Bug 1854072 - Change parallel marking threshold pref to use MB instead of KB r=sfink

While the limit when setting the pref is surprising, I think it  makes more
sense to change this pref to use MB like most of the other GC prefs after which
the problem will not arise.

Differential Revision: https://phabricator.services.mozilla.com/D188715

dom/base/nsJSEnvironment.cpp

@@ -2087,8 +2087,8 @@ void nsJSContext::EnsureStatics() {
 
   Preferences::RegisterCallbackAndCall(
       SetMemoryPrefChangedCallbackInt,
-      "javascript.options.mem.gc_parallel_marking_threshold_kb",
-      (void*)JSGC_PARALLEL_MARKING_THRESHOLD_KB);
+      "javascript.options.mem.gc_parallel_marking_threshold_mb",
+      (void*)JSGC_PARALLEL_MARKING_THRESHOLD_MB);
 
   Preferences::RegisterCallbackAndCall(
       SetMemoryGCSliceTimePrefChangedCallback,

js/public/GCAPI.h

@@ -477,9 +477,9 @@ typedef enum JSGCParamKey {
   /**
    * The heap size above which to use parallel marking.
    *
-   * Default: ParallelMarkingThresholdKB
+   * Default: ParallelMarkingThresholdMB
    */
-  JSGC_PARALLEL_MARKING_THRESHOLD_KB = 50,
+  JSGC_PARALLEL_MARKING_THRESHOLD_MB = 50,
 } JSGCParamKey;
 
 /*

js/src/gc/GC.h

@@ -67,7 +67,7 @@ class TenuredChunk;
   _("maxEmptyChunkCount", JSGC_MAX_EMPTY_CHUNK_COUNT, true)                 \
   _("compactingEnabled", JSGC_COMPACTING_ENABLED, true)                     \
   _("parallelMarkingEnabled", JSGC_PARALLEL_MARKING_ENABLED, true)          \
-  _("parallelMarkingThresholdKB", JSGC_PARALLEL_MARKING_THRESHOLD_KB, true) \
+  _("parallelMarkingThresholdKB", JSGC_PARALLEL_MARKING_THRESHOLD_MB, true) \
   _("minLastDitchGCPeriod", JSGC_MIN_LAST_DITCH_GC_PERIOD, true)            \
   _("nurseryFreeThresholdForIdleCollection",                                \
     JSGC_NURSERY_FREE_THRESHOLD_FOR_IDLE_COLLECTION, true)                  \

js/src/gc/Scheduling.h

@@ -516,10 +516,10 @@
     TimeDuration::FromSeconds(60))                                             \
                                                                                \
   /*                                                                           \
-   * JSGC_PARALLEL_MARKING_THRESHOLD_KB                                        \
+   * JSGC_PARALLEL_MARKING_THRESHOLD_MB                                        \
    */                                                                          \
-  _(JSGC_PARALLEL_MARKING_THRESHOLD_KB, size_t, parallelMarkingThresholdBytes, \
-    ConvertKB, NoCheck, 10 * 1024 * 1024)
+  _(JSGC_PARALLEL_MARKING_THRESHOLD_MB, size_t, parallelMarkingThresholdBytes, \
+    ConvertMB, NoCheck, 10 * 1024 * 1024)
 
 namespace js {
 

modules/libpref/init/all.js

@@ -941,16 +941,16 @@ pref("javascript.options.mem.gc_compacting", true);
 // This only applies to the main runtime and does not affect workers.
 pref("javascript.options.mem.gc_parallel_marking", false);
 
-// JSGC_PARALLEL_MARKING_THRESHOLD_KB
+// JSGC_PARALLEL_MARKING_THRESHOLD_MB
 // Minimum heap size at which to use parallel marking, if enabled.
 #if defined(XP_WIN)
-pref("javascript.options.mem.gc_parallel_marking_threshold_kb", 20000);
+pref("javascript.options.mem.gc_parallel_marking_threshold_mb", 20);
 #elif defined(XP_MACOSX)
-pref("javascript.options.mem.gc_parallel_marking_threshold_kb", 4000);
+pref("javascript.options.mem.gc_parallel_marking_threshold_mb", 4);
 #elif defined(ANDROID)
-pref("javascript.options.mem.gc_parallel_marking_threshold_kb", 200000);
+pref("javascript.options.mem.gc_parallel_marking_threshold_mb", 200);
 #elif defined(XP_UNIX)
-pref("javascript.options.mem.gc_parallel_marking_threshold_kb", 200000);
+pref("javascript.options.mem.gc_parallel_marking_threshold_mb", 200);
 #endif
 
 // JSGC_HIGH_FREQUENCY_TIME_LIMIT