On Mon, 2008-04-21 at 13:31 -0400, Chuck Lever wrote: > Hi Trond- > > On Apr 19, 2008, at 4:40 PM, Trond Myklebust wrote: > > The rest of the networking layer uses SOCK_ASYNC_NOSPACE to signal > > whether > > or not we have someone waiting for buffer memory. Convert the SUNRPC > > layer > > to use the same idiom. > > As near as I can tell, SOCK_NOSPACE is used for this purpose. It > really isn't clear what SOCK_ASYNC_NOSPACE is used for. See sock_wake_async(): The SOCK_ASYNC_NOSPACE flag basically turns on and off the mechanism for notifying userland that the socket send congestion is over. > In fact I found at least one comment that suggested these flags > currently may be used inconsistently in the network layer. Did you > happen to find any unambiguous documentation explaining how the > network layer uses these flags? (I for one would like to understand > this better). > > I'm a little concerned about this patch overall because the > SOCK_NOSPACE flags interface is well understood by only a handful of > people in the universe, so it's difficult for us networking outsiders > to evaluate this patch. See net/ipv4/tcp_input.c:tcp_cwnd_application_limited(). The SOCK_NOSPACE flag is used to notify the code that regulates the TCP congestion window that the application hit the sndbuf limit. It is normally supposed to be cleared in sk_stream_write_space() if and only if we're below the low waterline for the sndbuf. Cheers Trond -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@xxxxxxxxxx www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
