em network issues

[Scott Long]

Bill Paul wrote:
> [Charset ISO-8859-1 unsupported, filtering to ASCII...]
> 
>>On 10/19/06, Kris Kennaway <kris at obsecurity.org> wrote:
>>
>>>On Thu, Oct 19, 2006 at 02:18:13PM -0700, Jack Vogel wrote:
>>>
>>>>The engineer in our test group has installed 6.2 BETA2 and attempted via a
>>>>number of tests to reproduce this problem, the machine even shares the em
>>>>interrupt with usb, and yet so far he has been unsuccessful.
>>>
>>>What tests is he running?
>>
>>He tried doing something Kip said reliably repro'd the issue, building a big
>>source archive over NFS. Then he has been running a continuous NFS data
>>back and forth copy since, that is still ongoing.
>>
>>Other suggestions?
>>
>>Jack
>>
> 
> 
> Just out of curiosity, what sort of torture tests does Intel do, in
> general, on the em driver on FreeBSD? One thing that I've found which
> works wonders at exposing race conditions is the Smartbits bi-directional
> IP forwarding test. Put two NICs in a system, configure for it for IP
> forwarding, then connect the Smartbits to each port and run the
> SmartApps router test in bi-directional mode. At 64 bytes per frame,
> it will try to push 2.96 million packets/second through both ports
> simultaneously (1.48 million in each direction). Of course, you won't
> actually be able to forward all the traffic, but the interfaces (not
> to mention the OS) should continue running regardless.
> 
> This test exercises both the RX and TX paths and generates hundreds of
> thousands of interrupts per second. You'd be amazed at the sort of
> things you can discover with it. The downside of course is that a
> Smartbits with gigE ports isn't cheap, but I'd be surprised if Intel
> didn't have one kicking around somewhere.
> 
> -Bill
> 

This is exactly the test that Andre and I were running, though only in
one direction (I think due to lack of hardware for a full test).
Prior to the INTR_FAST change, the machine would live-lock.  Now it
survives, stays responsive, and drops packets as needed.

Scott