[CentOS-virt] NIC Stability Problems Under Xen 4.4 / CentOS 6 / Linux 3.18


xlord.sl at gmail.com
Sun Feb 12 04:08:08 UTC 2017

Kevin Stange,
Good attempt, jumbo frame is extremely important if hosting for IaaS, not to
mention other provider who need feather for network specific application.

-----Original Message-----
From: CentOS-virt [mailto:centos-virt-bounces at centos.org] On Behalf Of Kevin
Sent: Saturday, February 11, 2017 3:30 AM
To: centos-virt at centos.org
Subject: Re: [CentOS-virt] NIC Stability Problems Under Xen 4.4 / CentOS 6 /
Linux 3.18

On 01/30/2017 06:41 PM, Kevin Stange wrote:
> On 01/30/2017 06:12 PM, Adi Pircalabu wrote:
>> On 31/01/17 10:49, Kevin Stange wrote:
>>> You said 3.x kernels specifically. The kernel on Xen Made Easy now 
>>> is a
>>> 4.4 kernel.  Any chance you have tested with that one?
>> Not yet, however the future Xen nodes we'll deploy will run CentOS 7 
>> and Xen with kernel 4.4.
> I'll keep you (and others here) posted on my own experiences with that
> 4.4 build over the next few weeks to report on any issues.  I'm hoping 
> something happened between 3.18 and 4.4 that fixed underlying problems.
>>> Did you ever try without MTU=9000 (default 1500 instead)?
>> Yes, also with all sorts of configuration combinations like LACP rate 
>> slow/fast, "options ixgbe LRO=0,0" and so on. No improvement.
> Alright, I'll assume that probably won't help then.  I tried it on one 
> box which hasn't had the issue again yet, but that doesn't guarantee 
> anything.

I was able to discover something new, which might not conclusively prove
anything, but it at least seems to rule out the pci=nomsi kernel option from
being effective.

I had one server booted with that option as well as MTU 1500.  It was stable
for quite a long time, so I decided to try turning the MTU back to 9000 and
within 12 hours, the interface on the expansion NIC with the jumbo MTU

The other NIC in the LACP bundle is onboard and didn't fail.  The other NIC
on the dual-port expansion card also didn't fail.  This leads me to believe
that ONE of the bugs I'm experiencing is related to 82575EB + jumbo frames.

I still think I'm also having a PCI-e issue that is separate and additional
on top of that, and which has not reared its head recently, making it
difficult for me to gather any new data.

One of the things I've done that seemed to help a lot with stability was
balance the LACP so that one NIC from onboard and one NIC from expansion
card is in each LAG.  Previously we just had the first LAG onboard and the
second on the expansion card.  This way, at least, given the expansion NIC's
propensity toward failing first, I don't have to crash the server and all
running VMs to recover.

I've seen absolutely no issues yet with the 4.4 kernel either, but I am not
willing to call that a win because of the quiet from even the servers on
which no tweaks have been applied yet.

I will continue the story as I have more material! :)

Kevin Stange
Chief Technology Officer
Steadfast | Managed Infrastructure, Datacenter and Cloud Services
800 S Wells, Suite 190 | Chicago, IL 60607
312.602.2689 X203 | Fax: 312.602.2688
kevin at steadfast.net | www.steadfast.net
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