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

[Keir Fraser <keir@xen.org>]

On 04/09/2012 09:38, "Jan Beulich" <JBeulich@suse.com> wrote:

>> My pragmatic take would be that: (a) Really long-running handlers that want
>> to dump every page mapping of every domain are pretty bloody stupid, and yes
>> we should consider if they are worthwhile at all; (b) moderately
>> long-running but useful handlers which nonetheless take a long time to dump
>> to Xen's console, I would consider a sysctl to allow dom0 to request dump
>> into a supplied memory buffer.
> 
> At a first glance that sounds like a viable option, assuming that
> the bulk of the time otherwise is being spent actually getting the
> data out through the serial line. But if the long-running-ness is
> in the nature of the keyhandler itself, then this wouldn't help
> much though. And I'd be afraid that ought to be the common
> case when not running with sync_console, since actual serial
> output happens asynchronously and hence shouldn't affect the
> latency of the keyhandler's completion too much.

Well then, have we actually seen problems with async serial output, a
decent-sized serial output buffer, and the 'd'/'0' handlers? Because if not,
we don't have a problem to be solved. :)