X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=20d389d38517d786477e4acff9f8a87fe5b6b1ae;hp=e8147178ada51bc333c27237ac806311c8bc08a0;hb=3967a8a8984fe5cb7ac83996db6709c8aae857c2;hpb=d95bd16028d250211f2e65cd583e422f4ecdf7d0 diff --git a/rculfhash.c b/rculfhash.c index e814717..20d389d 100644 --- a/rculfhash.c +++ b/rculfhash.c @@ -20,6 +20,80 @@ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ +/* + * Based on the following articles: + * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free + * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405. + * - Michael, M. M. High performance dynamic lock-free hash tables + * and list-based sets. In Proceedings of the fourteenth annual ACM + * symposium on Parallel algorithms and architectures, ACM Press, + * (2002), 73-82. + * + * Some specificities of this Lock-Free Expandable RCU Hash Table + * implementation: + * + * - RCU read-side critical section allows readers to perform hash + * table lookups and use the returned objects safely by delaying + * memory reclaim of a grace period. + * - Add and remove operations are lock-free, and do not need to + * allocate memory. They need to be executed within RCU read-side + * critical section to ensure the objects they read are valid and to + * deal with the cmpxchg ABA problem. + * - add and add_unique operations are supported. add_unique checks if + * the node key already exists in the hash table. It ensures no key + * duplicata exists. + * - The resize operation executes concurrently with add/remove/lookup. + * - Hash table nodes are contained within a split-ordered list. This + * list is ordered by incrementing reversed-bits-hash value. + * - An index of dummy nodes is kept. These dummy nodes are the hash + * table "buckets", and they are also chained together in the + * split-ordered list, which allows recursive expansion. + * - The resize operation only allows expanding the hash table. + * It is triggered either through an API call or automatically by + * detecting long chains in the add operation. + * - Resize operation initiated by long chain detection is executed by a + * call_rcu thread, which keeps lock-freedom of add and remove. + * - Resize operations are protected by a mutex. + * - The removal operation is split in two parts: first, a "removed" + * flag is set in the next pointer within the node to remove. Then, + * a "garbage collection" is performed in the bucket containing the + * removed node (from the start of the bucket up to the removed node). + * All encountered nodes with "removed" flag set in their next + * pointers are removed from the linked-list. If the cmpxchg used for + * removal fails (due to concurrent garbage-collection or concurrent + * add), we retry from the beginning of the bucket. This ensures that + * the node with "removed" flag set is removed from the hash table + * (not visible to lookups anymore) before the RCU read-side critical + * section held across removal ends. Furthermore, this ensures that + * the node with "removed" flag set is removed from the linked-list + * before its memory is reclaimed. Only the thread which removal + * successfully set the "removed" flag (with a cmpxchg) into a node's + * next pointer is considered to have succeeded its removal (and thus + * owns the node to reclaim). Because we garbage-collect starting from + * an invariant node (the start-of-bucket dummy node) up to the + * "removed" node (or find a reverse-hash that is higher), we are sure + * that a successful traversal of the chain leads to a chain that is + * present in the linked-list (the start node is never removed) and + * that is does not contain the "removed" node anymore, even if + * concurrent delete/add operations are changing the structure of the + * list concurrently. + * - The add operation performs gargage collection of buckets if it + * encounters nodes with removed flag set in the bucket where it wants + * to add its new node. This ensures lock-freedom of add