On 02/18/2014 02:39 PM, Matthew Garrett wrote:
> On Tue, Feb 18, 2014 at 02:28:55PM -0500, Prarit Bhargava wrote:
> 
>> The problem is that we've seen users (especially those using clusters) who do
>> not want ipmi built in.  Their systems generate a tonne of ipmi traffic on 
>> their
>> systems which they want to ignore.  Building IPMI into the kernel results in
>> situations where processing these messages causes kipmi to climb to 100% for
>> long periods of time.
> 
> If the system firmware is sending messages then the default assumption 
> ought to be that it's doing so for a reason.

It is -- it's likely sending health or power information back to the BMC.  But
that's not the issue.  Clusters (and others) don't care about the BMC on a
particular system so they disable IPMI.

> 
>> Maybe that can be solved through an 'ipmi=off' option, or maybe off should be
>> the default state for handling of these messages?
> 
> You can disable the various ipmi_si probings via the tryacpi, trydmi and 
> so on options.

That's not intuitive.  The current options are awful; one has to specify three
kernel parameters IIRC.  Keep it simple with "ipmi=off", and maybe a /sys
variable to do it at runtime as well (although ... maybe the ipmi_si module
parameters are available already?).

> 
>> In any case, I think you're going down the right path here by building this 
>> into
>> the kernel but IMO there's still some upstream work to do so that we don't 
>> hit
>> users with 100% kipmi usage and no way of avoiding it.
> 
> Sending enough traffic to keep kipmid at 100% for extended periods of 
> time implies that there's a *lot* of traffic appearing. What's sending 
> it, and why? 

From the reports I've gathered, which are all from users *who don't want IPMI
active on their systems*, it is some sort of health and power data about the
system and the cluster.  (I'm sure that's a ELI5 to me specifically BTW ;))

What kind of responses are expected?

I'm not sure, TBH.  I don't think it really matters at the point that there is a
huge amount of traffic.  I think the BMC is responding FWIW but the issue is
that the amount of traffic overwhelms the system.

Is the fact that we're
> sending nothing back upsetting it?
> 

I don't get that from the reports I've seen.  I think the issue is that there is
just a huge volume of traffic on these systems.  Googling for "centos kipmi
100%" has a lot of hits; we seemingly made a bad choice when we built in IPMI.
There is a glimmer of hope we can switch back to modular in RHEL.

P.

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