6.2 SHOWSTOPPER - em completely unusable on 6.2

[Jeremy Chadwick]

On Wed, Sep 27, 2006 at 05:28:24PM +0200, Oliver Brandmueller wrote:
> Disk activity does not trigger the problem, I hammered the disk with 
> around 85 MB/s (dd) for about half an hour without seeing any effect. A 
> CPU bound thing like a buildworld triggered the problem.
> 
> The SMBus Interface is not used at all (it's not even really usable). 
> Anyway, as soon as I unload the ichsmb module I cannot triger the 
> problem anymore. If I load it again, the problem cann again be triggered 
> by a buildworld. Statistical relevance: I did 4 buildworlds, alternating 
> the load/unload of ichsmb - both times with ichsmb loaded I saw 3 
> watchdog timeouts during the buildworld was running, while ichsmb was 
> not loaded I did not see a single watchdog timeout. The use of the 
> interface was around the same during all the time (constant NFS traffic 
> of around 1-2 MBit/s).

Interesting find.  For what it's worth -- I too load the appropriate
smbus drivers on the system with the "em0 problem" (loading smbus and
ichsmb).  That system is a single processor / single core system, with
HT disabled in the BIOS (which doesn't matter since FreeBSD disables
it anyways).  Kernel is non-SMP.  Only reason I mention this is:

> The UP/SMP idea seems to be only of interest, because on an UP machine 
> it's more likely to share interrupts than on SMP machines, it has 
> nothing to do with the fact of UP or SMP itself.

-- 
| Jeremy Chadwick                                 jdc at parodius.com |
| Parodius Networking                        http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, USA |
| Making life hard for others since 1977.               PGP: 4BD6C0CB |