operation by + * helping the remover unlink nodes from the list rather than to wait + * for it do to so. + * - A RCU "order table" indexed by log2(hash index) is copied and + * expanded by the resize operation. This order table allows finding + * the "dummy node" tables. + * - There is one dummy node table per hash index order. The size of + * each dummy node table is half the number of hashes contained in + * this order. + * - call_rcu is used to garbage-collect the old order table. + * - The per-order dummy node tables contain a compact version of the + * hash table nodes. These tables are invariant after they are + * populated into the hash table. + */ + #define _LGPL_SOURCE #include #include @@ -28,6 +102,7 @@ #include #include +#include "config.h" #include #include #include @@ -38,16 +113,21 @@ #include #include -#define DEBUG /* Test */ - #ifdef DEBUG -#define dbg_printf(args...) printf(args) +#define dbg_printf(fmt, args...) printf("[debug rculfhash] " fmt, ## args) #else -#define dbg_printf(args...) +#define dbg_printf(fmt, args...) #endif +/* + * Per-CPU split-counters lazily update the global counter each 1024 + * addition/removal. It automatically keeps track of resize required. + * We use the bucket length as indicator for need to expand for small + * tables and machines lacking per-cpu data suppport. + */ +#define COUNT_COMMIT_ORDER 10 #define CHAIN_LEN_TARGET 1 -#define CHAIN_LEN_RESIZE_THRESHOLD 2 +#define CHAIN_LEN_RESIZE_THRESHOLD 3 #ifndef max #define max(a, b) ((a) > (b) ? (a) : (b)) @@ -62,28 +142,34 @@ #define DUMMY_FLAG (1UL << 1) #define FLAGS_MASK ((1UL << 2) - 1) +struct ht_items_count { + unsigned long add, remove; +} __attribute__((aligned(CAA_CACHE_LINE_SIZE))); + struct rcu_table { unsigned long size; /* always a power of 2 */ unsigned long resize_target; int resize_initiated; struct rcu_head head; - struct rcu_ht_node *tbl[0]; + struct _cds_lfht_node *tbl[0]; }; -struct rcu_ht { +struct cds_lfht { struct rcu_table *t; /* shared */ - ht_hash_fct hash_fct; - ht_compare_fct compare_fct; + cds_lfht_hash_fct hash_fct; + cds_lfht_compare_fct compare_fct; unsigned long hash_seed; pthread_mutex_t resize_mutex; /* resize mutex: add/del mutex */ - unsigned int in_progress_resize; - void (*ht_call_rcu)(struct rcu_head *head, + unsigned int in_progress_resize, in_progress_destroy; + void (*cds_lfht_call_rcu)(struct rcu_head *head, void (*func)(struct rcu_head *head)); + unsigned long count; /* global approximate item count */ + struct ht_items_count *percpu_count; /* per-cpu item count */ }; struct rcu_resize_work { struct rcu_head head; - struct rcu_ht *ht; + struct cds_lfht *ht; }; /* @@ -144,72 +230,343 @@ unsigned long bit_reverse_ulong(unsigned long v) } /* - * Algorithm to find the log2 of a 32-bit unsigned integer. - * source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogLookup - * Originally from Public Domain. + * fls: returns the position of the most significant bit. + * Returns 0 if no bit is set, else returns the position of the most + * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit). */ -static const char LogTable256[256] = +#if defined(__i386) || defined(__x86_64) +static inline +unsigned int fls_u32(uint32_t x) { -#define LT(n) n, n, n, n, n, n, n, n, n, n, n, n, n, n, n, n - -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, - LT(4), LT(5), LT(5), LT(6), LT(6), LT(6), LT(6), - LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7) -}; + int r; + + asm("bsrl %1,%0\n\t" + "jnz 1f\n\t" + "movl $-1,%0\n\t" + "1:\n\t" + : "=r" (r) : "rm" (x)); + return r + 1; +} +#define HAS_FLS_U32 +#endif + +#if defined(__x86_64) +static inline +unsigned int fls_u64(uint64_t x) +{ + long r; + + asm("bsrq %1,%0\n\t" + "jnz 1f\n\t" + "movq $-1,%0\n\t" + "1:\n\t" + : "=r" (r) : "rm" (x)); + return r + 1; +} +#define HAS_FLS_U64 +#endif + +#ifndef HAS_FLS_U64 +static __attribute__((unused)) +unsigned int fls_u64(uint64_t x) +{ + unsigned int r = 64; + + if (!x) + return 0; + + if (!