3525MB RAM Limit

3525MB RAM Limit

[Daniel Scott]

Hi,

I'm running a KVM host using Fedora 10 (x86_64) on 4x Quad-Core AMD
Opteron(tm) Processor 8347 HE system with 16GB ram. I've created a
Fedora 10 (x86_64) guest and allocated 8 CPUs and 8GB ram which I can
see using 'virt-manager'. When I login to the guest, I can see the 8
CPUs, but apparently, I only have 3525MB RAM (output from 'free'). At
first I thought it was a 32bit problem, but I've double checked and
the host and guest are both running 64bit architectures. virt-manager
shows 50% ram usage which appears to be correct (4GB, out of 8). It
also correctly recognises the 16GB available in the host machine.

Is this expected? Will the extra ram become available once it is
required? If not, does anyone have any Ideas for how I can fix the
problem?

Thanks,

Dan

Re: 3525MB RAM Limit

[Brian Jackson]

Read the list archives. A fix was discussed recently.

--Brian Jackson


On Monday 06 April 2009 21:59:24 Daniel Scott wrote:
> Hi,
>
> I'm running a KVM host using Fedora 10 (x86_64) on 4x Quad-Core AMD
> Opteron(tm) Processor 8347 HE system with 16GB ram. I've created a
> Fedora 10 (x86_64) guest and allocated 8 CPUs and 8GB ram which I can
> see using 'virt-manager'. When I login to the guest, I can see the 8
> CPUs, but apparently, I only have 3525MB RAM (output from 'free'). At
> first I thought it was a 32bit problem, but I've double checked and
> the host and guest are both running 64bit architectures. virt-manager
> shows 50% ram usage which appears to be correct (4GB, out of 8). It
> also correctly recognises the 16GB available in the host machine.
>
> Is this expected? Will the extra ram become available once it is
> required? If not, does anyone have any Ideas for how I can fix the
> problem?
>
> Thanks,
>
> Dan
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: 3525MB RAM Limit

[Daniel Scott]

Hi,

Thanks for the response. I have read through the archives (I also did
so before posting :) ) but I haven't been able to find any information
about this. Do you know where I can find it? I tried searching for 4GB
and 3525MB and various combinations. Do you know if a specific limit
is mentioned?

Thanks,

Dan

2009/4/6 Brian Jackson <iggy@theiggy.com>:
> Read the list archives. A fix was discussed recently.
>
> --Brian Jackson
>
>
> On Monday 06 April 2009 21:59:24 Daniel Scott wrote:
>> Hi,
>>
>> I'm running a KVM host using Fedora 10 (x86_64) on 4x Quad-Core AMD
>> Opteron(tm) Processor 8347 HE system with 16GB ram. I've created a
>> Fedora 10 (x86_64) guest and allocated 8 CPUs and 8GB ram which I can
>> see using 'virt-manager'. When I login to the guest, I can see the 8
>> CPUs, but apparently, I only have 3525MB RAM (output from 'free'). At
>> first I thought it was a 32bit problem, but I've double checked and
>> the host and guest are both running 64bit architectures. virt-manager
>> shows 50% ram usage which appears to be correct (4GB, out of 8). It
>> also correctly recognises the 16GB available in the host machine.
>>
>> Is this expected? Will the extra ram become available once it is
>> required? If not, does anyone have any Ideas for how I can fix the
>> problem?
>>
>> Thanks,
>>
>> Dan
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>

Re: 3525MB RAM Limit

[Brian Jackson]

I was thinking of a bug when using large pages, which may not be your problem. 
There have been other reports recently, with workarounds, that are similar, 
just not the exact same number you have.

some subjects to look for:
* Can't boot guest with more than 3585MB when using large pages
There was a patch from Marcelo that was supposed to fix it.
* kvm-84 and guests with more than 3536 MB Ram?
there were suggestions to make sure to use the correct bios and the OP stated 
that upgrading his kernel actually fixed the problem

I could swear there was another one, but maybe I'm thinking of the IRC 
channel. If you are still unable to get it to work, you should reply back with 
more info. Kernel version, KVM version, etc.

Good luck.

