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From: Markus Armbruster <armbru@redhat.com>
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Date: Wed, 03 Feb 2016 16:42:21 +0100
In-Reply-To: <56B12A05.4060305@redhat.com> (Eric Blake's message of "Tue, 2
	Feb 2016 15:13:25 -0700")
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Subject: Re: [Qemu-devel] [PATCH 3/3] balloon: don't use NVDIMM for
	ballooning
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To: Eric Blake <eblake@redhat.com>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, Xiao Guangrong <guangrong.xiao@linux.intel.com>, "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, "Denis V. Lunev" <den@openvz.org>, Igor Mammedov <imammedo@redhat.com>

Eric Blake <eblake@redhat.com> writes:

> On 01/27/2016 11:51 PM, Vladimir Sementsov-Ogievskiy wrote:
>> 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 balloon almost
>> 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
>> commit 463756d03:
>>  virtio-balloon: Fix balloon not working correctly when hotplug memory
>> 
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> CC: Stefan Hajnoczi <stefanha@redhat.com>
>> CC: Xiao Guangrong <guangrong.xiao@linux.intel.com>
>> CC: "Michael S. Tsirkin" <mst@redhat.com>
>> CC: Igor Mammedov <imammedo@redhat.com>
>> CC: Eric Blake <eblake@redhat.com>
>> CC: Markus Armbruster <armbru@redhat.com>
>> ---
>
>> @@ -308,7 +309,9 @@ static ram_addr_t get_current_ram_size(void)
>>          if (value) {
>>              switch (value->type) {
>>              case MEMORY_DEVICE_INFO_KIND_DIMM:
>> -                size += value->u.dimm->size;
>> +                if (strcmp(value->u.dimm->type, TYPE_NVDIMM)) {
>
> If you fix 2/3 to use a QAPI enum, then this will be an integer compare
> instead of a strcmp().

Another option is to add a flag to the subtypes of TYPE_PC_DIMM, set it
for the subtypes that should be counted here, and accumulate the sizes
of devices where the flag is set.  Requires iterating directly over the
devices here (like qmp_pc_dimm_device_list() does under the hood) rather
than the MemoryDeviceInfoList returned by qmp_pc_dimm_device_list(),