Changeset 58346 in webkit for trunk/JavaScriptCore/wtf

Timestamp:

Apr 27, 2010, 3:55:22 PM (15 years ago)

Author:

Stephanie Lewis

Message:

​https://bugs.webkit.org/show_bug.cgi?id=38154 FastMalloc calls madvise too often.
<rdar://problem/7834433> REGRESSSION: 1.5% PLT regression due to 56028 (return memory quicker).
To save on madvise calls when recommitting memory recommit the entire span and then carve it
instead of carving the span up and only committing the part that will be used immediately.

Reviewed by Geoff Garen.

• wtf/FastMalloc.cpp:

(WTF::TCMalloc_PageHeap::New):
(WTF::TCMalloc_PageHeap::AllocLarge):
(WTF::TCMalloc_PageHeap::Carve):

File:

• trunk/JavaScriptCore/wtf/FastMalloc.cpp (modified) (6 diffs)

trunk/JavaScriptCore/wtf/FastMalloc.cpp

@@ -1584 +1584 @@
     Span* result = ll->next;
     Carve(result, n, released);
-    if (result->decommitted) {
-        TCMalloc_SystemCommit(reinterpret_cast<void*>(result->start << kPageShift), static_cast<size_t>(n << kPageShift));
-        result->decommitted = false;
-    }
 #if USE_BACKGROUND_THREAD_TO_SCAVENGE_MEMORY
-    else {
-        // The newly allocated memory is from a span that's in the normal span list (already committed).  Update the
-        // free committed pages count.
-        ASSERT(free_committed_pages_ >= n);
-        free_committed_pages_ -= n;
-        if (free_committed_pages_ < min_free_committed_pages_since_last_scavenge_)
-            min_free_committed_pages_since_last_scavenge_ = free_committed_pages_;
-    }
+    // The newly allocated memory is from a span that's in the normal span list (already committed).  Update the
+    // free committed pages count.
+    ASSERT(free_committed_pages_ >= n);
+    free_committed_pages_ -= n;
+    if (free_committed_pages_ < min_free_committed_pages_since_last_scavenge_) 
+      min_free_committed_pages_since_last_scavenge_ = free_committed_pages_;
 #endif  // USE_BACKGROUND_THREAD_TO_SCAVENGE_MEMORY
     ASSERT(Check());
@@ -1654 +1648 @@
   if (best != NULL) {
     Carve(best, n, from_released);
-    if (best->decommitted) {
-        TCMalloc_SystemCommit(reinterpret_cast<void*>(best->start << kPageShift), static_cast<size_t>(n << kPageShift));
-        best->decommitted = false;
-    }
 #if USE_BACKGROUND_THREAD_TO_SCAVENGE_MEMORY
-    else {
-        // The newly allocated memory is from a span that's in the normal span list (already committed).  Update the
-        // free committed pages count.
-        ASSERT(free_committed_pages_ >= n);
-        free_committed_pages_ -= n;
-        if (free_committed_pages_ < min_free_committed_pages_since_last_scavenge_)
-            min_free_committed_pages_since_last_scavenge_ = free_committed_pages_;
-    }
+    // The newly allocated memory is from a span that's in the normal span list (already committed).  Update the
+    // free committed pages count.
+    ASSERT(free_committed_pages_ >= n);
+    free_committed_pages_ -= n;
+    if (free_committed_pages_ < min_free_committed_pages_since_last_scavenge_)
+      min_free_committed_pages_since_last_scavenge_ = free_committed_pages_;
 #endif  // USE_BACKGROUND_THREAD_TO_SCAVENGE_MEMORY
     ASSERT(Check());
@@ -1692 +1680 @@
 }
 
-static ALWAYS_INLINE void propagateDecommittedState(Span* destination, Span* source)
-{
-    destination->decommitted = source->decommitted;
-}
-
 inline void TCMalloc_PageHeap::Carve(Span* span, Length n, bool released) {
   ASSERT(n > 0);
@@ -1703 +1686 @@
   Event(span, 'A', n);
 
+  if (released) {
+    // If the span chosen to carve from is decommited, commit the entire span at once to avoid committing spans 1 page at a time.
+    ASSERT(span->decommitted);
+    TCMalloc_SystemCommit(reinterpret_cast<void*>(span->start << kPageShift), static_cast<size_t>(span->length << kPageShift));
+    span->decommitted = false;
+    free_committed_pages_ += span->length;
+  }
+  
   const int extra = static_cast<int>(span->length - n);
   ASSERT(extra >= 0);
@@ -1708 +1699 @@
     Span* leftover = NewSpan(span->start + n, extra);
     leftover->free = 1;
-    propagateDecommittedState(leftover, span);
+    leftover->decommitted = false;
     Event(leftover, 'S', extra);
     RecordSpan(leftover);
@@ -1714 +1705 @@
     // Place leftover span on appropriate free list
     SpanList* listpair = (static_cast<size_t>(extra) < kMaxPages) ? &free_[extra] : &large_;
-    Span* dst = released ? &listpair->returned : &listpair->normal;
+    Span* dst = &listpair->normal;
     DLL_Prepend(dst, leftover);