Max. PV and HVM Guests

Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

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Hi,

I have observed that there is a maximum limit to the number of PV or HVM
virtual machines you can start before dom0 hangs or crashes.

For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the 7th
instance. Max I can start is 6 without crashing.

For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start the 4th
instance. Max I can start is 3 without crashing.

I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on Intel
DQ45CB motherboard.

Are the above limits reasonable considering the hardware specifications of
my computer?

I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host operating
system is Fedora 11 Linux x86-64.

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

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Re: Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

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Forgot to mention that each of my linux PV guest has 512 MB memory while
each of my linux HVM guest has 1024 MB memory.

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Sun, Nov 8, 2009 at 7:45 PM, Mr. Teo En Ming (Zhang Enming) <
space.time.universe@gmail.com> wrote:

> Hi,
>
> I have observed that there is a maximum limit to the number of PV or HVM
> virtual machines you can start before dom0 hangs or crashes.
>
> For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the 7th
> instance. Max I can start is 6 without crashing.
>
> For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start the
> 4th instance. Max I can start is 3 without crashing.
>
> I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on Intel
> DQ45CB motherboard.
>
> Are the above limits reasonable considering the hardware specifications of
> my computer?
>
> I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
> 2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host operating
> system is Fedora 11 Linux x86-64.
>
> --
> Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
> Engineering)
> Alma Maters:
> (1) Singapore Polytechnic
> (2) National University of Singapore
> My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
> My Secondary Blog: http://enmingteo.wordpress.com
> My Youtube videos: http://www.youtube.com/user/enmingteo
> Email: space.time.universe@gmail.com
> Mobile Phone (Starhub Prepaid): +65-8369-2618
> Street: Bedok Reservoir Road
> Country: Singapore
>

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Re: Max. PV and HVM Guests

[Moi meme]

Hello,

The maximum is a direct function of the available memory, every new
machine "eats" some memory and when there is no more memory ......
I had some servers (64bits, 2 quad core and 32Gb Ram) running 19 VM,
2003 server, 2000 Server,Fedora, Debian all in 32bits.
In my own system I have tested with upto 10 VMs of 512M each without
breaking the system.

Regards

JP Pozzi

Le dimanche 08 novembre 2009 à 19:45 +0800, Mr. Teo En Ming (Zhang
Enming) a écrit :
> Hi,
> 
> I have observed that there is a maximum limit to the number of PV or
> HVM virtual machines you can start before dom0 hangs or crashes.
> 
> For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the
> 7th instance. Max I can start is 6 without crashing.
> 
> For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start
> the 4th instance. Max I can start is 3 without crashing.
> 
> I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on
> Intel DQ45CB motherboard.
> 
> Are the above limits reasonable considering the hardware
> specifications of my computer?
> 
> I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
> 2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host
> operating system is Fedora 11 Linux x86-64.
> 
> -- 
> Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
> Engineering)
> Alma Maters:
> (1) Singapore Polytechnic
> (2) National University of Singapore
> My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
> My Secondary Blog: http://enmingteo.wordpress.com
> My Youtube videos: http://www.youtube.com/user/enmingteo
> Email: space.time.universe@gmail.com
> Mobile Phone (Starhub Prepaid): +65-8369-2618
> Street: Bedok Reservoir Road
> Country: Singapore
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users

Re: Max. PV and HVM Guests

[Pasi Kärkkäinen]

On Sun, Nov 08, 2009 at 07:45:01PM +0800, Mr. Teo En Ming (Zhang Enming) wrote:
>    Hi,
> 
>    I have observed that there is a maximum limit to the number of PV or HVM
>    virtual machines you can start before dom0 hangs or crashes.
> 
>    For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the 7th
>    instance. Max I can start is 6 without crashing.
> 
>    For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start the
>    4th instance. Max I can start is 3 without crashing.
> 
>    I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on
>    Intel DQ45CB motherboard.
> 
>    Are the above limits reasonable considering the hardware specifications of
>    my computer?
> 
>    I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
>    2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host
>    operating system is Fedora 11 Linux x86-64.
> 

Dom0 or Xen shouldn't crash for starting guests.
Sounds like a bug somewhere.

Any errors/tracebacks? Do you have serial console configured? 

-- Pasi

Re: [Xen-devel] Max. PV and HVM Guests

[Grant McWilliams]

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On Sun, Nov 8, 2009 at 5:50 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote:

> On Sun, Nov 08, 2009 at 07:45:01PM +0800, Mr. Teo En Ming (Zhang Enming)
> wrote:
> >    Hi,
> >
> >    I have observed that there is a maximum limit to the number of PV or
> HVM
> >    virtual machines you can start before dom0 hangs or crashes.
> >
>

Mr. Teo En Ming,
   I have a CentOS 5.3 x86_64 machine with 16GB of ram currently running 41
PV DomUs. Each DomU has 300 MB of ram.  I have to admit weird things do
happen if I decide to start them all at the same time but the machine never
crashes.

Grant

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Re: [Xen-devel] Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

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Yes. I will try to see if there's a traceback.

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Sun, Nov 8, 2009 at 9:50 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:

> On Sun, Nov 08, 2009 at 07:45:01PM +0800, Mr. Teo En Ming (Zhang Enming)
> wrote:
> >    Hi,
> >
> >    I have observed that there is a maximum limit to the number of PV or
> HVM
> >    virtual machines you can start before dom0 hangs or crashes.
> >
> >    For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the
> 7th
> >    instance. Max I can start is 6 without crashing.
> >
> >    For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start
> the
> >    4th instance. Max I can start is 3 without crashing.
> >
> >    I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on
> >    Intel DQ45CB motherboard.
> >
> >    Are the above limits reasonable considering the hardware
> specifications of
> >    my computer?
> >
> >    I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
> >    2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host
> >    operating system is Fedora 11 Linux x86-64.
> >
>
> Dom0 or Xen shouldn't crash for starting guests.
> Sounds like a bug somewhere.
>
> Any errors/tracebacks? Do you have serial console configured?
>
> -- Pasi
>
>

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RE: [Xen-users] Max. PV and HVM Guests

[Robert Dunkley]

There seems to also be a limit imposed by CPU context switching. Ie. Once you have enough VMs trying to grab a cpu core things come to a standstill as the cpu spends most of its time switching rather than processing. The most common bottleneck I find is disk performance but this depends hugely on what your VMs are doing.

-----Original Message-----
From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Moi meme
Sent: 08 November 2009 13:02
To: Mr. Teo En Ming (Zhang Enming)
Cc: xen-devel@lists.xensource.com; xen-users@lists.xensource.com
Subject: Re: [Xen-users] Max. PV and HVM Guests

Hello,

The maximum is a direct function of the available memory, every new
machine "eats" some memory and when there is no more memory ......
I had some servers (64bits, 2 quad core and 32Gb Ram) running 19 VM,
2003 server, 2000 Server,Fedora, Debian all in 32bits.
In my own system I have tested with upto 10 VMs of 512M each without
breaking the system.

