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doc: arrange perf_hooks entries alphabetically
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Entries in perf_hooks.md are almost-but-not-quite in alphabetical order.
Our docs (usually) list things in alphabetical order, so move a few
entries to make it so in perf_hooks.md.

PR-URL: #34973
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Harshitha K P <harshitha014@gmail.com>
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@Trott @richardlau
Trott authored and richardlau committed Sep 1, 2020
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202 changes: 102 additions & 100 deletions doc/api/perf_hooks.md
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Expand Up @@ -53,6 +53,62 @@ added: v8.5.0
If `name` is not provided, removes all `PerformanceMark` objects from the
Performance Timeline. If `name` is provided, removes only the named mark.

### `performance.eventLoopUtilization([util1][,util2])`
<!-- YAML
added: REPLACEME
-->

* `util1` {Object} The result of a previous call to `eventLoopUtilization()`
* `util2` {Object} The result of a previous call to `eventLoopUtilization()`
prior to `util1`
* Returns {Object}
* `idle` {number}
* `active` {number}
* `utilization` {number}

The `eventLoopUtilization()` method returns an object that contains the
cumulative duration of time the event loop has been both idle and active as a
high resolution milliseconds timer. The `utilization` value is the calculated
Event Loop Utilization (ELU). If bootstrapping has not yet finished, the
properties have the value of 0.

`util1` and `util2` are optional parameters.

If `util1` is passed then the delta between the current call's `active` and
`idle` times are calculated and returned (similar to [`process.hrtime()`][]).
Likewise the adjusted `utilization` value is calculated.

If `util1` and `util2` are both passed then the calculation adjustments are
done between the two arguments. This is a convenience option because unlike
[`process.hrtime()`][] additional work is done to calculate the ELU.

ELU is similar to CPU utilization except that it is calculated using high
precision wall-clock time. It represents the percentage of time the event loop
has spent outside the event loop's event provider (e.g. `epoll_wait`). No other
CPU idle time is taken into consideration. The following is an example of how
a mostly idle process will have a high ELU.

<!-- eslint-skip -->
```js
'use strict';
const { eventLoopUtilization } = require('perf_hooks').performance;
const { spawnSync } = require('child_process');

setImmediate(() => {
const elu = eventLoopUtilization();
spawnSync('sleep', ['5']);
console.log(eventLoopUtilization(elu).utilization);
});
```

While the CPU is mostly idle while running this script the value of
`utilization` is 1. This is because the call to [`child_process.spawnSync()`][]
blocks the event loop from proceeding.

Passing in a user-defined object instead of the result of a previous call to
`eventLoopUtilization()` will lead to undefined behavior. The return values
are not guaranteed to reflect any correct state of the event loop.

### `performance.mark([name])`
<!-- YAML
added: v8.5.0
Expand Down Expand Up @@ -163,62 +219,6 @@ obs.observe({ entryTypes: ['function'] });
wrapped();
```

### `performance.eventLoopUtilization([util1][,util2])`
<!-- YAML
added: REPLACEME
-->

* `util1` {Object} The result of a previous call to `eventLoopUtilization()`
* `util2` {Object} The result of a previous call to `eventLoopUtilization()`
prior to `util1`
* Returns {Object}
* `idle` {number}
* `active` {number}
* `utilization` {number}

The `eventLoopUtilization()` method returns an object that contains the
cumulative duration of time the event loop has been both idle and active as a
high resolution milliseconds timer. The `utilization` value is the calculated
Event Loop Utilization (ELU). If bootstrapping has not yet finished, the
properties have the value of 0.

`util1` and `util2` are optional parameters.

If `util1` is passed then the delta between the current call's `active` and
`idle` times are calculated and returned (similar to [`process.hrtime()`][]).
Likewise the adjusted `utilization` value is calculated.

If `util1` and `util2` are both passed then the calculation adjustments are
done between the two arguments. This is a convenience option because unlike
[`process.hrtime()`][] additional work is done to calculate the ELU.

ELU is similar to CPU utilization except that it is calculated using high
precision wall-clock time. It represents the percentage of time the event loop
has spent outside the event loop's event provider (e.g. `epoll_wait`). No other
CPU idle time is taken into consideration. The following is an example of how
a mostly idle process will have a high ELU.

<!-- eslint-skip -->
```js
'use strict';
const { eventLoopUtilization } = require('perf_hooks').performance;
const { spawnSync } = require('child_process');

