WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

RE: [Xen-devel] pre-reservation of memory for domain creation

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] pre-reservation of memory for domain creation
From: "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>
Date: Wed, 13 Jan 2010 10:34:11 +0800
Accept-language: en-US
Acceptlanguage: en-US
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Tue, 12 Jan 2010 18:35:30 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4B4CAEB9020000780002969A@xxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <4B4CA40C0200007800029657@xxxxxxxxxxxxxxxxxx> <C7724B76.6265%keir.fraser@xxxxxxxxxxxxx> <4B4CAEB9020000780002969A@xxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcqTosxswXHRC37ATwK/5dUIfPblxQAVRA4A
Thread-topic: [Xen-devel] pre-reservation of memory for domain creation
If we didn't add this change, as Keir said, Xen will crash during destruction 
of partially-created domain. 
However I didn't noticed the toolstack and shadow_min_acceptable_pages() side 
at that time...
For now, should we adjust the shadow pre-alloc size to match 
shadow_min_acceptable_pages() and modify toolstack accordingly?

Thanks!
Dongxiao

Jan Beulich wrote:
>>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 12.01.10 16:53 >>>
>> On 12/01/2010 15:32, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>> 
>>> Also - how did that fixed amount get determined?
>>> shadow_min_acceptable_pages() says 128 pages per vCPU, but 4Mb
>>> (1024 pages) is not matching this (given that it ought to be fine
>>> for 128 vCPU-s), just as the old value of 1Mb wasn't matching the
>>> supposed need of 32 vCPU-s.
>> 
>> I'm not sure I really believe the toolstack comment. As you say, it
>> wasn't correct before or after the patch we're talking about.
> 
> The tool stack comment was correct before that patch; it isn't now.
> The size in shadow_enable() doesn't match
> shadow_min_acceptable_pages(), but that's all hypervisor code.
> 
> And that's also no answer to the question on where the particular
> value came from (and namely why it being much smaller than what
> shadow_min_acceptable_pages() would determine still isn't going
> to be a problem).
> 
>>> And btw., I think that papering over a Xen crash during
>>> destruction of partially-created domain is rather bad a thing to do.
>> 
>> Depends on whether domain-creation failure at the point it failed --
>> and due to inadequate pre-reservation -- is expected and allowed for
>> by the HVM paging logic.
> 
> So you say it's acceptable for a flaw in the tools (exposed during
> guest creation) to bring down the whole machine?
> 
> Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel