X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=1487980c832c115154937cda4b185024636f9e44;hp=ec799dcc87a6d38bb37fd5e8320d5bfad63607a8;hb=b198f0fda77c816d80f63cfa2e71a7e0b4496736;hpb=a42cc6594389e8f88cc49e36a7779afdb6529135 diff --git a/rculfhash.c b/rculfhash.c index ec799dc..1487980 100644 --- a/rculfhash.c +++ b/rculfhash.c @@ -1,6 +1,134 @@ +/* + * rculfhash.c + * + * Userspace RCU library - Lock-Free Resizable RCU Hash Table + * + * Copyright 2010-2011 - Mathieu Desnoyers + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ /* - * TODO: keys are currently assumed <= sizeof(void *). Key target never freed. + * 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 Resizable 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 for small tables only allows expanding the hash table. + * It is triggered automatically by detecting long chains in the add + * operation. + * - The resize operation for larger tables (and available through an + * API) allows both expanding and shrinking the hash table. + * - Per-CPU Split-counters are used to keep track of the number of + * nodes within the hash table for automatic resize triggering. + * - 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. + * + * A bit of ascii art explanation: + * + * Order index is the off-by-one compare to the actual power of 2 because + * we use index 0 to deal with the 0 special-case. + * + * This shows the nodes for a small table ordered by reversed bits: + * + * bits reverse + * 0 000 000 + * 4 100 001 + * 2 010 010 + * 6 110 011 + * 1 001 100 + * 5 101 101 + * 3 011 110 + * 7 111 111 + * + * This shows the nodes in order of non-reversed bits, linked by + * reversed-bit order. + * + * order bits reverse + * 0 0 000 000 + * | + * 1 | 1 001 100 <- <- + * | | | | + * 2 | | 2 010 010 | | + * | | | 3 011 110 | <- | + * | | | | | | | + * 3 -> | | | 4 100 001 | | + * -> | | 5 101 101 | + * -> | 6 110 011 + * -> 7 111 111 */ #define _LGPL_SOURCE @@ -8,478 +136,1484 @@ #include #include #include +#include +#include +#include "config.h" #include -#include +#include #include #include #include #include +#include #include #include -#include + +#ifdef DEBUG +#define dbg_printf(fmt, args...) printf("[debug rculfhash] " fmt, ## args) +#else +#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 3 /* - * Maximum number of hash table buckets: 256M on 64-bit. - * Should take about 512MB max if we assume 1 node per 4 buckets. + * Define the minimum table size. */ -#define MAX_HT_BUCKETS ((256 << 10) / sizeof(void *)) +#define MIN_TABLE_SIZE 1 + +#if (CAA_BITS_PER_LONG == 32) +#define MAX_TABLE_ORDER 32 +#else +#define MAX_TABLE_ORDER 64 +#endif -/* node flags */ -#define NODE_STOLEN (1 << 0) +/* + * Minimum number of dummy nodes to touch per thread to parallelize grow/shrink. + */ +#define MIN_PARTITION_PER_THREAD_ORDER 12 +#define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER) -struct rcu_ht_node; +#ifndef min +#define min(a, b) ((a) < (b) ? (a) : (b)) +#endif -struct rcu_ht_node { - struct rcu_ht_node *next; - void *key; - void *data; - unsigned int flags; +#ifndef max +#define max(a, b) ((a) > (b) ? (a) : (b)) +#endif + +/* + * The removed flag needs to be updated atomically with the pointer. + * It indicates that no node must attach to the node scheduled for + * removal, and that node garbage collection must be performed. + * The dummy flag does not require to be updated atomically with the + * pointer, but it is added as a pointer low bit flag to save space. + */ +#define REMOVED_FLAG (1UL << 0) +#define DUMMY_FLAG (1UL << 1) +#define FLAGS_MASK ((1UL << 2) - 1) + +/* Value of the end pointer. Should not interact with flags. */ +#define END_VALUE NULL + +struct ht_items_count { + unsigned long add, del; +} __attribute__((aligned(CAA_CACHE_LINE_SIZE))); + +struct rcu_level { + struct rcu_head head; + struct _cds_lfht_node nodes[0]; }; struct rcu_table { - unsigned long size; - struct rcu_ht_node *tbl[0]; + unsigned long size; /* always a power of 2, shared (RCU) */ + unsigned long resize_target; + int resize_initiated; + struct rcu_level *tbl[MAX_TABLE_ORDER]; }; -struct rcu_ht { - struct rcu_table *t; /* shared */ - ht_hash_fct hash_fct; - void (*free_fct)(void *data); /* fct to free data */ - uint32_t keylen; - uint32_t hashseed; +struct cds_lfht { + struct rcu_table t; + cds_lfht_hash_fct hash_fct; + cds_lfht_compare_fct compare_fct; + unsigned long hash_seed; + int flags; + /* + * We need to put the work threads offline (QSBR) when taking this + * mutex, because we use synchronize_rcu within this mutex critical + * section, which waits on read-side critical sections, and could + * therefore cause grace-period deadlock if we hold off RCU G.P. + * completion. + */ pthread_mutex_t resize_mutex; /* resize mutex: add/del mutex */ - int resize_ongoing; /* fast-path resize check */ + unsigned int in_progress_resize, in_progress_destroy; + void (*cds_lfht_call_rcu)(struct rcu_head *head, + void (*func)(struct rcu_head *head)); + void (*cds_lfht_synchronize_rcu)(void); + void (*cds_lfht_rcu_read_lock)(void); + void (*cds_lfht_rcu_read_unlock)(void); + void (*cds_lfht_rcu_thread_offline)(void); + void (*cds_lfht_rcu_thread_online)(void); + void (*cds_lfht_rcu_register_thread)(void); + void (*cds_lfht_rcu_unregister_thread)(void); + pthread_attr_t *resize_attr; /* Resize threads attributes */ + unsigned long count; /* global approximate item count */ + struct ht_items_count *percpu_count; /* per-cpu item count */ }; -struct rcu_ht *ht_new(ht_hash_fct hash_fct, void (*free_fct)(void *data), - unsigned long init_size, uint32_t keylen, - uint32_t hashseed) +struct rcu_resize_work { + struct rcu_head head; + struct cds_lfht *ht; +}; + +struct partition_resize_work { + struct rcu_head head; + struct cds_lfht *ht; + unsigned long