(x & 0xFFFFFFFF00000000ULL)) { + x <<= 32; + r -= 32; + } + if (!(x & 0xFFFF000000000000ULL)) { + x <<= 16; + r -= 16; + } + if (!(x & 0xFF00000000000000ULL)) { + x <<= 8; + r -= 8; + } + if (!(x & 0xF000000000000000ULL)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xC000000000000000ULL)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x8000000000000000ULL)) { + x <<= 1; + r -= 1; + } + return r; +} +#endif -uint32_t log2_u32(uint32_t v) +#ifndef HAS_FLS_U32 +static __attribute__((unused)) +unsigned int fls_u32(uint32_t x) { - uint32_t t, tt; + unsigned int r = 32; + + if (!x) + return 0; + if (!(x & 0xFFFF0000U)) { + x <<= 16; + r -= 16; + } + if (!(x & 0xFF000000U)) { + x <<= 8; + r -= 8; + } + if (!(x & 0xF0000000U)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xC0000000U)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x80000000U)) { + x <<= 1; + r -= 1; + } + return r; +} +#endif + +unsigned int fls_ulong(unsigned long x) +{ +#if (CAA_BITS_PER_lONG == 32) + return fls_u32(x); +#else + return fls_u64(x); +#endif +} - if ((tt = (v >> 16))) - return (t = (tt >> 8)) - ? 24 + LogTable256[t] - : 16 + LogTable256[tt]; +int get_count_order_u32(uint32_t x) +{ + int order; + + order = fls_u32(x) - 1; + if (x & (x - 1)) + order++; + return order; +} + +int get_count_order_ulong(unsigned long x) +{ + int order; + + order = fls_ulong(x) - 1; + if (x & (x - 1)) + order++; + return order; +} + +static +void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, int growth); + +/* + * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are + * available, then we support hash table item accounting. + * In the unfortunate event the number of CPUs reported would be + * inaccurate, we use modulo arithmetic on the number of CPUs we got. + */ +#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) + +static +void cds_lfht_resize_lazy_count(struct cds_lfht *ht, struct rcu_table *t, + unsigned long count); + +static long nr_cpus_mask = -1; + +static +struct ht_items_count *alloc_per_cpu_items_count(void) +{ + struct ht_items_count *count; + + switch (nr_cpus_mask) { + case -2: + return NULL; + case -1: + { + long maxcpus; + + maxcpus = sysconf(_SC_NPROCESSORS_CONF); + if (maxcpus <= 0) { + nr_cpus_mask = -2; + return NULL; + } + /* + * round up number of CPUs to next power of two, so we + * can use & for modulo. + */ + maxcpus = 1UL << get_count_order_ulong(maxcpus); + nr_cpus_mask = maxcpus - 1; + } + /* Fall-through */ + default: + return calloc(nr_cpus_mask + 1, sizeof(*count)); + } +} + +static +void free_per_cpu_items_count(struct ht_items_count *count) +{ + free(count); +} + +static +int ht_get_cpu(void) +{ + int cpu; + + assert(nr_cpus_mask >= 0); + cpu = sched_getcpu(); + if (unlikely(cpu < 0)) + return cpu; else - return (t = (v >> 8)) - ? 8 + LogTable256[t] - : LogTable256[v]; + return cpu & nr_cpus_mask; } static -void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth); +void ht_count_add(struct cds_lfht *ht, struct rcu_table *t) +{ + unsigned long percpu_count; + int cpu; + + if (unlikely(!ht->percpu_count)) + return; + cpu = ht_get_cpu(); + if (unlikely(cpu < 0)) + return; + percpu_count = uatomic_add_return(&ht->percpu_count[cpu].add, 1); + if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) { + unsigned long count; + + dbg_printf("add percpu %lu\n", percpu_count); + count = uatomic_add_return(&ht->count, + 1UL << COUNT_COMMIT_ORDER); + /* If power of 2 */ + if (!(count & (count - 1))) { + if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) + < t->size) + return; + dbg_printf("add set global %lu\n", count); + cds_lfht_resize_lazy_count(ht, t, + count >> (CHAIN_LEN_TARGET - 1)); + } + } +} static -void check_resize(struct rcu_ht *ht, struct rcu_table *t, +void ht_count_remove(struct cds_lfht *ht, struct rcu_table *t) +{ + unsigned long percpu_count; + int cpu; + + if (unlikely(!ht->percpu_count)) + return; + cpu = ht_get_cpu(); + if (unlikely(cpu < 0)) + return; + percpu_count = uatomic_add_return(&ht->percpu_count[cpu].remove, -1); + if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) { + unsigned long count; + + dbg_printf("remove percpu %lu\n", percpu_count); + count = uatomic_add_return(&ht->count, + -(1UL << COUNT_COMMIT_ORDER)); + /* If power of 2 */ + if (!