Re: [PATCH] NFSv4: Use exponential backoff delay for NFS4_ERRDELAY

From: bfields@xxxxxxxxxxxx
Date: Thu Apr 25 2013 - 09:49:30 EST

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.

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