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src: export number_of_native_contexts and number_of_detached_contexts #27933

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src: export number_of_native_contexts and number_of_detached_contexts #27933

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84b1414
src: export number_of_native_contexts and number_of_detached_contexts
May 28, 2019
5cd3302
Update doc/api/v8.md
yvasiyarov May 28, 2019
86a2c21
Update doc/api/v8.md
yvasiyarov May 29, 2019
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15 changes: 14 additions & 1 deletion doc/api/v8.md
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Original file line number Diff line number Diff line change
Expand Up @@ -131,13 +131,24 @@ Returns an object with the following properties:
* `malloced_memory` {number}
* `peak_malloced_memory` {number}
* `does_zap_garbage` {number}
* `number_of_native_contexts` {number}
* `number_of_detached_contexts` {number}


`does_zap_garbage` is a 0/1 boolean, which signifies whether the
`--zap_code_space` option is enabled or not. This makes V8 overwrite heap
garbage with a bit pattern. The RSS footprint (resident memory set) gets bigger
because it continuously touches all heap pages and that makes them less likely
to get swapped out by the operating system.

`number_of_native_contexts` The value of native_context is the number of the
top-level contexts currently active. Increase of this number over time indicates
a memory leak.

`number_of_detached_contexts` The value of detached_context is the number
of contexts that were detached and not yet garbage collected. This number
being non-zero indicates a potential memory leak.

<!-- eslint-skip -->
```js
{
Expand All @@ -149,7 +160,9 @@ to get swapped out by the operating system.
heap_size_limit: 1535115264,
malloced_memory: 16384,
peak_malloced_memory: 1127496,
does_zap_garbage: 0
does_zap_garbage: 0,
number_of_native_contexts: 1,
number_of_detached_contexts: 0
}
```

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8 changes: 6 additions & 2 deletions lib/v8.js
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Expand Up @@ -109,7 +109,9 @@ const {
kSpaceSizeIndex,
kSpaceUsedSizeIndex,
kSpaceAvailableSizeIndex,
kPhysicalSpaceSizeIndex
kPhysicalSpaceSizeIndex,
kNumberOfNativeContextsIndex,
kNumberOfDetachedContextsIndex
} = internalBinding('v8');

const kNumberOfHeapSpaces = kHeapSpaces.length;
Expand Down Expand Up @@ -139,7 +141,9 @@ function getHeapStatistics() {
'heap_size_limit': buffer[kHeapSizeLimitIndex],
'malloced_memory': buffer[kMallocedMemoryIndex],
'peak_malloced_memory': buffer[kPeakMallocedMemoryIndex],
'does_zap_garbage': buffer[kDoesZapGarbageIndex]
'does_zap_garbage': buffer[kDoesZapGarbageIndex],
'number_of_native_contexts': buffer[kNumberOfNativeContextsIndex],
'number_of_detached_contexts': buffer[kNumberOfDetachedContextsIndex]
};
}

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4 changes: 3 additions & 1 deletion src/node_v8.cc
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Expand Up @@ -52,7 +52,9 @@ using v8::Value;
V(5, heap_size_limit, kHeapSizeLimitIndex) \
V(6, malloced_memory, kMallocedMemoryIndex) \
V(7, peak_malloced_memory, kPeakMallocedMemoryIndex) \
V(8, does_zap_garbage, kDoesZapGarbageIndex)
V(8, does_zap_garbage, kDoesZapGarbageIndex) \
V(9, number_of_native_contexts, kNumberOfNativeContextsIndex) \
V(10, number_of_detached_contexts, kNumberOfDetachedContextsIndex)

#define V(a, b, c) +1
static const size_t kHeapStatisticsPropertiesCount =
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2 changes: 2 additions & 0 deletions test/parallel/test-v8-stats.js
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Expand Up @@ -8,6 +8,8 @@ const keys = [
'does_zap_garbage',
'heap_size_limit',
'malloced_memory',
'number_of_detached_contexts',
'number_of_native_contexts',
'peak_malloced_memory',
'total_available_size',
'total_heap_size',
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