On Apr 21, 2015, at 10:10 , Gareth Wyn Roberts <[email protected]> 
wrote:
> This may be caused by DMA alignment problems.
> See 
> https://docs.freebsd.org/cgi/getmsg.cgi?fetch=145859+0+archive/2015/freebsd-stable/20150419.freebsd-stable
>  for a recent thread about the msk driver.  The msk maintainer Yonghyeon Pyun 
> has opted for super safe options of 32K alignment!
> 
> It's a long shot, but you could try increasing BCE_DMA_ALIGN and/or 
> BCE_RX_BUF_ALIGN in the include file if_bcereg.h, say up to 4096, to see 
> whether it makes any difference.

  Well, after making that change, I was able to confirm that the problem 
doesn't seem to occur.  However, in trying to verify the problem on an 
unmodified kernel, I've rebooted a GENERIC from r281672 without that change, 
and am also not seeing the problem.  :-/  I'm not sure whether the gremlins 
have "fixed" something, or if I was just too critical in my initial analysis.

  For now I'll take that change out of my tree and run without it.  If I see 
the flapping again, I'll confirm that it's repeatable, then change the 
alignments as suggested and see if I see a change.

  Thanks all...

                                         - Chris

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