Replace malloc() followed by memset() to zero with calloc()

Bionic's calloc() is smart enough to not zero out memory if it gets that memory
from an anonyous mmap.  Thus, if we use malloc for large allocations, we cause
unnecessary memory duplication by following the malloc() with a memset().

An even better approach would be to replace the known large calloc() calls with
dvmAllocRegion() allocation.

Change-Id: Id308f541c9a040d5929bf991b6c2bfdefb823c3c

2 files changed, 5 insertions, 10 deletions

diff --git a/vm/alloc/Copying.cpp b/vm/alloc/Copying.cpp
index 49c676052..ad5b8fc94 100644
--- a/vm/alloc/Copying.cpp
+++ b/vm/alloc/Copying.cpp
@@ -444,9 +444,8 @@ GcHeap *dvmHeapSourceStartup(size_t startSize, size_t absoluteMaxSize)
 
     assert(startSize <= absoluteMaxSize);
 
-    heapSource = malloc(sizeof(*heapSource));
+    heapSource = calloc(1, sizeof(*heapSource));
     assert(heapSource != NULL);
-    memset(heapSource, 0, sizeof(*heapSource));
 
     heapSource->minimumSize = alignUp(startSize, BLOCK_SIZE);
     heapSource->maximumSize = alignUp(absoluteMaxSize, BLOCK_SIZE);
@@ -475,9 +474,8 @@ GcHeap *dvmHeapSourceStartup(size_t startSize, size_t absoluteMaxSize)
     /* Byte indicating space residence or free status of block. */
     {
         size_t size = sizeof(heapSource->blockSpace[0]);
-        heapSource->blockSpace = malloc(heapSource->totalBlocks*size);
+        heapSource->blockSpace = calloc(1, heapSource->totalBlocks*size);
         assert(heapSource->blockSpace != NULL);
-        memset(heapSource->blockSpace, 0, heapSource->totalBlocks*size);
     }
 
     dvmHeapBitmapInit(&heapSource->allocBits,
@@ -489,9 +487,8 @@ GcHeap *dvmHeapSourceStartup(size_t startSize, size_t absoluteMaxSize)
     heapSource->allocPtr = allocateBlocks(heapSource, 1);
     heapSource->allocLimit = heapSource->allocPtr + BLOCK_SIZE;
 
-    gcHeap = malloc(sizeof(*gcHeap));
+    gcHeap = calloc(1, sizeof(*gcHeap));
     assert(gcHeap != NULL);
-    memset(gcHeap, 0, sizeof(*gcHeap));
     gcHeap->heapSource = heapSource;
 
     return gcHeap;
diff --git a/vm/alloc/HeapSource.cpp b/vm/alloc/HeapSource.cpp
index c0ad07df5..f051b4df6 100644
--- a/vm/alloc/HeapSource.cpp
+++ b/vm/alloc/HeapSource.cpp
@@ -535,20 +535,18 @@ GcHeap* dvmHeapSourceStartup(size_t startSize, size_t maximumSize,
         goto fail;
     }
 
-    gcHeap = (GcHeap *)malloc(sizeof(*gcHeap));
+    gcHeap = (GcHeap *)calloc(1, sizeof(*gcHeap));
     if (gcHeap == NULL) {
         LOGE_HEAP("Can't allocate heap descriptor");
         goto fail;
     }
-    memset(gcHeap, 0, sizeof(*gcHeap));
 
-    hs = (HeapSource *)malloc(sizeof(*hs));
+    hs = (HeapSource *)calloc(1, sizeof(*hs));
     if (hs == NULL) {
         LOGE_HEAP("Can't allocate heap source");
         free(gcHeap);
         goto fail;
     }
-    memset(hs, 0, sizeof(*hs));
 
     hs->targetUtilization = DEFAULT_HEAP_UTILIZATION;
     hs->startSize = startSize;