Convert rtree from (void *) to (uint8_t) storage.

Reduce rtree memory usage by storing booleans (1 byte each) rather than
pointers.  The rtree code is only used to record whether jemalloc manages
a chunk of memory, so there's no need to store pointers in the rtree.

Increase rtree node size to 64 KiB in order to reduce tree depth from 13
to 3 on 64-bit systems.  The conversion to more compact leaf nodes was
enough by itself to make the rtree depth 1 on 32-bit systems; due to the
fact that root nodes are smaller than the specified node size if
possible, the node size change has no impact on 32-bit systems (assuming
default chunk size).

include/jemalloc/internal/jemalloc_internal.h.in

@@ -853,7 +853,7 @@ ivsalloc(const void *ptr, bool demote)
 {
 
 	/* Return 0 if ptr is not within a chunk managed by jemalloc. */
-	if (rtree_get(chunks_rtree, (uintptr_t)CHUNK_ADDR2BASE(ptr)) == NULL)
+	if (rtree_get(chunks_rtree, (uintptr_t)CHUNK_ADDR2BASE(ptr)) == 0)
 		return (0);
 
 	return (isalloc(ptr, demote));

include/jemalloc/internal/rtree.h

@@ -14,11 +14,7 @@ typedef struct rtree_s rtree_t;
  * Size of each radix tree node (must be a power of 2).  This impacts tree
  * depth.
  */
-#if (LG_SIZEOF_PTR == 2)
-#  define RTREE_NODESIZE (1U << 14)
-#else
-#  define RTREE_NODESIZE CACHELINE
-#endif
+#define	RTREE_NODESIZE (1U << 16)
 
 typedef void *(rtree_alloc_t)(size_t);
 typedef void (rtree_dalloc_t)(void *);
@@ -52,19 +48,19 @@ void	rtree_postfork_child(rtree_t *rtree);
 
 #ifndef JEMALLOC_ENABLE_INLINE
 #ifdef JEMALLOC_DEBUG
-void	*rtree_get_locked(rtree_t *rtree, uintptr_t key);
+uint8_t rtree_get_locked(rtree_t *rtree, uintptr_t key);
 #endif
-void	*rtree_get(rtree_t *rtree, uintptr_t key);
-bool	rtree_set(rtree_t *rtree, uintptr_t key, void *val);
+uint8_t	rtree_get(rtree_t *rtree, uintptr_t key);
+bool	rtree_set(rtree_t *rtree, uintptr_t key, uint8_t val);
 #endif
 
 #if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_RTREE_C_))
 #define	RTREE_GET_GENERATE(f)						\
 /* The least significant bits of the key are ignored. */		\
-JEMALLOC_INLINE void *							\
+JEMALLOC_INLINE uint8_t							\
 f(rtree_t *rtree, uintptr_t key)					\
 {									\
-	void *ret;							\
+	uint8_t ret;							\
 	uintptr_t subkey;						\
 	unsigned i, lshift, height, bits;				\
 	void **node, **child;						\
@@ -79,7 +75,7 @@ f(rtree_t *rtree, uintptr_t key)					\
 		child = (void**)node[subkey];				\
 		if (child == NULL) {					\
 			RTREE_UNLOCK(&rtree->mutex);			\
-			return (NULL);					\
+			return (0);					\
 		}							\
 	}								\
 									\
@@ -90,7 +86,10 @@ f(rtree_t *rtree, uintptr_t key)					\
 	bits = rtree->level2bits[i];					\
 	subkey = (key << lshift) >> ((ZU(1) << (LG_SIZEOF_PTR+3)) -	\
 	    bits);							\
-	ret = node[subkey];						\
+	{								\
+		uint8_t *leaf = (uint8_t *)node;			\
+		ret = leaf[subkey];					\
+	}								\
 	RTREE_UNLOCK(&rtree->mutex);					\
 									\
 	RTREE_GET_VALIDATE						\
@@ -129,7 +128,7 @@ RTREE_GET_GENERATE(rtree_get)
 #undef RTREE_GET_VALIDATE
 