(count & (count - 1))) { + if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) + >= t->size) + return; + dbg_printf("remove set global %lu\n", count); + cds_lfht_resize_lazy_count(ht, t, + count >> (CHAIN_LEN_TARGET - 1)); + } + } +} + +#else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ + +static const long nr_cpus_mask = -1; + +static +struct ht_items_count *alloc_per_cpu_items_count(void) +{ + return NULL; +} + +static +void free_per_cpu_items_count(struct ht_items_count *count) +{ +} + +static +void ht_count_add(struct cds_lfht *ht, struct rcu_table *t) +{ +} + +static +void ht_count_remove(struct cds_lfht *ht, struct rcu_table *t) +{ +} + +#endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ + + +static +void check_resize(struct cds_lfht *ht, struct rcu_table *t, uint32_t chain_len) { + unsigned long count; + + count = uatomic_read(&ht->count); + /* + * Use bucket-local length for small table expand and for + * environments lacking per-cpu data support. + */ + if (count >= (1UL << COUNT_COMMIT_ORDER)) + return; + if (chain_len > 100) + dbg_printf("WARNING: large chain length: %u.\n", + chain_len); if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) - ht_resize_lazy(ht, t, - log2_u32(chain_len - CHAIN_LEN_TARGET - 1)); + cds_lfht_resize_lazy(ht, t, + get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1))); } static -struct rcu_ht_node *clear_flag(struct rcu_ht_node *node) +struct cds_lfht_node *clear_flag(struct cds_lfht_node *node) { - return (struct rcu_ht_node *) (((unsigned long) node) & ~FLAGS_MASK); + return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK); } static -int is_removed(struct rcu_ht_node *node) +int is_removed(struct cds_lfht_node *node) { return ((unsigned long) node) & REMOVED_FLAG; } static -struct rcu_ht_node *flag_removed(struct rcu_ht_node *node) +struct cds_lfht_node *flag_removed(struct cds_lfht_node *node) { - return (struct rcu_ht_node *) (((unsigned long) node) | REMOVED_FLAG); + return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG); } static -int is_dummy(struct rcu_ht_node *node) +int is_dummy(struct cds_lfht_node *node) { return ((unsigned long) node) & DUMMY_FLAG; } static -struct rcu_ht_node *flag_dummy(struct rcu_ht_node *node) +struct cds_lfht_node *flag_dummy(struct cds_lfht_node *node) { - return (struct rcu_ht_node *) (((unsigned long) node) | DUMMY_FLAG); + return (struct cds_lfht_node *) (((unsigned long) node) | DUMMY_FLAG); } static @@ -230,9 +587,9 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned long v) * Remove all logically deleted nodes from a bucket up to a certain node key. */ static -void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node) +void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node) { - struct rcu_ht_node *iter_prev, *iter, *next, *new_next; + struct cds_lfht_node *iter_prev, *iter, *next, *new_next; for (;;) { iter_prev = dummy; @@ -242,12 +599,12 @@ void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node) for (;;) { if (unlikely(!clear_flag(iter))) return; - if (clear_flag(iter)->p.reverse_hash > node->p.reverse_hash) + if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)) return; next = rcu_dereference(clear_flag(iter)->p.next); - if (is_removed(next)) + if (likely(is_removed(next))) break; - iter_prev = iter; + iter_prev = clear_flag(iter); iter = next; } assert(!is_removed(iter)); @@ -260,12 +617,13 @@ void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node) } static -struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t, - struct rcu_ht_node *node, int unique, int dummy) +struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht, struct rcu_table *t, + struct