i, start, len; + void (*fct)(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len); +}; + +enum add_mode { + ADD_DEFAULT = 0, + ADD_UNIQUE = 1, + ADD_REPLACE = 2, +}; + +static +struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht, + unsigned long size, + struct cds_lfht_node *node, + enum add_mode mode, int dummy); + +/* + * Algorithm to reverse bits in a word by lookup table, extended to + * 64-bit words. + * Source: + * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable + * Originally from Public Domain. + */ + +static const uint8_t BitReverseTable256[256] = { - struct rcu_ht *ht; +#define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64 +#define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16) +#define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 ) + R6(0), R6(2), R6(1), R6(3) +}; +#undef R2 +#undef R4 +#undef R6 - ht = calloc(1, sizeof(struct rcu_ht)); - ht->hash_fct = hash_fct; - ht->free_fct = free_fct; - ht->keylen = keylen; - ht->hashseed = hashseed; - /* this mutex should not nest in read-side C.S. */ - pthread_mutex_init(&ht->resize_mutex, NULL); - ht->resize_ongoing = 0; /* shared */ - ht->t = calloc(1, sizeof(struct rcu_table) - + (init_size * sizeof(struct rcu_ht_node *))); - ht->t->size = init_size; - return ht; +static +uint8_t bit_reverse_u8(uint8_t v) +{ + return BitReverseTable256[v]; } -void *ht_lookup(struct rcu_ht *ht, void *key) +static __attribute__((unused)) +uint32_t bit_reverse_u32(uint32_t v) { - struct rcu_table *t; - unsigned long hash; - struct rcu_ht_node *node; - void *ret; + return ((uint32_t) bit_reverse_u8(v) << 24) | + ((uint32_t) bit_reverse_u8(v >> 8) << 16) | + ((uint32_t) bit_reverse_u8(v >> 16) << 8) | + ((uint32_t) bit_reverse_u8(v >> 24)); +} - rcu_read_lock(); - t = rcu_dereference(ht->t); - smp_read_barrier_depends(); /* read t before size and table */ - hash = ht->hash_fct(key, ht->keylen, ht->hashseed) % t->size; - smp_read_barrier_depends(); /* read size before links */ - node = rcu_dereference(t->tbl[hash]); - for (;;) { - if (likely(!node)) { - ret = NULL; - break; - } - if (node->key == key) { - ret = node->data; - break; - } - node = rcu_dereference(node->next); +static __attribute__((unused)) +uint64_t bit_reverse_u64(uint64_t v) +{ + return ((uint64_t) bit_reverse_u8(v) << 56) | + ((uint64_t) bit_reverse_u8(v >> 8) << 48) | + ((uint64_t) bit_reverse_u8(v >> 16) << 40) | + ((uint64_t) bit_reverse_u8(v >> 24) << 32) | + ((uint64_t) bit_reverse_u8(v >> 32) << 24) | + ((uint64_t) bit_reverse_u8(v >> 40) << 16) | + ((uint64_t) bit_reverse_u8(v >> 48) << 8) | + ((uint64_t) bit_reverse_u8(v >> 56)); +} + +static +unsigned long bit_reverse_ulong(unsigned long v) +{ +#if (CAA_BITS_PER_LONG == 32) + return bit_reverse_u32(v); +#else + return bit_reverse_u64(v); +#endif +} + +/* + * 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). + */ +#if defined(__i386) || defined(__x86_64) +static inline +unsigned int fls_u32(uint32_t x) +{ + 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; } - rcu_read_unlock(); + if (!(x & 0xF000000000000000ULL)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xC000000000000000ULL)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x8000000000000000ULL)) { + x <<= 1; + r -= 1; + } + return r; +} +#endif - return ret; +#ifndef HAS_FLS_U32 +static __attribute__((unused)) +unsigned int fls_u32(uint32_t x) +{ + 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 } +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; +} + +#ifdef POISON_FREE +#define poison_free(ptr) \ + do { \ + memset(ptr, 0x42, sizeof(*(ptr))); \ + free(ptr); \ + } while (0) +#else +#define poison_free(ptr) free(ptr) +#endif + +static +void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth); + /* - * Will re-try until either: - * - The key is already there (-EEXIST) - * - We successfully add the key at the head of a table bucket. + * 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. */ -int ht_add(struct rcu_ht *ht, void *key, void *data) -{ - struct rcu_ht_node *node, *old_head, *new_head; - struct rcu_table *t; - unsigned long hash; - int ret = 0; - - new_head = calloc(1, sizeof(struct rcu_ht_node)); - new_head->key = key; - new_head->data = data; - new_head->flags = 0; - /* here comes the fun and tricky part. - * Add at the beginning with a cmpxchg. - * Hold a read lock between the moment the first element is read - * and the nodes traversal (to find duplicates). This ensures - * the head pointer has not been reclaimed when cmpxchg is done. - * Always adding at the head ensures that we would have to - * re-try if a new item has been added concurrently. So we ensure that - * we never add duplicates. */ -retry: - rcu_read_lock(); - - if (unlikely(LOAD_SHARED(ht->resize_ongoing))) { - rcu_read_unlock(); +#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) + +static +void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size, + 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; + } /* - * Wait for resize to complete before continuing. + * round up number of CPUs to next power of two, so we + * can use & for modulo. */ - ret = pthread_mutex_lock(&ht->resize_mutex); - assert(!ret); - ret = pthread_mutex_unlock(&ht->resize_mutex); - assert(!ret); - goto retry; + maxcpus = 1UL << get_count_order_ulong(maxcpus); + nr_cpus_mask = maxcpus - 1; } + /* Fall-through */ + default: + return calloc(nr_cpus_mask + 1, sizeof(*count)); + } +} - t = rcu_dereference(ht->t); - /* no read barrier needed, because no concurrency with resize */ - hash = ht->hash_fct(key, ht->keylen, ht->hashseed) % t->size; +static +void free_per_cpu_items_count(struct ht_items_count *count) +{ + poison_free(count); +} - old_head = node = rcu_dereference(t->tbl[hash]); - for (;;) { - if (likely(!node)) { - break; +static +int