rculfhash: document flags

[urcu.git] / rculfhash.c

diff --git a/rculfhash.c b/rculfhash.c
index 08d024c10996833462c94e1ea96162f609502195..ce1cbb79a55f4cc69ed729dddb170773a46d17d8 100644 (file)
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -813,7 +813,6 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
                        new_next = flag_dummy(clear_flag(next));
                else
                        new_next = clear_flag(next);
-               assert(new_next != NULL);
                (void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
                /* retry */
        }
@@ -849,7 +848,6 @@ int _cds_lfht_remove(struct cds_lfht *ht, unsigned long size,
                        assert(is_dummy(next));
                else
                        assert(!is_dummy(next));
-               assert(next != NULL);
                old = uatomic_cmpxchg(&node->p.next, next,
                                      flag_removed(next));
        } while (old != next);
@@ -881,32 +879,19 @@ end:
                return -ENOENT;
 }
 
-static
-void init_table_hash(struct cds_lfht *ht, unsigned long i,
-               unsigned long len)
-{
-       unsigned long j;
-
-       for (j = 0; j < len; j++) {
-               struct cds_lfht_node *new_node =
-                       (struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j];
-
-               dbg_printf("init hash entry: 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);
-               if (CMM_LOAD_SHARED(ht->in_progress_destroy))
-                       break;
-       }
-}
-
 /*
  * Holding RCU read lock to protect _cds_lfht_add against memory
  * reclaim that could be performed by other call_rcu worker threads (ABA
  * problem).
+ *
+ * TODO: 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_link(struct cds_lfht *ht, unsigned long i, unsigned long len)
+void init_table_populate(struct cds_lfht *ht, unsigned long i, unsigned long len)
 {
        unsigned long j;
 
@@ -916,8 +901,10 @@ void init_table_link(struct cds_lfht *ht, unsigned long i, unsigned long len)
                struct cds_lfht_node *new_node =
                        (struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j];
 
-               dbg_printf("init link: i %lu j %lu hash %lu\n",
+               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, 0, 1);
                if (CMM_LOAD_SHARED(ht->in_progress_destroy))
@@ -949,14 +936,11 @@ void init_table(struct cds_lfht *ht,
                ht->t.tbl[i] = calloc(1, sizeof(struct rcu_level)
                                + (len * sizeof(struct _cds_lfht_node)));
 
-               /* Set all dummy nodes reverse hash values for a level */
-               init_table_hash(ht, i, len);
-
                /*
-                * Link all dummy nodes into the table. Concurrent
-                * add/remove are helping us.
+                * Set all dummy nodes reverse hash values for a level and
+                * link all dummy nodes into the table.
                 */
-               init_table_link(ht, i, len);
+               init_table_populate(ht, i, len);
 
                /*
                 * Update table size.
@@ -989,6 +973,11 @@ void init_table(struct cds_lfht *ht,
  *
  * 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.
+ *
+ * TODO: 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(struct cds_lfht *ht, unsigned long i, unsigned long len)
@@ -1061,7 +1050,7 @@ void fini_table(struct cds_lfht *ht,
        }
 }
 
-struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
+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,