v8,src: expose statistics about heap spaces

Provide means to inspect information about the separate heap spaces
via a callable API. This is helpful to analyze memory issues.

Fixes: https://github.com/nodejs/node/issues/2079
PR-URL: https://github.com/nodejs/node/pull/4463
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 32 insertions, 1 deletions

diff --git a/lib/v8.js b/lib/v8.js
index acadfa64e0..551b2ada98 100644
--- a/lib/v8.js
+++ b/lib/v8.js
@@ -16,9 +16,9 @@
 
 const v8binding = process.binding('v8');
 
+// Properties for heap statistics buffer extraction.
 const heapStatisticsBuffer =
     new Uint32Array(v8binding.heapStatisticsArrayBuffer);
-
 const kTotalHeapSizeIndex = v8binding.kTotalHeapSizeIndex;
 const kTotalHeapSizeExecutableIndex = v8binding.kTotalHeapSizeExecutableIndex;
 const kTotalPhysicalSizeIndex = v8binding.kTotalPhysicalSizeIndex;
@@ -26,6 +26,18 @@ const kTotalAvailableSize = v8binding.kTotalAvailableSize;
 const kUsedHeapSizeIndex = v8binding.kUsedHeapSizeIndex;
 const kHeapSizeLimitIndex = v8binding.kHeapSizeLimitIndex;
 
+// Properties for heap space statistics buffer extraction.
+const heapSpaceStatisticsBuffer =
+    new Uint32Array(v8binding.heapSpaceStatisticsArrayBuffer);
+const kHeapSpaces = v8binding.kHeapSpaces;
+const kNumberOfHeapSpaces = kHeapSpaces.length;
+const kHeapSpaceStatisticsPropertiesCount =
+    v8binding.kHeapSpaceStatisticsPropertiesCount;
+const kSpaceSizeIndex = v8binding.kSpaceSizeIndex;
+const kSpaceUsedSizeIndex = v8binding.kSpaceUsedSizeIndex;
+const kSpaceAvailableSizeIndex = v8binding.kSpaceAvailableSizeIndex;
+const kPhysicalSpaceSizeIndex = v8binding.kPhysicalSpaceSizeIndex;
+
 exports.getHeapStatistics = function() {
   const buffer = heapStatisticsBuffer;
 
@@ -42,3 +54,22 @@ exports.getHeapStatistics = function() {
 };
 
 exports.setFlagsFromString = v8binding.setFlagsFromString;
+
+exports.getHeapSpaceStatistics = function() {
+  const heapSpaceStatistics = new Array(kNumberOfHeapSpaces);
+  const buffer = heapSpaceStatisticsBuffer;
+  v8binding.updateHeapSpaceStatisticsArrayBuffer();
+
+  for (let i = 0; i < kNumberOfHeapSpaces; i++) {
+    const propertyOffset = i * kHeapSpaceStatisticsPropertiesCount;
+    heapSpaceStatistics[i] = {
+      space_name: kHeapSpaces[i],
+      space_size: buffer[propertyOffset + kSpaceSizeIndex],
+      space_used_size: buffer[propertyOffset + kSpaceUsedSizeIndex],
+      space_available_size: buffer[propertyOffset + kSpaceAvailableSizeIndex],
+      physical_space_size: buffer[propertyOffset + kPhysicalSpaceSizeIndex]
+    };
+  }
+
+  return heapSpaceStatistics;
+};