ht_get_cpu(void) +{ + int cpu; + + assert(nr_cpus_mask >= 0); + cpu = sched_getcpu(); + if (unlikely(cpu < 0)) + return cpu; + else + return cpu & nr_cpus_mask; +} + +static +void ht_count_add(struct cds_lfht *ht, unsigned long size) +{ + 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) < size) + return; + dbg_printf("add set global %lu\n", count); + cds_lfht_resize_lazy_count(ht, size, + count >> (CHAIN_LEN_TARGET - 1)); } - if (node->key == key) { - ret = -EEXIST; - goto end; + } +} + +static +void ht_count_del(struct cds_lfht *ht, unsigned long size) +{ + 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].del, -1); + if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) { + unsigned long count; + + dbg_printf("del 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) >= size) + return; + dbg_printf("del set global %lu\n", count); + cds_lfht_resize_lazy_count(ht, size, + count >> (CHAIN_LEN_TARGET - 1)); } - node = rcu_dereference(node->next); } - new_head->next = old_head; - if (rcu_cmpxchg_pointer(&t->tbl[hash], old_head, new_head) != old_head) - goto restart; -end: - rcu_read_unlock(); - return ret; +} + +#else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ + +static const long nr_cpus_mask = -1; - /* restart loop, release and re-take the read lock to be kind to GP */ -restart: - rcu_read_unlock(); - goto retry; +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, unsigned long size) +{ +} + +static +void ht_count_del(struct cds_lfht *ht, unsigned long size) +{ +} + +#endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ + + +static +void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len) +{ + unsigned long count; + + if (!(ht->flags & CDS_LFHT_AUTO_RESIZE)) + return; + 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) + cds_lfht_resize_lazy(ht, size, + get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1))); +} + +static +struct cds_lfht_node *clear_flag(struct cds_lfht_node *node) +{ + return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK); +} + +static +int is_removed(struct cds_lfht_node *node) +{ + return ((unsigned long) node) & REMOVED_FLAG; +} + +static +struct cds_lfht_node *flag_removed(struct cds_lfht_node *node) +{ + return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG); +} + +static +int is_dummy(struct cds_lfht_node *node) +{ + return ((unsigned long) node) & DUMMY_FLAG; +} + +static +struct cds_lfht_node *flag_dummy(struct cds_lfht_node *node) +{ + return (struct cds_lfht_node *) (((unsigned long) node) | DUMMY_FLAG); +} + +static +struct cds_lfht_node *get_end(void) +{ + return (struct cds_lfht_node *) END_VALUE; +} + +static +int is_end(struct cds_lfht_node *node) +{ + return clear_flag(node) == (struct cds_lfht_node *) END_VALUE; +} + +static +unsigned long _uatomic_max(unsigned long *ptr, unsigned long v) +{ + unsigned long old1, old2; + + old1 = uatomic_read(ptr); + do { + old2 = old1; + if (old2 >= v) + return old2; + } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2); + return v; +} + +static +void cds_lfht_free_level(struct rcu_head *head) +{ + struct rcu_level *l = + caa_container_of(head, struct rcu_level, head); + poison_free(l); } /* - * Restart until we successfully remove the entry, or no entry is left - * ((void *)(unsigned long)-ENOENT). - * Deal with concurrent stealers by doing an extra verification pass to check - * that no element in the list are still pointing to the element stolen. - * This could happen if two concurrent steal for consecutive objects are - * executed. A pointer to an object being stolen could be saved by the - * concurrent stealer for the previous object. - * Also, given that in this precise scenario, another stealer can also want to - * delete the doubly-referenced object; use a "stolen" flag to let only one - * stealer delete the object. + * Remove all logically deleted nodes from a bucket up to a certain node key. */ -void *ht_steal(struct rcu_ht *ht, void *key) +static +void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node) { - struct rcu_ht_node **prev, *node, *del_node = NULL; - struct rcu_table *t; - unsigned long hash; - void *data; - int ret; + struct cds_lfht_node *iter_prev, *iter, *next, *new_next; -retry: - rcu_read_lock(); - - if (unlikely(LOAD_SHARED(ht->resize_ongoing))) { - rcu_read_unlock(); + assert(!is_dummy(dummy)); + assert(!is_removed(dummy)); + assert(!is_dummy(node)); + assert(!is_removed(node)); + for (;;) { + iter_prev = dummy; + /* 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); /* - * Wait for resize to complete before continuing. + * We should never be called with dummy (start of chain) + * and logically removed node (end of path compression + * marker) being the actual same node. This would be a + * bug in the algorithm implementation. */ - ret = pthread_mutex_lock(&ht->resize_mutex); - assert(!ret); - ret = pthread_mutex_unlock(&ht->resize_mutex); - assert(!ret); - goto retry; + assert(dummy != node); + for (;;) { + if (unlikely(is_end(iter))) + return; + if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)) + return; + next = rcu_dereference(clear_flag(iter)->p.next); + if (likely(is_removed(next))) + break; + iter_prev = clear_flag(iter); + iter = next; + } + assert(!is_removed(iter)); + if (is_dummy(iter)) + new_next = flag_dummy(clear_flag(next)); + else + new_next = clear_flag(next); + if (is_removed(iter)) + new_next = flag_removed(new_next); + (void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next); } + return; +} - t = rcu_dereference(ht->t); - /* no read barrier needed, because no concurrency with resize */ - hash = ht->hash_fct(key, ht->keylen, ht->hashseed) % t->size; +static +struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht, + unsigned long size, + struct cds_lfht_node *node, + enum add_mode mode, int dummy) +{ + struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next, + *dummy_node, *return_node; + struct _cds_lfht_node *lookup; + unsigned long hash, index, order; - prev = &t->tbl[hash]; - node = rcu_dereference(*prev); + assert(!is_dummy(node)); + assert(!is_removed(node)); + if (!size) { + assert(dummy); + node->p.next = flag_dummy(get_end()); + return node; /* Initial first add (head) */ + } + hash = bit_reverse_ulong(node->p.reverse_hash); for (;;) { - if (likely(!node)) { - if (del_node) { - goto end; - } else { - goto error; + uint32_t chain_len = 0; + + /* + * iter_prev points to the non-removed node prior to the + * insert location. + */ + index = hash & (size - 1); + order = get_count_order_ulong(index + 1); + lookup = &ht->t.tbl[order]->nodes[index & ((!order ? 