Paul Armor wrote:

> Hi,
>
> On Mon, 27 Mar 2006, Albert Chu wrote:
>
>> Hi Paul,
>>
>>> I'd enabled hardware flow control (as Steffen Grunewald had described
>>> on the ipmitool list, thanks Steffen!)
>>
>>
>> I can't remember the exact kernel internals logic/reason, but I believe
>> if hardware flow control is turned on, the kernel will spin(?) (atleast
>> eat up a lot of cycles) waiting for the ability to dump data out the
>> console.  We've only seen this with normal serial connections, but it
>> wouldn't surprise me if the same applied for SOL.
>
>
> While re-running this, via top I do see kipmi0 using ~1% - 7% (yes,
> not a good metric ;-)), but that's about it.  The machine is otherwise
> as snappy as usual.

This really doesn't have anything to do with SOL, this is just the IPMI
driver normal processing.  You don't need the IPMI driver installed to
use SOL.  A larger number here probably means that the BMC is busy
(kipmi basically spins while IPMI operations are in progress, though is
it the lowest priority task possible, so it would spin more if the BMC
was slower).

>
>> If the above case happend, it would suggest ipmitool wasn't capable of
>> handling the SOL traffic quickly enough.  That's unlikely.  But as you
>> said, perhaps things haven't been stress tested.
>
>
> I'm not sure... one thing about these BMC's is that they use what I
> think to be ridiculously small packets (with my test, 144B)... in fact
> a simple test shows that they'll only respond to pings of <= 302B.

Don't forget that most BMCs are generally underpowered microcontrollers
and aren't capable of much.

If you want to try some stress tests, openipmi 2.0 has SOL library
access (even from perl and python).

-Corey


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