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] failed to start centos 5 domU with maxmem=30000

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] failed to start centos 5 domU with maxmem=30000
From: Vasiliy G Tolstov <v.tolstov@xxxxxxxxx>
Date: Fri, 13 Aug 2010 09:54:57 +0400
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Thu, 12 Aug 2010 22:57:14 -0700
Dkim-signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=selfip.ru; s=dk; h=Content-Transfer-Encoding:Mime-Version:Message-ID:Date:Content-Type:References:In-Reply-To:Cc:To:Reply-To:From:Subject; bh=vsJf5kyiNEN+PbIkhj/urOLbml8+F5iZMWaweLO1f6s=; b=jUfMYhN0q0LzRV70VoR6339czWL5B8aZoGmA//5Jync+m404AtSUChzq2y4jEcovSqkOfEyW7P6+ZouvvbwLyVO/25WMZPv7rSx5fCH4hBi3DjAUSJgi6+HnF8A0vHRU;
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4C643EA2.1020300@xxxxxxxx>
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>
Organization: Selfip.Ru
References: <1281608645.5454.10.camel@xxxxxxxxx> <20100812113731.GP2804@xxxxxxxxxxx 1281613063.5454.15.camel@xxxxxxxxx> <042d87c1-bb13-436b-a5ba-9ec1578d53d0@default> <1281615845.5454.20.camel@xxxxxxxxx> <4C643EA2.1020300@xxxxxxxx>
Reply-to: v.tolstov@xxxxxxxxx
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
В Чтв, 12/08/2010 в 11:34 -0700, Jeremy Fitzhardinge пишет:
> On 08/12/2010 05:24 AM, Vasiliy G Tolstov wrote:
> > В Чтв, 12/08/2010 в 05:17 -0700, Dan Magenheimer пишет:
> >>> From: Vasiliy G Tolstov [mailto:v.tolstov@xxxxxxxxx]
> >>> Sent: Thursday, August 12, 2010 5:38 AM
> >>> To: Pasi Kärkkäinen
> >>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> >>> Subject: Re: [Xen-devel] failed to start centos 5 domU with
> >>> maxmem=30000
> >>>
> >>> В Чтв, 12/08/2010 в 14:37 +0300, Pasi Kärkkäinen пишет:
> >>>> On Thu, Aug 12, 2010 at 02:24:05PM +0400, Vasiliy G Tolstov wrote:
> >>>>> Hello. I'm try to start centos domU pvm under sles 11 sp1 xen
> >>> kernel
> >>>>> with memory=512 and maxmem=30000. Centos doing boot and freeze.
> >>>>> If i'm try to use maxmem=15000 all works.
> >>>>>
> >>>>> Can You tell me what's wrong?
> >>>>>
> >>>> Is the centos PV domU 32bit or 64bit ?
> >>> 64 bit kernel-xen.
> >>>
> >>> I found this in xen sources:
> >>>
> >>> /* Simple continuous piecewiese linear function:
> >>>           *  max MiB ->  min MiB  gradient
> >>>           *       0         0
> >>>           *      16        16
> >>>           *      32        24
> >>>           *     128        72    (1/2)
> >>>           *     512       168    (1/4)
> >>>           *    2048       360    (1/8)
> >>>           *    8192       552    (1/32)
> >>>           *   32768      1320
> >>>           *  131072      4392
> >>>           */
> >>>
> >>> Why this is not provided in documentation or on web site?
> >> Hi Vasily --
> >>
> >> This function limits how far memory can be reduced when
> >> ballooning a guest (including dom0).  It is only a heuristic
> >> but is intended to take into account the various overheads
> >> a guest Linux kernel requires to manage memory to avoid
> >> out-of-memory conditions.
> >>
> >> But I think you are correct... the same (or similar)
> >> function should be published as it also serves as a
> >> guideline for the ratio between memory= and maxmem=
> >> parameters when creating a guest:  If the ratio
> >> of maxmem divided by memory is too high, the guest
> >> will not even boot.
> >>
> > Is that possible to use memory=32 and maxmem=60000 ?
> 
> A factor of ~2000 between smallest and largest size won't work.  The 
> problem is that lots of kernel structures are scaled with the amount of 
> boot-time memory, and they'll simply be overloaded when you add more 
> memory.  For example, the page structure array for 60GB needs ~15.3 
> million entries, which at 64 bytes per entry will take ~980MB...
> 

Ok. Thank You. Bu can some one provide correct ratio for memory and
maxmemory that others not to make mistakes and not try to post bugs on
that? =)

> >> I am curious as to why you would specify memory= so
> >> much smaller than maxmem=.  Are you trying to overcommit
> >> memory for guests that are often idle but sometimes use
> >> a very large amount of memory?
> > We want to provide ability to use small as possible memory if the guest
> > is idle. And much as possible when the guest under heavy load.
> 
> This is exactly the use-case for the hotplug memory stuff Daniel is 
> working on - which I guess is why you've been testing it.

This is problem, because a'm using centos, debian, ubuntu, opensuse and
other systems in domU, but i read that tmem support needed in dom0 and
domU. Debian and Ubuntu i think, does not support this... But i'm try.


-- 
Vasiliy G Tolstov <v.tolstov@xxxxxxxxx>
Selfip.Ru


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