds from start to end of GC using hrtime()
pauseMS: pause expressed in milliseconds

gctype can have the following values:

1: Scavenge (minor GC)
2: Mark/Sweep/Compact (major GC)
3: Both 1 and 2

Installation

npm install gc-stats

Node version support

node-gcstats depends on C++ extensions which are compiled when the gc-stats module is installed. Compatibility information can be inspected via the Travis-CI build jobs.