From e9be0e993d95adbe5efe0e0f03b2a3e71f5bb2b6 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 25 May 2018 16:28:44 +0200 Subject: [PATCH] net: sched: shrink struct Qdisc The struct Qdisc has a lot of holes, especially after commit a53851e2c321 ("net: sched: explicit locking in gso_cpu fallback"), which as a side effect, moved the fields just after 'busylock' on a new cacheline. Since both 'padded' and 'refcnt' are not updated frequently, and there is a hole before 'gso_skb', we can move such fields there, saving a cacheline without any performance side effect. Before this commit: pahole -C Qdisc net/sche/sch_generic.o # ... /* size: 384, cachelines: 6, members: 25 */ /* sum members: 236, holes: 3, sum holes: 92 */ /* padding: 56 */ After this commit: pahole -C Qdisc net/sche/sch_generic.o # ... /* size: 320, cachelines: 5, members: 25 */ /* sum members: 236, holes: 2, sum holes: 28 */ /* padding: 56 */ Signed-off-by: Paolo Abeni Acked-by: Jiri Pirko Signed-off-by: David S. Miller --- include/net/sch_generic.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 98c10a28cd01..827a3711dc68 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -85,6 +85,8 @@ struct Qdisc { struct net_rate_estimator __rcu *rate_est; struct gnet_stats_basic_cpu __percpu *cpu_bstats; struct gnet_stats_queue __percpu *cpu_qstats; + int padded; + refcount_t refcnt; /* * For performance sake on SMP, we put highly modified fields at the end @@ -97,8 +99,6 @@ struct Qdisc { unsigned long state; struct Qdisc *next_sched; struct sk_buff_head skb_bad_txq; - int padded; - refcount_t refcnt; spinlock_t busylock ____cacheline_aligned_in_smp; spinlock_t seqlock; -- 2.30.2