Modifying RAM during runtime on guest

Modifying RAM during runtime on guest

[Daniel Bareiro]

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Hi all!

I'm trying to modify the amount of RAM that has some of guests. Host has
2.6.30 kernel with KVM-88.

In one of guest I didn't have problems when decreasing the amount of memory
from 3584 MIB to 1024 MiB. This guest has 2.6.26-2-686 stock kernel. Also I
was trying to decrease the amount RAM of another guest from 3584 MiB to
2048 MiB, but it didn't work. This other guest has
2.6.24-etchnhalf.1-686-bigmem stock kernel. Does Ballooning in guest
require 2.6.25 or superior?

Thinking that it could be an impediment related to the kernel version of
guest, I tried to increase the memory of another one guest with
2.6.26-2-686 from 512 MIB to 1024 MIB, but this didn't work either.

These are the statistics of of memory usage in host:

# free
             total       used       free     shared    buffers     cached
Mem:      16469828   14763460    1706368          0    7800712     202044
-/+ buffers/cache:    6760704    9709124
Swap:      8319948      19240    8300708



Which can be the cause?

Thanks in advance for your reply.

Regards,
Daniel
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Re: Modifying RAM during runtime on guest

[Brian Jackson]

On Tuesday 08 September 2009 03:52:07 pm Daniel Bareiro wrote:
> Hi all!
> 
> I'm trying to modify the amount of RAM that has some of guests. Host has
> 2.6.30 kernel with KVM-88.
> 
> In one of guest I didn't have problems when decreasing the amount of memory
> from 3584 MIB to 1024 MiB. This guest has 2.6.26-2-686 stock kernel. Also I
> was trying to decrease the amount RAM of another guest from 3584 MiB to
> 2048 MiB, but it didn't work. This other guest has
> 2.6.24-etchnhalf.1-686-bigmem stock kernel. Does Ballooning in guest
> require 2.6.25 or superior?


I don't know, if that kernel has a virtio-balloon driver, I'd think that was 
all you need to balloon memory.


> 
> Thinking that it could be an impediment related to the kernel version of
> guest, I tried to increase the memory of another one guest with
> 2.6.26-2-686 from 512 MIB to 1024 MIB, but this didn't work either.


You can only grow memory up to the amount you specified on the command line if 
you've already ballooned down. So if you specify "-m 1024M" on the command 
line, then shrink it to 512, you could then balloon it back up to a max of 
1024.


> 
> These are the statistics of of memory usage in host:
> 
> # free
>              total       used       free     shared    buffers     cached
> Mem:      16469828   14763460    1706368          0    7800712     202044
> -/+ buffers/cache:    6760704    9709124
> Swap:      8319948      19240    8300708
> 
> 
> 
> Which can be the cause?
> 
> Thanks in advance for your reply.
> 
> Regards,
> Daniel
> 

Re: Modifying RAM during runtime on guest

[Daniel Bareiro]

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Hi Brian.

On Tuesday, 08 September 2009 16:18:09 -0500,
Brian Jackson wrote:

> > I'm trying to modify the amount of RAM that has some of guests. Host
> > has 2.6.30 kernel with KVM-88.
> > 
> > In one of guest I didn't have problems when decreasing the amount of
> > memory from 3584 MIB to 1024 MiB. This guest has 2.6.26-2-686 stock
> > kernel. Also I was trying to decrease the amount RAM of another guest
> > from 3584 MiB to 2048 MiB, but it didn't work. This other guest has
> > 2.6.24-etchnhalf.1-686-bigmem stock kernel. Does Ballooning in guest
> > require 2.6.25 or superior?

> I don't know, if that kernel has a virtio-balloon driver, I'd think that
> was all you need to balloon memory.

Then can be that it is related to kernel that is using the guest:

# uname -a
Linux aprender01 2.6.24-etchnhalf.1-686-bigmem #1 SMP Mon Jul 27 03:56:49 UTC 2009 i686 GNU/Linux

# cat config-2.6.24-etchnhalf.1-686-bigmem | grep -i virtio
#

> > Thinking that it could be an impediment related to the kernel version
> > of guest, I tried to increase the memory of another one guest with
> > 2.6.26-2-686 from 512 MIB to 1024 MIB, but this didn't work either.

> You can only grow memory up to the amount you specified on the command
> line if you've already ballooned down.

Good. Thanks for clarifying to me this detail.

> So if you specify "-m 1024M" on the command line, then shrink it to 512,
> you could then balloon it back up to a max of 1024.

According to the tests that I was doing in guest with kernel with support
for virtio, shrinking works, but when trying to return to the amount of
initial memory, seems that it fails and I lose connectivity by serial
console and ssh.

