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] Memory allocation going seriously wonky on 4.1.1

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: Re: [Xen-devel] Memory allocation going seriously wonky on 4.1.1
From: Anthony Wright <anthony@xxxxxxxxxxxxxxx>
Date: Thu, 06 Oct 2011 15:59:32 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Thu, 06 Oct 2011 08:07:06 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <20111003190917.GF15608@xxxxxxxxxxxxxxxxx>
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: <4E85DB1A.5060606@xxxxxxxxxxxxxxx> <20111001120706.GZ12984@xxxxxxxxxxx> <4E89BC80.4030105@xxxxxxxxxxxxxxx> <20111003190917.GF15608@xxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1
On 03/10/2011 20:09, Konrad Rzeszutek Wilk wrote:
> On Mon, Oct 03, 2011 at 02:45:36PM +0100, Anthony Wright wrote:
>> On 01/10/2011 13:07, Pasi Kärkkäinen wrote:
>>> On Fri, Sep 30, 2011 at 04:07:06PM +0100, Anthony Wright wrote:
>>>> I have a machine with 16GB of RAM running 32 bit xen 4.1.1 with Dom0
>>>> running a 3.0.4 linux kernel and 23 paravirtualized DomUs.
>>>>
>>> Hey,
>>>
>>> Why 32bit Xen? I think all (most?) hypervisor testing happens with 64bit 
>>> Xen.
>>> Note that you can still have 32bit dom0 kernel with 64b hypervisor.
>> I'm going to investigate 64 bit xen on a 32 bit Dom0 soon, but as to the
>> 32 xen, I work quite a lot with older hardware and Xen since it does
>> paravirtualisation, and it's a really good way to re-use old hardware.
>>>> As the free ram gets to 2391 MB free the system behaves as if it's got
>>>> no more ram, and starts grabbing ram from Dom0, before getting even more
>>>> confused and failing to start DomUs and eventually crashing the whole
>>>> machine. I have attached a tarball with the output of xl dmesg, xl info
>>>> & xl list at various points.
>>>>
>>> - Do you use dom0_mem= parameter for Xen? 
>>> - Did you disable dom0 ballooning? 
>>>
>>> http://wiki.xen.org/xenwiki/XenBestPractices
>> I was already using the dom0_mem= parameter on the xen hypervisor, but I
>> disabled dom0 ballooning (enable-dom0-ballooning no), and just for good
>> measure I also set (dom0-min-mem 2000). This had no effect, when I
>> increase the 10-4 memory requirements, on restart the Dom0 memory is
>> reduced to 1713MB and xl info reports 2391MB free.
>>>> Stage 1
>>>> Everything is fine, Dom0 has 2000MB according to xl list, and 'xl info'
>>>> says there is 2405MB free.
>>> - How much memory did dom0 initially have? 
>>> - Did you use mem= parameter for dom0 kernel (vmlinuz) ?
>>>
>>> See: http://wiki.xen.org/xenwiki/Linux_30_bugs
>> dom0 starts with 2000MB.
>> I didn't use mem= on the linux kernel - I thought it wasn't neccessary.
> It is if your kernel does not have these two patches:
>
>     xen: use maximum reservation to limit amount of usable RAM
>     xen/e820: if there is no dom0_mem=, don't tweak extra_pages.
>
> .. oh and you also need to update the hypervisor to include:
> "
>     For dom0, this requires at patch to Xen ('x86: use 'dom0_mem' to limit
>     the number of pages for dom0') (c/s 23790)
> "
>
> Grrr.. Let me update the 3.0 bug-list
>From reading around some of the bug reports, I thought this was a
problem caused by the fact that I have 16GB of ram. As a result I
reduced the amount of physical ram in the machine down to 8GB, but still
got the same effect (with the two kernel patches, but not with the xen
patch as I can't find it). I've attached a log of xl info & xl list as
the domU that trips the machine up is started (10-5). Dom0 is supposed
to have 700MB of ram (dom0_mem=500M), dom0-min-mem is 700 and
enable-dom0-ballooning is no.

Attachment: dom-mem.log
Description: Text document

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel