Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit f0490980 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

[NET]: Force a cache line split in hh_cache in SMP. 



hh_lock was converted from rwlock to seqlock by Stephen.

To have a 100% benefit of this change, I suggest to place read mostly fields
of hh_cache in a separate cache line, because hh_refcnt may be changed quite
frequently on some busy machines.

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 47bbec02

include/linux/netdevice.h

+8 −1
Original line number Diff line number Diff line
@@ -193,7 +193,14 @@ struct hh_cache 
{

	struct hh_cache *hh_next;	/* Next entry			     */

	atomic_t	hh_refcnt;	/* number of users                   */

	__be16		hh_type;	/* protocol identifier, f.e ETH_P_IP

/*

 * We want hh_output, hh_len, hh_lock and hh_data be a in a separate

 * cache line on SMP.

 * They are mostly read, but hh_refcnt may be changed quite frequently,

 * incurring cache line ping pongs.

 */

	__be16		hh_type ____cacheline_aligned_in_smp;

					/* protocol identifier, f.e ETH_P_IP

                                         *  NOTE:  For VLANs, this will be the

                                         *  encapuslated type. --BLG

                                         */