From 5e140dfc1fe87eae27846f193086724806b33c7d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 20 Mar 2009 01:33:32 -0700 Subject: net: reorder struct Qdisc for better SMP performance dev_queue_xmit() needs to dirty fields "state", "q", "bstats" and "qstats" On x86_64 arch, they currently span three cache lines, involving more cache line ping pongs than necessary, making longer holding of queue spinlock. We can reduce this to one cache line, by grouping all read-mostly fields at the beginning of structure. (Or should I say, all highly modified fields at the end :) ) Before patch : offsetof(struct Qdisc, state)=0x38 offsetof(struct Qdisc, q)=0x48 offsetof(struct Qdisc, bstats)=0x80 offsetof(struct Qdisc, qstats)=0x90 sizeof(struct Qdisc)=0xc8 After patch : offsetof(struct Qdisc, state)=0x80 offsetof(struct Qdisc, q)=0x88 offsetof(struct Qdisc, bstats)=0xa0 offsetof(struct Qdisc, qstats)=0xac sizeof(struct Qdisc)=0xc0 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/gen_stats.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/gen_stats.h') diff --git a/include/linux/gen_stats.h b/include/linux/gen_stats.h index 13f4e74609ac..0ffa41df0ee8 100644 --- a/include/linux/gen_stats.h +++ b/include/linux/gen_stats.h @@ -22,7 +22,7 @@ struct gnet_stats_basic { __u64 bytes; __u32 packets; -}; +} __attribute__ ((packed)); /** * struct gnet_stats_rate_est - rate estimator -- cgit v1.2.3