Bug 859657 (part 1) - Don't measure MEMORY_EXPLICIT in telemetry because it can cause pauses. r=jlebar.

--HG--
extra : rebase_source : 93a9d3896ec62d54ccfdaa6a8a90a5e9188fe67c

toolkit/components/telemetry/Histograms.json

@@ -268,14 +268,6 @@
     "n_buckets": 25,
     "description": "Ratio of committed, unused memory to allocated memory in the heap (percentage)."
   },
-  "MEMORY_EXPLICIT": {
-    "kind": "exponential",
-    "low": 1024,
-    "high": "16 * 1024 * 1024",
-    "n_buckets": 200,
-    "extended_statistics_ok": true,
-    "description": "Explicit memory allocations (KB)"
-  },
   "GHOST_WINDOWS": {
     "kind": "exponential",
     "high": "128",

toolkit/components/telemetry/TelemetryPing.js

@@ -58,12 +58,13 @@ const RWX_OWNER = 0700;
 //   * MEMORY_JS_GC_HEAP, and
 //   * MEMORY_JS_COMPARTMENTS_SYSTEM.
 //
+// We used to measure "explicit" too, but it could cause hangs, and the data
+// was always really noisy anyway.  See bug 859657.
 const MEM_HISTOGRAMS = {
   "js-gc-heap": "MEMORY_JS_GC_HEAP",
   "js-compartments/system": "MEMORY_JS_COMPARTMENTS_SYSTEM",
   "js-compartments/user": "MEMORY_JS_COMPARTMENTS_USER",
   "js-main-runtime-temporary-peak": "MEMORY_JS_MAIN_RUNTIME_TEMPORARY_PEAK",
-  "explicit": "MEMORY_EXPLICIT",
   "resident-fast": "MEMORY_RESIDENT",
   "vsize": "MEMORY_VSIZE",
   "storage-sqlite": "MEMORY_STORAGE_SQLITE",