Add zcalloc and use it where appropriate

calloc is more effecient than malloc+memset when the system uses mmap to
allocate memory. mmap always returns zeroed memory so the memset can be
avoided.  The threshold to use mmap is 16k in osx libc and 128k in bsd
libc and glibc. The kernel can lazily allocate the pages, this reduces
memory usage when we have a page table or hash table that is mostly
empty.

This change is most visible when you start a new redis instance with vm
enabled.  You'll see no increased memory usage no matter how big your
page table is.

diff --git a/src/dict.c b/src/dict.c
index 0d4aacb7dfca58307d7eb2e79b6d7b180a4c5dd6..77ce90cb0c0eaadc68a8180b8f744b660ef13514 100644 (file)
--- a/src/dict.c
+++ b/src/dict.c
@@ -148,14 +148,12 @@ int dictExpand(dict *d, unsigned long size)
     if (dictIsRehashing(d) || d->ht[0].used > size)
         return DICT_ERR;
 
+    /* Allocate the new hashtable and initialize all pointers to NULL */
     n.size = realsize;
     n.sizemask = realsize-1;
-    n.table = zmalloc(realsize*sizeof(dictEntry*));
+    n.table = zcalloc(realsize*sizeof(dictEntry*));
     n.used = 0;
 
-    /* Initialize all the pointers to NULL */
-    memset(n.table, 0, realsize*sizeof(dictEntry*));
-
     /* Is this the first initialization? If so it's not really a rehashing
      * we just set the first hash table so that it can accept keys. */
     if (d->ht[0].table == NULL) {

diff --git a/src/vm.c b/src/vm.c
index 073cace2fbdc8a0b2a5a6095b14d7da2eaf54f49..0ccc5fe22658e8381cb4c7adfb0f40b0f7f82c11 100644 (file)
--- a/src/vm.c
+++ b/src/vm.c
@@ -86,10 +86,9 @@ void vmInit(void) {
     } else {
         redisLog(REDIS_NOTICE,"Swap file allocated with success");
     }
-    server.vm_bitmap = zmalloc((server.vm_pages+7)/8);
+    server.vm_bitmap = zcalloc((server.vm_pages+7)/8);
     redisLog(REDIS_VERBOSE,"Allocated %lld bytes page table for %lld pages",
         (long long) (server.vm_pages+7)/8, server.vm_pages);
-    memset(server.vm_bitmap,0,(server.vm_pages+7)/8);
 
     /* Initialize threaded I/O (used by Virtual Memory) */
     server.io_newjobs = listCreate();

diff --git a/src/zmalloc.c b/src/zmalloc.c
index 8658376a3462c9e4278c97eaf914b07dd6deaa8d..5c1b5e9aaeb86b714000fcf962b311f3dcbb5eec 100644 (file)
--- a/src/zmalloc.c
+++ b/src/zmalloc.c
@@ -89,6 +89,20 @@ void *zmalloc(size_t size) {
 #endif
 }
 
+void *zcalloc(size_t size) {
+    void *ptr = calloc(1, size+PREFIX_SIZE);
+
+    if (!ptr) zmalloc_oom(size);
+#ifdef HAVE_MALLOC_SIZE
+    increment_used_memory(redis_malloc_size(ptr));
+    return ptr;
+#else
+    *((size_t*)ptr) = size;
+    increment_used_memory(size+PREFIX_SIZE);
+    return (char*)ptr+PREFIX_SIZE;
+#endif
+}
+
 void *zrealloc(void *ptr, size_t size) {
 #ifndef HAVE_MALLOC_SIZE
     void *realptr;

diff --git a/src/zmalloc.h b/src/zmalloc.h
index 193e7eda5c04f6b7288a5f52b7dd35ac06c76ba1..db858bba0b75ffc50cc206c56c3ecd581e4204a7 100644 (file)
--- a/src/zmalloc.h
+++ b/src/zmalloc.h
@@ -32,6 +32,7 @@
 #define _ZMALLOC_H
 
 void *zmalloc(size_t size);
+void *zcalloc(size_t size);
 void *zrealloc(void *ptr, size_t size);
 void zfree(void *ptr);
 char *zstrdup(const char *s);