--Brian Jackson



On Thursday 09 April 2009 10:07:36 Daniel Scott wrote:
> Hi,
>
> Thanks for the response. I have read through the archives (I also did
> so before posting :) ) but I haven't been able to find any information
> about this. Do you know where I can find it? I tried searching for 4GB
> and 3525MB and various combinations. Do you know if a specific limit
> is mentioned?
>
> Thanks,
>
> Dan
>
> 2009/4/6 Brian Jackson <iggy@theiggy.com>:
> > Read the list archives. A fix was discussed recently.
> >
> > --Brian Jackson
> >
> > On Monday 06 April 2009 21:59:24 Daniel Scott wrote:
> >> Hi,
> >>
> >> I'm running a KVM host using Fedora 10 (x86_64) on 4x Quad-Core AMD
> >> Opteron(tm) Processor 8347 HE system with 16GB ram. I've created a
> >> Fedora 10 (x86_64) guest and allocated 8 CPUs and 8GB ram which I can
> >> see using 'virt-manager'. When I login to the guest, I can see the 8
> >> CPUs, but apparently, I only have 3525MB RAM (output from 'free'). At
> >> first I thought it was a 32bit problem, but I've double checked and
> >> the host and guest are both running 64bit architectures. virt-manager
> >> shows 50% ram usage which appears to be correct (4GB, out of 8). It
> >> also correctly recognises the 16GB available in the host machine.
> >>
> >> Is this expected? Will the extra ram become available once it is
> >> required? If not, does anyone have any Ideas for how I can fix the
> >> problem?
> >>
> >> Thanks,
> >>
> >> Dan
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe kvm" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Re: 3525MB RAM Limit

[Alex Williamson]

On Thu, 2009-04-09 at 10:39 -0500, Brian Jackson wrote:
> I was thinking of a bug when using large pages, which may not be your problem. 
> There have been other reports recently, with workarounds, that are similar, 
> just not the exact same number you have.
> 
> some subjects to look for:
> * Can't boot guest with more than 3585MB when using large pages
> There was a patch from Marcelo that was supposed to fix it.
> * kvm-84 and guests with more than 3536 MB Ram?
> there were suggestions to make sure to use the correct bios and the OP stated 
> that upgrading his kernel actually fixed the problem
> 
> I could swear there was another one, but maybe I'm thinking of the IRC 
> channel. If you are still unable to get it to work, you should reply back with 
> more info. Kernel version, KVM version, etc.

It could also be related to the guest trimming away memory due to the
way we used to report the MTRRs.  This would show up in dmesg on the
guest.  Try the latest kvm by hand and see if the problem goes away.
Thanks,

Alex

Re: 3525MB RAM Limit

[Mauricio Villarroel]

Thanks Brian,

The kvm host with the problem is running:

* Fedora release 10 (Cambridge)
* kernel: 2.6.27   (the actual fedora package is 2.6.27.21-170.2.56.fc10.x86_64)

* 4x Quad-Core AMD Opteron(tm) Processor 8347 HE
* KVM version:  74 (the actual fedora package is (kvm-74-10.fc10.x86_64)

Reading some other post in forums, it seems kvm should be able to
handle > 4gb ram. Is this correct?

Best,

Mauro


> On Thu, Apr 9, 2009 at 11:49 AM, Daniel Scott <djscott@mit.edu> wrote:
>>
>> ---------- Forwarded message ----------
>> From: Brian Jackson <iggy@theiggy.com>
>> Date: 2009/4/9
>> Subject: Re: 3525MB RAM Limit
>> To: Daniel Scott <djscott@mit.edu>
>> Cc: kvm@vger.kernel.org
>>
>>
>> I was thinking of a bug when using large pages, which may not be your problem.
>> There have been other reports recently, with workarounds, that are similar,
>> just not the exact same number you have.
>>
>> some subjects to look for:
>> * Can't boot guest with more than 3585MB when using large pages
>> There was a patch from Marcelo that was supposed to fix it.
>> * kvm-84 and guests with more than 3536 MB Ram?
>> there were suggestions to make sure to use the correct bios and the OP stated
>> that upgrading his kernel actually fixed the problem
>>
>> I could swear there was another one, but maybe I'm thinking of the IRC
>> channel. If you are still unable to get it to work, you should reply back with
>> more info. Kernel version, KVM version, etc.
>>
>> Good luck.
>>
>> --Brian Jackson
>>

Re: Re: 3525MB RAM Limit

[Daniel Scott]

Brian, Alex,

2009/4/9 Alex Williamson <alex.williamson@hp.com>:
> On Thu, 2009-04-09 at 10:39 -0500, Brian Jackson wrote:
>> some subjects to look for:
>> * Can't boot guest with more than 3585MB when using large pages
>> There was a patch from Marcelo that was supposed to fix it.
>> * kvm-84 and guests with more than 3536 MB Ram?
>> there were suggestions to make sure to use the correct bios and the OP stated
>> that upgrading his kernel actually fixed the problem
>>
>> I could swear there was another one, but maybe I'm thinking of the IRC
>> channel. If you are still unable to get it to work, you should reply back with
>> more info. Kernel version, KVM version, etc.
>
> It could also be related to the guest trimming away memory due to the
> way we used to report the MTRRs.  This would show up in dmesg on the
> guest.  Try the latest kvm by hand and see if the problem goes away.

