+/*
+ * rculfhash.c
+ *
+ * Userspace RCU library - Lock-Free Expandable RCU Hash Table
+ *
+ * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * 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 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 <errno.h>
#include <assert.h>
#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include "config.h"
#include <urcu.h>
-#include <urcu-defer.h>
+#include <urcu-call-rcu.h>
#include <urcu/arch.h>
#include <urcu/uatomic.h>
#include <urcu/jhash.h>
#include <urcu/compiler.h>
+#include <urcu/rculfhash.h>
#include <stdio.h>
#include <pthread.h>
-#include <urcu/rculfhash.h>
+
+#ifdef DEBUG
+#define dbg_printf(fmt, args...) printf("[debug rculfhash] " fmt, ## args)
+#else
+#define dbg_printf(fmt, args...)
+#endif
/*
- * Maximum number of hash table buckets: 256M on 64-bit.
- * Should take about 512MB max if we assume 1 node per 4 buckets.
+ * 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 MAX_HT_BUCKETS ((256 << 10) / sizeof(void *))
+#define COUNT_COMMIT_ORDER 10
+#define CHAIN_LEN_TARGET 1
+#define CHAIN_LEN_RESIZE_THRESHOLD 3
-/* node flags */
-#define NODE_STOLEN (1 << 0)
+#ifndef max
+#define max(a, b) ((a) > (b) ? (a) : (b))
+#endif
-struct rcu_ht_node;
+/*
+ * The removed flag needs to be updated atomically with the pointer.
+ * 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)
-struct rcu_ht_node {
- struct rcu_ht_node *next;
- void *key;
- void *data;
- unsigned int flags;
-};
+struct ht_items_count {
+ unsigned long add, remove;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
struct rcu_table {
- unsigned long size;
- struct rcu_ht_node *tbl[0];
+ unsigned long size; /* always a power of 2 */
+ unsigned long resize_target;
+ int resize_initiated;
+ struct rcu_head head;
+ struct _cds_lfht_node *tbl[0];
};
-struct rcu_ht {
+struct cds_lfht {
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;
+ 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 */
- 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));
+ 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;
+};
+
+/*
+ * 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);
- }
- rcu_read_unlock();
+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));
+}
- return ret;
+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
}
/*
- * Will re-try until either:
- * - The key is already there (-EEXIST)
- * - We successfully add the key at the head of a table bucket.
+ * 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).
*/
-int ht_add(struct rcu_ht *ht, void *key, void *data)
+#if defined(__i386) || defined(__x86_64)
+static inline
+unsigned int fls_u32(uint32_t x)
{
- 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();
- /*
- * Wait for resize to complete before continuing.
- */
- ret = pthread_mutex_lock(&ht->resize_mutex);
- assert(!ret);
- ret = pthread_mutex_unlock(&ht->resize_mutex);
- assert(!ret);
- goto retry;
+ 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
- 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;
+#ifndef HAS_FLS_U32
+static __attribute__((unused))
+unsigned int fls_u32(uint32_t x)
+{
+ unsigned int r = 32;
- old_head = node = rcu_dereference(t->tbl[hash]);
- for (;;) {
- if (likely(!node)) {
- break;
- }
- if (node->key == key) {
- ret = -EEXIST;
- goto end;
- }
- node = rcu_dereference(node->next);
+ if (!x)
+ return 0;
+ if (!(x & 0xFFFF0000U)) {
+ x <<= 16;
+ r -= 16;
}
- 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;
+ 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
- /* restart loop, release and re-take the read lock to be kind to GP */
-restart:
- rcu_read_unlock();
- goto retry;
+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;
+}
+
+static
+void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, int growth);
+
/*
- * 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.
+ * 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.
*/
-void *ht_steal(struct rcu_ht *ht, void *key)
+#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 rcu_ht_node **prev, *node, *del_node = NULL;
- struct rcu_table *t;
- unsigned long hash;
- void *data;
- int ret;
+ struct ht_items_count *count;
-retry:
- rcu_read_lock();
+ switch (nr_cpus_mask) {
+ case -2:
+ return NULL;
+ case -1:
+ {
+ long maxcpus;
- if (unlikely(LOAD_SHARED(ht->resize_ongoing))) {
- rcu_read_unlock();
+ 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)
+{
+ free(count);
+}
- prev = &t->tbl[hash];
- node = rcu_dereference(*prev);
- for (;;) {
- if (likely(!node)) {
- if (del_node) {
- goto end;
- } else {
- goto error;
- }
+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, 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));
}
- if (node->key == key) {
- break;
+ }
+}
+
+static
+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)
+ cds_lfht_resize_lazy(ht, t,
+ 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
+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;
+}
+
+/*
+ * Remove all logically deleted nodes from a bucket up to a certain node key.
