tcp: reorder tcp_congestion_ops for better cache locality

Group all the often used fields in the first cache line,
to reduce cache line misses.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 31b1696c62ba4bcae8972bebc6ea5d155cf38fd3..eaea43afcc97ba4399022f250dadb830d799e4fd 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1035,44 +1035,56 @@ struct rate_sample {
 };
 
 struct tcp_congestion_ops {
-       struct list_head        list;
-       u32 key;
-       u32 flags;
-
-       /* initialize private data (optional) */
-       void (*init)(struct sock *sk);
-       /* cleanup private data  (optional) */
-       void (*release)(struct sock *sk);
+/* fast path fields are put first to fill one cache line */
 
        /* return slow start threshold (required) */
        u32 (*ssthresh)(struct sock *sk);
+
        /* do new cwnd calculation (required) */
        void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
+
        /* call before changing ca_state (optional) */
        void (*set_state)(struct sock *sk, u8 new_state);
+
        /* call when cwnd event occurs (optional) */
        void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
+
        /* call when ack arrives (optional) */
        void (*in_ack_event)(struct sock *sk, u32 flags);
-       /* new value of cwnd after loss (required) */
-       u32  (*undo_cwnd)(struct sock *sk);
+
        /* hook for packet ack accounting (optional) */
        void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
+
        /* override sysctl_tcp_min_tso_segs */
        u32 (*min_tso_segs)(struct sock *sk);
-       /* returns the multiplier used in tcp_sndbuf_expand (optional) */
-       u32 (*sndbuf_expand)(struct sock *sk);
+
        /* call when packets are delivered to update cwnd and pacing rate,
         * after all the ca_state processing. (optional)
         */
        void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
+
+
+       /* new value of cwnd after loss (required) */
+       u32  (*undo_cwnd)(struct sock *sk);
+       /* returns the multiplier used in tcp_sndbuf_expand (optional) */
+       u32 (*sndbuf_expand)(struct sock *sk);
+
+/* control/slow paths put last */
        /* get info for inet_diag (optional) */
        size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
                           union tcp_cc_info *info);
 
-       char            name[TCP_CA_NAME_MAX];
-       struct module   *owner;
-};
+       char                    name[TCP_CA_NAME_MAX];
+       struct module           *owner;
+       struct list_head        list;
+       u32                     key;
+       u32                     flags;
+
+       /* initialize private data (optional) */
+       void (*init)(struct sock *sk);
+       /* cleanup private data  (optional) */
+       void (*release)(struct sock *sk);
+} ____cacheline_aligned_in_smp;
 
 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);