On Thu, Apr 25, 2013 at 02:10:36PM +0000, Myklebust, Trond wrote: > On Thu, 2013-04-25 at 09:49 -0400, bfields@xxxxxxxxxxxx wrote: > > On Thu, Apr 25, 2013 at 01:30:58PM +0000, Myklebust, Trond wrote: > > > On Thu, 2013-04-25 at 09:29 -0400, bfields@xxxxxxxxxxxx wrote: > > > > > > > My position is that we simply have no idea what order of magnitude even > > > > delay should be. And that in such a situation exponential backoff such > > > > as implemented in the synchronous case seems the reasonable default as > > > > it guarantees at worst doubling the delay while still bounding the > > > > long-term average frequency of retries. > > > > > > So we start with a 15 second delay, and then go to 60 seconds? > > > > I agree that a server should normally be doing the wait on its own if > > the wait would be on the order of an rpc round trip. > > > > So I'd be inclined to start with a delay that was an order of magnitude > > or two more than a round trip. > > > > And I'd expect NFS isn't common on networks with 1-second latencies. > > > > So the 1/10 second we're using in the synchronous case sounds closer to > > the right ballpark to me. > > OK, then. Now all I need is actual motivation for changing the existing > code other than handwaving arguments about "polling is better than flat > waits". > What actual use cases are impacting us now, other than the AIX design > decision to force CLOSE to retry at least once before succeeding? Nah, I've got nothing, and I agree that the AIX problem is there bug. Just for fun I looked at re-checked the Linux server cases. As far as I can tell they are: - delegations: returned immediately on detection of any conflict. The current behavior in the sync case looks reasonable to me. - allocation failures: not really sure it's the best error, but it seems to be all the protocol offers. We probably don't care much what the client does in this case. - some rare cases that would probably indicate bugs (e.g., attempting to destroy a client while other rpc's from that client are running.) Again we don't care what the client does here. - the 4.1 slot-inuse case. We also by default map four errors (ETIMEDOUT, EAGAIN, EWOULDBLOCK, ENOMEM) to delay. I thought I remembered one of those being used by some HFS system, but can't actually find an example now. A quick grep doesn't show anything interesting. --b. -- 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
