Re: [PATCH v2 net-next] net: poll/select low latency socket support

From: Eliezer Tamir
Date: Tue Jun 18 2013 - 09:25:34 EST

On 18/06/2013 13:25, Eric Dumazet wrote:
On Tue, 2013-06-18 at 11:58 +0300, Eliezer Tamir wrote:

@@ -731,7 +755,11 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
if (f.file->f_op && f.file->f_op->poll) {
pwait->_key = pollfd->events|POLLERR|POLLHUP;
+ if (try_ll)
+ pwait->_key |= POLL_LL;

Well, why enforce POLL_LL ?

Sure we do this for select() as the API doesn't allow us to add the LL
flag, but poll() can do that.

An application might set POLL_LL flag only on selected fds.

One other thing,
sock_poll() will only ll_poll if the flag was set _and_ the socket has a
none-zero value in sk->sk_ll_usec so you still only poll on sockets
that were enabled for LLS, not on every socket.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at