Open Stack

On Mon, Feb 3, 2020, at 1:36 PM, Albert Braden wrote:
>  
> When we build a Centos 7 VM with 1.4T RAM it fails with “[ 17.797177] 
> BUG: unable to handle kernel paging request at ffff988b19478000”
> 
> 
> I asked in #centos and they asked me to show a list of devices from a 
> working VM (if I use 720G RAM it works). This is the list:
> 
> 
> [root at alberttest1 ~]# lspci
> 
> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
> 
> 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
> 
> 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
> 
> 00:01.2 USB controller: Intel Corporation 82371SB PIIX3 USB 
> [Natoma/Triton II] (rev 01)
> 
> 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
> 
> 00:02.0 VGA compatible controller: Cirrus Logic GD 5446
> 
> 00:03.0 Ethernet controller: Red Hat, Inc. Virtio network device
> 
> 00:04.0 SCSI storage controller: Red Hat, Inc. Virtio block device
> 
> 00:05.0 SCSI storage controller: Red Hat, Inc. Virtio block device
> 
> 00:06.0 SCSI storage controller: Red Hat, Inc. Virtio block device
> 
> 00:07.0 Unclassified device [00ff]: Red Hat, Inc. Virtio memory balloon
> 
> [root at alberttest1 ~]# lsusb
> 
> Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
> 
> Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
> 
> 
> They suspect that the “Virtio memory balloon” driver is causing the 
> problem, and that we should disable it. I googled around and found this:
> 
> 
> http://www.linux-kvm.org/page/Projects/auto-ballooning
> 
> 
> It looks like memory ballooning is deprecated. How can I get rid of the driver?

Looking at Nova's code [0] the memballoon device is only set if mem_stats_period_seconds has a value greater than 0. The default [1] is 10 so you get it by default. I would try setting this config option to 0 and recreating the instance. Note I think this will apply to all VMs and was originally added so that tools could get memory usage statistics.

> 
> 
> Also they complained about my host bridge device; they say that we 
> should have a newer one:
> 
> 
> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
> 
> 
> Where can I specify the host bridge?

For this I think you need to set hw_machine_type [2]. Looking at this bug [3] I think the value you may want is q35.

> 
> 
> <bugs_> ok ozzzo one of the devices is called "virtio memory balloon"
> 
> [13:18:12] <bugs_> do you see that?
> 
> [13:18:21] <ozzzo> yes
> 
> [13:18:47] <bugs_> i suggest you google that and read about what it 
> does - i think it would
> 
> [13:19:02] <bugs_> be worth trying to disable that device on your 
> larger vm to see what happens
> 
> [13:19:18] <ozzzo> ok I will try that, thank you
> 
> [13:19:30] * Altiare (~Altiare at unaffiliated/altiare) has quit IRC 
> (Quit: Leaving)
> 
> [13:21:45] * Sheogorath[m] 
> (sheogora1 at gateway/shell/matrix.org/x-uiiwpoddodtgrwwz) joins #centos
> 
> [13:22:06] <@TrevorH> I also notice that the VM seems to be using the 
> very old 440FX and there's a newer model of hardware available that 
> might be worth checking
> 
> [13:22:21] <@TrevorH> 440FX chipset is the old old pentium Pro chipset!
> 
> [13:22:32] <@TrevorH> I had one of those in about 1996
>

[0] https://opendev.org/openstack/nova/src/branch/master/nova/virt/libvirt/driver.py#L5840-L5852
[1] https://docs.openstack.org/nova/train/configuration/config.html#libvirt.mem_stats_period_seconds
[2] https://docs.openstack.org/nova/train/configuration/config.html#libvirt.hw_machine_type
[3] https://bugs.launchpad.net/nova/+bug/1780138