Regards

JP Pozzi

Le dimanche 08 novembre 2009 à 19:45 +0800, Mr. Teo En Ming (Zhang
Enming) a écrit :
> Hi,
> 
> I have observed that there is a maximum limit to the number of PV or
> HVM virtual machines you can start before dom0 hangs or crashes.
> 
> For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the
> 7th instance. Max I can start is 6 without crashing.
> 
> For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start
> the 4th instance. Max I can start is 3 without crashing.
> 
> I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on
> Intel DQ45CB motherboard.
> 
> Are the above limits reasonable considering the hardware
> specifications of my computer?
> 
> I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
> 2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host
> operating system is Fedora 11 Linux x86-64.
> 
> -- 
> Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
> Engineering)
> Alma Maters:
> (1) Singapore Polytechnic
> (2) National University of Singapore
> My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
> My Secondary Blog: http://enmingteo.wordpress.com
> My Youtube videos: http://www.youtube.com/user/enmingteo
> Email: space.time.universe@gmail.com
> Mobile Phone (Starhub Prepaid): +65-8369-2618
> Street: Bedok Reservoir Road
> Country: Singapore
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users




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SAQ is the trading name of SEMTEC Limited. Registered in England & Wales
Company Number: 06481952

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Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit : Backups : Managed Networks : Remote Support.

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Re: Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

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Hi,

Please watch this 4-minute video at
http://www.youtube.com/watch?v=LbLaPpwNAx4

I have only started 3 HVM Linux guests with 1 GB ram each. I can't start the
4th HVM guest. If I attempt to start the 4th instance, it will crash dom0.

Are there anything in the xm dmesg output that could explain the low limit
to the number of VMs that I could start before dom0 becomes unresponsive?

Thank you.

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 4:17 PM, Robert Dunkley <Robert@saq.co.uk> wrote:

> There seems to also be a limit imposed by CPU context switching. Ie. Once
> you have enough VMs trying to grab a cpu core things come to a standstill as
> the cpu spends most of its time switching rather than processing. The most
> common bottleneck I find is disk performance but this depends hugely on what
> your VMs are doing.
>
> -----Original Message-----
> From: xen-users-bounces@lists.xensource.com [mailto:
> xen-users-bounces@lists.xensource.com] On Behalf Of Moi meme
> Sent: 08 November 2009 13:02
> To: Mr. Teo En Ming (Zhang Enming)
> Cc: xen-devel@lists.xensource.com; xen-users@lists.xensource.com
> Subject: Re: [Xen-users] Max. PV and HVM Guests
>
> Hello,
>
> The maximum is a direct function of the available memory, every new
> machine "eats" some memory and when there is no more memory ......
> I had some servers (64bits, 2 quad core and 32Gb Ram) running 19 VM,
> 2003 server, 2000 Server,Fedora, Debian all in 32bits.
> In my own system I have tested with upto 10 VMs of 512M each without
> breaking the system.
>
> Regards
>
> JP Pozzi
>
> Le dimanche 08 novembre 2009 à 19:45 +0800, Mr. Teo En Ming (Zhang
> Enming) a écrit :
> > Hi,
> >
> > I have observed that there is a maximum limit to the number of PV or
> > HVM virtual machines you can start before dom0 hangs or crashes.
> >
> > For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the
> > 7th instance. Max I can start is 6 without crashing.
> >
> > For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start
> > the 4th instance. Max I can start is 3 without crashing.
> >
> > I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on
> > Intel DQ45CB motherboard.
> >
> > Are the above limits reasonable considering the hardware
> > specifications of my computer?
> >
> > I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
> > 2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host
> > operating system is Fedora 11 Linux x86-64.
> >
> > --
> > Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
> > Engineering)
> > Alma Maters:
> > (1) Singapore Polytechnic
> > (2) National University of Singapore
> > My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
> > My Secondary Blog: http://enmingteo.wordpress.com
> > My Youtube videos: http://www.youtube.com/user/enmingteo
> > Email: space.time.universe@gmail.com
> > Mobile Phone (Starhub Prepaid): +65-8369-2618
> > Street: Bedok Reservoir Road
> > Country: Singapore
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@lists.xensource.com
> > http://lists.xensource.com/xen-users
>
>
>
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>
> The SAQ Group
>
> Registered Office: 18 Chapel Street, Petersfield, Hampshire GU32 3DZ
> SAQ is the trading name of SEMTEC Limited. Registered in England & Wales
> Company Number: 06481952
>
> http://www.saqnet.co.uk AS29219
>
> SAQ Group Delivers high quality, honestly priced communication and I.T.
> services to UK Business.
>
> Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit :
> Backups : Managed Networks : Remote Support.
>
> ISPA Member
>
>

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Re: Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

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Could it be that my Intel Pentium Dual Core E6300 2.8 GHz processor is not
powerful enough? Maybe need to upgrade to Intel Core 2 Quad?

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 6:52 PM, Mr. Teo En Ming (Zhang Enming) <
space.time.universe@gmail.com> wrote:

