Commit 27ed44a5 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller
Browse files

rhashtable: Add comment on choice of elasticity value 



This patch adds a comment on the choice of the value 16 as the
maximum chain length before we force a rehash.

Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8263d57e

lib/rhashtable.c

+12 −0
Original line number Diff line number Diff line
@@ -736,6 +736,18 @@ int rhashtable_init(struct rhashtable *ht, 


	ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);



	/* The maximum (not average) chain length grows with the

	 * size of the hash table, at a rate of (log N)/(log log N).

	 * The value of 16 is selected so that even if the hash

	 * table grew to 2^32 you would not expect the maximum

	 * chain length to exceed it unless we are under attack

	 * (or extremely unlucky).

	 *

	 * As this limit is only to detect attacks, we don't need

	 * to set it to a lower value as you'd need the chain

	 * length to vastly exceed 16 to have any real effect

	 * on the system.

	 */

	if (!params->insecure_elasticity)

		ht->elasticity = 16;