Thanks for the suggestions. After more research, it looks like
upgrading the software will fix the problem:

http://www.func.nl/community/knowledgebase/running-kvm-guest-35-gb-ram

We see the same BIOS message as in the above link. It seems like this
will be fixed in Fedora 11 so we'll probably wait for a month or two
and then upgrade Fedora on our host system.

Thanks again,

Dan

Re: Re: 3525MB RAM Limit

[Sterling Windmill]

Is this a problem in the latest (kvm-84) or just in an older version that Fedora 10 provides? 

----- Original Message ----- 
From: "Daniel Scott" <djscott@mit.edu> 
To: "Alex Williamson" <alex.williamson@hp.com> 
Cc: "Brian Jackson" <iggy@theiggy.com>, kvm@vger.kernel.org 
Sent: Thursday, April 9, 2009 2:54:11 PM GMT -05:00 US/Canada Eastern 
Subject: Re: [kvm] Re: 3525MB RAM Limit 

Brian, Alex, 

2009/4/9 Alex Williamson <alex.williamson@hp.com>: 
> On Thu, 2009-04-09 at 10:39 -0500, Brian Jackson wrote: 
>> some subjects to look for: 
>> * Can't boot guest with more than 3585MB when using large pages 
>> There was a patch from Marcelo that was supposed to fix it. 
>> * kvm-84 and guests with more than 3536 MB Ram? 
>> there were suggestions to make sure to use the correct bios and the OP stated 
>> that upgrading his kernel actually fixed the problem 
>> 
>> I could swear there was another one, but maybe I'm thinking of the IRC 
>> channel. If you are still unable to get it to work, you should reply back with 
>> more info. Kernel version, KVM version, etc. 
> 
> It could also be related to the guest trimming away memory due to the 
> way we used to report the MTRRs. This would show up in dmesg on the 
> guest. Try the latest kvm by hand and see if the problem goes away. 

Thanks for the suggestions. After more research, it looks like 
upgrading the software will fix the problem: 

http://www.func.nl/community/knowledgebase/running-kvm-guest-35-gb-ram 

We see the same BIOS message as in the above link. It seems like this 
will be fixed in Fedora 11 so we'll probably wait for a month or two 
and then upgrade Fedora on our host system. 

Thanks again, 

Dan 
-- 
To unsubscribe from this list: send the line "unsubscribe kvm" in 
the body of a message to majordomo@vger.kernel.org 
More majordomo info at http://vger.kernel.org/majordomo-info.html 

Re: 3525MB RAM Limit

[Brian Jackson]

Hi,

Thanks for the response. I have read through the archives (I also did
so before posting :) ) but I haven't been able to find any information
about this. Do you know where I can find it? I tried searching for 4GB
and 3525MB and various combinations. Do you know if a specific limit
is mentioned?

Thanks,

Dan

2009/4/6 Brian Jackson <iggy@theiggy.com>:
> Read the list archives. A fix was discussed recently.
>
> --Brian Jackson
>
>
> On Monday 06 April 2009 21:59:24 Daniel Scott wrote:
>> Hi,
>>
>> I'm running a KVM host using Fedora 10 (x86_64) on 4x Quad-Core AMD
>> Opteron(tm) Processor 8347 HE system with 16GB ram. I've created a
>> Fedora 10 (x86_64) guest and allocated 8 CPUs and 8GB ram which I can
>> see using 'virt-manager'. When I login to the guest, I can see the 8
>> CPUs, but apparently, I only have 3525MB RAM (output from 'free'). At
>> first I thought it was a 32bit problem, but I've double checked and
>> the host and guest are both running 64bit architectures. virt-manager
>> shows 50% ram usage which appears to be correct (4GB, out of 8). It
>> also correctly recognises the 16GB available in the host machine.
>>
>> Is this expected? Will the extra ram become available once it is
>> required? If not, does anyone have any Ideas for how I can fix the
>> problem?
>>
>> Thanks,
>>
>> Dan
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>