 JEMALLOC_INLINE bool
-rtree_set(rtree_t *rtree, uintptr_t key, void *val)
+rtree_set(rtree_t *rtree, uintptr_t key, uint8_t val)
 {
 	uintptr_t subkey;
 	unsigned i, lshift, height, bits;
@@ -144,14 +143,14 @@ rtree_set(rtree_t *rtree, uintptr_t key, void *val)
 		    bits);
 		child = (void**)node[subkey];
 		if (child == NULL) {
-			child = (void**)rtree->alloc(sizeof(void *) <<
-			    rtree->level2bits[i+1]);
+			size_t size = ((i + 1 < height - 1) ? sizeof(void *)
+			    : (sizeof(uint8_t))) << rtree->level2bits[i+1];
+			child = (void**)rtree->alloc(size);
 			if (child == NULL) {
 				malloc_mutex_unlock(&rtree->mutex);
 				return (true);
 			}
-			memset(child, 0, sizeof(void *) <<
-			    rtree->level2bits[i+1]);
+			memset(child, 0, size);
 			node[subkey] = child;
 		}
 	}
@@ -159,7 +158,10 @@ rtree_set(rtree_t *rtree, uintptr_t key, void *val)
 	/* node is a leaf, so it contains values rather than node pointers. */
 	bits = rtree->level2bits[i];
 	subkey = (key << lshift) >> ((ZU(1) << (LG_SIZEOF_PTR+3)) - bits);
-	node[subkey] = val;
+	{
+		uint8_t *leaf = (uint8_t *)node;
+		leaf[subkey] = val;
+	}
 	malloc_mutex_unlock(&rtree->mutex);
 
 	return (false);

src/chunk.c

@@ -180,7 +180,7 @@ chunk_alloc(size_t size, size_t alignment, bool base, bool *zero,
 label_return:
 	if (ret != NULL) {
 		if (config_ivsalloc && base == false) {
-			if (rtree_set(chunks_rtree, (uintptr_t)ret, ret)) {
+			if (rtree_set(chunks_rtree, (uintptr_t)ret, 1)) {
 				chunk_dealloc(ret, size, true);
 				return (NULL);
 			}
@@ -321,7 +321,7 @@ chunk_dealloc(void *chunk, size_t size, bool unmap)
 	assert((size & chunksize_mask) == 0);
 
 	if (config_ivsalloc)
-		rtree_set(chunks_rtree, (uintptr_t)chunk, NULL);
+		rtree_set(chunks_rtree, (uintptr_t)chunk, 0);
 	if (config_stats || config_prof) {
 		malloc_mutex_lock(&chunks_mtx);
 		assert(stats_chunks.curchunks >= (size / chunksize));

src/rtree.c

@@ -5,15 +5,20 @@ rtree_t *
 rtree_new(unsigned bits, rtree_alloc_t *alloc, rtree_dalloc_t *dalloc)
 {
 	rtree_t *ret;
-	unsigned bits_per_level, height, i;
+	unsigned bits_per_level, bits_in_leaf, height, i;
 
 	assert(bits > 0 && bits <= (sizeof(uintptr_t) << 3));
 
 	bits_per_level = ffs(pow2_ceil((RTREE_NODESIZE / sizeof(void *)))) - 1;
-	height = bits / bits_per_level;
-	if (height * bits_per_level != bits)
-		height++;
-	assert(height * bits_per_level >= bits);
+	bits_in_leaf = ffs(pow2_ceil((RTREE_NODESIZE / sizeof(uint8_t)))) - 1;
+	if (bits > bits_in_leaf) {
+		height = 1 + (bits - bits_in_leaf) / bits_per_level;
+		if ((height-1) * bits_per_level + bits_in_leaf != bits)
+			height++;
+	} else {
+		height = 1;
+	}
+	assert((height-1) * bits_per_level + bits_in_leaf >= bits);
 
 	ret = (rtree_t*)alloc(offsetof(rtree_t, level2bits) +
 	    (sizeof(unsigned) * height));
@@ -25,23 +30,27 @@ rtree_new(unsigned bits, rtree_alloc_t *alloc, rtree_dalloc_t *dalloc)
 	ret->alloc = alloc;
 	ret->dalloc = dalloc;
 	if (malloc_mutex_init(&ret->mutex)) {
-		/* Leak the rtree. */
+		if (dalloc != NULL)
+			dalloc(ret);
 		return (NULL);
 	}
 	ret->height = height;
-	if (bits_per_level * height > bits)
-		ret->level2bits[0] = bits % bits_per_level;
-	else
-		ret->level2bits[0] = bits_per_level;
-	for (i = 1; i < height; i++)
-		ret->level2bits[i] = bits_per_level;
+	if (height > 1) {
+		if ((height-1) * bits_per_level + bits_in_leaf > bits) {
+			ret->level2bits[0] = (bits - bits_in_leaf) %
+			    bits_per_level;
+		} else
+			ret->level2bits[0] = bits_per_level;
+		for (i = 1; i < height-1; i++)
+			ret->level2bits[i] = bits_per_level;
+		ret->level2bits[height-1] = bits_in_leaf;
+	} else
+		ret->level2bits[0] = bits;
 
