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Add direct access to rss without iterating pages #34291

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Add direct access to rss without iterating pages #34291

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22 changes: 22 additions & 0 deletions doc/api/process.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1589,6 +1589,28 @@ Will generate:
When using [`Worker`][] threads, `rss` will be a value that is valid for the
entire process, while the other fields will only refer to the current thread.

The `process.memoryUsage()` method iterate over each page to gather
informations about memory usage which can be slow depending on the
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I find can be slow quite vague - in special as a caller can't do anything to avoid this to test if it will be slow.
Are we talking about µs, ms, or seconds here?

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It depends on the program size in memory. Access the RSS take a fixed time but compute heap statistics is quite costly since you have to iterate over every memory page.
The difference can be in seconds. (see the benchmark in the PR description)

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The sample in PR description prints milli seconds not seconds so not that bad.
I tried it local on my machine and even for 4GB heaps it was below 0.2ms. But for sure the rss only API is much faster.

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At the beginning I have done this PR because I found very strange results while benchmarking promises (#33384).
So even if the difference is not that huge it can be misleading in some cases

program memory allocations.

## `process.memoryUsage.rss()`

* Returns: {integer}

The `process.memoryUsage.rss()` method returns an integer representing the
Resident Set Size (RSS) in bytes.

The Resident Set Size, is the amount of space occupied in the main
memory device (that is a subset of the total allocated memory) for the
process, including all C++ and JavaScript objects and code.
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This is the same value as the one returned by `process.memoryUsage()`.

```js
console.log(process.memoryUsage.rss());
// 35655680
```

## `process.nextTick(callback[, ...args])`
<!-- YAML
added: v0.1.26
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3 changes: 3 additions & 0 deletions lib/internal/process/per_thread.js
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Expand Up @@ -93,6 +93,7 @@ function wrapProcessMethods(binding) {
const {
cpuUsage: _cpuUsage,
memoryUsage: _memoryUsage,
rss,
resourceUsage: _resourceUsage
} = binding;

Expand Down Expand Up @@ -168,6 +169,8 @@ function wrapProcessMethods(binding) {
};
}

memoryUsage.rss = rss;

function exit(code) {
if (code || code === 0)
process.exitCode = code;
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15 changes: 14 additions & 1 deletion src/node_process_methods.cc
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Expand Up @@ -172,14 +172,20 @@ static void Kill(const FunctionCallbackInfo<Value>& args) {
args.GetReturnValue().Set(err);
}

static void MemoryUsage(const FunctionCallbackInfo<Value>& args) {
static void Rss(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args);

size_t rss;
int err = uv_resident_set_memory(&rss);
if (err)
return env->ThrowUVException(err, "uv_resident_set_memory");

args.GetReturnValue().Set(static_cast<double>(rss));
}
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static void MemoryUsage(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args);

Isolate* isolate = env->isolate();
// V8 memory usage
HeapStatistics v8_heap_stats;
Expand All @@ -192,6 +198,11 @@ static void MemoryUsage(const FunctionCallbackInfo<Value>& args) {
Local<ArrayBuffer> ab = get_fields_array_buffer(args, 0, 5);
double* fields = static_cast<double*>(ab->GetBackingStore()->Data());

size_t rss;
int err = uv_resident_set_memory(&rss);
if (err)
return env->ThrowUVException(err, "uv_resident_set_memory");

fields[0] = rss;
fields[1] = v8_heap_stats.total_heap_size();
fields[2] = v8_heap_stats.used_heap_size();
Expand Down Expand Up @@ -542,6 +553,7 @@ static void InitializeProcessMethods(Local<Object> target,
env->SetMethod(target, "umask", Umask);
env->SetMethod(target, "_rawDebug", RawDebug);
env->SetMethod(target, "memoryUsage", MemoryUsage);
env->SetMethod(target, "rss", Rss);
env->SetMethod(target, "cpuUsage", CPUUsage);
env->SetMethod(target, "resourceUsage", ResourceUsage);

Expand All @@ -568,6 +580,7 @@ void RegisterProcessMethodsExternalReferences(
registry->Register(Umask);
registry->Register(RawDebug);
registry->Register(MemoryUsage);
registry->Register(Rss);
registry->Register(CPUUsage);
registry->Register(ResourceUsage);

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2 changes: 2 additions & 0 deletions test/parallel/test-memory-usage.js
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Expand Up @@ -44,3 +44,5 @@ if (r.arrayBuffers > 0) {
assert.strictEqual(after.arrayBuffers - r.arrayBuffers, size,
`${after.arrayBuffers} - ${r.arrayBuffers} === ${size}`);
}

assert(process.memoryUsage.rss() > 0);