lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 28 Aug 2014 09:45:24 +0800 From: Ying Xue <ying.xue@...driver.com> To: <tgraf@...g.ch> CC: <davem@...emloft.net>, <eric.dumazet@...il.com>, <netdev@...r.kernel.org> Subject: [PATCH net-next v2] lib/rhashtable: allow users to set the minimum shifts of shrinking Now the resizeable hash table size is allowed to shrink a too smaller size - HASH_MIN_SIZE(4) although users initially specify a rather big size when table is created. Especially when the number of objects saved in the table keeps a small value in comparison with the initial setting of table size during a quite long time, lots of actions of expanding and shrinking are involved with objects being inserted or removed from table. However, as synchronize_rcu() has to be called during expanding and shrinking, these unnecessary actions would seriously hit users' performance. Therefore, we should permit users to set the minimum table size through configuring the minimum of number of shifts when table is created according to users specific requirement. Signed-off-by: Ying Xue <ying.xue@...driver.com> --- v2: Translate HASH_MIN_SIZE to .min_shift in rhashtable_init() by Thomas's suggestion. include/linux/rhashtable.h | 2 ++ lib/rhashtable.c | 15 +++++++++++---- 2 files changed, 13 insertions(+), 4 deletions(-) diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index 36826c0..fb298e9d 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -44,6 +44,7 @@ struct rhashtable; * @head_offset: Offset of rhash_head in struct to be hashed * @hash_rnd: Seed to use while hashing * @max_shift: Maximum number of shifts while expanding + * @min_shift: Minimum number of shifts while shrinking * @hashfn: Function to hash key * @obj_hashfn: Function to hash object * @grow_decision: If defined, may return true if table should expand @@ -57,6 +58,7 @@ struct rhashtable_params { size_t head_offset; u32 hash_rnd; size_t max_shift; + size_t min_shift; rht_hashfn_t hashfn; rht_obj_hashfn_t obj_hashfn; bool (*grow_decision)(const struct rhashtable *ht, diff --git a/lib/rhashtable.c b/lib/rhashtable.c index a2c7881..85a4ac2 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -298,7 +298,7 @@ int rhashtable_shrink(struct rhashtable *ht, gfp_t flags) ASSERT_RHT_MUTEX(ht); - if (tbl->size <= HASH_MIN_SIZE) + if (ht->shift <= ht->p.min_shift) return 0; ntbl = bucket_table_alloc(tbl->size / 2, flags); @@ -506,9 +506,10 @@ void *rhashtable_lookup_compare(const struct rhashtable *ht, u32 hash, } EXPORT_SYMBOL_GPL(rhashtable_lookup_compare); -static size_t rounded_hashtable_size(unsigned int nelem) +static size_t rounded_hashtable_size(struct rhashtable_params *params) { - return max(roundup_pow_of_two(nelem * 4 / 3), HASH_MIN_SIZE); + return max(roundup_pow_of_two(params->nelem_hint * 4 / 3), + 1UL << params->min_shift); } /** @@ -557,6 +558,7 @@ static size_t rounded_hashtable_size(unsigned int nelem) */ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) { + size_t min_shift = ilog2(HASH_MIN_SIZE); struct bucket_table *tbl; size_t size; @@ -566,8 +568,13 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) (!params->key_len && !params->obj_hashfn)) return -EINVAL; + if (params->min_shift) + params->min_shift = max(params->min_shift, min_shift); + else + params->min_shift = min_shift; + if (params->nelem_hint) - size = rounded_hashtable_size(params->nelem_hint); + size = rounded_hashtable_size(params); tbl = bucket_table_alloc(size, GFP_KERNEL); if (tbl == NULL) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists