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authorEric Dumazet <dada1@cosmosbay.com>2006-12-08 00:08:43 -0800
committerDavid S. Miller <davem@sunset.davemloft.net>2006-12-08 17:19:29 -0800
commitf0490980a152958d25ce9762bfb296d8fd4c5512 (patch)
treeb5f505b4bfbc770c1e15d7177fec4944e2df9c28
parent47bbec0282cce900f16a8dd6397260e076400edb (diff)
[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 <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/netdevice.h9
1 files changed, 8 insertions, 1 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 631cec4ff5e..6be767c76b3 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
*/