Messages in this thread Patch in this message |  | | | Subject | [PATCH] af_unix: optimize unix_dgram_poll() | | From | Eric Dumazet <> | | Date | Sat, 30 Oct 2010 11:53:40 +0200 |
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Le vendredi 29 octobre 2010 à 13:46 -0700, Davide Libenzi a écrit :
> Also, why not using the existing wait->key instead of adding a poll2()?
Indeed, if wait is not null, we have in wait->key the interest of poller. If a particular poll() function is expensive, it can test these bits.
Thanks !
Note: I chose the 'goto skip_write' to make this patch really obvious.
[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 <davidel@xmailserver.org> Reported-by: Alban Crequy <alban.crequy@collabora.co.uk> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> --- 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 3c95304..dcb84fe 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2090,6 +2090,9 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock, return mask; } + if (wait && !(wait->key & (POLLWRBAND | POLLWRNORM | POLLOUT))) + goto skip_write; + /* writable? */ writable = unix_writable(sk); if (writable) { @@ -2111,6 +2114,7 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock, else set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags); +skip_write: return mask; }
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