6f29a83924
rtree-based extent lookups remain more expensive than chunk-based run lookups, but with this optimization the fast path slowdown is ~3 CPU cycles per metadata lookup (on Intel Core i7-4980HQ), versus ~11 cycles prior. The path caching speedup tends to degrade gracefully unless allocated memory is spread far apart (as is the case when using a mixture of sbrk() and mmap()).
609 lines
18 KiB
C
609 lines
18 KiB
C
/*
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* This radix tree implementation is tailored to the singular purpose of
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* associating metadata with extents 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_elm_s rtree_elm_t;
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typedef struct rtree_elm_witness_s rtree_elm_witness_t;
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typedef struct rtree_elm_witness_tsd_s rtree_elm_witness_tsd_t;
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typedef struct rtree_level_s rtree_level_t;
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typedef struct rtree_ctx_s rtree_ctx_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 (1U << LG_RTREE_BITS_PER_LEVEL)
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/* Maximum rtree height. */
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#define RTREE_HEIGHT_MAX \
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((1U << (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_elm_t *)0x1)
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#define RTREE_CTX_INITIALIZER { \
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false, \
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0, \
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0, \
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{NULL /* C initializes all trailing elements to NULL. */} \
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}
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/*
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* Maximum number of concurrently acquired elements per thread. This controls
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* how many witness_t structures are embedded in tsd. Ideally rtree_elm_t would
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* have a witness_t directly embedded, but that would dramatically bloat the
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* tree. This must contain enough entries to e.g. coalesce two extents.
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*/
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#define RTREE_ELM_ACQUIRE_MAX 4
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/* Initializers for rtree_elm_witness_tsd_t. */
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#define RTREE_ELM_WITNESS_INITIALIZER { \
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NULL, \
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WITNESS_INITIALIZER("rtree_elm", WITNESS_RANK_RTREE_ELM) \
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}
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#define RTREE_ELM_WITNESS_TSD_INITIALIZER { \
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{ \
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RTREE_ELM_WITNESS_INITIALIZER, \
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RTREE_ELM_WITNESS_INITIALIZER, \
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RTREE_ELM_WITNESS_INITIALIZER, \
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RTREE_ELM_WITNESS_INITIALIZER \
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} \
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}
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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_elm_s {
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union {
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void *pun;
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rtree_elm_t *child;
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extent_t *extent;
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};
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};
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struct rtree_elm_witness_s {
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const rtree_elm_t *elm;
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witness_t witness;
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};
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struct rtree_elm_witness_tsd_s {
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rtree_elm_witness_t witnesses[RTREE_ELM_ACQUIRE_MAX];
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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 levels[2], the subtree prefixed by 0x0000 (excluding
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* 0x00000000) can be accessed via levels[1], and the remainder of the
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* tree can be accessed via levels[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] : [extent(0x000000000000) | extent(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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* levels[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_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_ctx_s {
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/* If false, key/elms have not yet been initialized by a lookup. */
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bool valid;
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/* Key that corresponds to the tree path recorded in elms. */
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uintptr_t key;
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/* Memoized rtree_start_level(key). */
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unsigned start_level;
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/*
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* A path through rtree, driven by key. Only elements that could
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* actually be used for subsequent lookups are initialized, i.e. if
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* start_level = rtree_start_level(key) is non-zero, the first
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* start_level elements are uninitialized. The last element contains a
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* pointer to the leaf node element that corresponds to key, so that
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* exact matches require no tree node offset computation.
