1 files changed, 24 insertions, 4 deletions

diff --git a/JavaScriptCore/interpreter/RegisterFile.h b/JavaScriptCore/interpreter/RegisterFile.h
index c320f04..09a3963 100644
--- a/JavaScriptCore/interpreter/RegisterFile.h
+++ b/JavaScriptCore/interpreter/RegisterFile.h
@@ -29,10 +29,11 @@
 #ifndef RegisterFile_h
 #define RegisterFile_h
 
+#include "Collector.h"
 #include "ExecutableAllocator.h"
 #include "Register.h"
-#include "Collector.h"
 #include <wtf/Noncopyable.h>
+#include <wtf/VMTags.h>
 
 #if HAVE(MMAP)
 #include <errno.h>
@@ -113,6 +114,8 @@ namespace JSC {
         static const size_t defaultCapacity = 524288;
         static const size_t defaultMaxGlobals = 8192;
         static const size_t commitSize = 1 << 14;
+        // Allow 8k of excess registers before we start trying to reap the registerfile
+        static const ptrdiff_t maxExcessCapacity = 8 * 1024;
 
         RegisterFile(size_t capacity = defaultCapacity, size_t maxGlobals = defaultMaxGlobals);
         ~RegisterFile();
@@ -137,12 +140,15 @@ namespace JSC {
         void markCallFrames(Heap* heap) { heap->markConservatively(m_start, m_end); }
 
     private:
+        void releaseExcessCapacity();
         size_t m_numGlobals;
         const size_t m_maxGlobals;
         Register* m_start;
         Register* m_end;
         Register* m_max;
         Register* m_buffer;
+        Register* m_maxUsed;
+
 #if HAVE(VIRTUALALLOC)
         Register* m_commitEnd;
 #endif
@@ -150,6 +156,9 @@ namespace JSC {
         JSGlobalObject* m_globalObject; // The global object whose vars are currently stored in the register file.
     };
 
+    // FIXME: Add a generic getpagesize() to WTF, then move this function to WTF as well.
+    inline bool isPageAligned(size_t size) { return size != 0 && size % (8 * 1024) == 0; }
+
     inline RegisterFile::RegisterFile(size_t capacity, size_t maxGlobals)
         : m_numGlobals(0)
         , m_maxGlobals(maxGlobals)
@@ -159,9 +168,13 @@ namespace JSC {
         , m_buffer(0)
         , m_globalObject(0)
     {
+        // Verify that our values will play nice with mmap and VirtualAlloc.
+        ASSERT(isPageAligned(maxGlobals));
+        ASSERT(isPageAligned(capacity));
+
         size_t bufferLength = (capacity + maxGlobals) * sizeof(Register);
     #if HAVE(MMAP)
-        m_buffer = static_cast<Register*>(mmap(0, bufferLength, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0));
+        m_buffer = static_cast<Register*>(mmap(0, bufferLength, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, VM_TAG_FOR_REGISTERFILE_MEMORY, 0));
         if (m_buffer == MAP_FAILED) {
             fprintf(stderr, "Could not allocate register file: %d\n", errno);
             CRASH();
@@ -184,13 +197,17 @@ namespace JSC {
     #endif
         m_start = m_buffer + maxGlobals;
         m_end = m_start;
+        m_maxUsed = m_end;
         m_max = m_start + capacity;
     }
 
     inline void RegisterFile::shrink(Register* newEnd)
     {
-        if (newEnd < m_end)
-            m_end = newEnd;
+        if (newEnd >= m_end)
+            return;
+        m_end = newEnd;
+        if (m_end == m_start && (m_maxUsed - m_start) > maxExcessCapacity)
+            releaseExcessCapacity();
     }
 
     inline bool RegisterFile::grow(Register* newEnd)
@@ -212,6 +229,9 @@ namespace JSC {
         }
 #endif
 
+        if (newEnd > m_maxUsed)
+            m_maxUsed = newEnd;
+
         m_end = newEnd;
         return true;
     }