> Hi,
>
> Please watch this 4-minute video at
> http://www.youtube.com/watch?v=LbLaPpwNAx4
>
> I have only started 3 HVM Linux guests with 1 GB ram each. I can't start
> the 4th HVM guest. If I attempt to start the 4th instance, it will crash
> dom0.
>
> Are there anything in the xm dmesg output that could explain the low limit
> to the number of VMs that I could start before dom0 becomes unresponsive?
>
> Thank you.
>
>
> --
> Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
> Engineering)
> Alma Maters:
> (1) Singapore Polytechnic
> (2) National University of Singapore
> My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
> My Secondary Blog: http://enmingteo.wordpress.com
> My Youtube videos: http://www.youtube.com/user/enmingteo
> Email: space.time.universe@gmail.com
> Mobile Phone (Starhub Prepaid): +65-8369-2618
> Street: Bedok Reservoir Road
> Country: Singapore
>
> On Mon, Nov 9, 2009 at 4:17 PM, Robert Dunkley <Robert@saq.co.uk> wrote:
>
>> There seems to also be a limit imposed by CPU context switching. Ie. Once
>> you have enough VMs trying to grab a cpu core things come to a standstill as
>> the cpu spends most of its time switching rather than processing. The most
>> common bottleneck I find is disk performance but this depends hugely on what
>> your VMs are doing.
>>
>> -----Original Message-----
>> From: xen-users-bounces@lists.xensource.com [mailto:
>> xen-users-bounces@lists.xensource.com] On Behalf Of Moi meme
>> Sent: 08 November 2009 13:02
>> To: Mr. Teo En Ming (Zhang Enming)
>> Cc: xen-devel@lists.xensource.com; xen-users@lists.xensource.com
>> Subject: Re: [Xen-users] Max. PV and HVM Guests
>>
>> Hello,
>>
>> The maximum is a direct function of the available memory, every new
>> machine "eats" some memory and when there is no more memory ......
>> I had some servers (64bits, 2 quad core and 32Gb Ram) running 19 VM,
>> 2003 server, 2000 Server,Fedora, Debian all in 32bits.
>> In my own system I have tested with upto 10 VMs of 512M each without
>> breaking the system.
>>
>> Regards
>>
>> JP Pozzi
>>
>> Le dimanche 08 novembre 2009 à 19:45 +0800, Mr. Teo En Ming (Zhang
>> Enming) a écrit :
>> > Hi,
>> >
>> > I have observed that there is a maximum limit to the number of PV or
>> > HVM virtual machines you can start before dom0 hangs or crashes.
>> >
>> > For Fedora 11 Linux x86-64 PV guests, dom0 will crash when I start the
>> > 7th instance. Max I can start is 6 without crashing.
>> >
>> > For CentOS 5.2 Linux x86-64 HVM guests, dom0 will crash when I start
>> > the 4th instance. Max I can start is 3 without crashing.
>> >
>> > I have 6 GB of DDR2-800 with Intel Pentium Dual Core E6300 2.8 GHz on
>> > Intel DQ45CB motherboard.
>> >
>> > Are the above limits reasonable considering the hardware
>> > specifications of my computer?
>> >
>> > I am using Xen 3.5-unstable changeset 20143 with pv-ops dom0 kernels
>> > 2.6.30-rc3, 2.6.31-rc6, 2.6.31.1, 2.6.31.4, and 2.6.31.5. My host
>> > operating system is Fedora 11 Linux x86-64.
>> >
>> > --
>> > Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
>> > Engineering)
>> > Alma Maters:
>> > (1) Singapore Polytechnic
>> > (2) National University of Singapore
>> > My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
>> > My Secondary Blog: http://enmingteo.wordpress.com
>> > My Youtube videos: http://www.youtube.com/user/enmingteo
>> > Email: space.time.universe@gmail.com
>> > Mobile Phone (Starhub Prepaid): +65-8369-2618
>> > Street: Bedok Reservoir Road
>> > Country: Singapore
>> > _______________________________________________
>> > Xen-users mailing list
>> > Xen-users@lists.xensource.com
>> > http://lists.xensource.com/xen-users
>>
>>
>>
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@lists.xensource.com
>> http://lists.xensource.com/xen-users
>>
>> The SAQ Group
>>
>> Registered Office: 18 Chapel Street, Petersfield, Hampshire GU32 3DZ
>> SAQ is the trading name of SEMTEC Limited. Registered in England & Wales
>> Company Number: 06481952
>>
>> http://www.saqnet.co.uk AS29219
>>
>> SAQ Group Delivers high quality, honestly priced communication and I.T.
>> services to UK Business.
>>
>> Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit :
>> Backups : Managed Networks : Remote Support.
>>
>> ISPA Member
>>
>>
>
>
>
>

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

Re: [Xen-devel] Re: Max. PV and HVM Guests

[Pasi Kärkkäinen]

On Mon, Nov 09, 2009 at 06:52:37PM +0800, Mr. Teo En Ming (Zhang Enming) wrote:
>    Hi,
> 
>    Please watch this 4-minute video at
>    [1]http://www.youtube.com/watch?v=LbLaPpwNAx4
> 
>    I have only started 3 HVM Linux guests with 1 GB ram each. I can't start
>    the 4th HVM guest. If I attempt to start the 4th instance, it will crash
>    dom0.
> 
>    Are there anything in the xm dmesg output that could explain the low limit
>    to the number of VMs that I could start before dom0 becomes unresponsive?
> 

Have you limited dom0 memory (by specifying dom0_mem=XMB option in
grub.conf for xen.gz) ?

What does "xm info" say about free memory before starting any guests? 

-- Pasi

Re: Re: [Xen-users] Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

[-- Attachment #1.1: Type: text/plain, Size: 2953 bytes --]

No, I didn't limit dom0 memory in grub.conf.

Here's my xm info output after I have shutdown all the virtual machines.

[root@fedora11-x86-64-host ~]# xm list
Name                                        ID   Mem VCPUs      State
Time(s)
Domain-0                                     0  2812     2     r-----
3242.5
[root@fedora11-x86-64-host ~]# xm info
host                   : fedora11-x86-64-host
release                : 2.6.30-rc3-enming.teo-tip
version                : #1 SMP Wed Aug 19 23:14:15 SGT 2009
machine                : x86_64
nr_cpus                : 2
nr_nodes               : 1
cores_per_socket       : 2
threads_per_core       : 1
cpu_mhz                : 2800
hw_caps                :
bfebfbff:20100800:00000000:00000140:0400e3bd:00000000:00000001:00000000
virt_caps              : hvm hvm_directio
total_memory           : 6039
free_memory            : 3124
node_to_cpu            : node0:0-1
node_to_memory         : node0:3124
xen_major              : 3
xen_minor              : 5
xen_extra              : -unstable
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Tue Sep 01 11:34:31 2009 +0100 20143:a7de5bd776ca
xen_commandline        : iommu=1
cc_compiler            : gcc version 4.4.1 20090725 (Red Hat 4.4.1-2) (GCC)
cc_compile_by          : root
cc_compile_domain      : (none)
cc_compile_date        : Thu Sep 10 07:01:13 SGT 2009
xend_config_format     : 4

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 7:54 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:

> On Mon, Nov 09, 2009 at 06:52:37PM +0800, Mr. Teo En Ming (Zhang Enming)
> wrote:
> >    Hi,
> >
> >    Please watch this 4-minute video at
> >    [1]http://www.youtube.com/watch?v=LbLaPpwNAx4
> >
> >    I have only started 3 HVM Linux guests with 1 GB ram each. I can't
> start
> >    the 4th HVM guest. If I attempt to start the 4th instance, it will
> crash
> >    dom0.
> >
> >    Are there anything in the xm dmesg output that could explain the low
> limit
> >    to the number of VMs that I could start before dom0 becomes
> unresponsive?
> >
>
> Have you limited dom0 memory (by specifying dom0_mem=XMB option in
> grub.conf for xen.gz) ?
>
> What does "xm info" say about free memory before starting any guests?
>
> -- Pasi
>
>
>

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

Re: Re: [Xen-users] Max. PV and HVM Guests

[Pasi Kärkkäinen]

On Mon, Nov 09, 2009 at 08:01:00PM +0800, Mr. Teo En Ming (Zhang Enming) wrote:
>    No, I didn't limit dom0 memory in grub.conf.
> 

You should. 

If dom0 has all the memory at boot time, you need to balloon down dom0 
memory every time you create a new guest - this can (and will) cause 
problems with the dom0 linux kernel.

Linux calculates some internal parameters/buffers/values based on the
_boot time_ amount of memory. And when the amount of memory goes down to
only a small fraction of that while creating new guests bad things can
happen..

It still shouldn't crash though.. I bet your problem will get fixed when
you limit the dom0 memory to say dom0_mem=512M and reboot.

