From 973a34aa8593dbfe84386343c694f5beecb51d8a Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 31 Oct 2010 05:38:25 +0000 Subject: [PATCH] af_unix: optimize unix_dgram_poll() unix_dgram_poll() is pretty expensive to check POLLOUT status, because it has to lock the socket to get its peer, take a reference on the peer to check its receive queue status, and queue another poll_wait on peer_wait. This all can be avoided if the process calling unix_dgram_poll() is not interested in POLLOUT status. It makes unix_dgram_recvmsg() faster by not queueing irrelevant pollers in peer_wait. On a test program provided by Alan Crequy : Before: real 0m0.211s user 0m0.000s sys 0m0.208s After: real 0m0.044s user 0m0.000s sys 0m0.040s Suggested-by: Davide Libenzi Reported-by: Alban Crequy Acked-by: Davide Libenzi Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/unix/af_unix.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index e8898758dd31..7ff31c60186a 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2091,6 +2091,10 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock, return mask; } + /* No write status requested, avoid expensive OUT tests. */ + if (wait && !(wait->key & (POLLWRBAND | POLLWRNORM | POLLOUT))) + return mask; + writable = unix_writable(sk); other = unix_peer_get(sk); if (other) { -- 2.20.1