netdev - [v2 PATCH 1/6] rhashtable: Remove shift from bucket

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Message-Id: <E1YY9ql-0005lr-Fw@gondolin.me.apana.org.au>
Date:	Wed, 18 Mar 2015 20:01:15 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>, tgraf@...g.ch,
	netdev@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>
Subject: [v2 PATCH 1/6] rhashtable: Remove shift from bucket_table

Keeping both size and shift is silly.  We only need one.

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
---

 include/linux/rhashtable.h |    2 --
 lib/rhashtable.c           |    5 ++---
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 1695378..f16e856 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -51,7 +51,6 @@ struct rhash_head {
  * @size: Number of hash buckets
  * @rehash: Current bucket being rehashed
  * @hash_rnd: Random seed to fold into hash
- * @shift: Current size (1 << shift)
  * @locks_mask: Mask to apply before accessing locks[]
  * @locks: Array of spinlocks protecting individual buckets
  * @walkers: List of active walkers
@@ -63,7 +62,6 @@ struct bucket_table {
 	unsigned int		size;
 	unsigned int		rehash;
 	u32			hash_rnd;
-	u32			shift;
 	unsigned int		locks_mask;
 	spinlock_t		*locks;
 	struct list_head	walkers;
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 09a7ada..0974003 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -162,7 +162,6 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
 		return NULL;
 
 	tbl->size = nbuckets;
-	tbl->shift = ilog2(nbuckets);
 
 	if (alloc_bucket_locks(ht, tbl) < 0) {
 		bucket_table_free(tbl);
@@ -189,7 +188,7 @@ static bool rht_grow_above_75(const struct rhashtable *ht,
 {
 	/* Expand table when exceeding 75% load */
 	return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
-	       (!ht->p.max_shift || tbl->shift < ht->p.max_shift);
+	       (!ht->p.max_shift || tbl->size < (1 << ht->p.max_shift));
 }
 
 /**
@@ -202,7 +201,7 @@ static bool rht_shrink_below_30(const struct rhashtable *ht,
 {
 	/* Shrink table beneath 30% load */
 	return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
-	       tbl->shift > ht->p.min_shift;
+	       tbl->size > (1 << ht->p.min_shift);
 }
 
 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned old_hash)
--
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