-- Pasi

>    Here's my xm info output after I have shutdown all the virtual machines.
> 
>    [root@fedora11-x86-64-host ~]# xm list
>    Name                                        ID   Mem VCPUs      State
>    Time(s)
>    Domain-0                                     0  2812     2     r-----
>    3242.5
>    [root@fedora11-x86-64-host ~]# xm info
>    host                   : fedora11-x86-64-host
>    release                : 2.6.30-rc3-enming.teo-tip
>    version                : #1 SMP Wed Aug 19 23:14:15 SGT 2009
>    machine                : x86_64
>    nr_cpus                : 2
>    nr_nodes               : 1
>    cores_per_socket       : 2
>    threads_per_core       : 1
>    cpu_mhz                : 2800
>    hw_caps                :
>    bfebfbff:20100800:00000000:00000140:0400e3bd:00000000:00000001:00000000
>    virt_caps              : hvm hvm_directio
>    total_memory           : 6039
>    free_memory            : 3124
>    node_to_cpu            : node0:0-1
>    node_to_memory         : node0:3124
>    xen_major              : 3
>    xen_minor              : 5
>    xen_extra              : -unstable
>    xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
>    hvm-3.0-x86_32p hvm-3.0-x86_64
>    xen_scheduler          : credit
>    xen_pagesize           : 4096
>    platform_params        : virt_start=0xffff800000000000
>    xen_changeset          : Tue Sep 01 11:34:31 2009 +0100 20143:a7de5bd776ca
>    xen_commandline        : iommu=1
>    cc_compiler            : gcc version 4.4.1 20090725 (Red Hat 4.4.1-2)
>    (GCC)
>    cc_compile_by          : root
>    cc_compile_domain      : (none)
>    cc_compile_date        : Thu Sep 10 07:01:13 SGT 2009
>    xend_config_format     : 4
> 
>    --
>    Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
>    Engineering)
>    Alma Maters:
>    (1) Singapore Polytechnic
>    (2) National University of Singapore
>    My Primary Blog: [1]http://teo-en-ming-aka-zhang-enming.blogspot.com
>    My Secondary Blog: [2]http://enmingteo.wordpress.com
>    My Youtube videos: [3]http://www.youtube.com/user/enmingteo
>    Email: [4]space.time.universe@gmail.com
>    Mobile Phone (Starhub Prepaid): +65-8369-2618
>    Street: Bedok Reservoir Road
>    Country: Singapore
> 
>    On Mon, Nov 9, 2009 at 7:54 PM, Pasi Kärkkäinen <[5]pasik@iki.fi> wrote:
> 
>      On Mon, Nov 09, 2009 at 06:52:37PM +0800, Mr. Teo En Ming (Zhang Enming)
>      wrote:
>      >    Hi,
>      >
>      >    Please watch this 4-minute video at
>      >    [1][6]http://www.youtube.com/watch?v=LbLaPpwNAx4
>      >
>      >    I have only started 3 HVM Linux guests with 1 GB ram each. I can't
>      start
>      >    the 4th HVM guest. If I attempt to start the 4th instance, it will
>      crash
>      >    dom0.
>      >
>      >    Are there anything in the xm dmesg output that could explain the
>      low limit
>      >    to the number of VMs that I could start before dom0 becomes
>      unresponsive?
>      >
> 
>      Have you limited dom0 memory (by specifying dom0_mem=XMB option in
>      grub.conf for xen.gz) ?
> 
>      What does "xm info" say about free memory before starting any guests?
>      -- Pasi
> 
> References
> 
>    Visible links
>    1. http://teo-en-ming-aka-zhang-enming.blogspot.com/
>    2. http://enmingteo.wordpress.com/
>    3. http://www.youtube.com/user/enmingteo
>    4. mailto:space.time.universe@gmail.com
>    5. mailto:pasik@iki.fi
>    6. http://www.youtube.com/watch?v=LbLaPpwNAx4

Re: Re: [Xen-users] Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

[-- Attachment #1.1: Type: text/plain, Size: 5225 bytes --]

What is a good value for dom0_mem if I want to start X server and run GNOME?
Will 512 MB be too little?

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 8:05 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:

> On Mon, Nov 09, 2009 at 08:01:00PM +0800, Mr. Teo En Ming (Zhang Enming)
> wrote:
> >    No, I didn't limit dom0 memory in grub.conf.
> >
>
> You should.
>
> If dom0 has all the memory at boot time, you need to balloon down dom0
> memory every time you create a new guest - this can (and will) cause
> problems with the dom0 linux kernel.
>
> Linux calculates some internal parameters/buffers/values based on the
> _boot time_ amount of memory. And when the amount of memory goes down to
> only a small fraction of that while creating new guests bad things can
> happen..
>
> It still shouldn't crash though.. I bet your problem will get fixed when
> you limit the dom0 memory to say dom0_mem=512M and reboot.
>
> -- Pasi
>
> >    Here's my xm info output after I have shutdown all the virtual
> machines.
> >
> >    [root@fedora11-x86-64-host ~]# xm list
> >    Name                                        ID   Mem VCPUs      State
> >    Time(s)
> >    Domain-0                                     0  2812     2     r-----
> >    3242.5
> >    [root@fedora11-x86-64-host ~]# xm info
> >    host                   : fedora11-x86-64-host
> >    release                : 2.6.30-rc3-enming.teo-tip
> >    version                : #1 SMP Wed Aug 19 23:14:15 SGT 2009
> >    machine                : x86_64
> >    nr_cpus                : 2
> >    nr_nodes               : 1
> >    cores_per_socket       : 2
> >    threads_per_core       : 1
> >    cpu_mhz                : 2800
> >    hw_caps                :
> >
>  bfebfbff:20100800:00000000:00000140:0400e3bd:00000000:00000001:00000000
> >    virt_caps              : hvm hvm_directio
> >    total_memory           : 6039
> >    free_memory            : 3124
> >    node_to_cpu            : node0:0-1
> >    node_to_memory         : node0:3124
> >    xen_major              : 3
> >    xen_minor              : 5
> >    xen_extra              : -unstable
> >    xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
> >    hvm-3.0-x86_32p hvm-3.0-x86_64
> >    xen_scheduler          : credit
> >    xen_pagesize           : 4096
> >    platform_params        : virt_start=0xffff800000000000
> >    xen_changeset          : Tue Sep 01 11:34:31 2009 +0100
> 20143:a7de5bd776ca
> >    xen_commandline        : iommu=1
> >    cc_compiler            : gcc version 4.4.1 20090725 (Red Hat 4.4.1-2)
> >    (GCC)
> >    cc_compile_by          : root
> >    cc_compile_domain      : (none)
> >    cc_compile_date        : Thu Sep 10 07:01:13 SGT 2009
> >    xend_config_format     : 4
> >
> >    --
> >    Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
> >    Engineering)
> >    Alma Maters:
> >    (1) Singapore Polytechnic
> >    (2) National University of Singapore
> >    My Primary Blog: [1]http://teo-en-ming-aka-zhang-enming.blogspot.com
> >    My Secondary Blog: [2]http://enmingteo.wordpress.com
> >    My Youtube videos: [3]http://www.youtube.com/user/enmingteo
> >    Email: [4]space.time.universe@gmail.com
> >    Mobile Phone (Starhub Prepaid): +65-8369-2618
> >    Street: Bedok Reservoir Road
> >    Country: Singapore
> >
> >    On Mon, Nov 9, 2009 at 7:54 PM, Pasi Kärkkäinen <[5]pasik@iki.fi>
> wrote:
> >
> >      On Mon, Nov 09, 2009 at 06:52:37PM +0800, Mr. Teo En Ming (Zhang
> Enming)
> >      wrote:
> >      >    Hi,
> >      >
> >      >    Please watch this 4-minute video at
> >      >    [1][6]http://www.youtube.com/watch?v=LbLaPpwNAx4
> >      >
> >      >    I have only started 3 HVM Linux guests with 1 GB ram each. I
> can't
> >      start
> >      >    the 4th HVM guest. If I attempt to start the 4th instance, it
> will
> >      crash
> >      >    dom0.
> >      >
> >      >    Are there anything in the xm dmesg output that could explain
> the
> >      low limit
> >      >    to the number of VMs that I could start before dom0 becomes
> >      unresponsive?
> >      >
> >
> >      Have you limited dom0 memory (by specifying dom0_mem=XMB option in
> >      grub.conf for xen.gz) ?
> >
> >      What does "xm info" say about free memory before starting any
> guests?
> >      -- Pasi
> >
> > References
> >
> >    Visible links
> >    1. http://teo-en-ming-aka-zhang-enming.blogspot.com/
> >    2. http://enmingteo.wordpress.com/
> >    3. http://www.youtube.com/user/enmingteo
> >    4. mailto:space.time.universe@gmail.com
> >    5. mailto:pasik@iki.fi
> >    6. http://www.youtube.com/watch?v=LbLaPpwNAx4
>

