From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: long latency of domain shutdown Date: Wed, 14 May 2008 17:08:58 +0100 Message-ID: References: <482B273B.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <482B273B.76E4.0078.0@novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 14/5/08 16:54, "Jan Beulich" wrote: > I'm afraid that's not the case - after they are now using the domain > shutdown fix successfully, they upgraded the machine to 64G and > the system fails to boot. Sounds exactly like other reports we had on > the list regarding boot failures with lots of memory that can be avoided > using dom0_mem=. As I understand it, this is > due to the way the kernel creates its 1:1 mapping - the hypervisor has > to validate the whole tree from each L4 entry being installed in a single > step - for a 4G machine I measured half a second for this operation, so > obviously anything beyond 32G is open for problems when the PM timer > is in use. Hmm, yes that makes sense. 32GB is 8M ptes, so I could imagine that taking a while to validate. Anyhow this obviously needs fixing regardless of the specific details of this specific failure case. > Unless you tell me that this is on your very short term agenda to work on, > I'll make an attempt at finding a reasonable solution starting tomorrow. Yes, I'll sort this one out hopefully by next week. I think this can be solved pretty straightforwardly. It's the encoding of the continuation into the page_info structure, and synchronisation of that, that needs some back-of-envelope thought. As long as there are not too many callers of {get,put}_page_type(L{2,3,4}_pagetable), and I don't think we have that many, then the changes should be pretty localised. Only those callers have to deal with 'EAGAIN' (or equivalent). -- Keir