cds_lfht_node *node, int unique, int dummy) { - struct rcu_ht_node *iter_prev, *iter, *next, *new_node, *new_next, + struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next, *dummy_node; - unsigned long hash; + struct _cds_lfht_node *lookup; + unsigned long hash, index, order; if (!t->size) { assert(dummy); @@ -280,17 +638,20 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t, * iter_prev points to the non-removed node prior to the * insert location. */ - iter_prev = rcu_dereference(t->tbl[hash & (t->size - 1)]); + index = hash & (t->size - 1); + order = get_count_order_ulong(index + 1); + lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)]; + iter_prev = (struct cds_lfht_node *) lookup; /* We can always skip the dummy node initially */ iter = rcu_dereference(iter_prev->p.next); assert(iter_prev->p.reverse_hash <= node->p.reverse_hash); for (;;) { if (unlikely(!clear_flag(iter))) goto insert; - if (clear_flag(iter)->p.reverse_hash > node->p.reverse_hash) + if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)) goto insert; next = rcu_dereference(clear_flag(iter)->p.next); - if (is_removed(next)) + if (unlikely(is_removed(next))) goto gc_node; if (unique && !is_dummy(next) @@ -299,7 +660,8 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t, clear_flag(iter)->key_len)) return clear_flag(iter); /* Only account for identical reverse hash once */ - if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash) + if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash + && !is_dummy(next)) check_resize(ht, t, ++chain_len); iter_prev = clear_flag(iter); iter = next; @@ -332,23 +694,28 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t, } gc_end: /* Garbage collect logically removed nodes in the bucket */ - dummy_node = rcu_dereference(t->tbl[hash & (t->size - 1)]); - _ht_gc_bucket(dummy_node, node); + index = hash & (t->size - 1); + order = get_count_order_ulong(index + 1); + lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)]; + dummy_node = (struct cds_lfht_node *) lookup; + _cds_lfht_gc_bucket(dummy_node, node); return node; } static -int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node) +int _cds_lfht_remove(struct cds_lfht *ht, struct rcu_table *t, + struct cds_lfht_node *node) { - struct rcu_ht_node *dummy, *next, *old; + struct cds_lfht_node *dummy, *next, *old; + struct _cds_lfht_node *lookup; int flagged = 0; - unsigned long hash; + unsigned long hash, index, order; /* logically delete the node */ old = rcu_dereference(node->p.next); do { next = old; - if (is_removed(next)) + if (unlikely(is_removed(next))) goto end; assert(!is_dummy(next)); old = uatomic_cmpxchg(&node->p.next, next, @@ -364,8 +731,11 @@ int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node) * if found. */ hash = bit_reverse_ulong(node->p.reverse_hash); - dummy = rcu_dereference(t->tbl[hash & (t->size - 1)]); - _ht_gc_bucket(dummy, node); + index = hash & (t->size - 1); + order = get_count_order_ulong(index + 1); + lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)]; + dummy = (struct cds_lfht_node *) lookup; + _cds_lfht_gc_bucket(dummy, node); end: /* * Only the flagging action indicated that we (and no other) @@ -379,61 +749,124 @@ end: } static -void init_table(struct rcu_ht *ht, struct rcu_table *t, - unsigned long first, unsigned long len) +void init_table(struct cds_lfht *ht, struct rcu_table *t, + unsigned long first_order, unsigned long len_order) { - unsigned long i, end; - - end = first + len; - for (i = first; i < end; i++) { - /* Update table size when power of two */ - if (i != 0 && !(i & (i - 1))) - t->size = i; - t->tbl[i] = calloc(1, sizeof(struct _rcu_ht_node)); - t->tbl[i]->p.reverse_hash = bit_reverse_ulong(i); - (void) _ht_add(ht, t, t->tbl[i], 0, 1); + unsigned long i, end_order; + + dbg_printf("init table: first_order %lu end_order %lu\n", + first_order, first_order + len_order); + end_order = first_order + len_order; + t->size = !first_order ? 