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*/
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rtree_elm_t *elms[RTREE_HEIGHT_MAX + 1];
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};
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struct rtree_s {
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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 + 1];
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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);
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#ifdef JEMALLOC_JET
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typedef rtree_elm_t *(rtree_node_alloc_t)(tsdn_t *, rtree_t *, size_t);
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extern rtree_node_alloc_t *rtree_node_alloc;
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typedef void (rtree_node_dalloc_t)(tsdn_t *, rtree_t *, rtree_elm_t *);
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extern rtree_node_dalloc_t *rtree_node_dalloc;
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void rtree_delete(tsdn_t *tsdn, rtree_t *rtree);
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#endif
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rtree_elm_t *rtree_subtree_read_hard(tsdn_t *tsdn, rtree_t *rtree,
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unsigned level);
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rtree_elm_t *rtree_child_read_hard(tsdn_t *tsdn, rtree_t *rtree,
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rtree_elm_t *elm, unsigned level);
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void rtree_elm_witness_acquire(tsdn_t *tsdn, const rtree_t *rtree,
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uintptr_t key, const rtree_elm_t *elm);
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void rtree_elm_witness_access(tsdn_t *tsdn, const rtree_t *rtree,
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const rtree_elm_t *elm);
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void rtree_elm_witness_release(tsdn_t *tsdn, const rtree_t *rtree,
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const rtree_elm_t *elm);
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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(const rtree_t *rtree, uintptr_t key);
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unsigned rtree_ctx_start_level(const rtree_t *rtree,
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const rtree_ctx_t *rtree_ctx, 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_elm_t *node);
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rtree_elm_t *rtree_child_tryread(rtree_elm_t *elm, bool dependent);
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rtree_elm_t *rtree_child_read(tsdn_t *tsdn, rtree_t *rtree, rtree_elm_t *elm,
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unsigned level, bool dependent);
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extent_t *rtree_elm_read(rtree_elm_t *elm, bool dependent);
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void rtree_elm_write(rtree_elm_t *elm, const extent_t *extent);
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rtree_elm_t *rtree_subtree_tryread(rtree_t *rtree, unsigned level,
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bool dependent);
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rtree_elm_t *rtree_subtree_read(tsdn_t *tsdn, rtree_t *rtree,
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unsigned level, bool dependent);
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rtree_elm_t *rtree_elm_lookup(tsdn_t *tsdn, rtree_t *rtree,
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rtree_ctx_t *rtree_ctx, uintptr_t key, bool dependent, bool init_missing);
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bool rtree_write(tsdn_t *tsdn, rtree_t *rtree, rtree_ctx_t *rtree_ctx,
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uintptr_t key, const extent_t *extent);
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extent_t *rtree_read(tsdn_t *tsdn, rtree_t *rtree,
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rtree_ctx_t *rtree_ctx, uintptr_t key, bool dependent);
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rtree_elm_t *rtree_elm_acquire(tsdn_t *tsdn, rtree_t *rtree,
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rtree_ctx_t *rtree_ctx, uintptr_t key, bool dependent, bool init_missing);
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extent_t *rtree_elm_read_acquired(tsdn_t *tsdn, const rtree_t *rtree,
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rtree_elm_t *elm);
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void rtree_elm_write_acquired(tsdn_t *tsdn, const rtree_t *rtree,
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rtree_elm_t *elm, const extent_t *extent);
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void rtree_elm_release(tsdn_t *tsdn, const rtree_t *rtree, rtree_elm_t *elm);
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void rtree_clear(tsdn_t *tsdn, rtree_t *rtree, rtree_ctx_t *rtree_ctx,
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uintptr_t key);
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#endif
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#if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_RTREE_C_))
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JEMALLOC_ALWAYS_INLINE unsigned
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rtree_start_level(const 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) + 1) >>
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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_ALWAYS_INLINE unsigned
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rtree_ctx_start_level(const rtree_t *rtree, const rtree_ctx_t *rtree_ctx,
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uintptr_t key)
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{
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unsigned start_level;
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uintptr_t key_diff;
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/* Compute the difference between old and new lookup keys. */
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key_diff = key ^ rtree_ctx->key;
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assert(key_diff != 0); /* Handled in rtree_elm_lookup(). */
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/*
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* Compute the last traversal path element at which the keys' paths
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* are the same.
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*/
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start_level = rtree->start_level[(lg_floor(key_diff) + 1) >>
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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_ALWAYS_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_ALWAYS_INLINE bool
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rtree_node_valid(rtree_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_ALWAYS_INLINE rtree_elm_t *
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rtree_child_tryread(rtree_elm_t *elm, bool dependent)
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{
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rtree_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 (!dependent && !rtree_node_valid(child))
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child = atomic_read_p(&elm->pun);
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assert(!dependent || child != NULL);
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return (child);
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}
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JEMALLOC_ALWAYS_INLINE rtree_elm_t *
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rtree_child_read(tsdn_t *tsdn, rtree_t *rtree, rtree_elm_t *elm, unsigned level,
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bool dependent)
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{
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rtree_elm_t *child;
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child = rtree_child_tryread(elm, dependent);
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if (!dependent && unlikely(!rtree_node_valid(child)))
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child = rtree_child_read_hard(tsdn, rtree, elm, level);
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assert(!dependent || child != NULL);
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return (child);
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}
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JEMALLOC_ALWAYS_INLINE extent_t *
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rtree_elm_read(rtree_elm_t *elm, bool dependent)
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{
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extent_t *extent;
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if (dependent) {
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/*
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* Reading a value on behalf of a pointer to a valid allocation
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* is guaranteed to be a clean read even without
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* synchronization, because the rtree update became visible in
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* memory before the pointer came into existence.
