Revert of Oilpan: adjust GC policy under memory pressure.

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index 6922e73080d86c64374966e14b4fd72e86bb5635..566a5d870169535154565190a55428a0391e09f5 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -532,19 +532,18 @@
     if (gcState() != NoGCScheduled)
         return false;
 #if ENABLE(IDLE_GC)
-    // Avoid potential overflow by truncating to Kb.
-    size_t allocatedObjectSizeKb = Heap::allocatedObjectSize() >> 10;
     // The estimated size is updated when the main thread finishes lazy
     // sweeping. If this thread reaches here before the main thread finishes
     // lazy sweeping, the thread will use the estimated size of the last GC.
-    size_t estimatedLiveObjectSizeKb = Heap::estimatedLiveObjectSize() >> 10;
+    size_t estimatedLiveObjectSize = Heap::estimatedLiveObjectSize();
+    size_t allocatedObjectSize = Heap::allocatedObjectSize();
     // Heap::markedObjectSize() may be underestimated if any thread has not
     // finished completeSweep().
-    size_t currentObjectSizeKb = allocatedObjectSizeKb + ((Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages()) >> 10);
+    size_t currentObjectSize = allocatedObjectSize + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages();
     // Schedule an idle GC if Oilpan has allocated more than 1 MB since
     // the last GC and the current memory usage is >50% larger than
     // the estimated live memory usage.
-    return allocatedObjectSizeKb >= 1024 && currentObjectSizeKb > estimatedLiveObjectSizeKb * 3 / 2;
+    return allocatedObjectSize >= 1024 * 1024 && currentObjectSize > estimatedLiveObjectSize * 3 / 2;
 #else
     return false;
 #endif
@@ -559,33 +558,19 @@
 #if ENABLE(IDLE_GC)
     return false;
 #else
-    // Avoid potential overflow by truncating to Kb.
-    size_t allocatedObjectSizeKb = Heap::allocatedObjectSize() >> 10;
     // The estimated size is updated when the main thread finishes lazy
     // sweeping. If this thread reaches here before the main thread finishes
     // lazy sweeping, the thread will use the estimated size of the last GC.
-    size_t estimatedLiveObjectSizeKb = Heap::estimatedLiveObjectSize() >> 10;
+    size_t estimatedLiveObjectSize = Heap::estimatedLiveObjectSize();
+    size_t allocatedObjectSize = Heap::allocatedObjectSize();
     // Heap::markedObjectSize() may be underestimated if any thread has not
     // finished completeSweep().
-    size_t currentObjectSizeKb = allocatedObjectSizeKb + ((Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages()) >> 10);
+    size_t currentObjectSize = allocatedObjectSize + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages();
     // Schedule a precise GC if Oilpan has allocated more than 1 MB since
     // the last GC and the current memory usage is >50% larger than
     // the estimated live memory usage.
-    return allocatedObjectSizeKb >= 1024 && currentObjectSizeKb > estimatedLiveObjectSizeKb * 3 / 2;
-#endif
-}
-
-bool ThreadState::shouldForceMemoryPressureGC()
-{
-    // Avoid potential overflow by truncating to Kb.
-    size_t currentObjectSizeKb = (Heap::allocatedObjectSize() + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages()) >> 10;
-    size_t estimatedLiveObjectSizeKb = (Heap::estimatedLiveObjectSize()) >> 10;
-    if (currentObjectSizeKb < 300 * 1024)
-        return false;
-
-    // If we're consuming too much memory, trigger a conservative GC
-    // aggressively. This is a safe guard to avoid OOM.
-    return currentObjectSizeKb > (estimatedLiveObjectSizeKb * 3) / 2;
+    return allocatedObjectSize >= 1024 * 1024 && currentObjectSize > estimatedLiveObjectSize * 3 / 2;
+#endif
 }
 
 // TODO(haraken): We should improve the GC heuristics.
@@ -595,24 +580,24 @@
     if (UNLIKELY(isGCForbidden()))
         return false;
 
