WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Re: new netfront and occasional receive path lockup

To: Gerald Turner <gturner@xxxxxxxxxx>
Subject: Re: [Xen-devel] Re: new netfront and occasional receive path lockup
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Sun, 12 Sep 2010 18:55:48 +1000
Cc: "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sun, 12 Sep 2010 01:56:47 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <87aannepx2.fsf@xxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <1282495384.12843.11.camel@xxxxxxxxxxxxxxxxxxxx> <4C73166D.3030000@xxxxxxxx> <D5AB6E638E5A3E4B8F4406B113A5A19A2A44184D@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> <20100909185058.GR2804@xxxxxxxxxxx> <4C8981E5.6010000@xxxxxxxx> <D5AB6E638E5A3E4B8F4406B113A5A19A2A5ED71F@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> <87aannepx2.fsf@xxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.8) Gecko/20100806 Fedora/3.1.2-1.fc13 Lightning/1.0b2pre Thunderbird/3.1.2
 On 09/12/2010 11:00 AM, Gerald Turner wrote:
> I examined the Debian linux-image-2.6.32-5-xen-amd64 package and
> confirmed the netfront driver is patched with an earlier version the
> smartpoll code.
>
> I manually merged Debian's kernel with Jeremy's updates to the netfront
> driver in his git repository.
>
>   $ git diff 
> 5473680bdedb7a62e641970119e6e9381a8d80f4..3b966565a89659f938a4fd662c8475f0c00e0606
>
> Deployed this new image on all domU's (except for two of them, as a
> control group) and updated grub kernel parameter with
> xen_netfront.use_smartpoll=0.

That's good to hear.  But I also included a fix from Dongxiao which, if
correct, means it should work with use_smartpoll=1 (or nothing, as
that's the default).  Could you verify whether the fix in
cb09635065163a933d0d00d077ddd9f0c0a908a1 does actually work or not?

> Problem solved.  Only the two domU's I left unpatched get victimized.
> The rest of the hosts have been up for over a day and have not lost any
> packets.
>
> P.S. this is my first NNTP post thru gmane, I have no idea if it will
> reach the list, keep Message-Id/References intact, and CC Christophe,
> Jeremy, Dongxiao et al.

There were no cc:s.

Thanks,
    J

>
>> Jeremy Fitzhardinge wrote:
>>>  On 09/10/2010 04:50 AM, Pasi Kärkkäinen wrote:
>>>> On Wed, Aug 25, 2010 at 08:51:09AM +0800, Xu, Dongxiao wrote:
>>>>> Hi Christophe,
>>>>>
>>>>> Thanks for finding and checking the problem.
>>>>> I will try to reproduce the issue and check what caused the
>>>>> problem.
>>>>>
>>>> Hello,
>>>>
>>>> Was this issue resolved? Some users have been complaining "network
>>>> freezing up" issues recently on ##xen on irc..
>>> Yeah, I'll add a command-line parameter to disable smartpoll (and
>>> leave it off by default).
>>>
>>>     J
>>>
>>>> -- Pasi
>>>>
>>>>> Thanks,
>>>>> Dongxiao
>>>>>
>>>>> Jeremy Fitzhardinge wrote:
>>>>>>  On 08/22/2010 09:43 AM, Christophe Saout wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I've been playing with some of the new pvops code, namely DomU
>>>>>>> guest code.  What I've been observing on one of the virtual
>>>>>>> machines is that the network (vif) is dying after about ten to
>>>>>>> sixty minutes of uptime. The unfortunate thing here is that I can
>>>>>>> only repoduce it on a production VM and have been unlucky so far
>>>>>>> to trigger the bug on a test machine.  While this has not been
>>>>>>> tragic - rebooting fixed the issue, unfortunately I can't spend
>>>>>>> very much time on debugging after the issue pops up.
>>>>>> Ah, OK.  I've seen this a couple of times as well.  And it just
>>>>>> happened to me then...
>>>>>>
>>>>>>
>>>>>>> Now, what is happening is that the receive path goes dead.  The
>>>>>>> DomU can send packets to Dom0 and those are visible using tcpdump
>>>>>>> on the Dom0 on the virtual interface, but not the other way
>>>>>>> around.
>>>>>> I hadn't got to that level of diagnosis, but I can confirm that
>>>>>> that's what seems to be happening here too.
>>>>>>
>>>>>>> Now, I have done more than one change at a time (I'd like to
>>>>>>> avoid going into pinning it down since I can only reproduce it on
>>>>>>> a production machine, as I said, so suggestions are welcome), but
>>>>>>> my suspicion is that it might have to do with the new "smart
>>>>>>> polling" feature in xen/netfront.  Note that I have also updated
>>>>>>> Dom0 to pull in the latest dom0/backend and netback changes, just
>>>>>>> to make sure it's not due to an issue that has been fixed there,
>>>>>>> but I'm still seeing the same.
>>>>>> I agree.  I think I started seeing this once I merged smartpoll
>>>>>> into netfront.
>>>>>>
>>>>>>     J
>>>>>>
>>>>>>> The production machine is a machine that doesn't have much
>>>>>>> network load, but deals with a lot of small network requests (DNS
>>>>>>> and smtp mostly).  A workload which is hard to reproduce on the
>>>>>>> test machine. Heavy network load (NFS, FTP and so on) for days
>>>>>>> hasn't triggered the problem.  Also, segmentation offloading and
>>>>>>> similar settings don't have any effect.
>>>>>>>
>>>>>>> The machine has 2 physical and the VM 2 virtual CPUs, DomU has
>>>>>>> PREEMPT enabled.
>>>>>>>
>>>>>>> I've been looking at the code, if there might be a race condition
>>>>>>> somewhere, something like where one could run into a situation
>>>>>>> where the hrtimer doesn't run and Dom0 believes the DomU should
>>>>>>> be polling and doesn't emit an interrupt or something, but I'm
>>>>>>> afraid I don't know enough to judge this (I mean, there are
>>>>>>> spinlocks which look safe to me).
>>>>>>>
>>>>>>> Do you have any suggestions what to try?  I can trigger the issue
>>>>>>> on the production VM again, but debugging should not take more
>>>>>>> than a few minutes if it happens.  Access is only possible via
>>>>>>> the console. Neither Dom0 nor the guest show anything unusual in
>>>>>>> the kernel message and continue to behave normally after the
>>>>>>> network goes dead (also able to shut down the guest normally).
>>>>>>>


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>