Re: Using debug-key 'o: Dump IOMMU p2m table, locks up machine

[Keir Fraser <keir.xen@gmail.com>]

On 04/09/2012 07:35, "Jan Beulich" <JBeulich@suse.com> wrote:

>>>> On 02.09.12 at 09:42, Keir Fraser <keir.xen@gmail.com> wrote:
>> On 31/08/2012 22:45, "Sander Eikelenboom" <linux@eikelenboom.it> wrote:
>>> - When using serial console: I get a infinite stream of "gfn:  mfn: " lines,
>>> mean while on the normal console, S-ATA devices are starting to give errors.
>> 
>> In this case the handler must be running in tasklet context. Not sure why
>> SATA interrupts would be affected as hardirq and softirq work will still be
>> carried out during execution of the keyhandler (the handler voluntarily
>> preempts itself for softirq work).
>> 
>> Would need more investigation. :)
> 
> Isn't that because tasklets (i.e. idle vCPU-s with tasklets active)
> get preferred in the schedulers? Some compensation might be
> needed for the penalized vCPU, at least if that one is pinned
> (not sure whether load balancing would be able to steal the
> head of the run queue from a remote CPU). Sander - are you
> by chance pinning Dom0 vCPU-s? And how many of them does
> your Dom0 have?

Jan, Yes you could be right, if Sander is pinning CPUs. Anyway, I wasn't
going to expend too much brain power on this situation. The case of spending
a few minutes in one key handler is not one I think is particularly sane.

 -- Keir

> Jan
>