Hot add memory to RHEL 5.3 x64

[tehberg]

Hi!

Per the GuestOS guide at http://www.vmware.com/pdf/GuestOS_guide.pdf, hotplug memory is supported for RHEL 5 AP x64. However, when I try to add memory to the VM, I get ACPI errors complaining about not being able to extend some addresses, and the hotplug memory device failing.

Is there anything I need to do on the guest to enable this? I have the tools installed, not sure what else to do.

Thanks.

Rob

[admin]

Could you please ensure 'acpiphp' and 'acpi_memhotplug' modules are loaded.

"lsmod | grep acpi" should show "acpiphp" and "acpi_memhotplug"

If any of the above modules are not loaded then load them manually and retry.

1. modprobe acpiphp

1. modprobe acpi_memhotplug

[tehberg]

Hi!

Thanks for the response. Bot modules are loaded, but the first time I try to add more memory, I get this in my dmesg and messages file:

late_phys_pmd_init trying to trample pte entry 1f4001e3@1f600000

Then subsequent attempts to add memory I get:

VMCIUtil: updating context id from <some addr> to <some addr> on event 0.

Hotplug Mem Device

System RAM resource 20000000 - 27ffffff cannot be added

ACPI: add_memory failed

ACPI: Cannot enable memory device

[petr]

Unfortunately both are bugs in the kernel. late_phys_pmd_init got fixed upstream sometime in past two years, and it should not have any negative effect except warning.

Second one is caused also by Linux kernel bug - if you'll look at /proc/iomem, you'll see that Linux kernel programmed svga's and scsi0 ROM into 0x20000000-0x27ffffff region, and later when memory is hot-added there kernel fails to bring that memory online - causing loss of 64MB of memory on 32bit kernels, and 128MB on 64bit kernels if your VM has less than 3GB of memory. One of our engineers submitted fix for that (http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=809d9a8f93bd8504dcc34b16bbfdfd1a8c9bb1ed), but it got later reverted, so depending on your VM configuration you may be missing 64-128MB of memory after hot-add. It has no impact on VM's memory consumption, except that *.vmss suspend file will be 128MB bigger than it could be.

[tehberg]

Thanks petr.

I'm curious as to why the memory is not reflected in top or any other system monitoring tool. When I add 1G or 2G of mem, the original amount is still shown in top and other tools.

Am I missing a step?

Thanks.

Rob

[Datto]

See if the text toward the bottom of this article helps:

And this article:

http://communities.vmware.com/docs/DOC-10492

Datto

[Allimuthu]

Hi,

I am using RHEL 5.7 and enabled hot plug memory addition in my Vsphere client and I am able to modify the memory in Vsphere. However, it sometimes not working when we check at console. I could see the following error message in the messages log.

Note: I have made online state in all memory$/state file.

Kernel: Adding memory would exceeded 4GB boundry. If you need this, please reboot with 'iommu=soft'

Kernel: ACPI : add_memory failed

Kernel: ACPI : can not enable memory device.

I am using kenel version 2.6.

any idea?