+ */
+static
+void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node)
+{
+ struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
+
+ 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);
+ for (;;) {
+ if (unlikely(!clear_flag(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;
}
- prev = &node->next;
- node = rcu_dereference(*prev);
+ 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);
}
+}
+
+static
+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 cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
+ *dummy_node;
+ struct _cds_lfht_node *lookup;
+ unsigned long hash, index, order;
+
+ if (!t->size) {
+ assert(dummy);
+ node->p.next = flag_dummy(NULL);
+ return node; /* Initial first add (head) */
+ }
+ hash = bit_reverse_ulong(node->p.reverse_hash);
+ for (;;) {
+ uint32_t chain_len = 0;
- if (!del_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.
+ * iter_prev points to the non-removed node prior to the
+ * insert location.
*/
- if (cmpxchg(&node->flags, 0, NODE_STOLEN) != 0)
- goto error;
+ 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 (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 (unique
+ && !is_dummy(next)
+ && !ht->compare_fct(node->key, node->key_len,
+ clear_flag(iter)->key,
+ 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
+ && !is_dummy(next))
+ check_resize(ht, t, ++chain_len);
+ iter_prev = clear_flag(iter);
+ iter = next;
+ }
+ insert:
+ assert(node != clear_flag(iter));
+ assert(!is_removed(iter_prev));
+ 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
+ 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 & (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 _cds_lfht_remove(struct cds_lfht *ht, struct rcu_table *t,
+ struct cds_lfht_node *node)
+{
+ struct cds_lfht_node *dummy, *next, *old;
+ struct _cds_lfht_node *lookup;
+ int flagged = 0;
+ unsigned long hash, index, order;
- /* Found it ! pointer to object is in "prev" */
- if (rcu_cmpxchg_pointer(prev, node, node->next) == node)
- del_node = node;
- goto restart;
+ /* logically delete the node */
+ old = rcu_dereference(node->p.next);
+ do {
+ next = old;
+ if (unlikely(is_removed(next)))
+ goto end;
+ assert(!is_dummy(next));
+ old = uatomic_cmpxchg(&node->p.next, next,
+ flag_removed(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);
+ 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:
/*
- * 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 init_table(struct cds_lfht *ht, struct rcu_table *t,
+ unsigned long first_order, unsigned long len_order)
+{
+ unsigned long i, end_order;
-error:
- data = (void *)(unsigned long)-ENOENT;
- rcu_read_unlock();
- return data;
+ 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;
- /* restart loop, release and re-take the read lock to be kind to GP */
-restart:
- rcu_read_unlock();
- goto retry;
+ 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;
+ t->resize_initiated = 0;
}
-int ht_delete(struct rcu_ht *ht, void *key)
+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)))
{
- void *data;
+ struct cds_lfht *ht;
+ unsigned long order;
- 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;
- }
+ /* 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->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);
+ 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, order);
+ pthread_mutex_unlock(&ht->resize_mutex);
+ return ht;
}
-/* Delete all old elements. Allow concurrent writer accesses. */
-int ht_delete_all(struct rcu_ht *ht)
+struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len)
{
- unsigned long i;
- struct rcu_ht_node **prev, *node, *inext;
struct rcu_table *t;
- int cnt = 0;
- int ret;
+ struct cds_lfht_node *node, *next;
+ struct _cds_lfht_node *lookup;
+ unsigned long hash, reverse_hash, index, order;
- /*
- * 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);
+ hash = ht->hash_fct(key, key_len, ht->hash_seed);
+ reverse_hash = bit_reverse_ulong(hash);
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.
- */
- node = rcu_xchg_pointer(prev, NULL);
- if (!node) {
- rcu_read_unlock();
- continue;
+ 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;
}
- /*
- * 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.
