/*
* rculfhash.c
*
- * Userspace RCU library - Lock-Free Expandable RCU Hash Table
+ * Userspace RCU library - Lock-Free Resizable RCU Hash Table
*
* Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
+/*
+ * Based on the following articles:
+ * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free
+ * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405.
+ * - Michael, M. M. High performance dynamic lock-free hash tables
+ * and list-based sets. In Proceedings of the fourteenth annual ACM
+ * symposium on Parallel algorithms and architectures, ACM Press,
+ * (2002), 73-82.
+ *
+ * Some specificities of this Lock-Free 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
#include <stdlib.h>
#include <errno.h>
#include <stdint.h>
#include <string.h>
+#include "config.h"
#include <urcu.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>
-#define DEBUG /* Test */
-
#ifdef DEBUG
-#define dbg_printf(args...) printf(args)
+#define dbg_printf(fmt, args...) printf("[debug rculfhash] " fmt, ## args)
+#else
+#define dbg_printf(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
+
+/*
+ * Define the minimum table size.
+ */
+#define MIN_TABLE_SIZE 1
+
+#if (CAA_BITS_PER_LONG == 32)
+#define MAX_TABLE_ORDER 32
#else
-#define dbg_printf(args...)
+#define MAX_TABLE_ORDER 64
#endif
-#define CHAIN_LEN_TARGET 4
-#define CHAIN_LEN_RESIZE_THRESHOLD 16
+/*
+ * 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)
+
+#ifndef min
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#endif
#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; /* always a power of 2 */
+ unsigned long size; /* always a power of 2, shared (RCU) */
unsigned long resize_target;
int resize_initiated;
- struct rcu_head head;
- struct rcu_ht_node *tbl[0];
+ struct rcu_level *tbl[MAX_TABLE_ORDER];
};
-struct rcu_ht {
- struct rcu_table *t; /* shared */
- ht_hash_fct hash_fct;
- ht_compare_fct compare_fct;
+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 */
- void (*ht_call_rcu)(struct rcu_head *head,
+ unsigned int in_progress_resize, in_progress_destroy;
+ void (*cds_lfht_call_rcu)(struct rcu_head *head,
void (*func)(struct rcu_head *head));
+ 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 */
+ long count; /* global approximate item count */
+ struct ht_items_count *percpu_count; /* per-cpu item count */
};
struct rcu_resize_work {
struct rcu_head head;
- struct rcu_ht *ht;
+ struct cds_lfht *ht;
+};
+
+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.
}
/*
- * Algorithm to find the log2 of a 32-bit unsigned integer.
- * source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogLookup
- * Originally from Public Domain.
+ * fls: returns the position of the most significant bit.
+ * Returns 0 if no bit is set, else returns the position of the most
+ * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
*/
-static const char LogTable256[256] =
+#if defined(__i386) || defined(__x86_64)
+static inline
+unsigned int fls_u32(uint32_t x)
{
-#define LT(n) n, n, n, n, n, n, n, n, n, n, n, n, n, n, n, n
- -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
- LT(4), LT(5), LT(5), LT(6), LT(6), LT(6), LT(6),
- LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7)
-};
+ int r;
+
+ asm("bsrl %1,%0\n\t"
+ "jnz 1f\n\t"
+ "movl $-1,%0\n\t"
+ "1:\n\t"
+ : "=r" (r) : "rm" (x));
+ return r + 1;
+}
+#define HAS_FLS_U32
+#endif
+
+#if defined(__x86_64)
+static inline
+unsigned int fls_u64(uint64_t x)
+{
+ long r;
+
+ asm("bsrq %1,%0\n\t"
+ "jnz 1f\n\t"
+ "movq $-1,%0\n\t"
+ "1:\n\t"
+ : "=r" (r) : "rm" (x));
+ return r + 1;
+}
+#define HAS_FLS_U64
+#endif
+
+#ifndef HAS_FLS_U64
+static __attribute__((unused))
+unsigned int fls_u64(uint64_t x)
+{
+ unsigned int r = 64;
+
+ if (!x)
+ return 0;
+
+ if (!(x & 0xFFFFFFFF00000000ULL)) {
+ x <<= 32;
+ r -= 32;
+ }
+ if (!(x & 0xFFFF000000000000ULL)) {
+ x <<= 16;
+ r -= 16;
+ }
+ if (!(x & 0xFF00000000000000ULL)) {
+ x <<= 8;
+ r -= 8;
+ }
+ if (!(x & 0xF000000000000000ULL)) {
+ x <<= 4;
+ r -= 4;
+ }
+ if (!(x & 0xC000000000000000ULL)) {
+ x <<= 2;
+ r -= 2;
+ }
+ if (!(x & 0x8000000000000000ULL)) {
+ x <<= 1;
+ r -= 1;
+ }
+ return r;
+}
+#endif
+
+#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);
+
+/*
+ * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
+ * available, then we support hash table item accounting.
