Re: [PATCH 00/10] Introduce virtio-mem <memory/> model

This is a bummer. What this represents is the actual value of membaloon. Yes and no. It shows that we need <actual/> because guest might ignore request to change the requested size. What you're probably experiencing is that you haven't loaded virtio_mem module and thus the virtio-mem device is ignoring requests for change (well, kernel is ignoring them, whatever).

On 2/3/21 7:11 AM, Jing Qi wrote: > I did some test for virtio-mem with libvirt upstream version > v7.0.0-153-g5ea3ecd07d > & qemu-kvm-5.2.0-0.7.rc2.fc34.x86_64 > > S1. Start domain with memory device > > 1. Domain configuration- > <maxMemory slots='16' unit='KiB'>10485760</maxMemory> > <memory unit='KiB'>1572864</memory> > <currentMemory unit='KiB'>1572864</currentMemory> > ... > <cpu mode='host-model' check='partial'> > <numa> > <cell id='0' cpus='0-3' memory='1048576' unit='KiB'/> > </numa> > </cpu> > ... > <memory model='virtio-mem'> > <target> > <size unit='KiB'>524288</size> > <node>0</node> > <block unit='KiB'>2048</block> > <requested unit='KiB'>393216</requested> > </target> > <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' > function='0x0'/> > </memory> > #virsh start pc > Domain 'pc' started > > 2. The domain is started and check mem status, the actual size is "1048576" > #virsh dommemstat pc > actual 1048576 This is a bummer. What this represents is the actual value of membaloon. > swap_in 0 > swap_out 0 > major_fault 257 > minor_fault 130540 > unused 604064 > available 761328 > usable 578428 > last_update 1612325471 > disk_caches 49632 > hugetlb_pgalloc 0 > hugetlb_pgfail 0 > rss 460260 > > 3. Then, check the active xml - > # virsh dumpxml pc > ... > <memory unit='KiB'>1572864</memory> > <currentMemory unit='KiB'>1048576</currentMemory> > .... > <memory model='virtio-mem'> > <target> > <size unit='KiB'>524288</size> > <node>0</node> > <block unit='KiB'>2048</block> > <requested unit='KiB'>393216</requested> > <actual unit='KiB'>0</actual> > </target> > <alias name='virtiomem0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' > function='0x0'/> > </memory> > > Question1 : the value of actual is "0". Is it expected? Yes and no. It shows that we need <actual/> because guest might ignore request to change the requested size. What you're probably experiencing is that you haven't loaded virtio_mem module and thus the virtio-mem device is ignoring requests for change (well, kernel is ignoring them, whatever). > > S2. Also, tried to use hugepage to start the domain - > > <memory model='virtio-mem'> > <target> > <size unit='KiB'>524288</size> > <node>0</node> > <block unit='KiB'>2048</block> > <requested unit='KiB'>393216</requested> > <actual unit='KiB'>0</actual> > </target> > <alias name='virtiomem0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' > function='0x0'/> > </memory> > > #virsh start pc > error: Failed to start domain 'pc' > error: internal error: process exited while connecting to monitor: > 2021-02-03T05:50:33.157836Z qemu-system-x86_64: -object > memory-backend-file,id=memvirtiomem0,mem-path=/dev/hugepages/libvirt/qemu/9-pc,size=536870912,host-nodes=0,policy=bind: > can't open backing store /dev/hugepages/libvirt/qemu/9-pc for guest RAM: > Permission denied > > Question 2: any bug here? Ah, good catch! I'll fix this in v2. Michal