Changeset 236296 in webkit for trunk/Source/JavaScriptCore/runtime/JSString.cpp

Timestamp:

Sep 20, 2018, 6:11:19 PM (7 years ago)

Author:

[email protected]

Message:

[JSC] Heap::reportExtraMemoryVisited shows contention if we have many JSString
​https://bugs.webkit.org/show_bug.cgi?id=189558

Reviewed by Mark Lam.

When running web-tooling-benchmark postcss test on Linux JSCOnly port, we get the following result in perf report.

10.95% AutomaticThread libJavaScriptCore.so.1.0.0 . JSC::Heap::reportExtraMemoryVisited

This is because postcss produces bunch of JSString, which require reportExtraMemoryVisited calls in JSString::visitChildren.
And since reportExtraMemoryVisited attempts to update atomic counter, if we have bunch of marking threads, it becomes super contended.

This patch reduces the frequency of updating the atomic counter. Each SlotVisitor has per-SlotVisitor m_extraMemorySize counter.
And we propagate this value to the global atomic counter when rebalance happens.

We also reduce HeapCell::heap() access by using vm.heap.

• heap/SlotVisitor.cpp:

(JSC::SlotVisitor::didStartMarking):
(JSC::SlotVisitor::propagateExternalMemoryVisitedIfNecessary):
(JSC::SlotVisitor::drain):
(JSC::SlotVisitor::performIncrementOfDraining):

• heap/SlotVisitor.h:
• heap/SlotVisitorInlines.h:

(JSC::SlotVisitor::reportExtraMemoryVisited):

• runtime/JSString.cpp:

(JSC::JSRopeString::resolveRopeToAtomicString const):
(JSC::JSRopeString::resolveRope const):

• runtime/JSString.h:

(JSC::JSString::finishCreation):

• wasm/js/JSWebAssemblyInstance.cpp:

(JSC::JSWebAssemblyInstance::finishCreation):

• wasm/js/JSWebAssemblyMemory.cpp:

(JSC::JSWebAssemblyMemory::finishCreation):

File:

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

trunk/Source/JavaScriptCore/runtime/JSString.cpp

@@ -206 +206 @@
     // If we resolved a string that didn't previously exist, notify the heap that we've grown.
     if (m_value.impl()->hasOneRef())
-        Heap::heap(this)->reportExtraMemoryAllocated(m_value.impl()->cost());
+        vm.heap.reportExtraMemoryAllocated(m_value.impl()->cost());
 }
 
@@ -265 +265 @@
         LChar* buffer;
         if (auto newImpl = StringImpl::tryCreateUninitialized(length(), buffer)) {
-            Heap::heap(this)->reportExtraMemoryAllocated(newImpl->cost());
+            exec->vm().heap.reportExtraMemoryAllocated(newImpl->cost());
             m_value = WTFMove(newImpl);
         } else {
@@ -279 +279 @@
     UChar* buffer;
     if (auto newImpl = StringImpl::tryCreateUninitialized(length(), buffer)) {
-        Heap::heap(this)->reportExtraMemoryAllocated(newImpl->cost());
+        exec->vm().heap.reportExtraMemoryAllocated(newImpl->cost());
         m_value = WTFMove(newImpl);
     } else {