+ * In the unfortunate event the number of CPUs reported would be
+ * inaccurate, we use modulo arithmetic on the number of CPUs we got.
+ */
+#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
+
+static
+void cds_lfht_resize_lazy_count(struct cds_lfht *ht, 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;
+ }
+ /*
+ * round up number of CPUs to next power of two, so we
+ * can use & for modulo.
+ */
+ maxcpus = 1UL << get_count_order_ulong(maxcpus);
+ nr_cpus_mask = maxcpus - 1;
+ }
+ /* Fall-through */
+ default:
+ return calloc(nr_cpus_mask + 1, sizeof(*count));
+ }
+}
+
+static
+void free_per_cpu_items_count(struct ht_items_count *count)
+{
+ poison_free(count);
+}
-uint32_t log2_u32(uint32_t v)
+static
+int ht_get_cpu(void)
{
- uint32_t t, tt;
+ int cpu;
- if ((tt = (v >> 16)))
- return (t = (tt >> 8))
- ? 24 + LogTable256[t]
- : 16 + LogTable256[tt];
+ assert(nr_cpus_mask >= 0);
+ cpu = sched_getcpu();
+ if (unlikely(cpu < 0))
+ return cpu;
else
- return (t = (v >> 8))
- ? 8 + LogTable256[t]
- : LogTable256[v];
+ return cpu & nr_cpus_mask;
+}
+
+static
+void ht_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)))) {
+ 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 %ld\n", count);
+ cds_lfht_resize_lazy_count(ht, size,
+ count >> (CHAIN_LEN_TARGET - 1));
+ }
+ }
+}
+
+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)))) {
+ 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 %ld\n", count);
+ /*
+ * Don't shrink table if the number of nodes is below a
+ * certain threshold.
+ */
+ if (count < (1UL << COUNT_COMMIT_ORDER) * (nr_cpus_mask + 1))
+ return;
+ cds_lfht_resize_lazy_count(ht, size,
+ count >> (CHAIN_LEN_TARGET - 1));
+ }
+ }
+}
+
+#else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
+
+static const long nr_cpus_mask = -2;
+
+static
+struct ht_items_count *alloc_per_cpu_items_count(void)
+{
+ return NULL;
}
static
-void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth);
+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 rcu_ht *ht, struct rcu_table *t,
- uint32_t chain_len)
+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)
- ht_resize_lazy(ht, t,
- log2_u32(chain_len - CHAIN_LEN_TARGET));
+ 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
-struct rcu_ht_node *clear_flag(struct rcu_ht_node *node)
+int is_dummy(struct cds_lfht_node *node)
{
- return (struct rcu_ht_node *) (((unsigned long) node) & ~0x1);
+ return ((unsigned long) node) & DUMMY_FLAG;
}
static
-int is_removed(struct rcu_ht_node *node)
+struct cds_lfht_node *flag_dummy(struct cds_lfht_node *node)
{
- return ((unsigned long) node) & 0x1;
+ return (struct cds_lfht_node *) (((unsigned long) node) | DUMMY_FLAG);
}
static
-struct rcu_ht_node *flag_removed(struct rcu_ht_node *node)
+struct cds_lfht_node *get_end(void)
{
- return (struct rcu_ht_node *) (((unsigned long) node) | 0x1);
+ 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
}
static
-void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
+void cds_lfht_free_level(struct rcu_head *head)
{
- struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next;
+ struct rcu_level *l =
+ caa_container_of(head, struct rcu_level, head);
+ poison_free(l);
+}
- if (!t->size)
- return;
+/*
+ * 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;
+
+ 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);
+ /*
+ * 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.
+ */
+ 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;
+}
+
+static
+int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
+ struct cds_lfht_node *old_node,
+ struct cds_lfht_node *ret_next,
+ struct cds_lfht_node *new_node)
+{
+ struct cds_lfht_node *dummy, *old_next;
+ struct _cds_lfht_node *lookup;
+ int flagged = 0;
+ unsigned long hash, index, order;
+
+ if (!old_node) /* Return -ENOENT if asked to replace NULL node */
+ goto end;
+
+ assert(!is_removed(old_node));
+ assert(!is_dummy(old_node));
+ assert(!is_removed(new_node));
+ assert(!is_dummy(new_node));
+ assert(new_node != old_node);
+ do {
+ /* Insert after node to be replaced */
+ old_next = ret_next;
+ if (is_removed(old_next)) {
+ /*
+ * Too late, the old node has been removed under us
+ * between lookup and replace. Fail.
+ */
+ goto end;
+ }
+ assert(!is_dummy(old_next));
+ assert(new_node != clear_flag(old_next));
+ new_node->p.next = clear_flag(old_next);
+ /*
+ * 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.
+ */
+ ret_next = uatomic_cmpxchg(&old_node->p.next,
+ old_next, flag_removed(new_node));
+ } while (ret_next != old_next);
+
+ /* We performed the replacement. */
+ flagged = 1;
+
+ /*
+ * Ensure that the old 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(old_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, new_node);
+end:
+ /*
+ * Only the flagging action indicated that we (and no other)
+ * replaced the node from the hash table.
+ */
+ if (flagged) {
+ assert(is_removed(rcu_dereference(old_node->p.next)));
+ return 0;
+ } else {
+ return -ENOENT;
+ }
+}
+
+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;
+
+ 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 (;;) {
uint32_t chain_len = 0;
/*
* iter_prev points to the non-removed node prior to the
* insert location.
- * iter iterates until it finds the next non-removed
- * node.
*/
- iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
+ 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_prev_next = next = rcu_dereference(iter_prev->next);
- assert(iter_prev);
- assert(iter_prev->reverse_hash <= node->reverse_hash);
+ iter = rcu_dereference(iter_prev->p.next);
+ assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
for (;;) {
- iter = next;
- if (unlikely(!clear_flag(iter)))
- break;
- next = rcu_dereference(clear_flag(iter)->next);
+ 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)))
- continue;
- if (clear_flag(iter)->reverse_hash > node->reverse_hash)
- break;
+ 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->reverse_hash != clear_flag(iter)->reverse_hash)
- check_resize(ht, t, ++chain_len);
+ 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_prev_next = next;
+ iter = next;
}
- assert(node != iter);
+
+ insert:
+ assert(node != clear_flag(iter));
assert(!is_removed(iter_prev));
+ assert(!is_removed(iter));
assert(iter_prev != node);
- node->next = iter;
- if (uatomic_cmpxchg(&iter_prev->next, iter_prev_next,
- node) != iter_prev_next)
- continue;
+ if (!dummy)
+ node->p.next = clear_flag(iter);
else
- break;
+ 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;
+ }
+
+ replace:
+
+ if (!_cds_lfht_replace(ht, size, clear_flag(iter), next,
+ node)) {
+ return_node = clear_flag(iter);
+ goto end; /* gc already done */
+ } else {
+ continue; /* retry */
+ }
+
+ 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);
+end:
+ return return_node;
}
static
-int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
+int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
+ struct cds_lfht_node *node,
+ int dummy_removal)
{
- struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next, *old;
- unsigned long chain_len;
- int found;
+ struct cds_lfht_node *dummy, *next, *old;
+ struct _cds_lfht_node *lookup;
int flagged = 0;
+ unsigned long hash, index, order;
-retry:
- chain_len = 0;
- found = 0;
- /*
- * iter_prev points to the non-removed node prior to the remove
- * location.
