[heap] Introduce hard limit for external memory

src/globals.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_GLOBALS_H_
 #define V8_GLOBALS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 175 matching lines @@
 const size_t kCodeRangeAreaAlignment = 64 * KB;  // OS page on PPC Linux
 #else
 const bool kRequiresCodeRange = false;
 const size_t kMaximalCodeRangeSize = 0 * MB;
 const size_t kMinimumCodeRangeSize = 0 * MB;
 const size_t kCodeRangeAreaAlignment = 4 * KB;  // OS page.
 #endif
 const size_t kReservedCodeRangePages = 0;
 #endif
 
-// The external allocation limit should be below 256 MB on all architectures
-// to avoid that resource-constrained embedders run low on memory.
-const int kExternalAllocationLimit = 192 * 1024 * 1024;
+// Trigger an incremental GCs once the external memory reaches this limit.
+const int kExternalAllocationSoftLimit = 64 * MB;
 
 STATIC_ASSERT(kPointerSize == (1 << kPointerSizeLog2));
 
 const int kBitsPerByte = 8;
 const int kBitsPerByteLog2 = 3;
 const int kBitsPerPointer = kPointerSize * kBitsPerByte;
 const int kBitsPerInt = kIntSize * kBitsPerByte;
 
 // IEEE 754 single precision floating point number bit layout.
 const uint32_t kBinary32SignMask = 0x80000000u;
@@ skipping 942 matching lines @@
  public:
   enum { kNone = 0x00, kSignedSmall = 0x01, kNumber = 0x3, kAny = 0x7 };
 };
 
 }  // namespace internal
 }  // namespace v8
 
 namespace i = v8::internal;
 
 #endif  // V8_GLOBALS_H_