[libvirt] [PATCH 0/5] Introduce NVDIMM support
mprivozn at redhat.com
Thu Aug 11 08:12:04 UTC 2016
On 04.08.2016 10:42, Stefan Hajnoczi wrote:
> On Mon, Aug 1, 2016 at 4:10 PM, Michal Privoznik <mprivozn at redhat.com> wrote:
>> NVDIMM was introduced to qemu in v2.6.0-rc0~248^2~25. So it's
>> been a while since then.
>> It's not the next big thing, but it is very interesting feature
>> enabling higher performance as reading/writing to the module (and
>> subsequently to the file on the host) does not require a VMEXIT.
>> It can be used to access host files directly bypassing page cache
>> whilst doing so.
>> How to test the feature?
>> 1) you need PMEM enabled kernel:
>> 2) Create a file in the host:
>> truncate -s 512M /tmp/nvdimm
>> 3) Add the following to the domain XML:
>> <memory model='nvdimm' memAccess='shared'>
>> <size unit='KiB'>523264</size>
> The "nvdimm" device also has a label-size property. This determines
> the size of the Namespace Label area described in:
> By default no Namespace Label area is reserved in the file. If the
> user specifies label-size then the memory at the end of the file is
> used as the Namespace Label area.
> It is necessary to expose label-size so users can choose whether or
> not to have a Namespace Label area.
> I have CCed Guangrong Xiao who authored the QEMU patches.
Ah, thank you for that. From the code I understand that the minimum
value for that is 128K, but what about other restrictions? Does the
number need to be aligned? What is the minimal step between two
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