perf_hooks: implement histogram based api

Add a sampling-based event loop delay monitor.

```js
const { monitorEventLoopDelay } = require('perf_hooks');

const h = monitorEventLoopDelay();

h.enable();

h.disable();

console.log(h.percentiles);
console.log(h.min);
console.log(h.max);
console.log(h.mean);
console.log(h.stddev);
console.log(h.percentile(50));
```

PR-URL: https://github.com/nodejs/node/pull/25378
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

1 files changed, 36 insertions, 0 deletions

diff --git a/src/node_perf.h b/src/node_perf.h
index e3ef69c0fb..a8e43dc347 100644
--- a/src/node_perf.h
+++ b/src/node_perf.h
@@ -7,6 +7,7 @@
 #include "node_perf_common.h"
 #include "env.h"
 #include "base_object-inl.h"
+#include "histogram-inl.h"
 
 #include "v8.h"
 #include "uv.h"
@@ -124,6 +125,41 @@ class GCPerformanceEntry : public PerformanceEntry {
   PerformanceGCKind gckind_;
 };
 
+class ELDHistogram : public BaseObject, public Histogram {
+ public:
+  ELDHistogram(Environment* env,
+               Local<Object> wrap,
+               int32_t resolution);
+
+  ~ELDHistogram() override;
+
+  bool RecordDelta();
+  bool Enable();
+  bool Disable();
+  void ResetState() {
+    Reset();
+    exceeds_ = 0;
+    prev_ = 0;
+  }
+  int64_t Exceeds() { return exceeds_; }
+
+  void MemoryInfo(MemoryTracker* tracker) const override {
+    tracker->TrackFieldWithSize("histogram", GetMemorySize());
+  }
+
+  SET_MEMORY_INFO_NAME(ELDHistogram)
+  SET_SELF_SIZE(ELDHistogram)
+
+ private:
+  void CloseTimer();
+
+  bool enabled_ = false;
+  int32_t resolution_ = 0;
+  int64_t exceeds_ = 0;
+  uint64_t prev_ = 0;
+  uv_timer_t* timer_;
+};
+
 }  // namespace performance
 }  // namespace node