Re: [E1000-devel] Bringing down igb interface causes 200ms latency in unrelated processes

[Rustad, M. D <mar...@in...>]

On Mar 26, 2014, at 10:24 AM, Aaron Brice <aar...@gm...> wrote:

> On Tue, Mar 25, 2014 at 10:39 PM, Ronciak, John <joh...@in...> wrote:
>> How are the different PCIe slots connected into the system?  In a lot of cases some of the slots are not all equal in terms of how they are laid out in the system.  If you move the interface doing the 20ms read to a NIC in a different slot does the behavior change?  Does the i/f on the m/b if used for the 20ms read work correctly?
> 
> The odd part is that the process doing the 20ms read is reading from a
> virtual tap interface (/dev/net/tun) and not from one of the NICs.  It
> seems like bringing down the igb interface is causing some system
> level lock at least for network I/O?
> 
> Aaron

That sounds like the rtnl lock to me. Are you doing ioctls on the tap interface at that time? I believe that the ioctls will take the rtnl lock, which is likely to delay things for you.

-- 
Mark Rustad, Networking Division, Intel Corporation