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| author | Ying Xue <ying.xue@windriver.com> | 2014-09-03 09:22:36 +0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-09-03 20:56:32 -0700 |
| commit | 940001762ac514810e305aab356983829e5fa82a (patch) | |
| tree | 4f63ce59f54641741fb0c148db9c7e400e0c41a7 /lib | |
| parent | 1f59533f9ca5634e7b8914252e48aee9d9cbe501 (diff) | |
| download | linux-940001762ac514810e305aab356983829e5fa82a.tar.gz | |
lib/rhashtable: allow user to set the minimum shifts of shrinking
Although rhashtable library allows user to specify a quiet big size for user's created hash table, the table may be shrunk to a very small size - HASH_MIN_SIZE(4) after object is removed from the table at the first time. Subsequently, even if the total amount of objects saved in the table is quite lower than user's initial setting in a long time, the hash table size is still dynamically adjusted by rhashtable_shrink() or rhashtable_expand() each time object is inserted or removed from the table. However, as synchronize_rcu() has to be called when table is shrunk or expanded by the two functions, we should permit user to set the minimum table size through configuring the minimum number of shifts according to user specific requirement, avoiding these expensive actions of shrinking or expanding because of calling synchronize_rcu(). Signed-off-by: Ying Xue <ying.xue@windriver.com> Acked-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/rhashtable.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index a2c78810ebc1..8dfec3f26d4c 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); } /** @@ -566,8 +567,11 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) (!params->key_len && !params->obj_hashfn)) return -EINVAL; + params->min_shift = max_t(size_t, params->min_shift, + ilog2(HASH_MIN_SIZE)); + 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) |