295 lines
8.5 KiB
C
295 lines
8.5 KiB
C
/*
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* This radix tree implementation is tailored to the singular purpose of
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* associating metadata with chunks that are currently owned by jemalloc.
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*
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*******************************************************************************
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*/
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#ifdef JEMALLOC_H_TYPES
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typedef struct rtree_node_elm_s rtree_node_elm_t;
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typedef struct rtree_level_s rtree_level_t;
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typedef struct rtree_s rtree_t;
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/*
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* RTREE_BITS_PER_LEVEL must be a power of two that is no larger than the
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* machine address width.
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*/
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#define LG_RTREE_BITS_PER_LEVEL 4
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#define RTREE_BITS_PER_LEVEL (ZU(1) << LG_RTREE_BITS_PER_LEVEL)
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#define RTREE_HEIGHT_MAX \
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((ZU(1) << (LG_SIZEOF_PTR+3)) / RTREE_BITS_PER_LEVEL)
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/* Used for two-stage lock-free node initialization. */
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#define RTREE_NODE_INITIALIZING ((rtree_node_elm_t *)0x1)
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/*
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* The node allocation callback function's argument is the number of contiguous
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* rtree_node_elm_t structures to allocate, and the resulting memory must be
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* zeroed.
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*/
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typedef rtree_node_elm_t *(rtree_node_alloc_t)(size_t);
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typedef void (rtree_node_dalloc_t)(rtree_node_elm_t *);
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#endif /* JEMALLOC_H_TYPES */
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/******************************************************************************/
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#ifdef JEMALLOC_H_STRUCTS
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struct rtree_node_elm_s {
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union {
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void *pun;
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rtree_node_elm_t *child;
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extent_node_t *val;
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};
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};
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struct rtree_level_s {
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/*
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* A non-NULL subtree points to a subtree rooted along the hypothetical
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* path to the leaf node corresponding to key 0. Depending on what keys
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* have been used to store to the tree, an arbitrary combination of
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* subtree pointers may remain NULL.
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*
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* Suppose keys comprise 48 bits, and LG_RTREE_BITS_PER_LEVEL is 4.
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* This results in a 3-level tree, and the leftmost leaf can be directly
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* accessed via subtrees[2], the subtree prefixed by 0x0000 (excluding
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* 0x00000000) can be accessed via subtrees[1], and the remainder of the
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* tree can be accessed via subtrees[0].
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*
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* levels[0] : [<unused> | 0x0001******** | 0x0002******** | ...]
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*
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* levels[1] : [<unused> | 0x00000001**** | 0x00000002**** | ... ]
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*
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* levels[2] : [val(0x000000000000) | val(0x000000000001) | ...]
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*
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* This has practical implications on x64, which currently uses only the
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* lower 47 bits of virtual address space in userland, thus leaving
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* subtrees[0] unused and avoiding a level of tree traversal.
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*/
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union {
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void *subtree_pun;
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rtree_node_elm_t *subtree;
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};
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/* Number of key bits distinguished by this level. */
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unsigned bits;
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/*
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* Cumulative number of key bits distinguished by traversing to
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* corresponding tree level.
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*/
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unsigned cumbits;
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};
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struct rtree_s {
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rtree_node_alloc_t *alloc;
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rtree_node_dalloc_t *dalloc;
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unsigned height;
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/*
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* Precomputed table used to convert from the number of leading 0 key
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* bits to which subtree level to start at.
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*/
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unsigned start_level[RTREE_HEIGHT_MAX];
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rtree_level_t levels[RTREE_HEIGHT_MAX];
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};
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#endif /* JEMALLOC_H_STRUCTS */
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/******************************************************************************/
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#ifdef JEMALLOC_H_EXTERNS
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bool rtree_new(rtree_t *rtree, unsigned bits, rtree_node_alloc_t *alloc,
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rtree_node_dalloc_t *dalloc);
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void rtree_delete(rtree_t *rtree);
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rtree_node_elm_t *rtree_subtree_read_hard(rtree_t *rtree,
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unsigned level);
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rtree_node_elm_t *rtree_child_read_hard(rtree_t *rtree,
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rtree_node_elm_t *elm, unsigned level);
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#endif /* JEMALLOC_H_EXTERNS */
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/******************************************************************************/
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#ifdef JEMALLOC_H_INLINES
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#ifndef JEMALLOC_ENABLE_INLINE
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unsigned rtree_start_level(rtree_t *rtree, uintptr_t key);
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uintptr_t rtree_subkey(rtree_t *rtree, uintptr_t key, unsigned level);
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bool rtree_node_valid(rtree_node_elm_t *node);
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rtree_node_elm_t *rtree_child_tryread(rtree_node_elm_t *elm);
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rtree_node_elm_t *rtree_child_read(rtree_t *rtree, rtree_node_elm_t *elm,
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unsigned level);
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extent_node_t *rtree_val_read(rtree_t *rtree, rtree_node_elm_t *elm,
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bool dependent);
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void rtree_val_write(rtree_t *rtree, rtree_node_elm_t *elm,
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const extent_node_t *val);
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rtree_node_elm_t *rtree_subtree_tryread(rtree_t *rtree, unsigned level);
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rtree_node_elm_t *rtree_subtree_read(rtree_t *rtree, unsigned level);
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extent_node_t *rtree_get(rtree_t *rtree, uintptr_t key, bool dependent);
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bool rtree_set(rtree_t *rtree, uintptr_t key, const extent_node_t *val);
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#endif
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#if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_RTREE_C_))
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JEMALLOC_INLINE unsigned
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rtree_start_level(rtree_t *rtree, uintptr_t key)
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{
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unsigned start_level;
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if (unlikely(key == 0))
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return (rtree->height - 1);
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start_level = rtree->start_level[lg_floor(key) >>
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LG_RTREE_BITS_PER_LEVEL];
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assert(start_level < rtree->height);
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return (start_level);
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}
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JEMALLOC_INLINE uintptr_t
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rtree_subkey(rtree_t *rtree, uintptr_t key, unsigned level)
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{
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return ((key >> ((ZU(1) << (LG_SIZEOF_PTR+3)) -
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rtree->levels[level].cumbits)) & ((ZU(1) <<
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rtree->levels[level].bits) - 1));
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}
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JEMALLOC_INLINE bool
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rtree_node_valid(rtree_node_elm_t *node)
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{
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return ((uintptr_t)node > (uintptr_t)RTREE_NODE_INITIALIZING);
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}
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JEMALLOC_INLINE rtree_node_elm_t *
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rtree_child_tryread(rtree_node_elm_t *elm)
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{
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rtree_node_elm_t *child;
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/* Double-checked read (first read may be stale. */
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child = elm->child;
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if (!rtree_node_valid(child))
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child = atomic_read_p(&elm->pun);
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return (child);
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}
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JEMALLOC_INLINE rtree_node_elm_t *
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rtree_child_read(rtree_t *rtree, rtree_node_elm_t *elm, unsigned level)
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{
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rtree_node_elm_t *child;
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child = rtree_child_tryread(elm);
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if (unlikely(!rtree_node_valid(child)))
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child = rtree_child_read_hard(rtree, elm, level);
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return (child);
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}
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JEMALLOC_INLINE extent_node_t *
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rtree_val_read(rtree_t *rtree, rtree_node_elm_t *elm, bool dependent)
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{
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if (dependent) {
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/*
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* Reading a val on behalf of a pointer to a valid allocation is
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* guaranteed to be a clean read even without synchronization,
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* because the rtree update became visible in memory before the
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* pointer came into existence.
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*/
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return (elm->val);
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} else {
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/*
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* An arbitrary read, e.g. on behalf of ivsalloc(), may not be
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* dependent on a previous rtree write, which means a stale read
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* could result if synchronization were omitted here.
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*/
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return (atomic_read_p(&elm->pun));
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}
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}
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JEMALLOC_INLINE void
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rtree_val_write(rtree_t *rtree, rtree_node_elm_t *elm, const extent_node_t *val)
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{
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atomic_write_p(&elm->pun, val);
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}
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JEMALLOC_INLINE rtree_node_elm_t *
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rtree_subtree_tryread(rtree_t *rtree, unsigned level)
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{
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rtree_node_elm_t *subtree;
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/* Double-checked read (first read may be stale. */
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subtree = rtree->levels[level].subtree;
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if (!rtree_node_valid(subtree))
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subtree = atomic_read_p(&rtree->levels[level].subtree_pun);
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return (subtree);
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}
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JEMALLOC_INLINE rtree_node_elm_t *
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rtree_subtree_read(rtree_t *rtree, unsigned level)
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{
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rtree_node_elm_t *subtree;
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subtree = rtree_subtree_tryread(rtree, level);
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if (unlikely(!rtree_node_valid(subtree)))
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subtree = rtree_subtree_read_hard(rtree, level);
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return (subtree);
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}
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JEMALLOC_INLINE extent_node_t *
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rtree_get(rtree_t *rtree, uintptr_t key, bool dependent)
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{
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uintptr_t subkey;
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unsigned i, start_level;
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rtree_node_elm_t *node, *child;
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start_level = rtree_start_level(rtree, key);
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for (i = start_level, node = rtree_subtree_tryread(rtree, start_level);
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/**/; i++, node = child) {
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if (!dependent && unlikely(!rtree_node_valid(node)))
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return (NULL);
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subkey = rtree_subkey(rtree, key, i);
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if (i == rtree->height - 1) {
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/*
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* node is a leaf, so it contains values rather than
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* child pointers.
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*/
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return (rtree_val_read(rtree, &node[subkey],
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dependent));
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}
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assert(i < rtree->height - 1);
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child = rtree_child_tryread(&node[subkey]);
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}
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not_reached();
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}
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JEMALLOC_INLINE bool
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rtree_set(rtree_t *rtree, uintptr_t key, const extent_node_t *val)
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{
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uintptr_t subkey;
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unsigned i, start_level;
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rtree_node_elm_t *node, *child;
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start_level = rtree_start_level(rtree, key);
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node = rtree_subtree_read(rtree, start_level);
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if (node == NULL)
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return (true);
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for (i = start_level; /**/; i++, node = child) {
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subkey = rtree_subkey(rtree, key, i);
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if (i == rtree->height - 1) {
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/*
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* node is a leaf, so it contains values rather than
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* child pointers.
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*/
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rtree_val_write(rtree, &node[subkey], val);
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return (false);
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}
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assert(i + 1 < rtree->height);
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child = rtree_child_read(rtree, &node[subkey], i);
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if (child == NULL)
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return (true);
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}
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not_reached();
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}
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#endif
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#endif /* JEMALLOC_H_INLINES */
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/******************************************************************************/
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