0 : (1UL << (first_order - 1)); + for (i = first_order; i < end_order; i++) { + unsigned long j, len; + + len = !i ? 1 : 1UL << (i - 1); + dbg_printf("init order %lu len: %lu\n", i, len); + t->tbl[i] = calloc(len, sizeof(struct _cds_lfht_node)); + for (j = 0; j < len; j++) { + dbg_printf("init entry: i %lu j %lu hash %lu\n", + i, j, !i ? 0 : (1UL << (i - 1)) + j); + struct cds_lfht_node *new_node = + (struct cds_lfht_node *) &t->tbl[i][j]; + new_node->p.reverse_hash = + bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j); + (void) _cds_lfht_add(ht, t, new_node, 0, 1); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; + } + /* Update table size */ + t->size = !i ? 1 : (1UL << i); + dbg_printf("init new size: %lu\n", t->size); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; } - t->resize_target = t->size = end; + t->resize_target = t->size; t->resize_initiated = 0; } -struct rcu_ht *ht_new(ht_hash_fct hash_fct, - ht_compare_fct compare_fct, - unsigned long hash_seed, - unsigned long init_size, - void (*ht_call_rcu)(struct rcu_head *head, - void (*func)(struct rcu_head *head))) +struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct, + cds_lfht_compare_fct compare_fct, + unsigned long hash_seed, + unsigned long init_size, + void (*cds_lfht_call_rcu)(struct rcu_head *head, + void (*func)(struct rcu_head *head))) { - struct rcu_ht *ht; + struct cds_lfht *ht; + unsigned long order; - ht = calloc(1, sizeof(struct rcu_ht)); + /* init_size must be power of two */ + if (init_size && (init_size & (init_size - 1))) + return NULL; + ht = calloc(1, sizeof(struct cds_lfht)); ht->hash_fct = hash_fct; ht->compare_fct = compare_fct; ht->hash_seed = hash_seed; - ht->ht_call_rcu = ht_call_rcu; + ht->cds_lfht_call_rcu = cds_lfht_call_rcu; ht->in_progress_resize = 0; + ht->percpu_count = alloc_per_cpu_items_count(); /* this mutex should not nest in read-side C.S. */ pthread_mutex_init(&ht->resize_mutex, NULL); - ht->t = calloc(1, sizeof(struct rcu_table) - + (max(init_size, 1) * sizeof(struct rcu_ht_node *))); + order = get_count_order_ulong(max(init_size, 1)) + 1; + ht->t = calloc(1, sizeof(struct cds_lfht) + + (order * sizeof(struct _cds_lfht_node *))); ht->t->size = 0; pthread_mutex_lock(&ht->resize_mutex); - init_table(ht, ht->t, 0, max(init_size, 1)); + init_table(ht, ht->t, 0, order); pthread_mutex_unlock(&ht->resize_mutex); return ht; } -struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len) +struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len) { struct rcu_table *t; - struct rcu_ht_node *node, *next; - unsigned long hash, reverse_hash; + struct cds_lfht_node *node, *next; + struct _cds_lfht_node *lookup; + unsigned long hash, reverse_hash, index, order; hash = ht->hash_fct(key, key_len, ht->hash_seed); reverse_hash = bit_reverse_ulong(hash); t = rcu_dereference(ht->t); - node = rcu_dereference(t->tbl[hash & (t->size - 1)]); + index = hash & (t->size - 1); + order = get_count_order_ulong(index + 1); + lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)]; + dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n", + hash, index, order, index & ((1UL << (order - 1)) - 1)); + node = (struct cds_lfht_node *) lookup; + for (;;) { + if (unlikely(!node)) + break; + if (unlikely(node->p.reverse_hash > reverse_hash)) { + node = NULL; + break; + } + next = rcu_dereference(node->p.next); + if (likely(!is_removed(next)) + && !is_dummy(next) + && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) { + break; + } + node = clear_flag(next); + } + assert(!node || !is_dummy(rcu_dereference(node->p.next))); + return node; +} + +struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht, + struct cds_lfht_node *node) +{ + struct cds_lfht_node *next; + unsigned long reverse_hash; + void *key; + size_t key_len; + + reverse_hash = node->p.reverse_hash; + key = node->key; + key_len = node->key_len; + next = rcu_dereference(node->p.next); + node = clear_flag(next); + for (;;) { if (unlikely(!node)) break; @@ -453,7 +886,7 @@ struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len) return node; } -void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node) +void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node) { struct rcu_table *t; unsigned long hash; @@ -462,39 +895,51 @@ void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node) node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash); t = rcu_dereference(ht->t); - (void) _ht_add(ht, t, node, 0, 0); + (void) _cds_lfht_add(ht, t, node, 0, 0); + ht_count_add(ht, t); } -struct rcu_ht_node *ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node) +struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, + struct cds_lfht_node *node) { struct rcu_table *t; unsigned long hash; + struct cds_lfht_node *ret; hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed); node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash); t = rcu_dereference(ht->t); - return _ht_add(ht, t, node, 1, 0); + ret = _cds_lfht_add(ht, t, node, 1, 0); + if (ret != node) + ht_count_add(ht, t); + return ret; } -int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node) +int cds_lfht_remove(struct cds_lfht *ht, struct cds_lfht_node *node) { struct rcu_table *t; + int ret; t = rcu_dereference(ht->t); - return _ht_remove(ht, t, node); + ret = _cds_lfht_remove(ht, t, node); + if (!ret) + ht_count_remove(ht, t); + return ret; } static -int ht_delete_dummy(struct rcu_ht *ht) +int cds_lfht_delete_dummy(struct cds_lfht *ht) { struct rcu_table *t; - struct rcu_ht_node *node; - unsigned long i; + struct cds_lfht_node *node; + struct _cds_lfht_node *lookup; + unsigned long order, i; t = ht->t; /* Check that the table is empty */ - node = t->tbl[0]; + lookup = &t->tbl[0][0]; + node = (struct cds_lfht_node *) lookup; do { node = clear_flag(node)->p.next; if (!is_dummy(node)) @@ -502,9 +947,17 @@ int ht_delete_dummy(struct rcu_ht *ht) assert(!is_removed(node)); } while (clear_flag(node)); /* Internal sanity check: all nodes left should be dummy */ - for (i = 0; i < t->size; i++) { - assert(is_dummy(t->tbl[i]->p.next)); - free(t->tbl[i]); + for (order = 0; order < get_count_order_ulong(t->size) + 1; order++) { + unsigned long len; + + len = !order ? 1 : 1UL << (order - 1); + for (i = 0; i < len; i++) { + dbg_printf("delete order %lu i %lu hash %lu\n", + order, i, + bit_reverse_ulong(t->tbl[order][i].reverse_hash)); + assert(is_dummy(t->tbl[order][i].next)); + } + free(t->tbl[order]); } return 0; } @@ -513,34 +966,39 @@ int ht_delete_dummy(struct rcu_ht *ht) * Should only be called when no more concurrent readers nor writers can * possibly access the table. */ -int ht_destroy(struct rcu_ht *ht) +int cds_lfht_destroy(struct cds_lfht *ht) { int ret; /* Wait for in-flight resize operations to complete */ + CMM_STORE_SHARED(ht->in_progress_destroy, 1); while (uatomic_read(&ht->in_progress_resize)) poll(NULL, 0, 100); /* wait for 100ms */ - ret = ht_delete_dummy(ht); + ret = cds_lfht_delete_dummy(ht); if (ret) return ret; free(ht->t); + free_per_cpu_items_count(ht->percpu_count); free(ht); return ret; } -void ht_count_nodes(struct rcu_ht *ht, +void cds_lfht_count_nodes(struct cds_lfht *ht, unsigned long *count, unsigned long *removed) { struct rcu_table *t; - struct rcu_ht_node *node, *next; + struct cds_lfht_node *node, *next; + struct _cds_lfht_node *lookup; + unsigned long nr_dummy = 0; *count = 0; *removed = 0; t = rcu_dereference(ht->t); - /* Check that the table is empty */ - node = rcu_dereference(t->tbl[0]); + /* Count non-dummy nodes in the table */ + lookup = &t->tbl[0][0]; + node = (struct cds_lfht_node *) lookup; do { next = rcu_dereference(node->p.next); if (is_removed(next)) { @@ -548,12 +1006,15 @@ void ht_count_nodes(struct rcu_ht *ht, (*removed)++; } else if (!is_dummy(next)) (*count)++; + else + (nr_dummy)++; node = clear_flag(next); } while (node); + dbg_printf("number of dummy nodes: %lu\n", nr_dummy); } static -void ht_free_table_cb(struct rcu_head *head) +void