PartitionAlloc: Distinguish OOMs where a lot of super pages are not committed

Source/wtf/PartitionAlloc.cpp

Index: Source/wtf/PartitionAlloc.cpp
diff --git a/Source/wtf/PartitionAlloc.cpp b/Source/wtf/PartitionAlloc.cpp
index 50987147696f2ecfd8977d2b70b4fa33d0e54cf7..4cd439ad03ca1e20691b7eb559d1ecbe8272ff2b 100644
--- a/Source/wtf/PartitionAlloc.cpp
+++ b/Source/wtf/PartitionAlloc.cpp
@@ -114,6 +114,7 @@ static void parititonAllocBaseInit(PartitionRootBase* root)
     root->initialized = true;
     root->totalSizeOfCommittedPages = 0;
     root->totalSizeOfSuperPages = 0;
+    root->totalSizeOfDirectMappedPages = 0;
     root->nextSuperPage = 0;
     root->nextPartitionPage = 0;
     root->nextPartitionPageEnd = 0;
@@ -296,15 +297,41 @@ bool partitionAllocGenericShutdown(PartitionRootGeneric* root)
     return noLeaks;
 }
 
-static NEVER_INLINE void partitionOutOfMemory()
+#if CPU(32BIT)
+static NEVER_INLINE void partitionOutOfMemoryWithLotsOfUncommitedPages()
 {
+#if OS(WIN)
+    // Crash at a special address (0x9b)
+    // to be easily distinguished on crash reports.
+    // This is because crash stack traces are inaccurate on Windows and
+    // partitionOutOfMemoryWithLotsOfUncommitedPages might be not included
+    // in the stack traces.
+    ((void(*)())0x9b)();

[Chris Evans, 2014/11/12 23:01:30]

Nit: should probably use reinterpret_cast to comply with coding standards?

[hiroshige, 2014/11/13 06:26:31]

Done.

+#endif
+
+    // On non-Windows environment, IMMEDIATE_CRASH is sufficient
+    // because partitionOutOfMemoryWithLotsOfUncommitedPages will appear
+    // in crash stack traces.
+    IMMEDIATE_CRASH();
+}
+#endif
+
+static NEVER_INLINE void partitionOutOfMemory(const PartitionRootBase* root)
+{
+#if CPU(32BIT)
+    // Check whether this OOM is due to a lot of super pages that are allocated
+    // but not committed, probably due to http://crbug.com/421387.
+    if (root->totalSizeOfSuperPages + root->totalSizeOfDirectMappedPages - root->totalSizeOfCommittedPages > kReasonableSizeOfUnusedPages) {
+        partitionOutOfMemoryWithLotsOfUncommitedPages();
+    }
+#endif
     IMMEDIATE_CRASH();
 }
 
 static ALWAYS_INLINE void partitionDecommitSystemPages(PartitionRootBase* root, void* addr, size_t len)
 {
     decommitSystemPages(addr, len);
-    ASSERT(root->totalSizeOfCommittedPages > len);
+    ASSERT(root->totalSizeOfCommittedPages >= len);
     root->totalSizeOfCommittedPages -= len;
 }
 
@@ -312,6 +339,7 @@ static ALWAYS_INLINE void partitionRecommitSystemPages(PartitionRootBase* root,
 {
     recommitSystemPages(addr, len);
     root->totalSizeOfCommittedPages += len;
+    ASSERT(root->totalSizeOfCommittedPages <= root->totalSizeOfSuperPages + root->totalSizeOfDirectMappedPages);
 }
 
 static ALWAYS_INLINE void* partitionAllocPartitionPages(PartitionRootBase* root, int flags, uint16_t numPartitionPages)
@@ -327,6 +355,7 @@ static ALWAYS_INLINE void* partitionAllocPartitionPages(PartitionRootBase* root,
         char* ret = root->nextPartitionPage;
         root->nextPartitionPage += totalSize;
         root->totalSizeOfCommittedPages += totalSize;
+        ASSERT(root->totalSizeOfCommittedPages <= root->totalSizeOfSuperPages + root->totalSizeOfDirectMappedPages);
         return ret;
     }
 
@@ -338,6 +367,7 @@ static ALWAYS_INLINE void* partitionAllocPartitionPages(PartitionRootBase* root,
 
     root->totalSizeOfSuperPages += kSuperPageSize;
     root->totalSizeOfCommittedPages += totalSize;
+    ASSERT(root->totalSizeOfCommittedPages <= root->totalSizeOfSuperPages + root->totalSizeOfDirectMappedPages);
 
     root->nextSuperPage = superPage + kSuperPageSize;
     char* ret = superPage + kPartitionPageSize;
@@ -568,7 +598,10 @@ static ALWAYS_INLINE void* partitionDirectMap(PartitionRootBase* root, int flags
     mapSize += kPageAllocationGranularityOffsetMask;
     mapSize &= kPageAllocationGranularityBaseMask;
 
-    root->totalSizeOfCommittedPages += size + kSystemPageSize;
+    size_t committedPageSize = size + kSystemPageSize;
+    root->totalSizeOfCommittedPages += committedPageSize;
+    root->totalSizeOfDirectMappedPages += committedPageSize;
+    ASSERT(root->totalSizeOfCommittedPages <= root->totalSizeOfSuperPages + root->totalSizeOfDirectMappedPages);
 
     // TODO: we may want to let the operating system place these allocations
     // where it pleases. On 32-bit, this might limit address space
@@ -624,7 +657,11 @@ static ALWAYS_INLINE void partitionDirectUnmap(PartitionPage* page)
     unmapSize += kPartitionPageSize + kSystemPageSize;
 
     PartitionRootBase* root = partitionPageToRoot(page);
-    root->totalSizeOfCommittedPages -= page->bucket->slotSize + kSystemPageSize;
+    size_t uncommittedPageSize = page->bucket->slotSize + kSystemPageSize;
+    ASSERT(root->totalSizeOfCommittedPages >= uncommittedPageSize);
+    root->totalSizeOfCommittedPages -= uncommittedPageSize;
+    ASSERT(root->totalSizeOfDirectMappedPages >= uncommittedPageSize);
+    root->totalSizeOfDirectMappedPages -= uncommittedPageSize;
 
     ASSERT(!(unmapSize & kPageAllocationGranularityOffsetMask));
 
@@ -709,7 +746,7 @@ partitionAllocSlowPathFailed:
         bucket->activePagesHead = &PartitionRootGeneric::gSeedPage;
         return nullptr;
     }
-    partitionOutOfMemory();
+    partitionOutOfMemory(root);
     return nullptr;
 }