On Mon, Jul 7, 2008 at 2:51 PM, Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> wrote: > On Mon, 2008-07-07 at 14:43 -0400, Chuck Lever wrote: >> On Jul 7, 2008, at 2:20 PM, Trond Myklebust wrote: >> > On Thu, 2008-07-03 at 16:45 -0400, J. Bruce Fields wrote: >> >> On Mon, Jun 30, 2008 at 06:38:35PM -0400, Chuck Lever wrote: >> >>> Hi Trond- >> >>> >> >>> Seven patches that implement kernel RPC service registration via >> >>> rpcbind v4. >> >>> This allows the kernel to advertise IPv4-only services on hosts >> >>> with IPv6 >> >>> addresses, for example. >> >> >> >> This is Trond's baliwick, but I read through all 7 quickly and they >> >> looked good to me.... >> > >> > They look more or less OK to me too, however I'm a bit unhappy about >> > the >> > RPC_TASK_ONESHOT name: it isn't at all descriptive. >> >> Open to suggestions. I thought RPC_TASK_FAIL_WITHOUT_CONNECTION was a >> bit wordy ;-) > > RPC_TASK_CONNECT_ONCE ? That's not the semantic I was really going for. FAIL_ON_CONNRESET is probably closer. >> > I also have questions about the change to a TCP socket here. Why not >> > just implement connected UDP sockets? >> >> Changing rpcb_register() to use a TCP socket is less work overall, and >> we get a positive hand shake between the kernel and user space when >> the TCP connection is opened. >> >> Other services might also want to use TCP+ONESHOT for several short >> requests over a real network with actual packet loss, but they might >> find CUDP+ONESHOT less practical/reliable (or even forbidden in the >> case of NFSv4). So we would end up with something of a one-off >> implementation for rpcb_register. > > I don't see what that has to do with anything: the connection failed > codepath in call_connect_status() should be the same in both the TCP and > the UDP case. If you would like connected UDP, I won't object to you implementing it. However, I never tested whether a connected UDP socket will give the desired semantics without extra code in the UDP transport (for example, an ->sk_error callback). I don't think it's worth the hassle if we have to add code to UDP that only this tiny use case would need. >> The downside of using TCP in this case is that it's more overhead: 8 >> packets instead of two for registration in the common case, and it >> leaves a single privileged port in TIME_WAIT for each registered >> service. I don't think this matters much as registration happens >> quite infrequently. > > The problem is that registration usually happens at boot time, which is > also when most of the NFS 'mount' requests will be eating privileged > ports. You're talking about the difference between supporting say 1358 mounts at boot time versus 1357 mounts at boot time. In most cases, a client with hundreds of mounts will use up exactly one extra privileged TCP port to register NLM during the first lockd_up() call. If these are all NFSv4 mounts, it will use exactly zero extra ports, since the NFSv4 callback service is not even registered. Considering that _each_ mount operation can take between 2 and 5 privileged ports, while registering NFSD and NLM both would take exactly two ports at boot time, I think that registration is wrong place to optimize. -- Chuck Lever -- 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
