[libvirt-users] what is the xml fomat about memory-backend-file
Linhaifeng
haifeng.lin at huawei.com
Wed Oct 8 01:35:30 UTC 2014
On 2014/9/28 16:19, Jincheng Miao wrote:
>
> On 09/28/2014 01:38 PM, Linhaifeng wrote:
>>
>> On 2014/9/25 2:05, Eric Blake wrote:
>>> On 09/24/2014 02:05 AM, Linhaifeng wrote:
>>>> Hi,
>>>>
>>>> I want to use virsh to create a VM with the qemu parameter '-object memory-backend-file,id=mem,size=2048M,mem-path=/mnt/huge,share=on -numa node,memdev=mem'.
>>> Looking at tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages.args, I
>>> see several instances of "-object memory-backend-file...", so look at
>>> the counterpart .xml file for some examples:
>>>
>>> <memoryBacking>
>>> <hugepages>
>>> <page size='2048' unit='KiB' nodeset='1'/>
>>> <page size='1048576' unit='KiB' nodeset='0,2-3'/>
>>> </hugepages>
>>> </memoryBacking>
>>>
>>>
>> Thank you.
>>
>> I use this xml:
>> <cpu>
>> <numa>
>> <cell id='0' cpus='0' memory='1073741824' memAccess='shared'/>
>> <cell id='1' cpus='1' memory='1073741824' memAccess='shared'/>
>> </numa>
>> </cpu>
>> <memoryBacking>
>> <hugepages>
>> <page size="2" unit="M" nodeset="0,1"/>
>> </hugepages>
>> </memoryBacking>
>>
>> but there is also some error:
>> [2014-09-28T05:28:32.373335Z] migration_configure:652 Parameter 'cache size' expects exceeds guest ram size
>> [2014-09-28T05:28:32.373422Z] main:3517 start memory options parse
>> 2014-09-28T05:28:32.373802Z qemu-kvm: -object memory-backend-file,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu,size=1048576M,id=ram-node0: unable to map backing store for hugepages: Cannot allocate memory
>> 2014-09-28T05:28:32.373895Z qemu-kvm: -object memory-backend-file,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu,size=1048576M,id=ram-node1: unable to map backing store for hugepages: Cannot allocate memory
>
> get total number of the hugepages you could use:
> # cat /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
>
> From your xml:
> <cell id='0' cpus='0' memory='1073741824' memAccess='shared'/>
> <cell id='1' cpus='1' memory='1073741824' memAccess='shared'/>
> I guess your machine doesn't have so much hugepage memory: sum(1073741824 + 1073741824)=2048G !!!
>
Thank you.
Yes,you are right.This is my mistake.Actually i want to use 1G.
>>
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