Bug 457189 to use MAP_ALIGN to request chunksize-aligned blocks from mmap r=jasone

memory/jemalloc/jemalloc.c

@@ -344,6 +344,10 @@ __FBSDID("$FreeBSD: head/lib/libc/stdlib/malloc.c 180599 2008-07-18 19:35:44Z ja
 static const bool __isthreaded = true;
 #endif
 
+#if defined(MOZ_MEMORY_SOLARIS) && defined(MAP_ALIGN) && !defined(JEMALLOC_NEVER_USES_MAP_ALIGN)
+#define JEMALLOC_USES_MAP_ALIGN	 /* Required on Solaris 10. Might improve performance elsewhere. */
+#endif
+
 #define __DECONST(type, var) ((type)(uintptr_t)(const void *)(var))
 
 #include "qr.h"
@@ -2160,6 +2164,34 @@ pages_copy(void *dest, const void *src, size_t n)
 	    (vm_address_t)dest);
 }
 #else /* MOZ_MEMORY_DARWIN */
+#ifdef JEMALLOC_USES_MAP_ALIGN
+static void *
+pages_map_align(size_t size, int pfd)
+{
+	void *ret;
+
+	/*
+	 * We don't use MAP_FIXED here, because it can cause the *replacement*
+	 * of existing mappings, and we only want to create new mappings.
+	 */
+#ifdef MALLOC_PAGEFILE
+	if (pfd != -1) {
+		ret = mmap((void *)chunksize, size, PROT_READ | PROT_WRITE, MAP_PRIVATE |
+		    MAP_NOSYNC | MAP_ALIGN, pfd, 0);
+	} else
+#endif
+	       {
+		ret = mmap((void *)chunksize, size, PROT_READ | PROT_WRITE, MAP_PRIVATE |
+		    MAP_NOSYNC | MAP_ALIGN | MAP_ANON, -1, 0);
+	}
+	assert(ret != NULL);
+
+	if (ret == MAP_FAILED)
+		ret = NULL;
+	return (ret);
+}
+#endif
+
 static void *
 pages_map(void *addr, size_t size, int pfd)
 {
@@ -2330,7 +2362,9 @@ static void *
 chunk_alloc_mmap(size_t size, bool pagefile)
 {
 	void *ret;
+#ifndef JEMALLOC_USES_MAP_ALIGN
 	size_t offset;
+#endif
 	int pfd;
 
 #ifdef MALLOC_PAGEFILE
@@ -2352,6 +2386,9 @@ chunk_alloc_mmap(size_t size, bool pagefile)
 	 * since it reduces the number of page files.
 	 */
 
+#ifdef JEMALLOC_USES_MAP_ALIGN
+	ret = pages_map_align(size, pfd);
+#else
 	ret = pages_map(NULL, size, pfd);
 	if (ret == NULL)
 		goto RETURN;
@@ -2390,6 +2427,7 @@ chunk_alloc_mmap(size_t size, bool pagefile)
 	}
 
 RETURN:
+#endif
 #ifdef MALLOC_PAGEFILE
 	if (pfd != -1)
 		pagefile_close(pfd);
@@ -5747,6 +5785,15 @@ MALLOC_OUT:
 	arena_maxclass = chunksize - (arena_chunk_header_npages <<
 	    pagesize_2pow);
 
+#ifdef JEMALLOC_USES_MAP_ALIGN
+	/*
+	 * When using MAP_ALIGN, the alignment parameter must be a power of two
+	 * multiple of the system pagesize, or mmap will fail.
+	 */
+	assert((chunksize % pagesize) == 0);
+	assert((1 << (ffs(chunksize / pagesize) - 1)) == (chunksize/pagesize));
+#endif
+
 	UTRACE(0, 0, 0);
 
 #ifdef MALLOC_STATS