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*/
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extent = elm->extent;
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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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extent = (extent_t *)atomic_read_p(&elm->pun);
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}
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/* Mask the lock bit. */
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extent = (extent_t *)((uintptr_t)extent & ~((uintptr_t)0x1));
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return (extent);
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}
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JEMALLOC_INLINE void
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rtree_elm_write(rtree_elm_t *elm, const extent_t *extent)
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{
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atomic_write_p(&elm->pun, extent);
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}
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JEMALLOC_ALWAYS_INLINE rtree_elm_t *
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rtree_subtree_tryread(rtree_t *rtree, unsigned level, bool dependent)
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{
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rtree_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 (!dependent && unlikely(!rtree_node_valid(subtree)))
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subtree = atomic_read_p(&rtree->levels[level].subtree_pun);
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assert(!dependent || subtree != NULL);
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return (subtree);
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}
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JEMALLOC_ALWAYS_INLINE rtree_elm_t *
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rtree_subtree_read(tsdn_t *tsdn, rtree_t *rtree, unsigned level, bool dependent)
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{
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rtree_elm_t *subtree;
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subtree = rtree_subtree_tryread(rtree, level, dependent);
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if (!dependent && unlikely(!rtree_node_valid(subtree)))
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subtree = rtree_subtree_read_hard(tsdn, rtree, level);
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assert(!dependent || subtree != NULL);
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return (subtree);
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}
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JEMALLOC_ALWAYS_INLINE rtree_elm_t *
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rtree_elm_lookup(tsdn_t *tsdn, rtree_t *rtree, rtree_ctx_t *rtree_ctx,
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uintptr_t key, bool dependent, bool init_missing)
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{
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uintptr_t subkey;
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unsigned start_level;
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rtree_elm_t *node;
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assert(!dependent || !init_missing);
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if (dependent || init_missing) {
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if (likely(rtree_ctx->valid)) {
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if (key == rtree_ctx->key)
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return (rtree_ctx->elms[rtree->height]);
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else {
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unsigned no_ctx_start_level =
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rtree_start_level(rtree, key);
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unsigned ctx_start_level;
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if (likely(no_ctx_start_level <=
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rtree_ctx->start_level && (ctx_start_level =
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rtree_ctx_start_level(rtree, rtree_ctx,
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key)) >= rtree_ctx->start_level)) {
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start_level = ctx_start_level;
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node = rtree_ctx->elms[ctx_start_level];
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} else {
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start_level = no_ctx_start_level;
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node = init_missing ?
