From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: Using debug-key 'o: Dump IOMMU p2m table, locks up machine Date: Tue, 04 Sep 2012 09:54:02 +0100 Message-ID: References: <5045DA360200007800098688@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5045DA360200007800098688@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich , George Dunlap Cc: wei.wang2@amd.com, Sander Eikelenboom , Santosh Jodh , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 04/09/2012 09:38, "Jan Beulich" 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. :)