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

Re: Re: [Xen-users] Max. PV and HVM Guests

[Pasi Kärkkäinen]

On Mon, Nov 09, 2009 at 08:14:27PM +0800, Mr. Teo En Ming (Zhang Enming) wrote:
>    What is a good value for dom0_mem if I want to start X server and run
>    GNOME? Will 512 MB be too little?
> 

Go for 1024 MB then..

-- Pasi

Re: Re: [Xen-users] Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

[-- Attachment #1.1: Type: text/plain, Size: 6094 bytes --]

Great! After setting dom0_mem=1024M, I can start all 5 nodes of my Rocks HPC
cluster without crashing dom0 as compared to the previous limit of 3 nodes
when I did not set dom0_mem.

Thank you Pasi! Another resource problem solved.

Here's my latest grub.conf:

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro
root=/dev/mapper/vg_fedora11_host-lv_root
#          initrd /initrd-version.img
#boot=/dev/sda
default=4
timeout=100
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.31.5-xen-enming.teo)
    root (hd0,0)
#    kernel /vmlinuz-2.6.31.5-xen-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#    initrd /initrd-2.6.31.5-xen-enming.teo.img
    kernel /xen.gz dom0_mem=1024M iommu=1
    module /vmlinuz-2.6.31.5-xen-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
    module /initrd-2.6.31.5-xen-enming.teo.img
title Fedora (2.6.31.4-xen-enming.teo)
    root (hd0,0)
#    kernel /vmlinuz-2.6.31.4-xen-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#    initrd /initrd-2.6.31.4-xen-enming.teo.img
    kernel /xen.gz dom0_mem=1024M iommu=1
    module /vmlinuz-2.6.31.4-xen-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
    module /initrd-2.6.31.4-xen-enming.teo.img
title Fedora (2.6.31.1-xen-enming.teo)
    root (hd0,0)
#    kernel /vmlinuz-2.6.31.1-xen-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#    initrd /initrd-2.6.31.1-xen-enming.teo.img
    kernel /xen.gz dom0_mem=1024M iommu=1
    module /vmlinuz-2.6.31.1-xen-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
    module /initrd-2.6.31.1-xen-enming.teo.img
title Fedora (2.6.31-enming.teo)
    root (hd0,0)
    kernel /vmlinuz-2.6.31-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
    initrd /initrd-2.6.31-enming.teo.img
title Fedora (2.6.30.5-enming.teo)
    root (hd0,0)
    kernel /vmlinuz-2.6.30.5-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
    initrd /initrd-2.6.30.5-enming.teo.img
title Fedora (2.6.18.8-enming.teo)
    root (hd0,0)
#    kernel /vmlinuz-2.6.18.8-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#    initrd /initrd-2.6.18.8-enming.teo.img
    kernel /xen.gz dom0_mem=1024M iommu=1
    module /vmlinuz-2.6.18.8-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root
    module /initrd-2.6.18.8-enming.teo.img
title Fedora (2.6.31-rc6-enming.teo) with Serial Console
        root (hd0,0)
#       kernel /vmlinuz-2.6.31-rc6-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#       initrd /initrd-2.6.31-rc6-enming.teo.img
        kernel /xen.gz dom0_mem=1024M iommu=1 iommu_inclusive_mapping=1
com1=115200,8n1 console=com1
#       module /vmlinuz-2.6.31-rc6-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 xencons=ttyS0
console=ttyS0,115200
    module /vmlinuz-2.6.31-rc6-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 console=hvc0
earlyprintk=xen
        module /initrd-2.6.31-rc6-enming.teo.img
title Fedora (2.6.30-rc3-enming.teo-tip) with Serial Console
        root (hd0,0)
#       kernel /vmlinuz-2.6.30-rc3-enming.teo-tip ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#       initrd /initrd-2.6.30-rc3-enming.teo-tip.img
        kernel /xen.gz dom0_mem=1024M iommu=1 iommu_inclusive_mapping=1
com1=115200,8n1 console=com1
#       module /vmlinuz-2.6.30-rc3-enming.teo-tip ro
root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 xencons=ttyS0
console=ttyS0,115200
    module /vmlinuz-2.6.30-rc3-enming.teo-tip ro
root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 console=hvc0
earlyprintk=xen
        module /initrd-2.6.30-rc3-enming.teo-tip.img

title Fedora (2.6.31-rc6-enming.teo)
    root (hd0,0)
#    kernel /vmlinuz-2.6.31-rc6-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#    initrd /initrd-2.6.31-rc6-enming.teo.img
    kernel /xen.gz dom0_mem=1024M iommu=1
    module /vmlinuz-2.6.31-rc6-enming.teo ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
    module /initrd-2.6.31-rc6-enming.teo.img
title Fedora (2.6.30-rc3-enming.teo-tip)
    root (hd0,0)
#    kernel /vmlinuz-2.6.30-rc3-enming.teo-tip ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
#    initrd /initrd-2.6.30-rc3-enming.teo-tip.img
    kernel /xen.gz dom0_mem=1024M iommu=1
    module /vmlinuz-2.6.30-rc3-enming.teo-tip ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
    module /initrd-2.6.30-rc3-enming.teo-tip.img
title Fedora (2.6.29.4-167.fc11.x86_64)
    root (hd0,0)
    kernel /vmlinuz-2.6.29.4-167.fc11.x86_64 ro
root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
    initrd /initrd-2.6.29.4-167.fc11.x86_64.img

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 8:18 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:

> On Mon, Nov 09, 2009 at 08:14:27PM +0800, Mr. Teo En Ming (Zhang Enming)
> wrote:
> >    What is a good value for dom0_mem if I want to start X server and run
> >    GNOME? Will 512 MB be too little?
> >
>
> Go for 1024 MB then..
>
> -- Pasi
>
>

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Re: [Xen-devel] Re: Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

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Hi All,

I have discovered that setting dom0_mem also solves another problem I am
facing.