In the guest:

# uname -a
Linux central 2.6.26-2-amd64 #1 SMP Sun Jul 26 20:35:48 UTC 2009 x86_64 GNU/Linux

# cat config-2.6.26-2-amd64 | grep -i virtio
CONFIG_NET_9P_VIRTIO=m
CONFIG_VIRTIO_BLK=m
CONFIG_VIRTIO_NET=m
CONFIG_HW_RANDOM_VIRTIO=m
CONFIG_VIRTIO=m
CONFIG_VIRTIO_RING=m
CONFIG_VIRTIO_PCI=m
CONFIG_VIRTIO_BALLOON=m

In the host:

# telnet localhost 4045
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
QEMU 0.10.50 monitor - type 'help' for more information
(qemu)
(qemu) info balloon
balloon: actual=512
(qemu) balloon 256
(qemu) info balloon
balloon: actual=256
(qemu)
(qemu) balloon 512
(qemu) info balloon
balloon: actual=36

At this moment I'm unable to connect by serial console to the guest and the
ssh sessions are freeze nevertheless kvm process of the guest is running.
Using a VNC client I see several messages of this type in the guest:

Out of memory: kill process xxxx (<name>) score xx or a child
Killed process xxxx (<name>)

Finally:

Kernel panic - not syncing - Out of memory and no killable processes...



Thanks for your reply.

Regards,
Daniel
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Re: Modifying RAM during runtime on guest

[Jim Paris]

Daniel Bareiro wrote:
> Hi Brian.
> 
> On Tuesday, 08 September 2009 16:18:09 -0500,
> Brian Jackson wrote:
> 
> > > I'm trying to modify the amount of RAM that has some of guests. Host
> > > has 2.6.30 kernel with KVM-88.
> > > 
> > > In one of guest I didn't have problems when decreasing the amount of
> > > memory from 3584 MIB to 1024 MiB. This guest has 2.6.26-2-686 stock
> > > kernel. Also I was trying to decrease the amount RAM of another guest
> > > from 3584 MiB to 2048 MiB, but it didn't work. This other guest has
> > > 2.6.24-etchnhalf.1-686-bigmem stock kernel. Does Ballooning in guest
> > > require 2.6.25 or superior?
> 
> > I don't know, if that kernel has a virtio-balloon driver, I'd think that
> > was all you need to balloon memory.
> 
> Then can be that it is related to kernel that is using the guest:
> 
> # uname -a
> Linux aprender01 2.6.24-etchnhalf.1-686-bigmem #1 SMP Mon Jul 27 03:56:49 UTC 2009 i686 GNU/Linux
> 
> # cat config-2.6.24-etchnhalf.1-686-bigmem | grep -i virtio
> #
> 
> > > Thinking that it could be an impediment related to the kernel version
> > > of guest, I tried to increase the memory of another one guest with
> > > 2.6.26-2-686 from 512 MIB to 1024 MIB, but this didn't work either.
> 
> > You can only grow memory up to the amount you specified on the command
> > line if you've already ballooned down.
> 
> Good. Thanks for clarifying to me this detail.
> 
> > So if you specify "-m 1024M" on the command line, then shrink it to 512,
> > you could then balloon it back up to a max of 1024.
> 
> According to the tests that I was doing in guest with kernel with support
> for virtio, shrinking works, but when trying to return to the amount of
> initial memory, seems that it fails and I lose connectivity by serial
> console and ssh.
> 
> In the guest:
> 
> # uname -a
> Linux central 2.6.26-2-amd64 #1 SMP Sun Jul 26 20:35:48 UTC 2009 x86_64 GNU/Linux
> 
> # cat config-2.6.26-2-amd64 | grep -i virtio
> CONFIG_NET_9P_VIRTIO=m
> CONFIG_VIRTIO_BLK=m
> CONFIG_VIRTIO_NET=m
> CONFIG_HW_RANDOM_VIRTIO=m
> CONFIG_VIRTIO=m
> CONFIG_VIRTIO_RING=m
> CONFIG_VIRTIO_PCI=m
> CONFIG_VIRTIO_BALLOON=m
> 
> In the host:
> 
> # telnet localhost 4045
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> QEMU 0.10.50 monitor - type 'help' for more information
> (qemu)
> (qemu) info balloon
> balloon: actual=512
> (qemu) balloon 256
> (qemu) info balloon
> balloon: actual=256
> (qemu)
> (qemu) balloon 512
> (qemu) info balloon
> balloon: actual=36
> 
> At this moment I'm unable to connect by serial console to the guest and the
> ssh sessions are freeze nevertheless kvm process of the guest is running.
> Using a VNC client I see several messages of this type in the guest:
> 
> Out of memory: kill process xxxx (<name>) score xx or a child
> Killed process xxxx (<name>)
> 
> Finally:
> 
> Kernel panic - not syncing - Out of memory and no killable processes...
> 
> 
> 
> Thanks for your reply.

