ount on pid and credentials can be eliminated from the receive path. Until we destroy the skb, we already set a reference when we created the skb on the send side. On the send path, there are two increments of ref count on pid and credentials, once in scm_send and once in unix_scm_to_skb. Then there is a decrement of the reference counts in scm_destroy's call to scm_destroy_cred at the end of unix_dgram_sendmsg functions. One pair of increment and decrement of the reference counts can be removed so we only need to increment the ref counts once. By incorporating these changes, for hackbench running on a 4 socket NHM-EX machine with 40 cores, the execution of hackbench on 50 groups of 20 threads sped up by factor of 2. Hackbench command used for testing: ./hackbench 50 thread 2000 Signed-off-by: Tim Chen Signed-off-by: David S. Miller ‡JÒ