Previously I have complained that, after starting a HVM guest, in any pv-ops
dom0 kernels 2.6.31.X, dom0 will be very slow, sluggish, and unresponsive,
such that it is nearly impossible to start another HVM virtual machine.

Now, after setting dom0_mem, I booted up into pvops dom0 kernel 2.6.31.5, I
started all 5 Rocks HPC cluster compute nodes at one go. And guess what?
Dom0 is not even sluggish! I could still do desktop screen video capturing!

Voila! Setting dom0_mem is really killing two birds with one stone. It
raises the number of VMs that I can start and also resolves the sluggishness
in dom0 (pvops kernels 2.6.31.X affected; 2.6.30-rc3 is NOT affected) after
starting a virtual machine.

Setting dom0_mem really does wonders.

Thank you Pasi!

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 9:10 PM, Mr. Teo En Ming (Zhang Enming) <
space.time.universe@gmail.com> wrote:

> Great! After setting dom0_mem=1024M, I can start all 5 nodes of my Rocks
> HPC cluster without crashing dom0 as compared to the previous limit of 3
> nodes when I did not set dom0_mem.
>
> Thank you Pasi! Another resource problem solved.
>
> Here's my latest grub.conf:
>
> # grub.conf generated by anaconda
> #
> # Note that you do not have to rerun grub after making changes to this file
> # NOTICE:  You have a /boot partition.  This means that
> #          all kernel and initrd paths are relative to /boot/, eg.
> #          root (hd0,0)
> #          kernel /vmlinuz-version ro
> root=/dev/mapper/vg_fedora11_host-lv_root
> #          initrd /initrd-version.img
> #boot=/dev/sda
> default=4
> timeout=100
> splashimage=(hd0,0)/grub/splash.xpm.gz
> hiddenmenu
> title Fedora (2.6.31.5-xen-enming.teo)
>     root (hd0,0)
> #    kernel /vmlinuz-2.6.31.5-xen-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #    initrd /initrd-2.6.31.5-xen-enming.teo.img
>     kernel /xen.gz dom0_mem=1024M iommu=1
>     module /vmlinuz-2.6.31.5-xen-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
>     module /initrd-2.6.31.5-xen-enming.teo.img
> title Fedora (2.6.31.4-xen-enming.teo)
>     root (hd0,0)
> #    kernel /vmlinuz-2.6.31.4-xen-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #    initrd /initrd-2.6.31.4-xen-enming.teo.img
>     kernel /xen.gz dom0_mem=1024M iommu=1
>     module /vmlinuz-2.6.31.4-xen-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
>     module /initrd-2.6.31.4-xen-enming.teo.img
> title Fedora (2.6.31.1-xen-enming.teo)
>     root (hd0,0)
> #    kernel /vmlinuz-2.6.31.1-xen-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #    initrd /initrd-2.6.31.1-xen-enming.teo.img
>     kernel /xen.gz dom0_mem=1024M iommu=1
>     module /vmlinuz-2.6.31.1-xen-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
>     module /initrd-2.6.31.1-xen-enming.teo.img
> title Fedora (2.6.31-enming.teo)
>     root (hd0,0)
>     kernel /vmlinuz-2.6.31-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
>     initrd /initrd-2.6.31-enming.teo.img
> title Fedora (2.6.30.5-enming.teo)
>     root (hd0,0)
>     kernel /vmlinuz-2.6.30.5-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
>     initrd /initrd-2.6.30.5-enming.teo.img
> title Fedora (2.6.18.8-enming.teo)
>     root (hd0,0)
> #    kernel /vmlinuz-2.6.18.8-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #    initrd /initrd-2.6.18.8-enming.teo.img
>     kernel /xen.gz dom0_mem=1024M iommu=1
>     module /vmlinuz-2.6.18.8-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root
>     module /initrd-2.6.18.8-enming.teo.img
> title Fedora (2.6.31-rc6-enming.teo) with Serial Console
>         root (hd0,0)
> #       kernel /vmlinuz-2.6.31-rc6-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #       initrd /initrd-2.6.31-rc6-enming.teo.img
>         kernel /xen.gz dom0_mem=1024M iommu=1 iommu_inclusive_mapping=1
> com1=115200,8n1 console=com1
> #       module /vmlinuz-2.6.31-rc6-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 xencons=ttyS0
> console=ttyS0,115200
>     module /vmlinuz-2.6.31-rc6-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 console=hvc0
> earlyprintk=xen
>         module /initrd-2.6.31-rc6-enming.teo.img
> title Fedora (2.6.30-rc3-enming.teo-tip) with Serial Console
>         root (hd0,0)
> #       kernel /vmlinuz-2.6.30-rc3-enming.teo-tip ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #       initrd /initrd-2.6.30-rc3-enming.teo-tip.img
>         kernel /xen.gz dom0_mem=1024M iommu=1 iommu_inclusive_mapping=1
> com1=115200,8n1 console=com1
> #       module /vmlinuz-2.6.30-rc3-enming.teo-tip ro
> root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 xencons=ttyS0
> console=ttyS0,115200
>     module /vmlinuz-2.6.30-rc3-enming.teo-tip ro
> root=/dev/mapper/vg_fedora11_host-lv_root selinux=0 console=hvc0
> earlyprintk=xen
>         module /initrd-2.6.30-rc3-enming.teo-tip.img
>
> title Fedora (2.6.31-rc6-enming.teo)
>     root (hd0,0)
> #    kernel /vmlinuz-2.6.31-rc6-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #    initrd /initrd-2.6.31-rc6-enming.teo.img
>     kernel /xen.gz dom0_mem=1024M iommu=1
>     module /vmlinuz-2.6.31-rc6-enming.teo ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
>     module /initrd-2.6.31-rc6-enming.teo.img
> title Fedora (2.6.30-rc3-enming.teo-tip)
>     root (hd0,0)
> #    kernel /vmlinuz-2.6.30-rc3-enming.teo-tip ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
> #    initrd /initrd-2.6.30-rc3-enming.teo-tip.img
>     kernel /xen.gz dom0_mem=1024M iommu=1
>     module /vmlinuz-2.6.30-rc3-enming.teo-tip ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0 nomodeset
>     module /initrd-2.6.30-rc3-enming.teo-tip.img
> title Fedora (2.6.29.4-167.fc11.x86_64)
>     root (hd0,0)
>     kernel /vmlinuz-2.6.29.4-167.fc11.x86_64 ro
> root=/dev/mapper/vg_fedora11_host-lv_root rhgb quiet selinux=0
>     initrd /initrd-2.6.29.4-167.fc11.x86_64.img
>
>
> --
> Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
> Engineering)
> Alma Maters:
> (1) Singapore Polytechnic
> (2) National University of Singapore
> My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
> My Secondary Blog: http://enmingteo.wordpress.com
> My Youtube videos: http://www.youtube.com/user/enmingteo
> Email: space.time.universe@gmail.com
> Mobile Phone (Starhub Prepaid): +65-8369-2618
> Street: Bedok Reservoir Road
> Country: Singapore
>
> On Mon, Nov 9, 2009 at 8:18 PM, Pasi Kärkkäinen <pasik@iki.fi> wrote:
>
>> On Mon, Nov 09, 2009 at 08:14:27PM +0800, Mr. Teo En Ming (Zhang Enming)
>> wrote:
>> >    What is a good value for dom0_mem if I want to start X server and run
>> >    GNOME? Will 512 MB be too little?
>> >
>>
>> Go for 1024 MB then..
>>
>> -- Pasi
>>
>>
>
>
>
>

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Re: [Xen-devel] Re: Max. PV and HVM Guests

[Mr. Teo En Ming (Zhang Enming)]

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Hi,

This is the new video demo of my Rocks HPC compute cluster after I have set
dom0_mem=1024M for my Xen hypervisor.

