Optimize ixalloc by avoiding a size lookup.

include/jemalloc/internal/arena_externs.h

@@ -64,7 +64,7 @@ void arena_dalloc_bin_junked_locked(tsdn_t *tsdn, arena_t *arena,
     extent_t *extent, void *ptr);
 void arena_dalloc_small(tsdn_t *tsdn, void *ptr);
 bool arena_ralloc_no_move(tsdn_t *tsdn, void *ptr, size_t oldsize, size_t size,
-    size_t extra, bool zero);
+    size_t extra, bool zero, size_t *newsize);
 void *arena_ralloc(tsdn_t *tsdn, arena_t *arena, void *ptr, size_t oldsize,
     size_t size, size_t alignment, bool zero, tcache_t *tcache,
     hook_ralloc_args_t *hook_args);

include/jemalloc/internal/jemalloc_internal_inlines_c.h

@@ -203,7 +203,7 @@ iralloc(tsd_t *tsd, void *ptr, size_t oldsize, size_t size, size_t alignment,
 
 JEMALLOC_ALWAYS_INLINE bool
 ixalloc(tsdn_t *tsdn, void *ptr, size_t oldsize, size_t size, size_t extra,
-    size_t alignment, bool zero) {
+    size_t alignment, bool zero, size_t *newsize) {
 	assert(ptr != NULL);
 	assert(size != 0);
 	witness_assert_depth_to_rank(tsdn_witness_tsdp_get(tsdn),
@@ -212,10 +212,12 @@ ixalloc(tsdn_t *tsdn, void *ptr, size_t oldsize, size_t size, size_t extra,
 	if (alignment != 0 && ((uintptr_t)ptr & ((uintptr_t)alignment-1))
 	    != 0) {
 		/* Existing object alignment is inadequate. */
+		*newsize = oldsize;
 		return true;
 	}
 
-	return arena_ralloc_no_move(tsdn, ptr, oldsize, size, extra, zero);
+	return arena_ralloc_no_move(tsdn, ptr, oldsize, size, extra, zero,
+	    newsize);
 }
 
 #endif /* JEMALLOC_INTERNAL_INLINES_C_H */

src/arena.c

@@ -1585,15 +1585,17 @@ arena_dalloc_small(tsdn_t *tsdn, void *ptr) {
 
 bool
 arena_ralloc_no_move(tsdn_t *tsdn, void *ptr, size_t oldsize, size_t size,
-    size_t extra, bool zero) {
+    size_t extra, bool zero, size_t *newsize) {
+	bool ret;
 	/* Calls with non-zero extra had to clamp extra. */
 	assert(extra == 0 || size + extra <= LARGE_MAXCLASS);
 
+	extent_t *extent = iealloc(tsdn, ptr);
 	if (unlikely(size > LARGE_MAXCLASS)) {
-		return true;
+		ret = true;
+		goto done;
 	}
 
-	extent_t *extent = iealloc(tsdn, ptr);
 	size_t usize_min = sz_s2u(size);
 	size_t usize_max = sz_s2u(size + extra);
 	if (likely(oldsize <= SMALL_MAXCLASS && usize_min <= SMALL_MAXCLASS)) {
@@ -1606,17 +1608,23 @@ arena_ralloc_no_move(tsdn_t *tsdn, void *ptr, size_t oldsize, size_t size,
 		if ((usize_max > SMALL_MAXCLASS || sz_size2index(usize_max) !=
 		    sz_size2index(oldsize)) && (size > oldsize || usize_max <
 		    oldsize)) {
-			return true;
+			ret = true;
+			goto done;
 		}
 
 		arena_decay_tick(tsdn, extent_arena_get(extent));
-		return false;
+		ret = false;
 	} else if (oldsize >= LARGE_MINCLASS && usize_max >= LARGE_MINCLASS) {
-		return large_ralloc_no_move(tsdn, extent, usize_min, usize_max,
+		ret = large_ralloc_no_move(tsdn, extent, usize_min, usize_max,
 		    zero);
+	} else {
+		ret = true;
 	}
+done:
+	assert(extent == iealloc(tsdn, ptr));
+	*newsize = extent_usize_get(extent);
 
-	return true;
+	return ret;
 }
 
 static void *
@@ -1644,7 +1652,9 @@ arena_ralloc(tsdn_t *tsdn, arena_t *arena, void *ptr, size_t oldsize,
 
 	if (likely(usize <= SMALL_MAXCLASS)) {
 		/* Try to avoid moving the allocation. */
-		if (!arena_ralloc_no_move(tsdn, ptr, oldsize, usize, 0, zero)) {
+		UNUSED size_t newsize;
+		if (!arena_ralloc_no_move(tsdn, ptr, oldsize, usize, 0, zero,
+		    &newsize)) {
 			hook_invoke_expand(hook_args->is_realloc
 			    ? hook_expand_realloc : hook_expand_rallocx,
 			    ptr, oldsize, usize, (uintptr_t)ptr,

src/jemalloc.c

@@ -2834,14 +2834,14 @@ label_oom:
 JEMALLOC_ALWAYS_INLINE size_t
 ixallocx_helper(tsdn_t *tsdn, void *ptr, size_t old_usize, size_t size,
     size_t extra, size_t alignment, bool zero) {
-	size_t usize;
+	size_t newsize;
 
-	if (ixalloc(tsdn, ptr, old_usize, size, extra, alignment, zero)) {
+	if (ixalloc(tsdn, ptr, old_usize, size, extra, alignment, zero,
+	    &newsize)) {
 		return old_usize;
 	}
-	usize = isalloc(tsdn, ptr);
 
-	return usize;
+	return newsize;
 }
 
 static size_t