-    if (shouldForceMemoryPressureGC())
-        return true;
-
-    // Avoid potential overflow by truncating to Kb.
-    size_t allocatedObjectSizeKb = Heap::allocatedObjectSize() >> 10;
     // The estimated size is updated when the main thread finishes lazy
     // sweeping. If this thread reaches here before the main thread finishes
     // lazy sweeping, the thread will use the estimated size of the last GC.
-    size_t estimatedLiveObjectSizeKb = Heap::estimatedLiveObjectSize() >> 10;
+    size_t estimatedLiveObjectSize = Heap::estimatedLiveObjectSize();
+    size_t allocatedObjectSize = Heap::allocatedObjectSize();
     // Heap::markedObjectSize() may be underestimated if any thread has not
     // finished completeSweep().
-    size_t currentObjectSizeKb = allocatedObjectSizeKb + ((Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages()) >> 10);
-
+    size_t currentObjectSize = allocatedObjectSize + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages();
+    if (currentObjectSize >= 300 * 1024 * 1024) {
+        // If we're consuming too much memory, trigger a conservative GC
+        // aggressively. This is a safe guard to avoid OOM.
+        return currentObjectSize > estimatedLiveObjectSize * 3 / 2;
+    }
     // Schedule a conservative GC if Oilpan has allocated more than 32 MB since
     // the last GC and the current memory usage is >400% larger than
     // the estimated live memory usage.
     // TODO(haraken): 400% is too large. Lower the heap growing factor.
-    return allocatedObjectSizeKb >= 32 * 1024 && currentObjectSizeKb > 5 * estimatedLiveObjectSizeKb;
+    return allocatedObjectSize >= 32 * 1024 * 1024 && currentObjectSize > 5 * estimatedLiveObjectSize;
 }
 
 void ThreadState::scheduleGCIfNeeded()
@@ -804,7 +789,7 @@
     return m_gcState;
 }
 
-void ThreadState::didV8MajorGC(bool forceGC)
+void ThreadState::didV8GC()
 {
     checkThread();
     if (isMainThread()) {
@@ -812,45 +797,6 @@
         // expected to have collected a lot of DOM wrappers and dropped
         // references to their DOM objects.
         Heap::setEstimatedLiveObjectSize(Heap::estimatedLiveObjectSize() / 2);
-
-        if (forceGC) {
-            // This single GC is not enough for two reasons:
-            //   (1) The GC is not precise because the GC scans on-stack pointers conservatively.
-            //   (2) One GC is not enough to break a chain of persistent handles. It's possible that
-            //       some heap allocated objects own objects that contain persistent handles
-            //       pointing to other heap allocated objects. To break the chain, we need multiple GCs.
-            //
-            // Regarding (1), we force a precise GC at the end of the current event loop. So if you want
-            // to collect all garbage, you need to wait until the next event loop.
-            // Regarding (2), it would be OK in practice to trigger only one GC per gcEpilogue, because
-            // GCController.collectAll() forces 7 V8's GC.
-            Heap::collectGarbage(ThreadState::HeapPointersOnStack, ThreadState::GCWithSweep, Heap::ForcedGC);
-
-            // Forces a precise GC at the end of the current event loop.
-            ThreadState::current()->setGCState(ThreadState::FullGCScheduled);
-            return;
-        }
-
-        // If under memory pressure, complete sweeping before initiating
-        // the urgent conservative GC.
-        if (shouldForceMemoryPressureGC())
-            completeSweep();
-
-        // Schedule an Oilpan GC to avoid the following scenario:
-        // (1) A DOM object X holds a v8::Persistent to a V8 object.
-        //     Assume that X is small but the V8 object is huge.
-        //     The v8::Persistent is released when X is destructed.
-        // (2) X's DOM wrapper is created.
-        // (3) The DOM wrapper becomes unreachable.
-        // (4) V8 triggers a GC. The V8's GC collects the DOM wrapper.
-        //     However, X is not collected until a next Oilpan's GC is
-        //     triggered.
-        // (5) If a lot of such DOM objects are created, we end up with
-        //     a situation where V8's GC collects the DOM wrappers but
-        //     the DOM objects are not collected forever. (Note that
-        //     Oilpan's GC is not triggered unless Oilpan's heap gets full.)
-        // (6) V8 hits OOM.
-        scheduleGCIfNeeded();
     }
 }