I started all 5 nodes at one go without crashing and without sluggishness.

Please watch the video at http://www.youtube.com/watch?v=vWHIImVBr4o

It's only 6 minutes.

Previous video demo shows that I can only start 3 nodes with-out setting
dom0_mem for the Xen hypervisor. If I try to start the 4th node, dom0 will
freeze.

This is proof that setting dom0_mem really works and improves overall system
performance.

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical
Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@gmail.com
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Mon, Nov 9, 2009 at 11:29 PM, Nick Couchman <Nick.Couchman@seakr.com>wrote:

> Thanks for the information!  Looks like I'll be adjusting some boot-time
> options on my Xen servers.  I have seen a couple of issues now and then with
> either migration or starting a domU, but it happens once every few months at
> the most, and usually I blame the migration issues on a fault network
> connection or something like that.  I'll have to try out limiting my dom0s
> to 1 or 2 GB of RAM and see if those issues go away!
>
> Thanks!
> -Nick
>
> >>> On 2009/11/09 at 08:18, Keir Fraser <keir.fraser@eu.citrix.com> wrote:
> > On 09/11/2009 15:06, "Nick Couchman" <Nick.Couchman@seakr.com> wrote:
> >
> >> Really?  I thought current conventional wisdom was to allow Xen to
> >> self-manage memory in both dom0 and domUs, and not to manually adjust
> >> this?  I run several Xen systems with anywhere from 8 to 24 GB of RAM
> >> and 20 to 30 domUs on some of these systems and have *never* specified
> >> the dom0 memory at boot time - the Xen ballooning has always functioned
> >> perfectly fine, and never crashed my dom0.  Furthermore, while I'm not
> >> Linux developer and so not familiar with how Linux calculates buffering
> >> and caching, I do know that my Linux systems dynamically manage buffers
> >> and caches, and when memory is reduced or some application requires a
> >> larger amount of physical memory, Linux reduces the amount of data in
> >> buffers and caches.
> >
> > If you are not using dom0 as a general-purpose OS then it is a very good
> > idea to specify dom0's memory allowance via dom0_mem= and disable
> > auto-ballooning in the xend-config.sxp. There are a few reasons for this,
> > the most compelling being that Linux will have a metadata overhead for
> > tracking memory usage, and this will be a fraction (say a percent or so)
> of
> > its initial memory allocation. So, that overhead may be just 2% of 24GB,
> > say, but then if dom0 gets ballooned down to 1GB it'll be more like 50%!
> > Clearly you are limited in how far you can balloon down without risking
> the
> > OOM killer in dom0.
> >
> > Apart from that, the auto-ballooner has been implicated in various quirky
> > bugs in the past -- failing domain creations and migrations for the most
> > part -- so it's nice to turn it off if you can, as that's one less thing
> to
> > fail. And if dom0 is single-purpose you should be able to work out how
> much
> > memory it needs for that purpose and statically allocate it. Using
> > auto-ballooner is actually perverse in this scenario, in that dom0 gets
> the
> > least memory when it needs it the most (because it presumably has highest
> > load when servicing the most VMs, but in that case auto-ballooner has
> stolen
> > lots of memory from dom0).
> >
> > My 2c!
> >
> >  -- Keir
>
>
>
>
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Re: [Xen-devel] Re: Max. PV and HVM Guests

[Keir Fraser]

On 09/11/2009 15:17, "Pasi Kärkkäinen" <pasik@iki.fi> wrote:

>> Furthermore, while I'm not
>> Linux developer and so not familiar with how Linux calculates buffering
>> and caching, I do know that my Linux systems dynamically manage buffers
>> and caches, and when memory is reduced or some application requires a
>> larger amount of physical memory, Linux reduces the amount of data in
>> buffers and caches.
>> 
> 
> Yeah, it has to do with sizing the network buffers, caches etc..
> 
> It shouldn't _crash_, so Teo is seeing some bug I believe. But it has
> always been "best practice" to limit dom0 memory - and prevent weird
> things happening later (like "memory squeeze in netback driver").

The issue is not really kernel data like network buffers and buffer cache.
It is kernel memory metadata -- primarily the per-page info structure that
the kernel maintains. The metadata doesn't get shrunk with memory size when
ballooning out, hence it increases as a proportion of memory still assigned
to the domain. That really is significant when aggressively ballooning down
a large-memory domain.

 -- Keir

Re: [Xen-devel] Re: Max. PV and HVM Guests

[Keir Fraser]

On 09/11/2009 15:06, "Nick Couchman" <Nick.Couchman@seakr.com> wrote:

> Really?  I thought current conventional wisdom was to allow Xen to
> self-manage memory in both dom0 and domUs, and not to manually adjust
> this?  I run several Xen systems with anywhere from 8 to 24 GB of RAM
> and 20 to 30 domUs on some of these systems and have *never* specified
> the dom0 memory at boot time - the Xen ballooning has always functioned
> perfectly fine, and never crashed my dom0.  Furthermore, while I'm not
> Linux developer and so not familiar with how Linux calculates buffering
> and caching, I do know that my Linux systems dynamically manage buffers
> and caches, and when memory is reduced or some application requires a
> larger amount of physical memory, Linux reduces the amount of data in
> buffers and caches.

If you are not using dom0 as a general-purpose OS then it is a very good
idea to specify dom0's memory allowance via dom0_mem= and disable
auto-ballooning in the xend-config.sxp. There are a few reasons for this,
the most compelling being that Linux will have a metadata overhead for
tracking memory usage, and this will be a fraction (say a percent or so) of
its initial memory allocation. So, that overhead may be just 2% of 24GB,
say, but then if dom0 gets ballooned down to 1GB it'll be more like 50%!
Clearly you are limited in how far you can balloon down without risking the
OOM killer in dom0.

Apart from that, the auto-ballooner has been implicated in various quirky
bugs in the past -- failing domain creations and migrations for the most
part -- so it's nice to turn it off if you can, as that's one less thing to
fail. And if dom0 is single-purpose you should be able to work out how much
memory it needs for that purpose and statically allocate it. Using
auto-ballooner is actually perverse in this scenario, in that dom0 gets the
least memory when it needs it the most (because it presumably has highest
load when servicing the most VMs, but in that case auto-ballooner has stolen
lots of memory from dom0).