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rtree_subtree_read(tsdn, rtree,
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no_ctx_start_level, dependent) :
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rtree_subtree_tryread(rtree,
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no_ctx_start_level, dependent);
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rtree_ctx->start_level =
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no_ctx_start_level;
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rtree_ctx->elms[no_ctx_start_level] =
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node;
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}
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}
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} else {
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unsigned no_ctx_start_level = rtree_start_level(rtree,
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key);
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start_level = no_ctx_start_level;
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node = init_missing ? rtree_subtree_read(tsdn, rtree,
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no_ctx_start_level, dependent) :
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rtree_subtree_tryread(rtree, no_ctx_start_level,
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dependent);
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rtree_ctx->valid = true;
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rtree_ctx->start_level = no_ctx_start_level;
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rtree_ctx->elms[no_ctx_start_level] = node;
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}
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rtree_ctx->key = key;
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} else {
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start_level = rtree_start_level(rtree, key);
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node = init_missing ? rtree_subtree_read(tsdn, rtree,
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start_level, dependent) : rtree_subtree_tryread(rtree,
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start_level, dependent);
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}
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#define RTREE_GET_BIAS (RTREE_HEIGHT_MAX - rtree->height)
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switch (start_level + RTREE_GET_BIAS) {
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#define RTREE_GET_SUBTREE(level) \
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case level: \
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assert(level < (RTREE_HEIGHT_MAX-1)); \
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if (!dependent && unlikely(!rtree_node_valid(node))) { \
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if (init_missing) \
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rtree_ctx->valid = false; \
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return (NULL); \
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} \
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subkey = rtree_subkey(rtree, key, level - \
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RTREE_GET_BIAS); \
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node = init_missing ? rtree_child_read(tsdn, rtree, \
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&node[subkey], level - RTREE_GET_BIAS, dependent) : \
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rtree_child_tryread(&node[subkey], dependent); \
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if (dependent || init_missing) { \
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rtree_ctx->elms[level - RTREE_GET_BIAS + 1] = \
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node; \
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} \
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/* Fall through. */
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#define RTREE_GET_LEAF(level) \
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case level: \
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assert(level == (RTREE_HEIGHT_MAX-1)); \
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if (!dependent && unlikely(!rtree_node_valid(node))) { \
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if (init_missing) \
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rtree_ctx->valid = false; \
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return (NULL); \
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} \
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subkey = rtree_subkey(rtree, key, level - \
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RTREE_GET_BIAS); \
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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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node = &node[subkey]; \
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if (dependent || init_missing) { \
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rtree_ctx->elms[level - RTREE_GET_BIAS + 1] = \
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node; \
