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    tcp/dccp: remove twchain · 05dbc7b5
    Eric Dumazet 提交于
    TCP listener refactoring, part 3 :
    
    Our goal is to hash SYN_RECV sockets into main ehash for fast lookup,
    and parallel SYN processing.
    
    Current inet_ehash_bucket contains two chains, one for ESTABLISH (and
    friend states) sockets, another for TIME_WAIT sockets only.
    
    As the hash table is sized to get at most one socket per bucket, it
    makes little sense to have separate twchain, as it makes the lookup
    slightly more complicated, and doubles hash table memory usage.
    
    If we make sure all socket types have the lookup keys at the same
    offsets, we can use a generic and faster lookup. It turns out TIME_WAIT
    and ESTABLISHED sockets already have common lookup fields for IPv4.
    
    [ INET_TW_MATCH() is no longer needed ]
    
    I'll provide a follow-up to factorize IPv6 lookup as well, to remove
    INET6_TW_MATCH()
    
    This way, SYN_RECV pseudo sockets will be supported the same.
    
    A new sock_gen_put() helper is added, doing either a sock_put() or
    inet_twsk_put() [ and will support SYN_RECV later ].
    
    Note this helper should only be called in real slow path, when rcu
    lookup found a socket that was moved to another identity (freed/reused
    immediately), but could eventually be used in other contexts, like
    sock_edemux()
    
    Before patch :
    
    dmesg | grep "TCP established"
    
    TCP established hash table entries: 524288 (order: 11, 8388608 bytes)
    
    After patch :
    
    TCP established hash table entries: 524288 (order: 10, 4194304 bytes)
    Signed-off-by: NEric Dumazet <edumazet@google.com>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    05dbc7b5
tcp.h 47.9 KB