From: Mathieu Desnoyers Date: Tue, 6 Sep 2011 17:44:30 +0000 (-0400) Subject: rculfhash: count nodes (per-cpu) as expand criterion X-Git-Tag: v0.7.0~43^2~180 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=df44348d52532adf7b7a28edc5fdf5b43255c36b;p=userspace-rcu.git rculfhash: count nodes (per-cpu) as expand criterion Signed-off-by: Mathieu Desnoyers --- diff --git a/rculfhash.c b/rculfhash.c index 174c11c..6bc25ae 100644 --- a/rculfhash.c +++ b/rculfhash.c @@ -102,6 +102,7 @@ #include #include +#include "config.h" #include #include #include @@ -121,6 +122,9 @@ #define CHAIN_LEN_TARGET 4 #define CHAIN_LEN_RESIZE_THRESHOLD 8 +/* Commit counter changes to global counter each 1024 steps */ +#define COUNT_COMMIT_ORDER 10 + #ifndef max #define max(a, b) ((a) > (b) ? (a) : (b)) #endif @@ -134,6 +138,10 @@ #define DUMMY_FLAG (1UL << 1) #define FLAGS_MASK ((1UL << 2) - 1) +struct ht_items_count { + unsigned long v; +} __attribute__((aligned(CAA_CACHE_LINE_SIZE))); + struct rcu_table { unsigned long size; /* always a power of 2 */ unsigned long resize_target; @@ -151,6 +159,8 @@ struct cds_lfht { unsigned int in_progress_resize, in_progress_destroy; void (*cds_lfht_call_rcu)(struct rcu_head *head, void (*func)(struct rcu_head *head)); + unsigned long count; /* global approximate item count */ + struct ht_items_count *percpu_count; /* per-cpu item count */ }; struct rcu_resize_work { @@ -353,10 +363,152 @@ int get_count_order_ulong(unsigned long x) static void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, int growth); +/* + * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are + * available, then we support hash table item accounting. + * In the unfortunate event the number of CPUs reported would be + * inaccurate, we use modulo arithmetic on the number of CPUs we got. + */ + +#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) + +static long nr_cpus_mask = -1; + +static +struct ht_items_count *alloc_per_cpu_items_count(void) +{ + struct ht_items_count *count; + + switch (nr_cpus_mask) { + case -2: + return NULL; + case -1: + { + long maxcpus; + + maxcpus = sysconf(_SC_NPROCESSORS_CONF); + if (maxcpus <= 0) { + nr_cpus_mask = -2; + return NULL; + } + /* + * round up number of CPUs to next power of two, so we + * can use & for modulo. + */ + maxcpus = 1UL << get_count_order_ulong(maxcpus); + nr_cpus_mask = maxcpus - 1; + } + /* Fall-through */ + default: + return calloc(nr_cpus_mask + 1, sizeof(*count)); + } +} + +static +void free_per_cpu_items_count(struct ht_items_count *count) +{ + free(count); +} + +static +int ht_get_cpu(void) +{ + int cpu; + + assert(nr_cpus_mask >= 0); + cpu = sched_getcpu(); + if (unlikely(cpu < 0)) + return cpu; + else + return cpu & nr_cpus_mask; +} + +static +unsigned long ht_count_update(struct cds_lfht *ht, unsigned int value) +{ + int cpu; + + if (unlikely(!ht->percpu_count)) + return 0; + cpu = ht_get_cpu(); + if (unlikely(cpu < 0)) + return 0; + return uatomic_add_return(&ht->percpu_count[cpu].v, 1); +} + +static +void ht_count_add(struct cds_lfht *ht, struct rcu_table *t) +{ + unsigned long percpu_count; + + percpu_count = ht_count_update(ht, 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))) { + dbg_printf("add global %lu\n", count); + cds_lfht_resize_lazy(ht, t, 1); + } + } +} + +static +void ht_count_remove(struct cds_lfht *ht, struct rcu_table *t) +{ + unsigned long percpu_count; + + percpu_count = ht_count_update(ht, -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))) { + dbg_printf("remove global %lu\n", count); + cds_lfht_resize_lazy(ht, t, -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) +{ +} + +static +void ht_count_remove(struct cds_lfht *ht) +{ +} + +#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) { + return; //TEST if (chain_len > 100) dbg_printf("WARNING: large chain length: %u.\n", chain_len); @@ -630,6 +782,7 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_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; @@ -721,6 +874,7 @@ void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node) 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, @@ -728,20 +882,28 @@ struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, { struct rcu_table *t; unsigned long hash; + struct cds_lfht_node *ret; hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed); node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash); t = rcu_dereference(ht->t); - return _cds_lfht_add(ht, t, node, 1, 0); + ret = _cds_lfht_add(ht, t, node, 1, 0); + if (ret != node) + ht_count_add(ht, t); + return ret; } int cds_lfht_remove(struct cds_lfht *ht, struct cds_lfht_node *node) { struct rcu_table *t; + int ret; t = rcu_dereference(ht->t); - return _cds_lfht_remove(ht, t, node); + ret = _cds_lfht_remove(ht, t, node); + if (!ret) + ht_count_remove(ht, t); + return ret; } static @@ -794,6 +956,7 @@ int cds_lfht_destroy(struct cds_lfht *ht) if (ret) return ret; free(ht->t); + free_per_cpu_items_count(ht->percpu_count); free(ht); return ret; } @@ -851,7 +1014,7 @@ void _do_cds_lfht_resize(struct cds_lfht *ht) if (old_size == new_size) return; new_order = get_count_order_ulong(new_size) + 1; - dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n", + 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 *)));