- * node is the node to remove.
- */
- iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
- /* We can always skip the dummy node initially */
- iter_prev_next = next = rcu_dereference(iter_prev->next);
- assert(iter_prev);
- assert(iter_prev->reverse_hash <= node->reverse_hash);
- for (;;) {
- iter = next;
- if (unlikely(!clear_flag(iter)))
- break;
- next = rcu_dereference(clear_flag(iter)->next);
- if (iter == node) {
- found = 1;
- break;
- }
- if (unlikely(is_removed(next)))
- continue;
- if (clear_flag(iter)->reverse_hash > node->reverse_hash)
- break;
- iter_prev = clear_flag(iter);
- iter_prev_next = next;
- }
- if (!found)
+ if (!node) /* Return -ENOENT if asked to delete NULL node */
goto end;
- if (!flagged) {
- if (is_removed(next))
+
+ /* 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;
- /* set deletion flag */
- if ((old = uatomic_cmpxchg(&iter->next, next,
- flag_removed(next))) != next) {
- if (old == flag_removed(next))
- goto end;
- else
- goto retry;
- }
- flagged = 1;
- }
+ 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;
+
/*
- * Remove the element from the list.
- * - Retry if there has been a concurrent add before us.
- * - Retry if the prev node has been deleted (its next removed
- * flag would be set).
- * - There cannot be a concurrent delete for our position, because
- * we won the deletion flag cmpxchg.
- * - If there is a concurrent add or remove after us while our
- * removed flag is set, it will skip us and link directly after
- * the prior non-removed node before us. In this case, the
- * retry will not find the node in the list anymore.
+ * 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.
*/
- if (uatomic_cmpxchg(&iter_prev->next, iter_prev_next,
- clear_flag(next)) != iter_prev_next)
- goto retry;
+ 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:
/*
* Only the flagging action indicated that we (and no other)
* removed the node from the hash.
*/
- if (flagged)
+ if (flagged) {
+ assert(is_removed(rcu_dereference(node->p.next)));
return 0;
- else
+ } else {
return -ENOENT;
+ }
+}
+
+static
+void *partition_resize_thread(void *arg)
+{
+ struct partition_resize_work *work = arg;
+
+ 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;
+}
+
+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.
+ */
+ if (nr_cpus_mask > 0) {
+ nr_threads = min(nr_cpus_mask + 1,
+ len >> MIN_PARTITION_PER_THREAD_ORDER);
+ } else {
+ nr_threads = 1;
+ }
+ 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);
+}
+
+/*
+ * 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)
+{
+ unsigned long j;
+
+ 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();
+}
+
+static
+void init_table_populate(struct cds_lfht *ht, unsigned long i,
+ unsigned long len)
+{
+ 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]);
+
+ /*
+ * Set all dummy nodes reverse hash values for a level and
+ * link all dummy nodes into the table.
+ */
+ init_table_populate(ht, i, len);
+
+ /*
+ * Update table size.
+ */
+ cmm_smp_wmb(); /* populate data before RCU size */
+ CMM_STORE_SHARED(ht->t.size, !i ? 1 : (1UL << i));
+
+ dbg_printf("init new size: %lu\n", !i ? 1 : (1UL << i));
+ if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+ break;
+ }
+}
+
+/*
+ * 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.
