• Arnaldo Carvalho de Melo's avatar
    net: Introduce recvmmsg socket syscall · a2e27255
    Arnaldo Carvalho de Melo authored
    
    
    Meaning receive multiple messages, reducing the number of syscalls and
    net stack entry/exit operations.
    
    Next patches will introduce mechanisms where protocols that want to
    optimize this operation will provide an unlocked_recvmsg operation.
    
    This takes into account comments made by:
    
    . Paul Moore: sock_recvmsg is called only for the first datagram,
      sock_recvmsg_nosec is used for the rest.
    
    . Caitlin Bestler: recvmmsg now has a struct timespec timeout, that
      works in the same fashion as the ppoll one.
    
      If the underlying protocol returns a datagram with MSG_OOB set, this
      will make recvmmsg return right away with as many datagrams (+ the OOB
      one) it has received so far.
    
    . Rémi Denis-Courmont & Steven Whitehouse: If we receive N < vlen
      datagrams and then recvmsg returns an error, recvmmsg will return
      the successfully received datagrams, store the error and return it
      in the next call.
    
    This paves the way for a subsequent optimization, sk_prot->unlocked_recvmsg,
    where we will be able to acquire the lock only at batch start and end, not at
    every underlying recvmsg call.
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    a2e27255