cds_lfht_free_table_cb(struct rcu_head *head) { struct rcu_table *t = caa_container_of(head, struct rcu_table, head); @@ -562,28 +1023,30 @@ void ht_free_table_cb(struct rcu_head *head) /* called with resize mutex held */ static -void _do_ht_resize(struct rcu_ht *ht) +void _do_cds_lfht_resize(struct cds_lfht *ht) { - unsigned long new_size, old_size; + unsigned long new_size, old_size, old_order, new_order; struct rcu_table *new_t, *old_t; old_t = ht->t; old_size = old_t->size; + old_order = get_count_order_ulong(old_size) + 1; new_size = CMM_LOAD_SHARED(old_t->resize_target); - dbg_printf("rculfhash: resize from %lu to %lu buckets\n", - old_size, new_size); if (old_size == new_size) return; - new_t = malloc(sizeof(struct rcu_table) - + (new_size * sizeof(struct rcu_ht_node *))); + new_order = get_count_order_ulong(new_size) + 1; + printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n", + old_size, old_order, new_size, new_order); + new_t = malloc(sizeof(struct cds_lfht) + + (new_order * sizeof(struct _cds_lfht_node *))); assert(new_size > old_size); memcpy(&new_t->tbl, &old_t->tbl, - old_size * sizeof(struct rcu_ht_node *)); - init_table(ht, new_t, old_size, new_size - old_size); + old_order * sizeof(struct _cds_lfht_node *)); + init_table(ht, new_t, old_order, new_order - old_order); /* Changing table and size atomically wrt lookups */ rcu_assign_pointer(ht->t, new_t); - ht->ht_call_rcu(&old_t->head, ht_free_table_cb); + ht->cds_lfht_call_rcu(&old_t->head, cds_lfht_free_table_cb); } static @@ -594,16 +1057,24 @@ unsigned long resize_target_update(struct rcu_table *t, t->size << growth_order); } -void ht_resize(struct rcu_ht *ht, int growth) +void cds_lfht_resize(struct cds_lfht *ht, int growth) { struct rcu_table *t = rcu_dereference(ht->t); unsigned long target_size; + if (growth < 0) { + /* + * Silently refuse to shrink hash table. (not supported) + */ + dbg_printf("shrinking hash table not supported.\n"); + return; + } + target_size = resize_target_update(t, growth); if (t->size < target_size) { CMM_STORE_SHARED(t->resize_initiated, 1); pthread_mutex_lock(&ht->resize_mutex); - _do_ht_resize(ht); + _do_cds_lfht_resize(ht); pthread_mutex_unlock(&ht->resize_mutex); } } @@ -613,10 +1084,10 @@ void do_resize_cb(struct rcu_head *head) { struct rcu_resize_work *work = caa_container_of(head, struct rcu_resize_work, head); - struct rcu_ht *ht = work->ht; + struct cds_lfht *ht = work->ht; pthread_mutex_lock(&ht->resize_mutex); - _do_ht_resize(ht); + _do_cds_lfht_resize(ht); pthread_mutex_unlock(&ht->resize_mutex); free(work); cmm_smp_mb(); /* finish resize before decrement */ @@ -624,7 +1095,7 @@ void do_resize_cb(struct rcu_head *head) } static -void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth) +void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, int growth) { struct rcu_resize_work *work; unsigned long target_size; @@ -635,7 +1106,36 @@ void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth) cmm_smp_mb(); /* increment resize count before calling it */ work = malloc(sizeof(*work)); work->ht = ht; - ht->ht_call_rcu(&work->head, do_resize_cb); + ht->cds_lfht_call_rcu(&work->head, do_resize_cb); + CMM_STORE_SHARED(t->resize_initiated, 1); + } +} + +#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) + +static +unsigned long resize_target_update_count(struct rcu_table *t, + unsigned long count) +{ + return uatomic_set(&t->resize_target, count); +} + +static +void cds_lfht_resize_lazy_count(struct cds_lfht *ht, struct rcu_table *t, + unsigned long count) +{ + struct rcu_resize_work *work; + unsigned long target_size; + + target_size = resize_target_update_count(t, count); + if (!CMM_LOAD_SHARED(t->resize_initiated) && t->size < target_size) { + uatomic_inc(&ht->in_progress_resize); + cmm_smp_mb(); /* increment resize count before calling it */ + work = malloc(sizeof(*work)); + work->ht = ht; + ht->cds_lfht_call_rcu(&work->head, do_resize_cb); CMM_STORE_SHARED(t->resize_initiated, 1); } } + +#endif