+ */
+static
+void remove_table_partition(struct cds_lfht *ht, unsigned long i,
+ unsigned long start, unsigned long len)
+{
+ unsigned long j;
+
+ 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 remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
+{
+
+ 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 init_table(struct rcu_ht *ht, struct rcu_table *t,
- unsigned long first, unsigned long len)
+void fini_table(struct cds_lfht *ht,
+ unsigned long first_order, unsigned long len_order)
{
- unsigned long i, end;
+ 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);
+
+ /* 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));
+
+ /*
+ * 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.
+ */
+ ht->cds_lfht_synchronize_rcu();
- end = first + len;
- for (i = first; i < end; i++) {
- /* Update table size when power of two */
- if (i != 0 && !(i & (i - 1)))
- t->size = i;
- t->tbl[i] = calloc(1, sizeof(struct rcu_ht_node));
- t->tbl[i]->dummy = 1;
- t->tbl[i]->hash = i;
- t->tbl[i]->reverse_hash = bit_reverse_ulong(i);
- _ht_add(ht, t, t->tbl[i]);
+ /*
+ * 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;
}
- t->resize_target = t->size = end;
- t->resize_initiated = 0;
}
-struct rcu_ht *ht_new(ht_hash_fct hash_fct,
- ht_compare_fct compare_fct,
- unsigned long hash_seed,
- unsigned long init_size,
- void (*ht_call_rcu)(struct rcu_head *head,
- void (*func)(struct rcu_head *head)))
+struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
+ cds_lfht_compare_fct compare_fct,
+ unsigned long hash_seed,
+ unsigned long init_size,
+ 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 rcu_ht *ht;
+ struct cds_lfht *ht;
+ unsigned long order;
- ht = calloc(1, sizeof(struct rcu_ht));
+ /* init_size must be power of two */
+ if (init_size && (init_size & (init_size - 1)))
+ return NULL;
+ ht = calloc(1, sizeof(struct cds_lfht));
+ assert(ht);
ht->hash_fct = hash_fct;
ht->compare_fct = compare_fct;
ht->hash_seed = hash_seed;
- ht->ht_call_rcu = ht_call_rcu;
+ ht->cds_lfht_call_rcu = cds_lfht_call_rcu;
+ ht->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);
- ht->t = calloc(1, sizeof(struct rcu_table)
- + (max(init_size, 1) * sizeof(struct rcu_ht_node *)));
- ht->t->size = 0;
+ 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);
- init_table(ht, ht->t, 0, max(init_size, 1));
+ 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;
}
-struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
+void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
+ struct cds_lfht_iter *iter)
{
- struct rcu_table *t;
- struct rcu_ht_node *node;
- unsigned long hash, reverse_hash;
+ struct cds_lfht_node *node, *next, *dummy_node;
+ struct _cds_lfht_node *lookup;
+ unsigned long hash, reverse_hash, index, order, size;
hash = ht->hash_fct(key, key_len, ht->hash_seed);
reverse_hash = bit_reverse_ulong(hash);
- t = rcu_dereference(ht->t);
- node = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+ 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 = next = NULL;
+ break;
+ }
+ if (unlikely(node->p.reverse_hash > reverse_hash)) {
+ node = next = 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)));
+ iter->node = node;
+ iter->next = next;
+}
+
+void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter)
+{
+ struct cds_lfht_node *node, *next;
+ unsigned long reverse_hash;
+ void *key;
+ size_t key_len;
+
+ 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 (;;) {
- if (unlikely(!node))
+ if (unlikely(is_end(node))) {
+ node = next = NULL;
break;
- if (unlikely(node->reverse_hash > reverse_hash)) {
- node = NULL;
+ }
+ if (unlikely(node->p.reverse_hash > reverse_hash)) {
+ node = next = NULL;
break;
}
- if (!ht->compare_fct(node->key, node->key_len, key, key_len)) {
- if (unlikely(is_removed(rcu_dereference(node->next))))
- node = NULL;
+ 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)));
+ iter->node = node;
+ iter->next = next;
+}
+
+void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
+{
+ struct cds_lfht_node *node, *next;
+
+ node = iter->node;
+ next = iter->next;
+ node = clear_flag(next);
+
+ for (;;) {
+ if (unlikely(is_end(node))) {
+ node = next = NULL;
break;
}
- node = clear_flag(rcu_dereference(node->next));
+ next = rcu_dereference(node->p.next);
+ if (likely(!is_removed(next))
+ && !is_dummy(next)) {
+ break;
+ }
+ node = clear_flag(next);
}
- return node;
+ assert(!node || !is_dummy(rcu_dereference(node->p.next)));
+ iter->node = node;
+ iter->next = next;
+}
+
+void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
+{
+ struct _cds_lfht_node *lookup;
+
+ /*
+ * Get next after first dummy node. The first dummy node is the
+ * first node of the linked list.
