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authorEric Dumazet <eric.dumazet@gmail.com>2010-10-31 06:38:25 +0100
committerDavid S. Miller <davem@davemloft.net>2010-11-08 22:50:09 +0100
commit973a34aa8593dbfe84386343c694f5beecb51d8a (patch)
treefc2531a0641cbf9caa474518dccb3266d8e2bf05
parentaf_unix: fix unix_dgram_poll() behavior for EPOLLOUT event (diff)
downloadlinux-973a34aa8593dbfe84386343c694f5beecb51d8a.tar.xz
linux-973a34aa8593dbfe84386343c694f5beecb51d8a.zip
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 <davidel@xmailserver.org> Reported-by: Alban Crequy <alban.crequy@collabora.co.uk> Acked-by: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/unix/af_unix.c4
1 files changed, 4 insertions, 0 deletions
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) {