Re: [Qemu-devel] [PATCH 1/1] nvdimm: disable balloon

[Eric Blake]

On 01/18/2016 04:42 AM, Denis V. Lunev wrote:
> From: Vladimir Sementsov-Ogievskiy <address@hidden>
> 
> NVDIMM for now is planned to use as a backing store for DAX filesystem
> in the guest and thus this memory is excluded from guest memory management
> and LRUs.
> 
> In this case libvirt running QEMU along with configured ballon almost

s/ballon/balloon/

> immediately inflates balloon and effectively kill the guest as
> qemu counts nvdimm as part of the ram.
> 
> Counting dimm devices as part of the ram for ballooning was started from
> patch
>  virtio-balloon: Fix balloon not working correctly when hotplug memory

Useful to mention the commit id: 463756d03

> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Stefan Hajnoczi <address@hidden>
> CC: Xiao Guangrong <address@hidden>
> CC: "Michael S. Tsirkin" <address@hidden>
> CC: Igor Mammedov <address@hidden>
> CC: Eric Blake <address@hidden>
> CC: Markus Armbruster <address@hidden>

I'm just doing an interface review.

> ---
> The patch is submitted start a discussion. It may be technically correct,
> but for us the situation is a bit shady.
> 

> +++ b/qapi-schema.json
> @@ -3922,6 +3922,8 @@
>  #
>  # @hotpluggable: true if device if could be added/removed while machine is 
> running
>  #
> +# @in-ram: true if device if should be counted in current ram size (since 
> 2.6)

Output-only, so you are okay adding a new non-optional field.  However,
is "should be counted" the right wording, or would it be better as "is
counted", given that the user doesn't have any way to change whether a
device gets counted or not, but is merely learning the state previously
chosen by the device.

As for whether it makes sense technically, I'll leave that to discussion.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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