From: Jesper Dangaard Brouer <brouer@redhat.com>
Date: Mon, 28 Jan 2013 23:44:14 +0000 (+0000)
Subject: net: cacheline adjust struct netns_frags for better frag performance
X-Git-Tag: firefly_0821_release~3680^2~1092^2~232^2~5
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=cd39a7890aed7433beb3188c7ad8591e260ebf10;p=firefly-linux-kernel-4.4.55.git

net: cacheline adjust struct netns_frags for better frag performance

This small cacheline adjustment of struct netns_frags improves
performance significantly for the fragmentation code.

Struct members 'lru_list' and 'mem' are both hot elements, and it
hurts performance, due to cacheline bouncing at every call point,
when they share a cacheline.  Also notice, how mem is placed
together with 'high_thresh' and 'low_thresh', as they are used in
the compare operations together.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index 32786a044718..91e77975eaa6 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -3,9 +3,12 @@
 
 struct netns_frags {
 	int			nqueues;
-	atomic_t		mem;
 	struct list_head	lru_list;
 
+	/* Its important for performance to keep lru_list and mem on
+	 * separate cachelines
+	 */
+	atomic_t		mem ____cacheline_aligned_in_smp;
 	/* sysctls */
 	int			timeout;
 	int			high_thresh;