Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:52548 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932257Ab3DYNtY (ORCPT ); Thu, 25 Apr 2013 09:49:24 -0400 Date: Thu, 25 Apr 2013 09:49:18 -0400 From: "bfields@fieldses.org" To: "Myklebust, Trond" Cc: David Wysochanski , Dave Chiluk , "linux-nfs@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] NFSv4: Use exponential backoff delay for NFS4_ERRDELAY Message-ID: <20130425134918.GC31851@fieldses.org> References: <1366836949-18465-1-git-send-email-chiluk@canonical.com> <1366838926.22397.25.camel@leira.trondhjem.org> <5178549A.7010402@canonical.com> <1366842905.22397.49.camel@leira.trondhjem.org> <1366892374.26249.294.camel@localhost.localdomain> <20130425132907.GB31851@fieldses.org> <1366896654.4719.18.camel@leira.trondhjem.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1366896654.4719.18.camel@leira.trondhjem.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Apr 25, 2013 at 01:30:58PM +0000, Myklebust, Trond wrote: > On Thu, 2013-04-25 at 09:29 -0400, bfields@fieldses.org 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. --b.