<rdar://problem/6050421> JavaScript register file should remap to release...

<rdar://problem/6050421> JavaScript register file should remap to release physical pages accumulated during deep recursion

Reviewed by Geoff Garen

We now track the maximum extent of the RegisterFile, and when we reach the final
return from JS (so the stack portion of the registerfile becomes empty) we see
if that extent is greater than maxExcessCapacity.  If it is we use madvise or
VirtualFree to release the physical pages that were backing the excess.

git-svn-id: svn://svn.chromium.org/blink/trunk@42842 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/JavaScriptCore/ChangeLog

+2009-04-23  Oliver Hunt  <oliver@apple.com>
+
+        Reviewed by Geoff Garen.
+
+        <rdar://problem/6050421> JavaScript register file should remap to release physical pages accumulated during deep recursion
+
+        We now track the maximum extent of the RegisterFile, and when we reach the final
+        return from JS (so the stack portion of the registerfile becomes empty) we see
+        if that extent is greater than maxExcessCapacity.  If it is we use madvise or
+        VirtualFree to release the physical pages that were backing the excess.
+
+        * interpreter/RegisterFile.cpp:
+        (JSC::RegisterFile::releaseExcessCapacity):
+        * interpreter/RegisterFile.h:
+        (JSC::RegisterFile::RegisterFile):
+        (JSC::RegisterFile::shrink):
+        (JSC::RegisterFile::grow):
+
 2009-04-23  Mark Rowe  <mrowe@apple.com>
 
         With great sadness and a heavy heart I switch us back from YARR to WREC in

third_party/WebKit/JavaScriptCore/interpreter/RegisterFile.cpp

@@ -42,4 +42,17 @@ RegisterFile::~RegisterFile()
 #endif
 }
 
+void RegisterFile::releaseExcessCapacity()
+{
+    m_maxUsed = m_start;
+    void* memoryToRelease = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(reinterpret_cast<char*>(m_start) + commitSize * 2 - 1) & ~(commitSize - 1));
+    ptrdiff_t size = reinterpret_cast<char*>(m_end) - reinterpret_cast<char*>(memoryToRelease);
+#if HAVE(MMAP) && !HAVE(VIRTUALALLOC)
+    while (madvise(memoryToRelease, size, MADV_FREE) == -1 && errno == EAGAIN) { }
+#elif HAVE(VIRTUALALLOC)
+    VirtualFree(memoryToRelease, size, MEM_DECOMMIT);
+    m_commitEnd = memoryToRelease;
+#endif
+}
+
 } // namespace JSC

third_party/WebKit/JavaScriptCore/interpreter/RegisterFile.h

@@ -114,6 +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();
@@ -138,12 +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
@@ -185,6 +190,7 @@ namespace JSC {
     #endif
         m_start = m_buffer + maxGlobals;
         m_end = m_start;
+        m_maxUsed = m_end;
         m_max = m_start + capacity;
     }
 
@@ -192,6 +198,8 @@ namespace JSC {
     {
         if (newEnd < m_end)
             m_end = newEnd;
+        if (m_end == m_start && (m_maxUsed - m_start) > maxExcessCapacity) 
+            releaseExcessCapacity();
     }
 
     inline bool RegisterFile::grow(Register* newEnd)
@@ -213,6 +221,9 @@ namespace JSC {
         }
 #endif
 
+        if (newEnd > m_maxUsed)
+            m_maxUsed = newEnd;
+
         m_end = newEnd;
         return true;
     }