src,lib: add constrainedMemory API for process

doc/api/process.md

@@ -1103,6 +1103,27 @@ and [Cluster][] documentation), the `process.connected` property will return
 Once `process.connected` is `false`, it is no longer possible to send messages
 over the IPC channel using `process.send()`.
 
+## `process.constrainedMemory()`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1 - Experimental
+
+* {number}
+
+Gets the amount of memory available to the process (in bytes) based on
+limits imposed by the OS. If there is no such constraint, or the constraint
+is unknown, `undefined` is returned.
+
+It is not unusual for this value to be less than or greater than `os.totalmem()`.
+This function currently only returns a non-zero value on Linux, based on cgroups
+if it is present, and on z/OS based on `RLIMIT_MEMLIMIT`.
+
+See [`uv_get_constrained_memory`][uv_get_constrained_memory] for more
+information.
+
 ## `process.cpuUsage([previousValue])`
 
 <!-- YAML
@@ -3901,6 +3922,7 @@ cases:
 [process_warning]: #event-warning
 [report documentation]: report.md
 [terminal raw mode]: tty.md#readstreamsetrawmodemode
+[uv_get_constrained_memory]: https://docs.libuv.org/en/v1.x/misc.html#c.uv_get_constrained_memory
 [uv_rusage_t]: https://docs.libuv.org/en/v1.x/misc.html#c.uv_rusage_t
 [wikipedia_major_fault]: https://en.wikipedia.org/wiki/Page_fault#Major
 [wikipedia_minor_fault]: https://en.wikipedia.org/wiki/Page_fault#Minor

lib/internal/bootstrap/node.js

@@ -184,6 +184,7 @@ const rawMethods = internalBinding('process_methods');
 
   process.hrtime = perThreadSetup.hrtime;
   process.hrtime.bigint = perThreadSetup.hrtimeBigInt;
+  process.constrainedMemory = perThreadSetup.constrainedMemory;
 
   process.openStdin = function() {
     process.stdin.resume();

lib/internal/process/per_thread.js

@@ -60,6 +60,7 @@ const binding = internalBinding('process_methods');
 
 let hrValues;
 let hrBigintValues;
+let constrainedMemoryValues;
 
 function refreshHrtimeBuffer() {
   // The 3 entries filled in by the original process.hrtime contains
@@ -100,6 +101,13 @@ function hrtimeBigInt() {
   return hrBigintValues[0];
 }
 
+function constrainedMemory() {
+  const value = binding.constrainedMemory();
+  if (value > 0) {
+    return value;
+  }
+}
+
 function nop() {}
 
 // The execution of this function itself should not cause any side effects.
@@ -427,4 +435,5 @@ module.exports = {
   hrtime,
   hrtimeBigInt,
   refreshHrtimeBuffer,
+  constrainedMemory,
 };

lib/internal/process/pre_execution.js

@@ -131,9 +131,7 @@ function refreshRuntimeOptions() {
 function patchProcessObject(expandArgv1) {
   const binding = internalBinding('process_methods');
   binding.patchProcessObject(process);
-
   require('internal/process/per_thread').refreshHrtimeBuffer();
-
   ObjectDefineProperty(process, 'argv0', {
     __proto__: null,
     enumerable: true,

src/node_process_methods.cc

@@ -207,6 +207,11 @@ static void MemoryUsage(const FunctionCallbackInfo<Value>& args) {
           : static_cast<double>(array_buffer_allocator->total_mem_usage());
 }
 
+static void GetConstrainedMemory(const FunctionCallbackInfo<Value>& args) {
+  double value = static_cast<double>(uv_get_constrained_memory());
+  args.GetReturnValue().Set(value);
+}
+
 void RawDebug(const FunctionCallbackInfo<Value>& args) {
   CHECK(args.Length() == 1 && args[0]->IsString() &&
         "must be called with a single string");
@@ -582,6 +587,7 @@ static void Initialize(Local<Object> target,
 
   SetMethod(context, target, "umask", Umask);
   SetMethod(context, target, "memoryUsage", MemoryUsage);
+  SetMethod(context, target, "constrainedMemory", GetConstrainedMemory);
   SetMethod(context, target, "rss", Rss);
   SetMethod(context, target, "cpuUsage", CPUUsage);
   SetMethod(context, target, "resourceUsage", ResourceUsage);
@@ -612,6 +618,7 @@ void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(Umask);
   registry->Register(RawDebug);
   registry->Register(MemoryUsage);
+  registry->Register(GetConstrainedMemory);
   registry->Register(Rss);
   registry->Register(CPUUsage);
   registry->Register(ResourceUsage);

test/parallel/test-process-constrained-memory.js

@@ -0,0 +1,12 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+const { Worker } = require('worker_threads');
+const constrainedMemory = process.constrainedMemory();
+if (constrainedMemory) {
+  assert(process.constrainedMemory() > 0);
+}
+if (!process.env.isWorker) {
+  process.env.isWorker = true;
+  new Worker(__filename);
+}