Changeset 58730 in webkit for trunk/JavaScriptCore/wtf/FastMalloc.cpp

Timestamp:

May 3, 2010, 7:39:23 PM (15 years ago)

Author:

Stephanie Lewis

Message:

​https://bugs.webkit.org/show_bug.cgi?id=38368
<rdar://problem/7834433> REGRESSSION: 1.5% PLT regression due to 56028
(return memory quicker).
Instead of returning everything but the smallest spans spread out
the spans kept over several size lists.

Reviewed by Geoff Garen.

• wtf/FastMalloc.cpp:

(WTF::TCMalloc_PageHeap::scavenge):

File:

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

trunk/JavaScriptCore/wtf/FastMalloc.cpp

@@ -1274 +1274 @@
 static const float kScavengePercentage = .5f;
 
-// Number of free committed pages that we want to keep around.
-static const size_t kMinimumFreeCommittedPageCount = 512;
+// number of span lists to keep spans in when memory is returned.
+static const int kMinSpanListsWithSpans = 32;
+
+// Number of free committed pages that we want to keep around.  The minimum number of pages used when there
+// is 1 span in each of the first kMinSpanListsWithSpans spanlists.  Currently 528 pages.
+static const size_t kMinimumFreeCommittedPageCount = kMinSpanListsWithSpans * ((1.0f+kMinSpanListsWithSpans) / 2.0f);
 
 #endif
@@ -1535 +1539 @@
     size_t targetPageCount = std::max<size_t>(kMinimumFreeCommittedPageCount, free_committed_pages_ - pagesToRelease);
 
-    for (int i = kMaxPages; i >= 0 && free_committed_pages_ > targetPageCount; i--) {
-        SpanList* slist = (static_cast<size_t>(i) == kMaxPages) ? &large_ : &free_[i];
-        while (!DLL_IsEmpty(&slist->normal) && free_committed_pages_ > targetPageCount) {
-            Span* s = slist->normal.prev; 
-            DLL_Remove(s);
-            ASSERT(!s->decommitted);
-            if (!s->decommitted) {
-                TCMalloc_SystemRelease(reinterpret_cast<void*>(s->start << kPageShift),
-                                       static_cast<size_t>(s->length << kPageShift));
-                ASSERT(free_committed_pages_ >= s->length);
-                free_committed_pages_ -= s->length;
-                s->decommitted = true;
+    while (free_committed_pages_ > targetPageCount) {
+        for (int i = kMaxPages; i > 0 && free_committed_pages_ >= targetPageCount; i--) {
+            SpanList* slist = (static_cast<size_t>(i) == kMaxPages) ? &large_ : &free_[i];
+            // If the span size is bigger than kMinSpanListsWithSpans pages return all the spans in the list, else return all but 1 span.  
+            // Return only 50% of a spanlist at a time so spans of size 1 are not the only ones left.
+            size_t numSpansToReturn = (i > kMinSpanListsWithSpans) ? DLL_Length(&slist->normal) : static_cast<size_t>(.5 * DLL_Length(&slist->normal));
+            for (int j = 0; static_cast<size_t>(j) < numSpansToReturn && !DLL_IsEmpty(&slist->normal) && free_committed_pages_ > targetPageCount; j++) {
+                Span* s = slist->normal.prev; 
+                DLL_Remove(s);
+                ASSERT(!s->decommitted);
+                if (!s->decommitted) {
+                    TCMalloc_SystemRelease(reinterpret_cast<void*>(s->start << kPageShift),
+                                           static_cast<size_t>(s->length << kPageShift));
+                    ASSERT(free_committed_pages_ >= s->length);
+                    free_committed_pages_ -= s->length;
+                    s->decommitted = true;
+                }
+                DLL_Prepend(&slist->returned, s);
             }
-            DLL_Prepend(&slist->returned, s);
         }
     }