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, 38 insertions, 0 deletions

diff --git a/src/histogram.h b/src/histogram.h
new file mode 100644
index 00000000000..eb94af5da2a
--- /dev/null
+++ b/src/histogram.h
@@ -0,0 +1,38 @@
+#ifndef SRC_HISTOGRAM_H_
+#define SRC_HISTOGRAM_H_
+
+#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#include "hdr_histogram.h"
+#include <functional>
+#include <map>
+
+namespace node {
+
+class Histogram {
+ public:
+  inline Histogram(int64_t lowest, int64_t highest, int figures = 3);
+  inline virtual ~Histogram();
+
+  inline bool Record(int64_t value);
+  inline void Reset();
+  inline int64_t Min();
+  inline int64_t Max();
+  inline double Mean();
+  inline double Stddev();
+  inline double Percentile(double percentile);
+  inline void Percentiles(std::function<void(double, double)> fn);
+
+  size_t GetMemorySize() const {
+    return hdr_get_memory_size(histogram_);
+  }
+
+ private:
+  hdr_histogram* histogram_;
+};
+
+}  // namespace node
+
+#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#endif  // SRC_HISTOGRAM_H_