 	ret->root = (void**)alloc(sizeof(void *) << ret->level2bits[0]);
 	if (ret->root == NULL) {
-		/*
-		 * We leak the rtree here, since there's no generic base
-		 * deallocation.
-		 */
+		if (dalloc != NULL)
+			dalloc(ret);
 		return (NULL);
 	}
 	memset(ret->root, 0, sizeof(void *) << ret->level2bits[0]);

test/unit/rtree.c

@@ -6,7 +6,7 @@ TEST_BEGIN(test_rtree_get_empty)
 
 	for (i = 1; i <= (sizeof(uintptr_t) << 3); i++) {
 		rtree_t *rtree = rtree_new(i, imalloc, idalloc);
-		assert_ptr_null(rtree_get(rtree, 0),
+		assert_u_eq(rtree_get(rtree, 0), 0,
 		    "rtree_get() should return NULL for empty tree");
 		rtree_delete(rtree);
 	}
@@ -20,12 +20,12 @@ TEST_BEGIN(test_rtree_extrema)
 	for (i = 1; i <= (sizeof(uintptr_t) << 3); i++) {
 		rtree_t *rtree = rtree_new(i, imalloc, idalloc);
 
-		rtree_set(rtree, 0, (void *)1);
-		assert_ptr_eq(rtree_get(rtree, 0), (void *)1,
+		rtree_set(rtree, 0, 1);
+		assert_u_eq(rtree_get(rtree, 0), 1,
 		    "rtree_get() should return previously set value");
 
-		rtree_set(rtree, ~((uintptr_t)0), (void *)1);
-		assert_ptr_eq(rtree_get(rtree, ~((uintptr_t)0)), (void *)1,
+		rtree_set(rtree, ~((uintptr_t)0), 1);
+		assert_u_eq(rtree_get(rtree, ~((uintptr_t)0)), 1,
 		    "rtree_get() should return previously set value");
 
 		rtree_delete(rtree);
@@ -43,21 +43,19 @@ TEST_BEGIN(test_rtree_bits)
 		rtree_t *rtree = rtree_new(i, imalloc, idalloc);
 
 		for (j = 0; j < sizeof(keys)/sizeof(uintptr_t); j++) {
-			rtree_set(rtree, keys[j], (void *)1);
+			rtree_set(rtree, keys[j], 1);
 			for (k = 0; k < sizeof(keys)/sizeof(uintptr_t); k++) {
-				assert_ptr_eq(rtree_get(rtree, keys[k]),
-				    (void *)1,
+				assert_u_eq(rtree_get(rtree, keys[k]), 1,
 				    "rtree_get() should return previously set "
 				    "value and ignore insignificant key bits; "
 				    "i=%u, j=%u, k=%u, set key=%#x, "
 				    "get key=%#x", i, j, k, keys[j], keys[k]);
 			}
-			assert_ptr_eq(rtree_get(rtree,
-			    (((uintptr_t)1) << (sizeof(uintptr_t)*8-i))),
-			    (void *)0,
+			assert_u_eq(rtree_get(rtree,
+			    (((uintptr_t)1) << (sizeof(uintptr_t)*8-i))), 0,
 			    "Only leftmost rtree leaf should be set; "
 			    "i=%u, j=%u", i, j);
-			rtree_set(rtree, keys[j], (void *)0);
+			rtree_set(rtree, keys[j], 0);
 		}
 
 		rtree_delete(rtree);
@@ -80,22 +78,22 @@ TEST_BEGIN(test_rtree_random)
 
 		for (j = 0; j < NSET; j++) {
 			keys[j] = (uintptr_t)gen_rand64(sfmt);
-			rtree_set(rtree, keys[j], (void *)1);
-			assert_ptr_eq(rtree_get(rtree, keys[j]), (void *)1,
+			rtree_set(rtree, keys[j], 1);
+			assert_u_eq(rtree_get(rtree, keys[j]), 1,
 			    "rtree_get() should return previously set value");
 		}
 		for (j = 0; j < NSET; j++) {
-			assert_ptr_eq(rtree_get(rtree, keys[j]), (void *)1,
+			assert_u_eq(rtree_get(rtree, keys[j]), 1,
 			    "rtree_get() should return previously set value");
 		}
 
 		for (j = 0; j < NSET; j++) {
-			rtree_set(rtree, keys[j], (void *)0);
-			assert_ptr_eq(rtree_get(rtree, keys[j]), (void *)0,
+			rtree_set(rtree, keys[j], 0);
+			assert_u_eq(rtree_get(rtree, keys[j]), 0,
 			    "rtree_get() should return previously set value");
 		}
 		for (j = 0; j < NSET; j++) {
-			assert_ptr_eq(rtree_get(rtree, keys[j]), (void *)0,
+			assert_u_eq(rtree_get(rtree, keys[j]), 0,
 			    "rtree_get() should return previously set value");
 		}