tcp: remove some holes in struct tcp_sock

By moving some fields around, this patch shrinks
holes size from 56 to 32, saving 24 bytes on 64bit arches.

After the patch pahole gives the following for 'struct tcp_sock':

	/* size: 2304, cachelines: 36, members: 162 */
	/* sum members: 2234, holes: 6, sum holes: 32 */
	/* sum bitfield members: 34 bits, bit holes: 5, sum bit holes: 14 bits */
	/* padding: 32 */
	/* paddings: 3, sum paddings: 10 */
	/* forced alignments: 1, forced holes: 1, sum forced holes: 12 */

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240227192721.3558982-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index a1c47a6d69b0efd7e62765fbd873c848da22aaec..988a30ef6bfe956fa573f1f18c8284aa382dc1cc 100644 (file)
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -264,10 +264,10 @@ struct tcp_sock {
        u32     pushed_seq;     /* Last pushed seq, required to talk to windows */
        u32     lsndtime;
        u32     mdev_us;        /* medium deviation                     */
+       u32     rtt_seq;        /* sequence number to update rttvar     */
        u64     tcp_wstamp_ns;  /* departure time for next sent data packet */
        u64     tcp_clock_cache; /* cache last tcp_clock_ns() (see tcp_mstamp_refresh()) */
        u64     tcp_mstamp;     /* most recent packet received/sent */
-       u32     rtt_seq;        /* sequence number to update rttvar     */
        struct list_head tsorted_sent_queue; /* time-sorted sent but un-SACKed skbs */
        struct sk_buff *highest_sack;   /* skb just after the highest
                                         * skb with SACKed bit set
@@ -350,7 +350,6 @@ struct tcp_sock {
        u32     dsack_dups;     /* RFC4898 tcpEStatsStackDSACKDups
                                 * total number of DSACK blocks received
                                 */
-       u32     last_oow_ack_time;  /* timestamp of last out-of-window ACK */
        u32     compressed_ack_rcv_nxt;
        struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
 
@@ -384,12 +383,12 @@ struct tcp_sock {
                syn_fastopen_ch:1, /* Active TFO re-enabling probe */
                syn_data_acked:1;/* data in SYN is acked by SYN-ACK */
 
+       u8      keepalive_probes; /* num of allowed keep alive probes   */
        u32     tcp_tx_delay;   /* delay (in usec) added to TX packets */
 
 /* RTT measurement */
        u32     mdev_max_us;    /* maximal mdev for the last rtt period */
 
-       u8      keepalive_probes; /* num of allowed keep alive probes   */
        u32     reord_seen;     /* number of data packet reordering events */
 
 /*
@@ -402,6 +401,7 @@ struct tcp_sock {
        u32     prior_cwnd;     /* cwnd right before starting loss recovery */
        u32     prr_delivered;  /* Number of newly delivered packets to
                                 * receiver in Recovery. */
+       u32     last_oow_ack_time;  /* timestamp of last out-of-window ACK */
 
        struct hrtimer  pacing_timer;
        struct hrtimer  compressed_ack_timer;
@@ -477,8 +477,8 @@ struct tcp_sock {
        bool    is_mptcp;
 #endif
 #if IS_ENABLED(CONFIG_SMC)
-       bool    (*smc_hs_congested)(const struct sock *sk);
        bool    syn_smc;        /* SYN includes SMC */
+       bool    (*smc_hs_congested)(const struct sock *sk);
 #endif
 
 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)