0 : (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(is_end(iter))) + goto insert; + if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)) + goto insert; + next = rcu_dereference(clear_flag(iter)->p.next); + if (unlikely(is_removed(next))) + goto gc_node; + if ((mode == ADD_UNIQUE || mode == ADD_REPLACE) + && !is_dummy(next) + && !ht->compare_fct(node->key, node->key_len, + clear_flag(iter)->key, + clear_flag(iter)->key_len)) { + if (mode == ADD_UNIQUE) + return clear_flag(iter); + else /* mode == ADD_REPLACE */ + goto replace; } + /* Only account for identical reverse hash once */ + if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash + && !is_dummy(next)) + check_resize(ht, size, ++chain_len); + iter_prev = clear_flag(iter); + iter = next; } - if (node->key == key) { - break; + + insert: + assert(node != clear_flag(iter)); + assert(!is_removed(iter_prev)); + assert(!is_removed(iter)); + assert(iter_prev != node); + if (!dummy) + node->p.next = clear_flag(iter); + else + node->p.next = flag_dummy(clear_flag(iter)); + if (is_dummy(iter)) + new_node = flag_dummy(node); + else + new_node = node; + if (uatomic_cmpxchg(&iter_prev->p.next, iter, + new_node) != iter) { + continue; /* retry */ + } else { + if (mode == ADD_REPLACE) + return_node = NULL; + else /* ADD_DEFAULT and ADD_UNIQUE */ + return_node = node; + goto gc_end; } - prev = &node->next; - node = rcu_dereference(*prev); - } - if (!del_node) { + replace: + /* Insert after node to be replaced */ + iter_prev = clear_flag(iter); + iter = next; + assert(node != clear_flag(iter)); + assert(!is_removed(iter_prev)); + assert(!is_removed(iter)); + assert(iter_prev != node); + assert(!dummy); + node->p.next = clear_flag(iter); + if (is_dummy(iter)) + new_node = flag_dummy(node); + else + new_node = node; /* - * Another concurrent thread stole it ? If so, let it deal with - * this. Assume NODE_STOLEN is the only flag. If this changes, - * read flags before cmpxchg. + * Here is the whole trick for lock-free replace: we add + * the replacement node _after_ the node we want to + * replace by atomically setting its next pointer at the + * same time we set its removal flag. Given that + * the lookups/get next use an iterator aware of the + * next pointer, they will either skip the old node due + * to the removal flag and see the new node, or use + * the old node, but will not see the new one. */ - if (cmpxchg(&node->flags, 0, NODE_STOLEN) != 0) - goto error; + new_node = flag_removed(new_node); + if (uatomic_cmpxchg(&iter_prev->p.next, + iter, new_node) != iter) { + continue; /* retry */ + } else { + return_node = iter_prev; + goto gc_end; + } + + gc_node: + assert(!is_removed(iter)); + if (is_dummy(iter)) + new_next = flag_dummy(clear_flag(next)); + else + new_next = clear_flag(next); + (void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next); + /* retry */ } +gc_end: + /* Garbage collect logically removed nodes in the bucket */ + index = hash & (size - 1); + order = get_count_order_ulong(index + 1); + lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))]; + dummy_node = (struct cds_lfht_node *) lookup; + _cds_lfht_gc_bucket(dummy_node, node); + return return_node; +} - /* Found it ! pointer to object is in "prev" */ - if (rcu_cmpxchg_pointer(prev, node, node->next) == node) - del_node = node; - goto restart; +static +int _cds_lfht_del(struct cds_lfht *ht, unsigned long size, + struct cds_lfht_node *node, + int dummy_removal) +{ + struct cds_lfht_node *dummy, *next, *old; + struct _cds_lfht_node *lookup; + int flagged = 0; + unsigned long hash, index, order; + + /* logically delete the node */ + assert(!is_dummy(node)); + assert(!is_removed(node)); + old = rcu_dereference(node->p.next); + do { + struct cds_lfht_node *new_next; + + next = old; + if (unlikely(is_removed(next))) + goto end; + if (dummy_removal) + assert(is_dummy(next)); + else + assert(!is_dummy(next)); + new_next = flag_removed(next); + old = uatomic_cmpxchg(&node->p.next, next, new_next); + } while (old != next); + + /* We performed the (logical) deletion. */ + flagged = 1; + /* + * Ensure that the node is not visible to readers anymore: lookup for + * the node, and remove it (along with any other logically removed node) + * if found. + */ + hash = bit_reverse_ulong(node->p.reverse_hash); + assert(size > 0); + index = hash & (size - 1); + order = get_count_order_ulong(index + 1); + lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))]; + dummy = (struct cds_lfht_node *) lookup; + _cds_lfht_gc_bucket(dummy, node); end: /* - * From that point, we own node. Note that there can still be concurrent - * RCU readers using it. We can free it outside of read lock after a GP. + * Only the flagging action indicated that we (and no other) + * removed the node from the hash. */ - rcu_read_unlock(); + if (flagged) { + assert(is_removed(rcu_dereference(node->p.next))); + return 0; + } else + return -ENOENT; +} - data = del_node->data; - call_rcu(free, del_node); - return data; +static +void *partition_resize_thread(void *arg) +{ + struct partition_resize_work *work = arg; -error: - data = (void *)(unsigned long)-ENOENT; - rcu_read_unlock(); - return data; + work->ht->cds_lfht_rcu_register_thread(); + work->fct(work->ht, work->i, work->start, work->len); + work->ht->cds_lfht_rcu_unregister_thread(); + return NULL; +} - /* restart loop, release and re-take the read lock to be kind to GP */ -restart: - rcu_read_unlock(); - goto retry; +static +void partition_resize_helper(struct cds_lfht *ht, unsigned long i, + unsigned long len, + void (*fct)(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len)) +{ + unsigned long partition_len; + struct partition_resize_work *work; + int thread, ret; + unsigned long nr_threads; + pthread_t *thread_id; + + /* + * Note: nr_cpus_mask + 1 is always power of 2. + * We spawn just the number of threads we need to satisfy the minimum + * partition size, up to the number of CPUs in the system. + */ + nr_threads = min(nr_cpus_mask + 1, + len >> MIN_PARTITION_PER_THREAD_ORDER); + partition_len = len >> get_count_order_ulong(nr_threads); + work = calloc(nr_threads, sizeof(*work)); + thread_id = calloc(nr_threads, sizeof(*thread_id)); + assert(work); + for (thread = 0; thread < nr_threads; thread++) { + work[thread].ht = ht; + work[thread].i = i; + work[thread].len = partition_len; + work[thread].start = thread * partition_len; + work[thread].fct = fct; + ret = pthread_create(&thread_id[thread], ht->resize_attr, + partition_resize_thread, &work[thread]); + assert(!ret); + } + for (thread = 0; thread < nr_threads; thread++) { + ret = pthread_join(thread_id[thread], NULL); + assert(!ret); + } + free(work); + free(thread_id); } -int ht_delete(struct rcu_ht *ht, void *key) +/* + * Holding RCU read lock to protect _cds_lfht_add against memory + * reclaim that could be performed by other call_rcu worker threads (ABA + * problem). + * + * When we reach a certain length, we can split this population phase over + * many worker threads, based on the number of CPUs available in the system. + * This should therefore take care of not having the expand lagging behind too + * many concurrent insertion threads by using the scheduler's ability to + * schedule dummy node population fairly with insertions. + */ +static +void init_table_populate_partition(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len) { - void *data; + unsigned long j; - data = ht_steal(ht, key); - if (data && data != (void *)(unsigned long)-ENOENT) { - if (ht->free_fct) - call_rcu(ht->free_fct, data); - return 0; - } else { - return -ENOENT; + ht->cds_lfht_rcu_read_lock(); + for (j = start; j < start + len; j++) { + struct cds_lfht_node *new_node = + (struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j]; + + dbg_printf("init populate: i %lu j %lu hash %lu\n", + i, j, !i ? 0 : (1UL << (i - 1)) + j); + new_node->p.reverse_hash = + bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j); + (void) _cds_lfht_add(ht, !i ? 0 : (1UL << (i - 1)), + new_node, ADD_DEFAULT, 1); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; } + ht->cds_lfht_rcu_read_unlock(); } -/* Delete all old elements. Allow concurrent writer accesses. */ -int ht_delete_all(struct rcu_ht *ht) +static +void init_table_populate(struct cds_lfht *ht, unsigned long i, + unsigned long len) { - unsigned long i; - struct rcu_ht_node **prev, *node, *inext; - struct rcu_table *t; - int cnt = 0; - int ret; + assert(nr_cpus_mask != -1); + if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) { + ht->cds_lfht_rcu_thread_online(); + init_table_populate_partition(ht, i, 0, len); + ht->cds_lfht_rcu_thread_offline(); + return; + } + partition_resize_helper(ht, i, len, init_table_populate_partition); +} + +static +void init_table(struct cds_lfht *ht, + unsigned long first_order, unsigned long len_order) +{ + 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; + for (i = first_order; i < end_order; i++) { + unsigned long len; + + len = !i ? 1 : 1UL << (i - 1); + dbg_printf("init order %lu len: %lu\n", i, len); + + /* Stop expand if the resize target changes under us */ + if (CMM_LOAD_SHARED(ht->t.resize_target) < (!i ? 1 : (1UL << i))) + break; + + ht->t.tbl[i] = calloc(1, sizeof(struct rcu_level) + + (len * sizeof(struct _cds_lfht_node))); + assert(ht->t.tbl[i]); - /* - * Mutual exclusion with resize operations, but leave add/steal execute - * concurrently. This is OK because we operate only on the heads. - */ - ret = pthread_mutex_lock(&ht->resize_mutex); - assert(!ret); - - t = rcu_dereference(ht->t); - /* no read barrier needed, because no concurrency with resize */ - for (i = 0; i < t->size; i++) { - rcu_read_lock(); - prev = &t->tbl[i]; /* - * Cut the head. After that, we own the first element. + * Set all dummy nodes reverse hash values for a level and + * link all dummy nodes into the table. */ - node = rcu_xchg_pointer(prev, NULL); - if (!node) { - rcu_read_unlock(); - continue; - } + init_table_populate(ht, i, len); + /* - * We manage a list shared with concurrent writers and readers. - * Note that a concurrent add may or may not be deleted by us, - * depending if it arrives before or after the head is cut. - * "node" points to our first node. Remove first elements - * iteratively. + * Update table size. */ - for (;;) { - inext = NULL; - prev = &node->next; - if (prev) - inext = rcu_xchg_pointer(prev, NULL); - /* - * "node" is the first element of the list we have cut. - * We therefore own it, no concurrent writer may delete - * it. There can only be concurrent lookups. Concurrent - * add can only be done on a bucket head, but we've cut - * it already. inext is also owned by us, because we - * have exchanged it for "NULL". It will therefore be - * safe to use it after a G.P. - */ - rcu_read_unlock(); - if (node->data) - call_rcu(ht->free_fct, node->data); - call_rcu(free, node); - cnt++; - if (likely(!inext)) - break; - rcu_read_lock(); - node = inext; - } - } + cmm_smp_wmb(); /* populate data before RCU size */ + CMM_STORE_SHARED(ht->t.size, !i ? 