+ */
+ lookup = &ht->t.tbl[0]->nodes[0];
+ iter->node = (struct cds_lfht_node *) lookup;
+ cds_lfht_next(ht, iter);
+}
+
+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);
+
+ size = rcu_dereference(ht->t.size);
+ (void) _cds_lfht_add(ht, size, node, ADD_DEFAULT, 0);
+ ht_count_add(ht, size);
}
-void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
+struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
+ struct cds_lfht_node *node)
{
- struct rcu_table *t;
+ unsigned long hash, size;
+ struct cds_lfht_node *ret;
- node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
- node->reverse_hash = bit_reverse_ulong((unsigned long) node->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);
- _ht_add(ht, t, node);
+ 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_add_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 ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)
+int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
+ struct cds_lfht_node *new_node)
{
- struct rcu_table *t;
+ unsigned long size;
- t = rcu_dereference(ht->t);
- return _ht_remove(ht, t, node);
+ size = rcu_dereference(ht->t.size);
+ return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
+ new_node);
+}
+
+int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter)
+{
+ unsigned long size;
+ int ret;
+
+ size = rcu_dereference(ht->t.size);
+ ret = _cds_lfht_del(ht, size, iter->node, 0);
+ if (!ret)
+ ht_count_del(ht, size);
+ return ret;
}
static
-int ht_delete_dummy(struct rcu_ht *ht)
+int cds_lfht_delete_dummy(struct cds_lfht *ht)
{
- struct rcu_table *t;
- struct rcu_ht_node *node;
- unsigned long i;
+ struct cds_lfht_node *node;
+ struct _cds_lfht_node *lookup;
+ unsigned long order, i, size;
- t = ht->t;
/* Check that the table is empty */
- node = t->tbl[0];
+ lookup = &ht->t.tbl[0]->nodes[0];
+ node = (struct cds_lfht_node *) lookup;
do {
- if (!node->dummy)
+ node = clear_flag(node)->p.next;
+ if (!is_dummy(node))
return -EPERM;
- node = node->next;
- } while (node);
+ 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 (i = 0; i < t->size; i++) {
- assert(t->tbl[i]->dummy);
- free(t->tbl[i]);
+ 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;
}
* 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, pthread_attr_t **attr)
{
int ret;
- ret = ht_delete_dummy(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(ht);
+ 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,
+ long *approx_before,
+ unsigned long *count,
+ unsigned long *removed,
+ long *approx_after)
+{
+ struct cds_lfht_node *node, *next;
+ struct _cds_lfht_node *lookup;
+ unsigned long nr_dummy = 0;
+
+ *approx_before = 0;
+ if (nr_cpus_mask >= 0) {
+ int i;
+
+ for (i = 0; i < nr_cpus_mask + 1; i++) {
+ *approx_before += uatomic_read(&ht->percpu_count[i].add);
+ *approx_before -= uatomic_read(&ht->percpu_count[i].del);
+ }
+ }
+
+ *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)) {
+ if (!is_dummy(next))
+ (*removed)++;
+ else
+ (nr_dummy)++;
+ } 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);
+ *approx_after = 0;
+ if (nr_cpus_mask >= 0) {
+ int i;
+
+ for (i = 0; i < nr_cpus_mask + 1; i++) {
+ *approx_after += uatomic_read(&ht->percpu_count[i].add);
