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:

``javascript
var gcStats = require('gcstats.js');

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

This will print blobs like this whenever a GC happens:

`
GC happened { start: 635817864674795,
end: 635817865774643,
gctype: 1,
before:
{ totalHeapSize: 277510912,
totalHeapExecutableSize: 5242880,
usedHeapSize: 273621856,
heapSizeLimit: 1535115264,
totalPhysicalSize: 277510912 },
after:
{ totalHeapSize: 277510912,
totalHeapExecutableSize: 5242880,
usedHeapSize: 273533760,
heapSizeLimit: 1535115264,
totalPhysicalSize: 277510912 } }
`

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()

gctype can have the following values:
* 1: Scavenge (minor GC)
* 2: Mark/Sweep/Compact (major GC)
* 3: Both 1 and 2

Installation

`
npm install --save gcstats.js
`

Node version compatibility

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 and the compatibility file.

Credits

node-gcstats` was written by @dainis and later adopted by @bripkens.