1 : (1UL << i)); - ret = pthread_mutex_unlock(&ht->resize_mutex); - assert(!ret); - return cnt; + dbg_printf("init new size: %lu\n", !i ? 1 : (1UL << i)); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; + } } /* - * Should only be called when no more concurrent readers nor writers can - * possibly access the table. + * Holding RCU read lock to protect _cds_lfht_remove against memory + * reclaim that could be performed by other call_rcu worker threads (ABA + * problem). + * For a single level, we logically remove and garbage collect each node. + * + * As a design choice, we perform logical removal and garbage collection on a + * node-per-node basis to simplify this algorithm. We also assume keeping good + * cache locality of the operation would overweight possible performance gain + * that could be achieved by batching garbage collection for multiple levels. + * However, this would have to be justified by benchmarks. + * + * Concurrent removal and add operations are helping us perform garbage + * collection of logically removed nodes. We guarantee that all logically + * removed nodes have been garbage-collected (unlinked) before call_rcu is + * invoked to free a hole level of dummy nodes (after a grace period). + * + * Logical removal and garbage collection can therefore be done in batch or on a + * node-per-node basis, as long as the guarantee above holds. + * + * When we reach a certain length, we can split this removal over many worker + * threads, based on the number of CPUs available in the system. This should + * take care of not letting resize process lag behind too many concurrent + * updater threads actively inserting into the hash table. */ -int ht_destroy(struct rcu_ht *ht) +static +void remove_table_partition(struct cds_lfht *ht, unsigned long i, + unsigned long start, unsigned long len) { - int ret; + unsigned long j; - ret = ht_delete_all(ht); - free(ht->t); - free(ht); - return ret; + ht->cds_lfht_rcu_read_lock(); + for (j = start; j < start + len; j++) { + struct cds_lfht_node *fini_node = + (struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j]; + + dbg_printf("remove entry: i %lu j %lu hash %lu\n", + i, j, !i ? 0 : (1UL << (i - 1)) + j); + fini_node->p.reverse_hash = + bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j); + (void) _cds_lfht_del(ht, !i ? 0 : (1UL << (i - 1)), + fini_node, 1); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; + } + ht->cds_lfht_rcu_read_unlock(); } -static void ht_resize_grow(struct rcu_ht *ht) +static +void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len) { - unsigned long i, new_size, old_size; - struct rcu_table *new_t, *old_t; - struct rcu_ht_node *node, *new_node, *tmp; - unsigned long hash; - - old_t = ht->t; - old_size = old_t->size; - if (old_size == MAX_HT_BUCKETS) + assert(nr_cpus_mask != -1); + if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) { + ht->cds_lfht_rcu_thread_online(); + remove_table_partition(ht, i, 0, len); + ht->cds_lfht_rcu_thread_offline(); return; + } + partition_resize_helper(ht, i, len, remove_table_partition); +} + +static +void fini_table(struct cds_lfht *ht, + unsigned long first_order, unsigned long len_order) +{ + long i, end_order; + + dbg_printf("fini table: first_order %lu end_order %lu\n", + first_order, first_order + len_order); + end_order = first_order + len_order; + assert(first_order > 0); + for (i = end_order - 1; i >= first_order; i--) { + unsigned long len; + + len = !i ? 1 : 1UL << (i - 1); + dbg_printf("fini order %lu len: %lu\n", i, len); - new_size = old_size << 1; - new_t = calloc(1, sizeof(struct rcu_table) - + (new_size * sizeof(struct rcu_ht_node *))); - new_t->size = new_size; + /* Stop shrink if the resize target changes under us */ + if (CMM_LOAD_SHARED(ht->t.resize_target) > (1UL << (i - 1))) + break; + + cmm_smp_wmb(); /* populate data before RCU size */ + CMM_STORE_SHARED(ht->t.size, 1UL << (i - 1)); - for (i = 0; i < old_size; i++) { /* - * Re-hash each entry, insert in new table. - * It's important that a reader looking for a key _will_ find it - * if it's in the table. - * Copy each node. (just the node, not ->data) + * We need to wait for all add operations to reach Q.S. (and + * thus use the new table for lookups) before we can start + * releasing the old dummy nodes. Otherwise their lookup will + * return a logically removed node as insert position. */ - node = old_t->tbl[i]; - while (node) { - hash = ht->hash_fct(node->key, ht->keylen, ht->hashseed) - % new_size; - new_node = malloc(sizeof(struct rcu_ht_node)); - new_node->key = node->key; - new_node->data = node->data; - new_node->flags = node->flags; - new_node->next = new_t->tbl[hash]; /* link to first */ - new_t->tbl[hash] = new_node; /* add to head */ - node = node->next; - } + ht->cds_lfht_synchronize_rcu(); + + /* + * Set "removed" flag in dummy nodes about to be removed. + * Unlink all now-logically-removed dummy node pointers. + * Concurrent add/remove operation are helping us doing + * the gc. + */ + remove_table(ht, i, len); + + ht->cds_lfht_call_rcu(&ht->t.tbl[i]->head, cds_lfht_free_level); + + dbg_printf("fini new size: %lu\n", 1UL << i); + if (CMM_LOAD_SHARED(ht->in_progress_destroy)) + break; } +} - /* Changing table and size atomically wrt lookups */ - rcu_assign_pointer(ht->t, new_t); +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, + int flags, + void (*cds_lfht_call_rcu)(struct rcu_head *head, + void (*func)(struct rcu_head *head)), + void (*cds_lfht_synchronize_rcu)(void), + void (*cds_lfht_rcu_read_lock)(void), + void (*cds_lfht_rcu_read_unlock)(void), + void (*cds_lfht_rcu_thread_offline)(void), + void (*cds_lfht_rcu_thread_online)(void), + void (*cds_lfht_rcu_register_thread)(void), + void (*cds_lfht_rcu_unregister_thread)(void), + pthread_attr_t *attr) +{ + struct cds_lfht *ht; + unsigned long order; - /* Ensure all concurrent lookups use new size and table */ - synchronize_rcu(); + /* init_size must be power of two */ + if (init_size && (init_size & (init_size - 1))) + return NULL; + ht = calloc(1, sizeof(struct cds_lfht)); + assert(ht); + ht->hash_fct = hash_fct; + ht->compare_fct = compare_fct; + ht->hash_seed = hash_seed; + ht->cds_lfht_call_rcu = cds_lfht_call_rcu; + ht->cds_lfht_synchronize_rcu = cds_lfht_synchronize_rcu; + ht->cds_lfht_rcu_read_lock = cds_lfht_rcu_read_lock; + ht->cds_lfht_rcu_read_unlock = cds_lfht_rcu_read_unlock; + ht->cds_lfht_rcu_thread_offline = cds_lfht_rcu_thread_offline; + ht->cds_lfht_rcu_thread_online = cds_lfht_rcu_thread_online; + ht->cds_lfht_rcu_register_thread = cds_lfht_rcu_register_thread; + ht->cds_lfht_rcu_unregister_thread = cds_lfht_rcu_unregister_thread; + ht->resize_attr = attr; + 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); + order = get_count_order_ulong(max(init_size, MIN_TABLE_SIZE)) + 1; + ht->flags = flags; + ht->cds_lfht_rcu_thread_offline(); + pthread_mutex_lock(&ht->resize_mutex); + ht->t.resize_target = 1UL << (order - 1); + init_table(ht, 0, order); + pthread_mutex_unlock(&ht->resize_mutex); + ht->cds_lfht_rcu_thread_online(); + return ht; +} + +void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len, + struct cds_lfht_iter *iter) +{ + struct cds_lfht_node *node, *next, *dummy_node; + struct _cds_lfht_node *lookup; + unsigned long hash, reverse_hash, index, order, size; - for (i = 0; i < old_size; i++) { - node = old_t->tbl[i]; - while (node) { - tmp = node->next; - free(node); - node = tmp; + hash = ht->hash_fct(key, key_len, ht->hash_seed); + reverse_hash = bit_reverse_ulong(hash); + + size = rcu_dereference(ht->t.size); + index = hash & (size - 1); + order = get_count_order_ulong(index + 1); + lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1))) - 1)]; + dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n", + hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1))); + dummy_node = (struct cds_lfht_node *) lookup; + /* We can always skip the dummy node initially */ + node = rcu_dereference(dummy_node->p.next); + node = clear_flag(node); + for (;;) { + if (unlikely(is_end(node))) { + node = NULL; + 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); } - free(old_t); + assert(!node || !is_dummy(rcu_dereference(node->p.next))); + iter->node = node; + iter->next = next; } -static void ht_resize_shrink(struct rcu_ht *ht) +void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter) { - unsigned long i, new_size; - struct rcu_table *new_t, *old_t; - struct rcu_ht_node **prev, *node; - - old_t = ht->t; - if (old_t->size == 1) - return; + struct cds_lfht_node *node, *next; + unsigned long reverse_hash; + void *key; + size_t key_len; - new_size = old_t->size >> 1; + node = iter->node; + reverse_hash = node->p.reverse_hash; + key = node->key; + key_len = node->key_len; + next = iter->next; + node = clear_flag(next); - for (i = 0; i < new_size; i++) { - /* Link end with first entry of i + new_size */ - prev = &old_t->tbl[i]; - node = *prev; - while (node) { - prev = &node->next; - node = *prev; + for (;;) { + if (unlikely(is_end(node))) { + node = NULL; + break; + } + if (unlikely(node->p.reverse_hash > reverse_hash)) { + node = NULL; + break; } - *prev = old_t->tbl[i + new_size]; + 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); } - smp_wmb(); /* write links before changing size */ - STORE_SHARED(old_t->size, new_size); + assert(!node || !is_dummy(rcu_dereference(node->p.next))); + iter->node = node; + iter->next = next; +} - /* Ensure all concurrent lookups use new size */ - synchronize_rcu(); +void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node) +{ + unsigned long hash, size; + + hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed); + node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash); - new_t = realloc(old_t, sizeof(struct rcu_table) - + (new_size * sizeof(struct rcu_ht_node *))); - /* shrinking, pointers should not move */ - assert(new_t == old_t); + size = rcu_dereference(ht->t.size); + (void) _cds_lfht_add(ht, size, node, ADD_DEFAULT, 0); + ht_count_add(ht, size); } -/* - * growth: >0: *2, <0: /2 - */ -void ht_resize(struct rcu_ht *ht, int growth) +struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, + struct cds_lfht_node *node) { + unsigned long hash, size; + 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); + + size = rcu_dereference(ht->t.size); + ret = _cds_lfht_add(ht, size, node, ADD_UNIQUE, 0); + if (ret == node) + ht_count_add(ht, size); + return ret; +} + +struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht, + struct cds_lfht_node *node) +{ + unsigned long hash, size; + 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); + + size = rcu_dereference(ht->t.size); + ret = _cds_lfht_add(ht, size, node, ADD_REPLACE, 0); + if (ret == NULL) + ht_count_add(ht, size); + return ret; +} + +int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node) +{ + unsigned long size; int ret; - ret = pthread_mutex_lock(&ht->resize_mutex); - assert(!ret); - STORE_SHARED(ht->resize_ongoing, 1); - synchronize_rcu(); - /* All add/remove are waiting on the mutex. */ - if (growth > 0) - ht_resize_grow(ht); - else if (growth < 0) - ht_resize_shrink(ht); - smp_mb(); - STORE_SHARED(ht->resize_ongoing, 0); - ret = pthread_mutex_unlock(&ht->resize_mutex); - assert(!ret); + size = rcu_dereference(ht->t.size); + ret = _cds_lfht_del(ht, size, node, 0); + if (!ret) + ht_count_del(ht, size); + return