PartitionAlloc: API changes to support new partitionPurgeMemoryGeneric() mode.

Source/wtf/PartitionAlloc.cpp

Index: Source/wtf/PartitionAlloc.cpp
diff --git a/Source/wtf/PartitionAlloc.cpp b/Source/wtf/PartitionAlloc.cpp
index 149730b1fd3152476404bdc6a52fcb4093a71669..f5c1dcfd792ad0ba61157bcd20bdc93d764f004b 100644
--- a/Source/wtf/PartitionAlloc.cpp
+++ b/Source/wtf/PartitionAlloc.cpp
@@ -906,15 +906,17 @@ static void partitionDecommitFreePages(PartitionRootBase* root)
     }
 }
 
-void partitionPurgeMemory(PartitionRoot* root)
+void partitionPurgeMemory(PartitionRoot* root, int flags)
 {
-    partitionDecommitFreePages(root);
+    if (flags & PartitionPurgeDecommitEmptyPages)
+        partitionDecommitFreePages(root);

[haraken, 2015/06/18 18:00:10]

Nit: We might want to rename this function to partitionDecommitEmptyPages.

 }
 
-void partitionPurgeMemoryGeneric(PartitionRootGeneric* root)
+void partitionPurgeMemoryGeneric(PartitionRootGeneric* root, int flags)
 {
     spinLockLock(&root->lock);
-    partitionDecommitFreePages(root);
+    if (flags & PartitionPurgeDecommitEmptyPages)
+        partitionDecommitFreePages(root);
     spinLockUnlock(&root->lock);
 }
 
@@ -1100,7 +1102,7 @@ static void partitionDumpPageStats(PartitionBucketMemoryStats* statsOut, const P
         size_t pageBytesResidentRounded = partitionRoundUpToSystemPage(pageBytesResident);
         statsOut->residentBytes += pageBytesResidentRounded;
         if (!page->numAllocatedSlots) {
-            statsOut->freeableBytes += pageBytesResidentRounded;
+            statsOut->decommittableBytes += pageBytesResidentRounded;

[haraken, 2015/06/18 18:00:10]

Here we're adding pageBytesResidentRounded to both statsOut->residentBytes and
statsOut->decommittableBytes. Is it an expected thing? I guess it shouldn't be
added to statsOut->residentBytes given that this is an empty page.

             ++statsOut->numEmptyPages;
         } else if (page->numAllocatedSlots == bucketNumSlots) {
             ++statsOut->numFullPages;