disadvantages of running 8.3 kernel on freebsd 8.2 system

[Steven Hartland]

----- Original Message ----- 
From: <dteske at freebsd.org>
> But I bet you're not sitting 88 units of Thunderbolt cards that don't work in 8.3.
> 
> 8.3 is also exhibiting major problems with the igb-based NICs on those same 88 units.

Only effects igb init but might want to make sure you have r245334 back ported to
avoid memory leaks when mbuf clusters are exhausted.

8.3 version of the patch attached ;-) 

For reference not only does this prevent the nic initialising properly it can also hang
the boot process as when routing initialises "route" appears to trigger mbuf allocation
with wait and as mbufs are exhaused and not freed correctly this hangs forever.

This will happen on an untuned kernel if more than 2 igb nics are configured as
each igb requires 8k of mbuf clusters (1k per queue x 8 queues on a machine with
8 or more cores) and the default kern.ipc.nmbclusters is only 25600.

For clarity by "configured" I mean if the nic is initialised either by assigning an IP
or "ifconfig igbX up" the queues are not allocated if the nic is present but unused.

    Regards
    Steve

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