em driver regression

[Pyun YongHyeon]

On Fri, Apr 09, 2010 at 09:17:07AM -0400, Mike Tancsa wrote:
> At 07:07 PM 4/8/2010, Pyun YongHyeon wrote:
> >On Thu, Apr 08, 2010 at 02:06:09PM -0700, Jack Vogel wrote:
> >> Only one device support by em does multiqueue right now, and that is
> >> Hartwell, 82574.
> >>
> >
> >Thanks for the info.
> >
> >Mike, here is updated patch. Now UDP bulk TX transfer performance
> >recovered a lot(about 890Mbps) but it still shows bad numbers
> >compared to other controllers. For example, bce(4) shows about
> >958Mbps for the same load.
> >During the testing I found a strong indication of packet reordering
> >issue of drbr interface. If I forcibly change to use single TX
> >queue, em(4) got 950Mbps as it used to be.
> >
> >Jack, as we talked about possible drbr issue with igb(4), UDP
> >transfer seems to suffer from packet reordering issue here. Can we
> >make em(4)/igb(4) use single TX queue until we solve drbr interface
> >issue? Given that only one em(4) controller supports multiqueue,
> >dropping multiqueue support for em(4) does not look bad to me.
> 
> No watchdog errors over night. I wonder if the issue was due to 
> 100Mb, or the patch from current fixed it.  I will try today with the 
> new patch below! I am guessing the rejection was due to the RX/TX fix ?
> 

The patch was generated against latest HEAD. This includes Jack's
latest fix too so it may not be applied cleanly on stable/8.
I think you can use em(4) in HEAD.