Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:36105 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751829Ab2HRLN6 (ORCPT ); Sat, 18 Aug 2012 07:13:58 -0400 Date: Sat, 18 Aug 2012 07:13:54 -0400 From: "J. Bruce Fields" To: Michael Tokarev Cc: "Myklebust, Trond" , "linux-nfs@vger.kernel.org" , Linux-kernel , Eric Dumazet Subject: Re: 3.0+ NFS issues (bisected) Message-ID: <20120818111354.GA16611@fieldses.org> References: <20120817145616.GC11172@fieldses.org> <20120817160057.GE11172@fieldses.org> <502E7B86.3060702@msgid.tls.msk.ru> <20120817171854.GA14015@fieldses.org> <502E7EC3.5030006@msgid.tls.msk.ru> <502E7F84.3060003@msgid.tls.msk.ru> <20120817191800.GA14620@fieldses.org> <20120817200807.GB14620@fieldses.org> <20120817223253.GA15659@fieldses.org> <502F3AFB.4080401@msgid.tls.msk.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <502F3AFB.4080401@msgid.tls.msk.ru> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sat, Aug 18, 2012 at 10:49:31AM +0400, Michael Tokarev wrote: > On 18.08.2012 02:32, J. Bruce Fields wrote: > > On Fri, Aug 17, 2012 at 04:08:07PM -0400, J. Bruce Fields wrote: > >> Wait a minute, that assumption's a problem because that calculation > >> depends in part on xpt_reserved, which is changed here.... > >> > >> In particular, svc_xprt_release() calls svc_reserve(rqstp, 0), which > >> subtracts rqstp->rq_reserved and then calls svc_xprt_enqueue, now with a > >> lower xpt_reserved value. That could well explain this. > > > > So, maybe something like this? > > Well. What can I say? With the change below applied (to 3.2 kernel > at least), I don't see any stalls or high CPU usage on the server > anymore. It survived several multi-gigabyte transfers, for several > hours, without any problem. So it is a good step forward ;) > > But the whole thing seems to be quite a bit fragile. I tried to follow > the logic in there, and the thing is quite a bit, well, "twisted", and > somewhat difficult to follow. So I don't know if this is the right > fix or not. At least it works! :) Suggestions welcomed. > And I really wonder why no one else reported this problem before. > Is me the only one in this world who uses linux nfsd? :) This, for example: http://marc.info/?l=linux-nfs&m=134131915612287&w=2 may well describe the same problem.... It just needed some debugging persistence, thanks! --b.