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# V8
Stability: 2 - Stable
This module exposes events and interfaces specific to the version of [V8][]
built with Node.js. These interfaces are subject to change by upstream and are
therefore not covered under the stability index.
## v8.getHeapStatistics()
<!-- YAML
added: v1.0.0
-->
Returns an object with the following properties
```js
{
total_heap_size: 7326976,
total_heap_size_executable: 4194304,
total_physical_size: 7326976,
total_available_size: 1152656,
used_heap_size: 3476208,
heap_size_limit: 1535115264
}
```
## v8.getHeapSpaceStatistics()
<!-- YAML
added: v6.0.0
-->
Returns statistics about the V8 heap spaces, i.e. the segments which make up
the V8 heap. Order of heap spaces nor availability of a heap space can be
guaranteed as the statistics are provided via the V8 `GetHeapSpaceStatistics`
function.
Example result:
```
[
{
"space_name": "new_space",
"space_size": 2063872,
"space_used_size": 951112,
"space_available_size": 80824,
"physical_space_size": 2063872
},
{
"space_name": "old_space",
"space_size": 3090560,
"space_used_size": 2493792,
"space_available_size": 0,
"physical_space_size": 3090560
},
{
"space_name": "code_space",
"space_size": 1260160,
"space_used_size": 644256,
"space_available_size": 960,
"physical_space_size": 1260160
},
{
"space_name": "map_space",
"space_size": 1094160,
"space_used_size": 201608,
"space_available_size": 0,
"physical_space_size": 1094160
},
{
"space_name": "large_object_space",
"space_size": 0,
"space_used_size": 0,
"space_available_size": 1490980608,
"physical_space_size": 0
}
]
```
## v8.setFlagsFromString(string)
<!-- YAML
added: v1.0.0
-->
Set additional V8 command line flags. Use with care; changing settings
after the VM has started may result in unpredictable behavior, including
crashes and data loss. Or it may simply do nothing.
The V8 options available for a version of Node.js may be determined by running
`node --v8-options`. An unofficial, community-maintained list of options
and their effects is available [here][].
Usage:
```js
// Print GC events to stdout for one minute.
const v8 = require('v8');
v8.setFlagsFromString('--trace_gc');
setTimeout(function() { v8.setFlagsFromString('--notrace_gc'); }, 60e3);
```
[V8]: https://developers.google.com/v8/
[here]: https://github.com/thlorenz/v8-flags/blob/master/flags-0.11.md
|
