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rhashtable: Add immediate rehash during insertion

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This patch reintroduces immediate rehash during insertion.  If
we find during insertion that the table is full or the chain
length exceeds a set limit (currently 16 but may be disabled
with insecure_elasticity) then we will force an immediate rehash.
The rehash will contain an expansion if the table utilisation
exceeds 75%.

If this rehash fails then the insertion will fail.  Otherwise the
insertion will be reattempted in the new hash table.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2015-03-24 00:50:28 +11:00 • committed by David S. Miller
parent b9ecfdaa10
commit ccd57b1bd3
2 changed files with 96 additions and 6 deletions
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60
lib/rhashtable.c
View file

@ -375,21 +375,76 @@ unlock:
schedule_work(&ht->run_work);
}
static bool rhashtable_check_elasticity(struct rhashtable *ht,
struct bucket_table *tbl,
unsigned hash)
{
unsigned elasticity = ht->elasticity;
struct rhash_head *head;
rht_for_each(head, tbl, hash)
if (!--elasticity)
return true;
return false;
}
int rhashtable_insert_rehash(struct rhashtable *ht)
{
struct bucket_table *old_tbl;
struct bucket_table *new_tbl;
struct bucket_table *tbl;
unsigned int size;
int err;
old_tbl = rht_dereference_rcu(ht->tbl, ht);
tbl = rhashtable_last_table(ht, old_tbl);
size = tbl->size;
if (rht_grow_above_75(ht, tbl))
size *= 2;
/* More than two rehashes (not resizes) detected. */
else if (WARN_ON(old_tbl != tbl && old_tbl->size == size))
return -EBUSY;
new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
if (new_tbl == NULL)
return -ENOMEM;
err = rhashtable_rehash_attach(ht, tbl, new_tbl);
if (err) {
bucket_table_free(new_tbl);
if (err == -EEXIST)
err = 0;
} else
schedule_work(&ht->run_work);
return err;
}
EXPORT_SYMBOL_GPL(rhashtable_insert_rehash);
int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
struct rhash_head *obj,
struct bucket_table *tbl)
{
struct rhash_head *head;
unsigned hash;
int err = -EEXIST;
int err;
tbl = rhashtable_last_table(ht, tbl);
hash = head_hashfn(ht, tbl, obj);
spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
err = -EEXIST;
if (key && rhashtable_lookup_fast(ht, key, ht->p))
goto exit;
err = -EAGAIN;
if (rhashtable_check_elasticity(ht, tbl, hash) ||
rht_grow_above_100(ht, tbl))
goto exit;
err = 0;
head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
@ -678,6 +733,9 @@ int rhashtable_init(struct rhashtable *ht,
ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
if (!params->insecure_elasticity)
ht->elasticity = 16;
if (params->locks_mul)
ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
else