Hi Daniel,

I noticed no-one answered this, and I just ran into the same thing
myself.  As Avi pointed out earlier, it is a guest bug, and upgrading
the guest to 2.6.27 should fix it:
  http://www.mail-archive.com/kvm@vger.kernel.org/msg10849.html

-jim

Re: Modifying RAM during runtime on guest

[Daniel Bareiro]

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On Tuesday, 29 September 2009 00:55:02 -0400,
Jim Paris wrote:

> > According to the tests that I was doing in guest with kernel with
> > support for virtio, shrinking works, but when trying to return to
> > the amount of initial memory, seems that it fails and I lose
> > connectivity by serial console and ssh.
> > 
> > In the guest:
> > 
> > # uname -a
> > Linux central 2.6.26-2-amd64 #1 SMP Sun Jul 26 20:35:48 UTC 2009 x86_64 GNU/Linux
> > 
> > # cat config-2.6.26-2-amd64 | grep -i virtio
> > CONFIG_NET_9P_VIRTIO=m
> > CONFIG_VIRTIO_BLK=m
> > CONFIG_VIRTIO_NET=m
> > CONFIG_HW_RANDOM_VIRTIO=m
> > CONFIG_VIRTIO=m
> > CONFIG_VIRTIO_RING=m
> > CONFIG_VIRTIO_PCI=m
> > CONFIG_VIRTIO_BALLOON=m
> > 
> > In the host:
> > 
> > # telnet localhost 4045
> > Trying 127.0.0.1...
> > Connected to localhost.
> > Escape character is '^]'.
> > QEMU 0.10.50 monitor - type 'help' for more information
> > (qemu)
> > (qemu) info balloon
> > balloon: actual=512
> > (qemu) balloon 256
> > (qemu) info balloon
> > balloon: actual=256
> > (qemu)
> > (qemu) balloon 512
> > (qemu) info balloon
> > balloon: actual=36
> > 
> > At this moment I'm unable to connect by serial console to the guest
> > and the ssh sessions are freeze nevertheless kvm process of the
> > guest is running.  Using a VNC client I see several messages of this
> > type in the guest:
> > 
> > Out of memory: kill process xxxx (<name>) score xx or a child
> > Killed process xxxx (<name>)
> > 
> > Finally:
> > 
> > Kernel panic - not syncing - Out of memory and no killable processes...

> Hi Daniel,

Hi, Jim.

> I noticed no-one answered this, and I just ran into the same thing
> myself. As Avi pointed out earlier, it is a guest bug, and upgrading
> the guest to 2.6.27 should fix it:

>   http://www.mail-archive.com/kvm@vger.kernel.org/msg10849.html

In this moment I doesn't have Internet connectivity in my house, but, as
soon as it be possible, I shall download the necessary software to
compile 2.6.27 or superior and then I tell you the result of the tests.

Thanks for your reply. 

Regards,
Daniel
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Re: Modifying RAM during runtime on guest

[Daniel Bareiro]

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Hi, Jim.

On Sunday, 04 October 2009 20:35:58 -0300,
Daniel Bareiro wrote:

> > > According to the tests that I was doing in guest with kernel with
> > > support for virtio, shrinking works, but when trying to return to
> > > the amount of initial memory, seems that it fails and I lose
> > > connectivity by serial console and ssh.
> > > 
> > > In the guest:
> > > 
> > > # uname -a
> > > Linux central 2.6.26-2-amd64 #1 SMP Sun Jul 26 20:35:48 UTC 2009 x86_64 GNU/Linux
> > > 
> > > # cat config-2.6.26-2-amd64 | grep -i virtio
> > > CONFIG_NET_9P_VIRTIO=m
> > > CONFIG_VIRTIO_BLK=m
> > > CONFIG_VIRTIO_NET=m
> > > CONFIG_HW_RANDOM_VIRTIO=m
> > > CONFIG_VIRTIO=m
> > > CONFIG_VIRTIO_RING=m
> > > CONFIG_VIRTIO_PCI=m
> > > CONFIG_VIRTIO_BALLOON=m
> > > 
> > > In the host:
> > > 
> > > # telnet localhost 4045
> > > Trying 127.0.0.1...
> > > Connected to localhost.
> > > Escape character is '^]'.
> > > QEMU 0.10.50 monitor - type 'help' for more information
> > > (qemu)
> > > (qemu) info balloon
> > > balloon: actual=512
> > > (qemu) balloon 256
> > > (qemu) info balloon
> > > balloon: actual=256
> > > (qemu)
> > > (qemu) balloon 512
> > > (qemu) info balloon
> > > balloon: actual=36
> > > 
> > > At this moment I'm unable to connect by serial console to the
> > > guest and the ssh sessions are freeze nevertheless kvm process of
> > > the guest is running. Using a VNC client I see several messages of
> > > this type in the guest:
> > > 
> > > Out of memory: kill process xxxx (<name>) score xx or a child
> > > Killed process xxxx (<name>)
> > > 
> > > Finally:
> > > 
> > > Kernel panic - not syncing - Out of memory and no killable processes...
 
