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

Source/wtf/PartitionAlloc.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 166 matching lines @@
 static const size_t kGenericSmallestBucket = 1 << (kGenericMinBucketedOrder - 1);
 static const size_t kGenericMaxBucketSpacing = 1 << ((kGenericMaxBucketedOrder - 1) - kGenericNumBucketsPerOrderBits);
 static const size_t kGenericMaxBucketed = (1 << (kGenericMaxBucketedOrder - 1)) + ((kGenericNumBucketsPerOrder - 1) * kGenericMaxBucketSpacing);
 static const size_t kGenericMinDirectMappedDownsize = kGenericMaxBucketed + 1; // Limit when downsizing a direct mapping using realloc().
 static const size_t kGenericMaxDirectMapped = INT_MAX - kSystemPageSize;
 static const size_t kBitsPerSizet = sizeof(void*) * CHAR_BIT;
 
 // Constants for the memory reclaim logic.
 static const size_t kMaxFreeableSpans = 16;
 
+// If the total size of allocated but not committed pages exceeds this value,

[Tom Sepez, 2014/11/06 17:32:51]

nit: size in bytes?  pages? 

[Chris Evans, 2014/11/06 20:43:22]

Nit: this comment doesn't really explain why we'd want to do this. Maybe explain
"this is to try and distinguish "out of address space" from "out of physical
memory" ?

[hiroshige, 2014/11/07 08:57:00]

In bytes. Add it to the comment.

[hiroshige, 2014/11/07 08:57:00]

Done.

[hiroshige, 2014/11/07 08:57:00]

Done.

+// special crash stack trace is generated at |partitionOutOfMemory|.

[Chris Evans, 2014/11/06 20:43:22]

Nit: "a special"?

[hiroshige, 2014/11/07 08:57:00]

Done.

+static const size_t kReasonableSizeOfUnusedPages = 1000000000;

[Chris Evans, 2014/11/06 20:43:22]

Nit: this looks to be about 1GB. Maybe formulate it as 1024 * 1024 * 1024 for
easy engineer readability?

[hiroshige, 2014/11/07 08:57:00]

Done.

+
 #if ENABLE(ASSERT)
 // These two byte values match tcmalloc.
 static const unsigned char kUninitializedByte = 0xAB;
 static const unsigned char kFreedByte = 0xCD;
 static const uint32_t kCookieValue = 0xDEADBEEFu;
 static const size_t kCookieSize = 16; // Handles alignment up to XMM instructions on Intel.
 #endif
 
 struct PartitionBucket;
 struct PartitionRootBase;
@@ skipping 460 matching lines @@
 using WTF::partitionAlloc;
 using WTF::partitionFree;
 using WTF::partitionAllocGeneric;
 using WTF::partitionFreeGeneric;
 using WTF::partitionReallocGeneric;
 using WTF::partitionAllocActualSize;
 using WTF::partitionAllocSupportsGetSize;
 using WTF::partitionAllocGetSize;
 
 #endif // WTF_PartitionAlloc_h