[PATCH] neigh: reorder struct neighbour

[PATCH] neigh: reorder struct neighbour

[Eric Dumazet]

It is important to move nud_state outside of the often modified cache
line (because of refcnt), to reduce false sharing in neigh_event_send()

This is a followup of commit 0ed8ddf4045f (neigh: Protect neigh->ha[]
with a seqlock)

This gives a 7% speedup on routing test with IP route cache disabled.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
David, it appears I forgot to push this patch, I have it in my tree
since one month. Thanks !

 include/net/neighbour.h |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 55590ab..815b2ce 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -96,16 +96,16 @@ struct neighbour {
 	struct neigh_parms	*parms;
 	unsigned long		confirmed;
 	unsigned long		updated;
-	__u8			flags;
-	__u8			nud_state;
-	__u8			type;
-	__u8			dead;
+	rwlock_t		lock;
 	atomic_t		refcnt;
 	struct sk_buff_head	arp_queue;
 	struct timer_list	timer;
 	unsigned long		used;
 	atomic_t		probes;
-	rwlock_t		lock;
+	__u8			flags;
+	__u8			nud_state;
+	__u8			type;
+	__u8			dead;
 	seqlock_t		ha_lock;
 	unsigned char		ha[ALIGN(MAX_ADDR_LEN, sizeof(unsigned long))];
 	struct hh_cache		*hh;

Re: [PATCH] neigh: reorder struct neighbour

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 11 Nov 2010 17:57:19 +0100

> It is important to move nud_state outside of the often modified cache
> line (because of refcnt), to reduce false sharing in neigh_event_send()
> 
> This is a followup of commit 0ed8ddf4045f (neigh: Protect neigh->ha[]
> with a seqlock)
> 
> This gives a 7% speedup on routing test with IP route cache disabled.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> ---
> David, it appears I forgot to push this patch, I have it in my tree
> since one month. Thanks !

Applied, thanks.