netdev - [PATCH] net: avoid reloads in SNMP_UPD_PO

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Date:	Sun, 05 Aug 2012 08:26:13 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [PATCH] net: avoid reloads in SNMP_UPD_PO_STATS

From: Eric Dumazet <edumazet@...gle.com>

Avoid two instructions to reload dev->nd_net->mib.ip_statistics pointer,
unsing a temp variable, in ip_rcv(), ip_output() paths for example.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/snmp.h |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/net/snmp.h b/include/net/snmp.h
index 0147b90..7159626 100644
--- a/include/net/snmp.h
+++ b/include/net/snmp.h
@@ -154,13 +154,15 @@ struct linux_xfrm_mib {
  */
 #define SNMP_UPD_PO_STATS(mib, basefield, addend)	\
 	do { \
-		this_cpu_inc(mib[0]->mibs[basefield##PKTS]);		\
-		this_cpu_add(mib[0]->mibs[basefield##OCTETS], addend);	\
+		__typeof__(*mib[0]->mibs) *ptr = mib[0]->mibs;	\
+		this_cpu_inc(ptr[basefield##PKTS]);		\
+		this_cpu_add(ptr[basefield##OCTETS], addend);	\
 	} while (0)
 #define SNMP_UPD_PO_STATS_BH(mib, basefield, addend)	\
 	do { \
-		__this_cpu_inc(mib[0]->mibs[basefield##PKTS]);		\
-		__this_cpu_add(mib[0]->mibs[basefield##OCTETS], addend);	\
+		__typeof__(*mib[0]->mibs) *ptr = mib[0]->mibs;	\
+		__this_cpu_inc(ptr[basefield##PKTS]);		\
+		__this_cpu_add(ptr[basefield##OCTETS], addend);	\
 	} while (0)
 
 


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