From f0490980a152958d25ce9762bfb296d8fd4c5512 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 8 Dec 2006 00:08:43 -0800 Subject: [PATCH] [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: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/netdevice.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 631cec4ff5e1..6be767c76b37 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -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 */ -- 2.20.1