- */
- 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))
+ 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;
- rcu_read_lock();
- node = inext;
}
+ node = clear_flag(next);
}
+ assert(!node || !is_dummy(rcu_dereference(node->p.next)));
+ return node;
+}
- ret = pthread_mutex_unlock(&ht->resize_mutex);
- assert(!ret);
- return cnt;
+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;
+ 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;
+}
+
+void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node)
+{
+ struct rcu_table *t;
+ unsigned long hash;
+
+ 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);
+ (void) _cds_lfht_add(ht, t, node, 0, 0);
+ ht_count_add(ht, t);
+}
+
+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);
+ ret = _cds_lfht_add(ht, t, node, 1, 0);
+ if (ret != node)
+ ht_count_add(ht, t);
+ return ret;
+}
+
+int cds_lfht_remove(struct cds_lfht *ht, struct cds_lfht_node *node)
+{
+ struct rcu_table *t;
+ int ret;
+
+ t = rcu_dereference(ht->t);
+ ret = _cds_lfht_remove(ht, t, node);
+ if (!ret)
+ ht_count_remove(ht, t);
+ return ret;
+}
+
+static
+int cds_lfht_delete_dummy(struct cds_lfht *ht)
+{
+ struct rcu_table *t;
+ struct cds_lfht_node *node;
+ struct _cds_lfht_node *lookup;
+ unsigned long order, i;
+
+ t = ht->t;
+ /* Check that the table is empty */
+ lookup = &t->tbl[0][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 (clear_flag(node));
+ /* Internal sanity check: all nodes left should be dummy */
+ 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;
}
/*
* 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;
- ret = ht_delete_all(ht);
+ /* 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(ht->t);
+ free_per_cpu_items_count(ht->percpu_count);
free(ht);
return ret;
}
-static void ht_resize_grow(struct rcu_ht *ht)
+void cds_lfht_count_nodes(struct cds_lfht *ht,
+ unsigned long *count,
+ unsigned long *removed)
{
- unsigned long i, new_size, old_size;
+ struct rcu_table *t;
+ 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);
+ /* 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)) {
+ assert(!is_dummy(next));
+ (*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 cds_lfht_free_table_cb(struct rcu_head *head)
+{
+ struct rcu_table *t =
+ caa_container_of(head, struct rcu_table, head);
+ free(t);
+}
+
+/* called with resize mutex held */
+static
+void _do_cds_lfht_resize(struct cds_lfht *ht)
+{
+ unsigned long new_size, old_size, old_order, new_order;
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;
+ old_order = get_count_order_ulong(old_size) + 1;
- if (old_size == MAX_HT_BUCKETS)
+ new_size = CMM_LOAD_SHARED(old_t->resize_target);
+ if (old_size == new_size)
return;
+ 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_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->cds_lfht_call_rcu(&old_t->head, cds_lfht_free_table_cb);
+}
+
+static
+unsigned long resize_target_update(struct rcu_table *t,
+ int growth_order)
+{
+ return _uatomic_max(&t->resize_target,
+ t->size << growth_order);
+}
- 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;
+void cds_lfht_resize(struct cds_lfht *ht, int growth)
+{
+ struct rcu_table *t = rcu_dereference(ht->t);
+ unsigned long target_size;
- for (i = 0; i < old_size; i++) {
+ if (growth < 0) {
/*
- * 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)
+ * Silently refuse to shrink hash table. (not supported)
*/
- 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;
- }
+ dbg_printf("shrinking hash table not supported.\n");
+ return;
}
- /* Changing table and size atomically wrt lookups */
- rcu_assign_pointer(ht->t, new_t);
-
- /* Ensure all concurrent lookups use new size and table */
- synchronize_rcu();
-
- for (i = 0; i < old_size; i++) {
- node = old_t->tbl[i];
- while (node) {
- tmp = node->next;
- free(node);
- node = tmp;
- }
+ 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_cds_lfht_resize(ht);
+ pthread_mutex_unlock(&ht->resize_mutex);
}
- free(old_t);
}
-static void ht_resize_shrink(struct rcu_ht *ht)
+static
+void do_resize_cb(struct rcu_head *head)
{
- unsigned long i, new_size;
- struct rcu_table *new_t, *old_t;
- struct rcu_ht_node **prev, *node;
+ struct rcu_resize_work *work =
+ caa_container_of(head, struct rcu_resize_work, head);
+ struct cds_lfht *ht = work->ht;
- old_t = ht->t;
- if (old_t->size == 1)
- return;
+ pthread_mutex_lock(&ht->resize_mutex);
+ _do_cds_lfht_resize(ht);
+ pthread_mutex_unlock(&ht->resize_mutex);
+ free(work);
+ cmm_smp_mb(); /* finish resize before decrement */
+ uatomic_dec(&ht->in_progress_resize);
+}
- new_size = old_t->size >> 1;
+static
+void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, int growth)
+{
+ struct rcu_resize_work *work;
+ unsigned long target_size;
- 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;
- }
- *prev = old_t->tbl[i + new_size];
+ target_size = resize_target_update(t, growth);
+ 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);
}
- smp_wmb(); /* write links before changing size */
- STORE_SHARED(old_t->size, new_size);
-
- /* Ensure all concurrent lookups use new size */
- synchronize_rcu();
-
- 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);
}
-/*
- * growth: >0: *2, <0: /2
- */
-void ht_resize(struct rcu_ht *ht, int growth)
-{
- int ret;
+#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
- 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);
+static
+unsigned long resize_target_update_count(struct rcu_table *t,
+ unsigned long count)
+{
+ return uatomic_set(&t->resize_target, count);
}
-/*
- * Expects keys <= than pointer size to be encoded in the pointer itself.
- */
-uint32_t ht_jhash(void *key, uint32_t length, uint32_t initval)
+static
+void cds_lfht_resize_lazy_count(struct cds_lfht *ht, struct rcu_table *t,
+ unsigned long count)
{
- uint32_t ret;
- void *vkey;
+ struct rcu_resize_work *work;
+ unsigned long target_size;
- if (length <= sizeof(void *))
- vkey = &key;
- else
- vkey = key;
- ret = jhash(vkey, length, initval);
- return ret;
+ 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
projects / urcu.git / blobdiff