My 2c!

 -- Keir

Re: [Xen-devel] Re: Max. PV and HVM Guests

[Pasi Kärkkäinen]

On Mon, Nov 09, 2009 at 08:06:54AM -0700, Nick Couchman wrote:
> 
> 
> >>> On 2009/11/09 at 05:05, Pasi Kärkkäinen<pasik@iki.fi> wrote: 
> > On Mon, Nov 09, 2009 at 08:01:00PM +0800, Mr. Teo En Ming (Zhang
> Enming) 
> > wrote:
> >>    No, I didn't limit dom0 memory in grub.conf.
> >> 
> > 
> > You should. 
> 
> Really?  I thought current conventional wisdom was to allow Xen to
> self-manage memory in both dom0 and domUs, and not to manually adjust
> this?  I run several Xen systems with anywhere from 8 to 24 GB of RAM
> and 20 to 30 domUs on some of these systems and have *never* specified
> the dom0 memory at boot time - the Xen ballooning has always functioned
> perfectly fine, and never crashed my dom0.  
>

Yes, Xen is totally OK with this, but dom0 Linux has more problems..

> Furthermore, while I'm not
> Linux developer and so not familiar with how Linux calculates buffering
> and caching, I do know that my Linux systems dynamically manage buffers
> and caches, and when memory is reduced or some application requires a
> larger amount of physical memory, Linux reduces the amount of data in
> buffers and caches.
> 

Yeah, it has to do with sizing the network buffers, caches etc.. 

It shouldn't _crash_, so Teo is seeing some bug I believe. But it has
always been "best practice" to limit dom0 memory - and prevent weird
things happening later (like "memory squeeze in netback driver").

> Of course, a lot of this depends on what you're doing in dom0 - on my
> Xen servers, my dom0 is strictly for Xen management - I'm not running
> anything else in dom0 that would require large amounts of memory, memory
> buffers and caches, etc.
> 

Teo is running graphical stuff, X etc so it's a bit different..

-- Pasi

> 
> > 
> > If dom0 has all the memory at boot time, you need to balloon down
> dom0 
> > memory every time you create a new guest - this can (and will) cause
> 
> > problems with the dom0 linux kernel.
> > 
> > Linux calculates some internal parameters/buffers/values based on
> the
> > _boot time_ amount of memory. And when the amount of memory goes down
> to
> > only a small fraction of that while creating new guests bad things
> can
> > happen..
> > 
> > It still shouldn't crash though.. I bet your problem will get fixed
> when
> > you limit the dom0 memory to say dom0_mem=512M and reboot.
> > 
> > -- Pasi
> > 
> >>    Here's my xm info output after I have shutdown all the virtual
> machines.
> >> 
> >>    [root@fedora11-x86-64-host ~]# xm list
> >>    Name                                        ID   Mem VCPUs     
> State
> >>    Time(s)
> >>    Domain-0                                     0  2812     2    
> r-----
> >>    3242.5
> >>    [root@fedora11-x86-64-host ~]# xm info
> >>    host                   : fedora11-x86-64-host
> >>    release                : 2.6.30-rc3-enming.teo-tip
> >>    version                : #1 SMP Wed Aug 19 23:14:15 SGT 2009
> >>    machine                : x86_64
> >>    nr_cpus                : 2
> >>    nr_nodes               : 1
> >>    cores_per_socket       : 2
> >>    threads_per_core       : 1
> >>    cpu_mhz                : 2800
> >>    hw_caps                :
> >>   
> bfebfbff:20100800:00000000:00000140:0400e3bd:00000000:00000001:00000000
> >>    virt_caps              : hvm hvm_directio
> >>    total_memory           : 6039
> >>    free_memory            : 3124
> >>    node_to_cpu            : node0:0-1
> >>    node_to_memory         : node0:3124
> >>    xen_major              : 3
> >>    xen_minor              : 5
> >>    xen_extra              : -unstable
> >>    xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p
> hvm-3.0-x86_32
> >>    hvm-3.0-x86_32p hvm-3.0-x86_64
> >>    xen_scheduler          : credit
> >>    xen_pagesize           : 4096
> >>    platform_params        : virt_start=0xffff800000000000
> >>    xen_changeset          : Tue Sep 01 11:34:31 2009 +0100 
> > 20143:a7de5bd776ca
> >>    xen_commandline        : iommu=1
> >>    cc_compiler            : gcc version 4.4.1 20090725 (Red Hat
> 4.4.1-2)
> >>    (GCC)
> >>    cc_compile_by          : root
> >>    cc_compile_domain      : (none)
> >>    cc_compile_date        : Thu Sep 10 07:01:13 SGT 2009
> >>    xend_config_format     : 4
> >> 
> >>    --
> >>    Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics)
> BEng(Hons)(Mechanical
> >>    Engineering)
> >>    Alma Maters:
> >>    (1) Singapore Polytechnic
> >>    (2) National University of Singapore
> >>    My Primary Blog:
> [1]http://teo-en-ming-aka-zhang-enming.blogspot.com
> >>    My Secondary Blog: [2]http://enmingteo.wordpress.com
> >>    My Youtube videos: [3]http://www.youtube.com/user/enmingteo
> >>    Email: [4]space.time.universe@gmail.com
> >>    Mobile Phone (Starhub Prepaid): +65-8369-2618
> >>    Street: Bedok Reservoir Road
> >>    Country: Singapore
> >> 
> >>    On Mon, Nov 9, 2009 at 7:54 PM, Pasi Kärkkäinen <[5]pasik@iki.fi>
> wrote:
> >> 
> >>      On Mon, Nov 09, 2009 at 06:52:37PM +0800, Mr. Teo En Ming
> (Zhang 
> > Enming)
> >>      wrote:
> >>      >    Hi,
> >>      >
> >>      >    Please watch this 4-minute video at
> >>      >    [1][6]http://www.youtube.com/watch?v=LbLaPpwNAx4
> >>      >
> >>      >    I have only started 3 HVM Linux guests with 1 GB ram each.
> I can't
> >>      start
> >>      >    the 4th HVM guest. If I attempt to start the 4th instance,
> it will
> >>      crash
> >>      >    dom0.
> >>      >
> >>      >    Are there anything in the xm dmesg output that could
> explain the
> >>      low limit
> >>      >    to the number of VMs that I could start before dom0
> becomes
> >>      unresponsive?
> >>      >
> >> 
> >>      Have you limited dom0 memory (by specifying dom0_mem=XMB option
> in
> >>      grub.conf for xen.gz) ?
> >> 
> >>      What does "xm info" say about free memory before starting any
> guests?
> >>      -- Pasi
> >> 
> >> References
> >> 
> >>    Visible links
> >>    1. http://teo-en-ming-aka-zhang-enming.blogspot.com/
> >>    2. http://enmingteo.wordpress.com/
> >>    3. http://www.youtube.com/user/enmingteo
> >>    4. mailto:space.time.universe@gmail.com
> >>    5. mailto:pasik@iki.fi
> >>    6. http://www.youtube.com/watch?v=LbLaPpwNAx4
> 
> 
> 
> --------
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