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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-10-31 05:38:25 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-11-08 13:50:09 -0800 |
| commit | 973a34aa8593dbfe84386343c694f5beecb51d8a (patch) | |
| tree | fc2531a0641cbf9caa474518dccb3266d8e2bf05 | |
| parent | 5456f09aaf88731e16dbcea7522cb330b6846415 (diff) | |
| download | lwn-973a34aa8593dbfe84386343c694f5beecb51d8a.tar.gz lwn-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.c | 4 |
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) { |