Return-Path: Received: from mx2.netapp.com ([216.240.18.37]:30425 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754490Ab0JASaA convert rfc822-to-8bit (ORCPT ); Fri, 1 Oct 2010 14:30:00 -0400 Subject: Re: pNFS DS session Content-Type: text/plain; charset=us-ascii From: Andy Adamson In-Reply-To: <20101001181455.GC32256@fieldses.org> Date: Fri, 1 Oct 2010 14:29:57 -0400 Cc: Marc Eshel , Benny Halevy , Boaz Harrosh , Tigran Mkrtchyan , NFS list , linux-nfs-owner@vger.kernel.org, Fred Isaman Message-Id: <2DE155F2-DCC3-4930-8CAE-D21F26730058@netapp.com> References: <4CA44AAA.4030803@panasas.com> <4CA45462.1070503@desy.de> <4CA455C4.4030705@panasas.com> <4CA57BC6.9030701@desy.de> <4CA5A012.2090404@panasas.com> <4CA5D537.30300@panasas.com> <4CA600F4.2010006@almaden.ibm.com> <20101001171012.GB30570@fieldses.org> <4CA621A4.2040508@almaden.ibm.com> <20101001181455.GC32256@fieldses.org> To: "J. Bruce Fields" Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Oct 1, 2010, at 2:14 PM, J. Bruce Fields wrote: > On Fri, Oct 01, 2010 at 11:00:04AM -0700, Marc Eshel wrote: >> On 10/1/2010 10:10 AM, J. Bruce Fields wrote: >>> On Fri, Oct 01, 2010 at 08:40:36AM -0700, Marc Eshel wrote: >>>> On 10/1/2010 5:33 AM, Benny Halevy wrote: >>>>> On 2010-10-01 10:47, Boaz Harrosh wrote: >>>>>> On 10/01/2010 08:12 AM, Tigran Mkrtchyan wrote: >>>>>>> On 10/01/2010 06:17 AM, Marc Eshel wrote: >>>>>>>> Hi Benny, >>>>>>>> >>>>>>>> Running connectathon I see that some times the clients decides to destroy >>>>>>>> the session with the DS. The test continue and the session is >>>>>>>> re-established. It looks like layout return reduces the hold on device >>>>>>>> info the reduces the hold on the client struct which decide to destroy the >>>>>>>> session. Is that a known problem? >>>>>>>> >>>>>> Yes, I want to emphasize on Marks words: "a known *problem*" >>>>> Marc, assuming the code behaves as expected, does this cause any other badness >>>>> like the GETATTRs you see going out to the DS? >>>>> >>>>> Benny >>>>> >>>> No i don't see any "badness" the test continues without errors and >>>> this problem is not related to the GETATTRs I see on the DS but I >>>> would consider destroying the session in short run of couple of >>>> minutes some times more than one time as something bad. >>> Why? >>> >>> I wouldn't expect session destruction/creation to be *that* expensive. >> >> I assumed that it is inexpensive. We are talking about potential >> destruction/creation of session from every DS for each file IO if >> there is no overlap in holding layouts, right ? > > Well, I guess the tradeoffs aren't obvious to me: if you end up having > to set up an enormous number of sessions (and tcp connections, etc.) all > at once, then I can see why it might be a problem. It would also seem > inefficient to keep around an enormous number of those when they aren't > being used for a while. The plan is to add some code that waits a lease time before destroying an un-referenced deviceid. The next submission patch set will include layoutreturn and the return-on-close code, so it will probably be added then. -->Andy > > --b. > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html