> > I noticed no-one answered this, and I just ran into the same thing
> > myself. As Avi pointed out earlier, it is a guest bug, and upgrading
> > the guest to 2.6.27 should fix it:
 
> >   http://www.mail-archive.com/kvm@vger.kernel.org/msg10849.html
 
> In this moment I doesn't have Internet connectivity in my house, but,
> as soon as it be possible, I shall download the necessary software to
> compile 2.6.27 or superior and then I tell you the result of the
> tests.

After to have compiled Linux 2.6.30.3 using the Debian way on guest
Debian GNU/Linux Lenny, when trying to boot the guest with this kernel,
the bootstrapping is freeze on "Loading, please wait..." message.

In logs I don't get entries of the bootstrapping process with 2.6.30 (I
think it is because the process in itself didn't start). Can it be due
to a bug using 2.6.30.3 in guest with host KVM-88?

Thanks in advance.

Regards,
Daniel
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Re: Modifying RAM during runtime on guest

[Jim Paris]

Daniel Bareiro wrote:
> Hi, Jim.
> > > I noticed no-one answered this, and I just ran into the same thing
> > > myself. As Avi pointed out earlier, it is a guest bug, and upgrading
> > > the guest to 2.6.27 should fix it:
>  
> > >   http://www.mail-archive.com/kvm@vger.kernel.org/msg10849.html
>  
> > In this moment I doesn't have Internet connectivity in my house, but,
> > as soon as it be possible, I shall download the necessary software to
> > compile 2.6.27 or superior and then I tell you the result of the
> > tests.
> 
> After to have compiled Linux 2.6.30.3 using the Debian way on guest
> Debian GNU/Linux Lenny, when trying to boot the guest with this kernel,
> the bootstrapping is freeze on "Loading, please wait..." message.
> 
> In logs I don't get entries of the bootstrapping process with 2.6.30 (I
> think it is because the process in itself didn't start). Can it be due
> to a bug using 2.6.30.3 in guest with host KVM-88?

2.6.30.3 should work fine, there must be some other problem.  If you
remove "quiet" from the boot command line you should see the kernel
messages which may indicate the problem.  I'd also recommend just
trying a standard prebuilt Debian kernel.
  http://packages.debian.org/squeeze/linux-image-2.6.30-1-amd64

-jim

Re: Modifying RAM during runtime on guest

[Daniel Bareiro]

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Hi Jim.

On Wednesday, 07 October 2009 14:21:15 -0400,
Jim Paris wrote:

> > > > I noticed no-one answered this, and I just ran into the same
> > > > thing myself. As Avi pointed out earlier, it is a guest bug, and
> > > > upgrading the guest to 2.6.27 should fix it:

> > > >   http://www.mail-archive.com/kvm@vger.kernel.org/msg10849.html

> > > In this moment I doesn't have Internet connectivity in my house,
> > > but, as soon as it be possible, I shall download the necessary
> > > software to compile 2.6.27 or superior and then I tell you the
> > > result of the tests.
 
> > After to have compiled Linux 2.6.30.3 using the Debian way on guest
> > Debian GNU/Linux Lenny, when trying to boot the guest with this
> > kernel, the bootstrapping is freeze on "Loading, please wait..."
> > message.
> > 
> > In logs I don't get entries of the bootstrapping process with 2.6.30
> > (I think it is because the process in itself didn't start). Can it
> > be due to a bug using 2.6.30.3 in guest with host KVM-88?
 
> 2.6.30.3 should work fine, there must be some other problem.  If you
> remove "quiet" from the boot command line you should see the kernel
> messages which may indicate the problem.  I'd also recommend just
> trying a standard prebuilt Debian kernel.

>   http://packages.debian.org/squeeze/linux-image-2.6.30-1-amd64

As we commented in this [1] thread, the problem was due to a patch that
Debian developers have applied to stock kernels enabling only libata for
the systems having a SATA controller.

For that reason the Debian stock kernel saw disks as hdX and kernels
2.6.31.2 and 2.6.30.3 compiled by myself saw disks like sdX. After
booting, with 2.6.3x, no longer panic is observed when restituting the
memory to its initial value.

Thanks for your reply.

Regards,
Daniel

[1] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/41158
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