• Eric Dumazet's avatar
    tcp/dccp: do not touch listener sk_refcnt under synflood · 3b24d854
    Eric Dumazet authored
    When a SYNFLOOD targets a non SO_REUSEPORT listener, multiple
    cpus contend on sk->sk_refcnt and sk->sk_wmem_alloc changes.
    
    By letting listeners use SOCK_RCU_FREE infrastructure,
    we can relax TCP_LISTEN lookup rules and avoid touching sk_refcnt
    
    Note that we still use SLAB_DESTROY_BY_RCU rules for other sockets,
    only listeners are impacted by this change.
    
    Peak performance under SYNFLOOD is increased by ~33% :
    
    On my test machine, I could process 3.2 Mpps instead of 2.4 Mpps
    
    Most consuming functions are now skb_set_owner_w() and sock_wfree()
    contending on sk->sk_wmem_alloc when cooking SYNACK and freeing them.
    Signed-off-by: 's avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
    3b24d854
inet_hashtables.h 12.3 KB