+ *approx_after -= uatomic_read(&ht->percpu_count[i].del);
+ }
+ }
+}
+
+/* called with resize mutex held */
static
-void ht_free_table_cb(struct rcu_head *head)
+void _do_cds_lfht_grow(struct cds_lfht *ht,
+ unsigned long old_size, unsigned long new_size)
{
- struct rcu_table *t =
- caa_container_of(head, struct rcu_table, head);
- free(t);
+ 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_ht_resize(struct rcu_ht *ht)
+void _do_cds_lfht_shrink(struct cds_lfht *ht,
+ unsigned long old_size, unsigned long new_size)
{
- unsigned long new_size, old_size;
- struct rcu_table *new_t, *old_t;
+ unsigned long old_order, new_order;
- old_t = ht->t;
- old_size = old_t->size;
+ 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);
- new_size = CMM_LOAD_SHARED(old_t->resize_target);
- dbg_printf("rculfhash: resize from %lu to %lu buckets\n",
- old_size, new_size);
- if (old_size == new_size)
- return;
- new_t = malloc(sizeof(struct rcu_table)
- + (new_size * sizeof(struct rcu_ht_node *)));
- assert(new_size > old_size);
- memcpy(&new_t->tbl, &old_t->tbl,
- old_size * sizeof(struct rcu_ht_node *));
- init_table(ht, new_t, old_size, new_size - old_size);
- /* Changing table and size atomically wrt lookups */
- rcu_assign_pointer(ht->t, new_t);
- ht->ht_call_rcu(&old_t->head, ht_free_table_cb);
+ /* 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 rcu_table *t,
+unsigned long resize_target_update(struct cds_lfht *ht, unsigned long size,
int growth_order)
{
- return _uatomic_max(&t->resize_target,
- t->size << growth_order);
+ return _uatomic_max(&ht->t.resize_target,
+ size << growth_order);
}
-void ht_resize(struct rcu_ht *ht, int growth)
+static
+void resize_target_update_count(struct cds_lfht *ht,
+ unsigned long count)
{
- struct rcu_table *t = rcu_dereference(ht->t);
- unsigned long target_size;
+ count = max(count, MIN_TABLE_SIZE);
+ uatomic_set(&ht->t.resize_target, count);
+}
- target_size = resize_target_update(t, growth);
- if (t->size < target_size) {
- CMM_STORE_SHARED(t->resize_initiated, 1);
- pthread_mutex_lock(&ht->resize_mutex);
- _do_ht_resize(ht);
- pthread_mutex_unlock(&ht->resize_mutex);
- }
+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
{
struct rcu_resize_work *work =
caa_container_of(head, struct rcu_resize_work, head);
- struct rcu_ht *ht = work->ht;
+ struct cds_lfht *ht = work->ht;
+ ht->cds_lfht_rcu_thread_offline();
pthread_mutex_lock(&ht->resize_mutex);
- _do_ht_resize(ht);
+ _do_cds_lfht_resize(ht);
pthread_mutex_unlock(&ht->resize_mutex);
- free(work);
+ ht->cds_lfht_rcu_thread_online();
+ poison_free(work);
+ cmm_smp_mb(); /* finish resize before decrement */
+ uatomic_dec(&ht->in_progress_resize);
}
static
-void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth)
+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(t, growth);
- if (!CMM_LOAD_SHARED(t->resize_initiated) && t->size < 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->ht_call_rcu(&work->head, do_resize_cb);
- CMM_STORE_SHARED(t->resize_initiated, 1);
+ ht->cds_lfht_call_rcu(&work->head, do_resize_cb);
+ CMM_STORE_SHARED(ht->t.resize_initiated, 1);
}
}
+
+#endif
projects / urcu.git / blobdiff