Changeset 240113 in webkit for trunk/Source/JavaScriptCore/jsc.cpp

Timestamp:

Jan 17, 2019, 9:32:38 AM (6 years ago)

Author:

[email protected]

Message:

[JSC] Add generateHeapSnapshotForGCDebugging function to dump GCDebugging data
​https://bugs.webkit.org/show_bug.cgi?id=193526

Reviewed by Michael Saboff.

This patch adds generateHeapSnapshotForGCDebugging to JSC shell to dump heap snapshot JSON string with GCDebugging option.
GCDebuggingSnapshot mode is slightly different from InspectorSnapshot in terms of both the output data and the behavior.
It always takes full snapshot, and it reports internal data too. This is useful to view the live heap objects after running
the code. Also, generateHeapSnapshotForGCDebugging returns String instead of parsing it to JSObject internally by calling
JSON.parse. If we convert the String to bunch of objects by using JSON.parse, it is difficult to call generateHeapSnapshotForGCDebugging
multiple times for debugging. Currently, it only generates a large string, which is easily distinguishable in the heap inspector tool.

• jsc.cpp:

(GlobalObject::finishCreation):
(functionGenerateHeapSnapshotForGCDebugging):

File:

• trunk/Source/JavaScriptCore/jsc.cpp (modified) (3 diffs)

trunk/Source/JavaScriptCore/jsc.cpp

@@ -329 +329 @@
 static EncodedJSValue JSC_HOST_CALL functionPlatformSupportsSamplingProfiler(ExecState*);
 static EncodedJSValue JSC_HOST_CALL functionGenerateHeapSnapshot(ExecState*);
+static EncodedJSValue JSC_HOST_CALL functionGenerateHeapSnapshotForGCDebugging(ExecState*);
 static EncodedJSValue JSC_HOST_CALL functionResetSuperSamplerState(ExecState*);
 static EncodedJSValue JSC_HOST_CALL functionEnsureArrayStorage(ExecState*);
@@ -563 +564 @@
         addFunction(vm, "platformSupportsSamplingProfiler", functionPlatformSupportsSamplingProfiler, 0);
         addFunction(vm, "generateHeapSnapshot", functionGenerateHeapSnapshot, 0);
+        addFunction(vm, "generateHeapSnapshotForGCDebugging", functionGenerateHeapSnapshotForGCDebugging, 0);
         addFunction(vm, "resetSuperSamplerState", functionResetSuperSamplerState, 0);
         addFunction(vm, "ensureArrayStorage", functionEnsureArrayStorage, 0);
@@ -2120 +2122 @@
 }
 
+EncodedJSValue JSC_HOST_CALL functionGenerateHeapSnapshotForGCDebugging(ExecState* exec)
+{
+    VM& vm = exec->vm();
+    JSLockHolder lock(vm);
+    auto scope = DECLARE_THROW_SCOPE(vm);
+    String jsonString;
+    {
+        DeferGCForAWhile deferGC(vm.heap); // Prevent concurrent GC from interfering with the full GC that the snapshot does.
+
+        HeapSnapshotBuilder snapshotBuilder(vm.ensureHeapProfiler(), HeapSnapshotBuilder::SnapshotType::GCDebuggingSnapshot);
+        snapshotBuilder.buildSnapshot();
+
+        jsonString = snapshotBuilder.json();
+    }
+    scope.releaseAssertNoException();
+    return JSValue::encode(jsString(&vm, jsonString));
+}
+
 EncodedJSValue JSC_HOST_CALL functionResetSuperSamplerState(ExecState*)
 {