setImmediate(() => {
const elu = eventLoopUtilization();
spawnSync('sleep', ['5']);
console.log(eventLoopUtilization(elu).utilization);
});
```

While the CPU is mostly idle while running this script the value of
`utilization` is 1. This is because the call to [`child_process.spawnSync()`][]
blocks the event loop from proceeding.

Passing in a user-defined object instead of the result of a previous call to
`eventLoopUtilization()` will lead to undefined behavior. The return values
are not guaranteed to reflect any correct state of the event loop.

## Class: `PerformanceEntry`
<!-- YAML
added: v8.5.0
Expand All @@ -234,41 +234,54 @@ added: v8.5.0
The total number of milliseconds elapsed for this entry. This value will not
be meaningful for all Performance Entry types.

### `performanceEntry.name`
### `performanceEntry.entryType`
<!-- YAML
added: v8.5.0
-->

* {string}

The name of the performance entry.
The type of the performance entry. It may be one of:

### `performanceEntry.startTime`
* `'node'` (Node.js only)
* `'mark'` (available on the Web)
* `'measure'` (available on the Web)
* `'gc'` (Node.js only)
* `'function'` (Node.js only)
* `'http2'` (Node.js only)
* `'http'` (Node.js only)

### performanceEntry.flags
<!-- YAML
added: v8.5.0
added:
- v13.9.0
- v12.17.0
-->

* {number}

The high resolution millisecond timestamp marking the starting time of the
Performance Entry.
_This property is an extension by Node.js. It is not available in Web browsers._

### `performanceEntry.entryType`
When `performanceEntry.entryType` is equal to `'gc'`, the `performance.flags`
property contains additional information about garbage collection operation.
The value may be one of:

* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_NO`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_CONSTRUCT_RETAINED`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_FORCED`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SYNCHRONOUS_PHANTOM_PROCESSING`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_AVAILABLE_GARBAGE`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_EXTERNAL_MEMORY`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SCHEDULE_IDLE`

### `performanceEntry.name`
<!-- YAML
added: v8.5.0
-->

* {string}

The type of the performance entry. It may be one of:

* `'node'` (Node.js only)
* `'mark'` (available on the Web)
* `'measure'` (available on the Web)
* `'gc'` (Node.js only)
* `'function'` (Node.js only)
* `'http2'` (Node.js only)
* `'http'` (Node.js only)
The name of the performance entry.

### `performanceEntry.kind`
<!-- YAML
Expand All @@ -288,26 +301,15 @@ The value may be one of:
* `perf_hooks.constants.NODE_PERFORMANCE_GC_INCREMENTAL`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_WEAKCB`

### performanceEntry.flags
### `performanceEntry.startTime`
<!-- YAML
added: v13.9.0
added: v8.5.0
-->

* {number}

_This property is an extension by Node.js. It is not available in Web browsers._

When `performanceEntry.entryType` is equal to `'gc'`, the `performance.flags`
property contains additional information about garbage collection operation.
The value may be one of:

* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_NO`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_CONSTRUCT_RETAINED`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_FORCED`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SYNCHRONOUS_PHANTOM_PROCESSING`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_AVAILABLE_GARBAGE`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_EXTERNAL_MEMORY`
* `perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SCHEDULE_IDLE`
The high resolution millisecond timestamp marking the starting time of the
Performance Entry.

## Class: `PerformanceNodeTiming extends PerformanceEntry`
<!-- YAML
Expand Down Expand Up @@ -340,6 +342,19 @@ added: v8.5.0
The high resolution millisecond timestamp at which the Node.js environment was
initialized.

### `performanceNodeTiming.idleTime`
<!-- YAML
added: REPLACEME
-->

* {number}

The high resolution millisecond timestamp of the amount of time the event loop
has been idle within the event loop's event provider (e.g. `epoll_wait`). This
does not take CPU usage into consideration. If the event loop has not yet
started (e.g., in the first tick of the main script), the property has the
value of 0.

### `performanceNodeTiming.loopExit`
<!-- YAML
added: v8.5.0
Expand Down Expand Up @@ -382,19 +397,6 @@ added: v8.5.0
The high resolution millisecond timestamp at which the V8 platform was
initialized.

### `performanceNodeTiming.idleTime`
<!-- YAML
added: REPLACEME
-->

* {number}

The high resolution millisecond timestamp of the amount of time the event loop
has been idle within the event loop's event provider (e.g. `epoll_wait`). This
does not take CPU usage into consideration. If the event loop has not yet
started (e.g., in the first tick of the main script), the property has the
value of 0.

## Class: `perf_hooks.PerformanceObserver`

### `new PerformanceObserver(callback)`
Expand Down

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