Bug 1569840 - Add a nurseryBytes runtime parameter r=jonco

Differential Revision: https://phabricator.services.mozilla.com/D39836

--HG--
extra : moz-landing-system : lando

js/public/GCAPI.h

@@ -345,6 +345,12 @@ typedef enum JSGCParamKey {
    */
   JSGC_ZONE_ALLOC_DELAY_KB = 33,
 
+  /*
+   * The current size of the nursery.
+   *
+   * read-only.
+   */
+  JSGC_NURSERY_BYTES = 34,
 } JSGCParamKey;
 
 /*

js/src/builtin/TestingFunctions.cpp

@@ -498,6 +498,7 @@ static bool MinorGC(JSContext* cx, unsigned argc, Value* vp) {
   _("minNurseryBytes", JSGC_MIN_NURSERY_BYTES, true)                         \
   _("maxNurseryBytes", JSGC_MAX_NURSERY_BYTES, true)                         \
   _("gcBytes", JSGC_BYTES, false)                                            \
+  _("nurseryBytes", JSGC_NURSERY_BYTES, false)                               \
   _("gcNumber", JSGC_NUMBER, false)                                          \
   _("mode", JSGC_MODE, true)                                                 \
   _("unusedChunks", JSGC_UNUSED_CHUNKS, false)                               \

js/src/gc/GC.cpp

@@ -1824,6 +1824,8 @@ uint32_t GCRuntime::getParameter(JSGCParamKey key, const AutoLockGC& lock) {
       return uint32_t(tunables.gcMaxNurseryBytes());
     case JSGC_BYTES:
       return uint32_t(heapSize.gcBytes());
+    case JSGC_NURSERY_BYTES:
+      return nursery().capacity();
     case JSGC_NUMBER:
       return uint32_t(number);
     case JSGC_MODE:

js/src/jit-test/tests/gc/bug-1569840.js

@@ -0,0 +1,9 @@
+
+gczeal(0);
+
+gcparam("maxNurseryBytes", 1024*1024);
+gcparam("minNurseryBytes", 1024*1024);
+var obj = { foo: 'bar', baz: [1, 2, 3]};
+minorgc();
+assertEq(gcparam("nurseryBytes"), 1024*1024);
+