Changeset 43988 in webkit for trunk/JavaScriptCore/wtf/TCSystemAlloc.cpp

Timestamp:

May 21, 2009, 3:12:39 PM (16 years ago)

Author:

[email protected]

Message:

2009-05-21 Cameron Zwarich <​[email protected]>

Reviewed by Mark Rowe.

Bug 25945: Add support for MADV_FREE to TCMalloc
<​https://bugs.webkit.org/show_bug.cgi?id=25945>
<rdar://problem/6910754>

Add support for MADV_FREE to TCMalloc_SystemRelease for platforms that
don't also support MADV_FREE_REUSE. The code is identical to the MADV_DONTNEED
case except for the advice passed to madvise(), so combining the two cases
makes the most sense.

• wtf/Platform.h: Only define HAVE_MADV_FREE when not building on Tiger or Leopard, because while it is defined on these platforms it actually does nothing.
• wtf/TCSystemAlloc.cpp: (TCMalloc_SystemRelease): use MADV_FREE if it is available; otherwise use MADV_DONTNEED.

File:

• trunk/JavaScriptCore/wtf/TCSystemAlloc.cpp (modified) (2 diffs)

trunk/JavaScriptCore/wtf/TCSystemAlloc.cpp

@@ -389 +389 @@
 }
 
-#elif HAVE(MADV_DONTNEED)
+#elif HAVE(MADV_FREE) || HAVE(MADV_DONTNEED)
 
 void TCMalloc_SystemRelease(void* start, size_t length)
 {
+    // MADV_FREE clears the modified bit on pages, which allows
+    // them to be discarded immediately.
+#if HAVE(MADV_FREE)
+    const int advice = MADV_FREE;
+#else
+    const int advice = MADV_DONTNEED;
+#endif
   if (FLAGS_malloc_devmem_start) {
     // It's not safe to use MADV_DONTNEED if we've been mapping
@@ -419 +426 @@
     // doesn't matter...
     while (madvise(reinterpret_cast<char*>(new_start), new_end - new_start,
-                   MADV_DONTNEED) == -1 &&
+                   advice) == -1 &&
            errno == EAGAIN) {
       // NOP