ret; +} + +static +int cds_lfht_delete_dummy(struct cds_lfht *ht) +{ + struct cds_lfht_node *node; + struct _cds_lfht_node *lookup; + unsigned long order, i, size; + + /* Check that the table is empty */ + lookup = &ht->t.tbl[0]->nodes[0]; + node = (struct cds_lfht_node *) lookup; + do { + node = clear_flag(node)->p.next; + if (!is_dummy(node)) + return -EPERM; + assert(!is_removed(node)); + } while (!is_end(node)); + /* + * size accessed without rcu_dereference because hash table is + * being destroyed. + */ + size = ht->t.size; + /* Internal sanity check: all nodes left should be dummy */ + for (order = 0; order < get_count_order_ulong(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(ht->t.tbl[order]->nodes[i].reverse_hash)); + assert(is_dummy(ht->t.tbl[order]->nodes[i].next)); + } + poison_free(ht->t.tbl[order]); + } + return 0; } /* - * Expects keys <= than pointer size to be encoded in the pointer itself. + * Should only be called when no more concurrent readers nor writers can + * possibly access the table. */ -uint32_t ht_jhash(void *key, uint32_t length, uint32_t initval) +int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr) { - uint32_t ret; - void *vkey; + int ret; - if (length <= sizeof(void *)) - vkey = &key; - else - vkey = key; - ret = jhash(vkey, length, initval); + /* 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 = cds_lfht_delete_dummy(ht); + if (ret) + return ret; + free_per_cpu_items_count(ht->percpu_count); + if (attr) + *attr = ht->resize_attr; + poison_free(ht); return ret; } + +void cds_lfht_count_nodes(struct cds_lfht *ht, + unsigned long *count, + unsigned long *removed) +{ + struct cds_lfht_node *node, *next; + struct _cds_lfht_node *lookup; + unsigned long nr_dummy = 0; + + *count = 0; + *removed = 0; + + /* Count non-dummy nodes in the table */ + lookup = &ht->t.tbl[0]->nodes[0]; + node = (struct cds_lfht_node *) lookup; + do { + next = rcu_dereference(node->p.next); + if (is_removed(next)) { + assert(!is_dummy(next)); + (*removed)++; + } else if (!is_dummy(next)) + (*count)++; + else + (nr_dummy)++; + node = clear_flag(next); + } while (!is_end(node)); + dbg_printf("number of dummy nodes: %lu\n", nr_dummy); +} + +/* called with resize mutex held */ +static +void _do_cds_lfht_grow(struct cds_lfht *ht, + unsigned long old_size, unsigned long new_size) +{ + unsigned long old_order, new_order; + + old_order = get_count_order_ulong(old_size) + 1; + 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); + assert(new_size > old_size); + init_table(ht, old_order, new_order - old_order); +} + +/* called with resize mutex held */ +static +void _do_cds_lfht_shrink(struct cds_lfht *ht, + unsigned long old_size, unsigned long new_size) +{ + unsigned long old_order, new_order; + + new_size = max(new_size, MIN_TABLE_SIZE); + old_order = get_count_order_ulong(old_size) + 1; + 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); + assert(new_size < old_size); + + /* Remove and unlink all dummy nodes to remove. */ + fini_table(ht, new_order, old_order - new_order); +} + + +/* called with resize mutex held */ +static +void _do_cds_lfht_resize(struct cds_lfht *ht) +{ + unsigned long new_size, old_size; + + /* + * Resize table, re-do if the target size has changed under us. + */ + do { + ht->t.resize_initiated = 1; + old_size = ht->t.size; + new_size = CMM_LOAD_SHARED(ht->t.resize_target); + if (old_size < new_size) + _do_cds_lfht_grow(ht, old_size, new_size); + else if (old_size > new_size) + _do_cds_lfht_shrink(ht, old_size, new_size); + ht->t.resize_initiated = 0; + /* write resize_initiated before read resize_target */ + cmm_smp_mb(); + } while (ht->t.size != CMM_LOAD_SHARED(ht->t.resize_target)); +} + +static +unsigned long resize_target_update(struct cds_lfht *ht, unsigned long size, + int growth_order) +{ + return _uatomic_max(&ht->t.resize_target, + size << growth_order); +} + +static +void resize_target_update_count(struct cds_lfht *ht, + unsigned long count) +{ + count = max(count, MIN_TABLE_SIZE); + uatomic_set(&ht->t.resize_target, count); +} + +void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size) +{ + resize_target_update_count(ht, new_size); + CMM_STORE_SHARED(ht->t.resize_initiated, 1); + ht->cds_lfht_rcu_thread_offline(); + pthread_mutex_lock(&ht->resize_mutex); + _do_cds_lfht_resize(ht); + pthread_mutex_unlock(&ht->resize_mutex); + ht->cds_lfht_rcu_thread_online(); +} + +static +void do_resize_cb(struct rcu_head *head) +{ + struct rcu_resize_work *work = + caa_container_of(head, struct rcu_resize_work, head); + struct cds_lfht *ht = work->ht; + + ht->cds_lfht_rcu_thread_offline(); + pthread_mutex_lock(&ht->resize_mutex); + _do_cds_lfht_resize(ht); + pthread_mutex_unlock(&ht->resize_mutex); + ht->cds_lfht_rcu_thread_online(); + poison_free(work); + cmm_smp_mb(); /* finish resize before decrement */ + uatomic_dec(&ht->in_progress_resize); +} + +static +void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth) +{ + struct rcu_resize_work *work; + unsigned long target_size; + + target_size = resize_target_update(ht, size, growth); + /* Store resize_target before read resize_initiated */ + cmm_smp_mb(); + if (!CMM_LOAD_SHARED(ht->t.resize_initiated) && 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(ht->t.resize_initiated, 1); + } +} + +#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) + +static +void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size, + unsigned long count) +{ + struct rcu_resize_work *work; + + if (!(ht->flags & CDS_LFHT_AUTO_RESIZE)) + return; + resize_target_update_count(ht, count); + /* Store resize_target before read resize_initiated */ + cmm_smp_mb(); + if (!CMM_LOAD_SHARED(ht->t.resize_initiated)) { + 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(ht->t.resize_initiated, 1); + } +} + +#endif