libvirt users - Mar 2020 - how can i get enough mem stat detai from win7 vm with virtio-win driver install and blnsrv started ?

hi，every one
I have some trouble with the virsh to get vm mem-usage in guest os.
[root@localhost ~]# virsh list --all
Id Name State

1 wwl_centos7_1708 running
2 windows-virtio-template running

I create two vms one guest os is centos, the other is window 7
virsh dommemstat wwl_centos7_1708
actual 4194304
swap_in 0
swap_out 0
major_fault 194
minor_fault 219454
unused 3729588
available 3881812
last_update 1581406529
rss 2969400
so i can get the vm mem-used detail,
but if my guest os is windows, though I install virtio-win driver and run
blnsrv.exe -i start the service,
I fail to get not enough vm mem stat info, as following:
virsh dommemstat windows-virtio-template
actual 8388608
last_update 1584947706
rss 8263664

can anyone tell me how can I succ to get window's vm with enough mem stat
info the same with centos ?
thanks u !