net_sched: sch_fq: change fq_flow size/layout

sizeof(struct fq_flow) is 112 bytes on 64bit arches.

This means that half of them use two cache lines, but 50% use
three cache lines.

This patch adds cache line alignment, and makes sure that only
the first cache line is touched by fq_enqueue(), which is more
expensive that fq_dequeue() in general.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index bc9ca1b..ced1f98 100644 (file)
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -66,6 +66,7 @@ static inline struct fq_skb_cb *fq_skb_cb(struct sk_buff *skb)
  * in linear list (head,tail), otherwise are placed in a rbtree (t_root).
  */
 struct fq_flow {
+/* First cache line : used in fq_gc(), fq_enqueue(), fq_dequeue() */
        struct rb_root  t_root;
        struct sk_buff  *head;          /* list of skbs for this flow : first skb */
        union {
@@ -74,14 +75,18 @@ struct fq_flow {
        };
        struct rb_node  fq_node;        /* anchor in fq_root[] trees */
        struct sock     *sk;
+       u32             socket_hash;    /* sk_hash */
        int             qlen;           /* number of packets in flow queue */
+
+/* Second cache line, used in fq_dequeue() */
        int             credit;
-       u32             socket_hash;    /* sk_hash */
+       /* 32bit hole on 64bit arches */
+
        struct fq_flow *next;           /* next pointer in RR lists */
 
        struct rb_node  rate_node;      /* anchor in q->delayed tree */
        u64             time_next_packet;
-};
+} ____cacheline_aligned_in_smp;
 
 struct fq_flow_head {
        struct fq_flow *first;