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} \
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return (node);
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#if RTREE_HEIGHT_MAX > 1
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RTREE_GET_SUBTREE(0)
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#endif
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#if RTREE_HEIGHT_MAX > 2
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RTREE_GET_SUBTREE(1)
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#endif
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#if RTREE_HEIGHT_MAX > 3
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RTREE_GET_SUBTREE(2)
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#endif
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#if RTREE_HEIGHT_MAX > 4
|
|
RTREE_GET_SUBTREE(3)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 5
|
|
RTREE_GET_SUBTREE(4)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 6
|
|
RTREE_GET_SUBTREE(5)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 7
|
|
RTREE_GET_SUBTREE(6)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 8
|
|
RTREE_GET_SUBTREE(7)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 9
|
|
RTREE_GET_SUBTREE(8)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 10
|
|
RTREE_GET_SUBTREE(9)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 11
|
|
RTREE_GET_SUBTREE(10)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 12
|
|
RTREE_GET_SUBTREE(11)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 13
|
|
RTREE_GET_SUBTREE(12)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 14
|
|
RTREE_GET_SUBTREE(13)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 15
|
|
RTREE_GET_SUBTREE(14)
|
|
#endif
|
|
#if RTREE_HEIGHT_MAX > 16
|
|
# error Unsupported RTREE_HEIGHT_MAX
|
|
#endif
|
|
RTREE_GET_LEAF(RTREE_HEIGHT_MAX-1)
|
|
#undef RTREE_GET_SUBTREE
|
|
#undef RTREE_GET_LEAF
|
|
default: not_reached();
|
|
}
|
|
#undef RTREE_GET_BIAS
|
|
not_reached();
|
|
}
|
|
|
|
JEMALLOC_INLINE bool
|
|
rtree_write(tsdn_t *tsdn, rtree_t *rtree, rtree_ctx_t *rtree_ctx, uintptr_t key,
|
|
const extent_t *extent)
|
|
{
|
|
rtree_elm_t *elm;
|
|
|
|
assert(extent != NULL); /* Use rtree_clear() for this case. */
|
|
assert(((uintptr_t)extent & (uintptr_t)0x1) == (uintptr_t)0x0);
|
|
|
|
elm = rtree_elm_lookup(tsdn, rtree, rtree_ctx, key, false, true);
|
|
if (elm == NULL)
|
|
return (true);
|
|
assert(rtree_elm_read(elm, false) == NULL);
|
|
rtree_elm_write(elm, extent);
|
|
|
|
return (false);
|
|
}
|
|
|
|
JEMALLOC_ALWAYS_INLINE extent_t *
|
|
rtree_read(tsdn_t *tsdn, rtree_t *rtree, rtree_ctx_t *rtree_ctx, uintptr_t key,
|
|
bool dependent)
|
|
{
|
|
rtree_elm_t *elm;
|
|
|
|
elm = rtree_elm_lookup(tsdn, rtree, rtree_ctx, key, dependent, false);
|
|
if (elm == NULL)
|
|
return (NULL);
|
|
|
|
return (rtree_elm_read(elm, dependent));
|
|
}
|
|
|
|
JEMALLOC_INLINE rtree_elm_t *
|
|
rtree_elm_acquire(tsdn_t *tsdn, rtree_t *rtree, rtree_ctx_t *rtree_ctx,
|
|
uintptr_t key, bool dependent, bool init_missing)
|
|
{
|
|
rtree_elm_t *elm;
|
|
|
|
elm = rtree_elm_lookup(tsdn, rtree, rtree_ctx, key, dependent,
|
|
init_missing);
|
|
if (!dependent && elm == NULL)
|
|
return (NULL);
|
|
{
|
|
extent_t *extent;
|
|
void *s;
|
|
|
|
do {
|
|
extent = rtree_elm_read(elm, false);
|
|
/* The least significant bit serves as a lock. */
|
|
s = (void *)((uintptr_t)extent | (uintptr_t)0x1);
|
|
} while (atomic_cas_p(&elm->pun, (void *)extent, s));
|
|
}
|
|
|
|
if (config_debug)
|
|
rtree_elm_witness_acquire(tsdn, rtree, key, elm);
|
|
|
|
return (elm);
|
|
}
|
|
|
|
JEMALLOC_INLINE extent_t *
|
|
rtree_elm_read_acquired(tsdn_t *tsdn, const rtree_t *rtree, rtree_elm_t *elm)
|
|
{
|
|
extent_t *extent;
|
|
|
|
assert(((uintptr_t)elm->pun & (uintptr_t)0x1) == (uintptr_t)0x1);
|
|
extent = (extent_t *)((uintptr_t)elm->pun & ~((uintptr_t)0x1));
|
|
assert(((uintptr_t)extent & (uintptr_t)0x1) == (uintptr_t)0x0);
|
|
|
|
if (config_debug)
|
|
rtree_elm_witness_access(tsdn, rtree, elm);
|
|
|
|
return (extent);
|
|
}
|
|
|
|
JEMALLOC_INLINE void
|
|
rtree_elm_write_acquired(tsdn_t *tsdn, const rtree_t *rtree, rtree_elm_t *elm,
|
|
const extent_t *extent)
|
|
{
|
|
|
|
assert(((uintptr_t)extent & (uintptr_t)0x1) == (uintptr_t)0x0);
|
|
assert(((uintptr_t)elm->pun & (uintptr_t)0x1) == (uintptr_t)0x1);
|
|
|
|
if (config_debug)
|
|
rtree_elm_witness_access(tsdn, rtree, elm);
|
|
|
|
elm->pun = (void *)((uintptr_t)extent | (uintptr_t)0x1);
|
|
assert(rtree_elm_read_acquired(tsdn, rtree, elm) == extent);
|
|
}
|
|
|
|
JEMALLOC_INLINE void
|
|
rtree_elm_release(tsdn_t *tsdn, const rtree_t *rtree, rtree_elm_t *elm)
|
|
{
|
|
|
|
rtree_elm_write(elm, rtree_elm_read_acquired(tsdn, rtree, elm));
|
|
if (config_debug)
|
|
rtree_elm_witness_release(tsdn, rtree, elm);
|
|
}
|
|
|
|
JEMALLOC_INLINE void
|
|
rtree_clear(tsdn_t *tsdn, rtree_t *rtree, rtree_ctx_t *rtree_ctx, uintptr_t key)
|
|
{
|
|
rtree_elm_t *elm;
|
|
|
|
elm = rtree_elm_acquire(tsdn, rtree, rtree_ctx, key, true, false);
|
|
rtree_elm_write_acquired(tsdn, rtree, elm, NULL);
|
|
rtree_elm_release(tsdn, rtree, elm);
|
|
}
|
|
#endif
|
|
|
|
#endif /* JEMALLOC_H_INLINES */
|
|
/******************************************************************************/
|