KVM - The Linux Kernel-Based Virtual Machine
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-mempath option
May 23, 2009 - 10:13am
I used to use the -mem-path option in KVM (83 as part of Proxmox 1.1) ... I have since upgraded to Proxmox 1.2 (with kvm-85). I found that what used to be -mem-path is now -mempath. Further, I find that it no longer uses the hugetlbfs share that used to work.
As a result the amount of memory it eats up is much higher causing the host server to perform swapping.
How can I utilize -mempath properly?
Thanks for a great job! I am sure that we all appreciate the hard work put into this project.
mspock2010
You are right in that -mem-path has now become -mempath. The problem might be that your kernel does not support mmu notifiers. A patch was applied back in January 2009 to disable mempath if mmu notifiers was not supported due to the fact that hugepages can cause memory corruption without it. Check if your kernel supports mmu notifiers with the following command
Haydn
Hi Haydn,
You were right! the MMU_NOTIFIER was not supported. Question now is, can I just recompile my kernel to support this? Or is there a danger in possibly corrupting things?
Thanks and best regards ...
You must be running at least kernel version 2.6.27 for mmu notifier support. I'm not sure but I would think that it should be enabled by default if you're running such a kernel. There's no risk of corrupting anything if you recompile your kernel to support it. mmu notifiers was actually accepted in 2.6.27-rc1. Below is the announcement by the actual developer of mmu notifiers, Andrea Arcangeli.
http://www.mail-archive.com/kvm@vger.kernel.org/msg02285.html
Note that the spelling has been corrected in kvm-86 so it's now -mem-path as originally spelt.
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