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authorHerbert Xu <herbert@gondor.apana.org.au>2015-03-24 00:50:25 +1100
committerDavid S. Miller <davem@davemloft.net>2015-03-23 22:07:52 -0400
commit18093d1c0d1e032142ee24825678b0a8977d74ba (patch)
tree2740fc6be545509613d41984d161efdb97f5d4f2 /lib/rhashtable.c
parent6d022949810b1ea82d46a576d6166035720bbb32 (diff)
downloadblackbird-op-linux-18093d1c0d1e032142ee24825678b0a8977d74ba.tar.gz
blackbird-op-linux-18093d1c0d1e032142ee24825678b0a8977d74ba.zip
rhashtable: Shrink to fit
This patch changes rhashtable_shrink to shrink to the smallest size possible rather than halving the table. This is needed because with multiple rehashing we will defer shrinking until all other rehashing is done, meaning that when we do shrink we may be able to shrink a lot. 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>
Diffstat (limited to 'lib/rhashtable.c')
-rw-r--r--lib/rhashtable.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 798f01d64ab0..9623be345d9c 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -261,8 +261,8 @@ EXPORT_SYMBOL_GPL(rhashtable_expand);
* rhashtable_shrink - Shrink hash table while allowing concurrent lookups
* @ht: the hash table to shrink
*
- * This function may only be called in a context where it is safe to call
- * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
+ * This function shrinks the hash table to fit, i.e., the smallest
+ * size would not cause it to expand right away automatically.
*
* The caller must ensure that no concurrent resizing occurs by holding
* ht->mutex.
@@ -276,10 +276,17 @@ EXPORT_SYMBOL_GPL(rhashtable_expand);
int rhashtable_shrink(struct rhashtable *ht)
{
struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+ unsigned size = roundup_pow_of_two(atomic_read(&ht->nelems) * 3 / 2);
ASSERT_RHT_MUTEX(ht);
- new_tbl = bucket_table_alloc(ht, old_tbl->size / 2);
+ if (size < ht->p.min_size)
+ size = ht->p.min_size;
+
+ if (old_tbl->size <= size)
+ return 0;
+
+ new_tbl = bucket_table_alloc(ht, size);
if (new_tbl == NULL)
return -ENOMEM;
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