On 4/12/19 12:11 PM, Daniel Henrique Barboza wrote:
On 4/12/19 6:10 AM, Michal Privoznik wrote:
On 4/11/19 7:29 PM, Daniel Henrique Barboza wrote:
On 4/11/19 11:56 AM, Michal Privoznik wrote:
On 4/11/19 4:23 PM, Daniel Henrique Barboza wrote:
Hi,
I've tested these patches again, twice, in similar setups like I
tested
the first version (first in a Power8, then in a Power9 server).
Same results, though. Libvirt will not avoid the launch of a
pseries guest,
with numanode=strict, even if the numa node does not have available
RAM. If I stress test the memory of the guest to force the allocation,
QEMU exits with an error as soon as the memory of the host numa node
is exhausted.
Yes, this is expected. I mean, by default qemu doesn't allocate
memory for the guest fully. You'd have to force it:
<memoryBacking>
<allocation mode='immediate'/>
</memoryBacking>
Tried with this extra setting, still no good. Domain still boots,
even if
there is not enough memory to load up all its ram in the NUMA node
I am setting. For reference, this is the top of the guest XML:
<name>vm1</name>
<uuid>f48e9e35-8406-4784-875f-5185cb4d47d7</uuid>
<memory unit='KiB'>314572800</memory>
<currentMemory unit='KiB'>314572800</currentMemory>
<memoryBacking>
<allocation mode='immediate'/>
</memoryBacking>
<vcpu placement='static'>16</vcpu>
<numatune>
<memory mode='strict' nodeset='0'/>
</numatune>
<os>
<type arch='ppc64' machine='pseries'>hvm</type>
<boot dev='hd'/>
</os>
<clock offset='utc'/>
While doing this test, I recalled that some of my IBM peers recently
mentioned that they were unable to do a pre-allocation of the RAM
of a pseries guest using Libvirt, but they were able to do it using QEMU
directly (using -realtime mlock=on). In fact, I just tried it out
with command
line QEMU and the guest allocated all the memory at boot.
Ah, so looks like -mem-prealloc doesn't work at Power? Can you please
check:
1) that -mem-prealloc is on the qemu command line
Yes. This is the cmd line generated:
/usr/bin/qemu-system-ppc64 \
-name guest=vm1,debug-threads=on \
-S \
-object
secret,id=masterKey0,format=raw,file=/home/user/usr/var/lib/libvirt/qemu/domain-2-vm1/master-key.aes
\
-machine pseries-2.11,accel=kvm,usb=off,dump-guest-core=off \
-bios /home/user/boot_rom.bin \
-m 307200 \
-mem-prealloc \
-realtime mlock=off \
This looks correct.
-smp 16,sockets=16,cores=1,threads=1 \
-uuid f48e9e35-8406-4784-875f-5185cb4d47d7 \
-display none \
-no-user-config \
-nodefaults \
-chardev
socket,id=charmonitor,path=/home/user/usr/var/lib/libvirt/qemu/domain-2-vm1/monitor.sock,server,nowait
\
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=utc \
-no-shutdown \
-boot strict=on \
-device spapr-pci-host-bridge,index=1,id=pci.1 \
-device qemu-xhci,id=usb,bus=pci.0,addr=0x3 \
-drive
file=/home/user/nv2-vm1.qcow2,format=qcow2,if=none,id=drive-virtio-disk0 \
-device
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
\
-chardev pty,id=charserial0 \
-device spapr-vty,chardev=charserial0,id=serial0,reg=0x30000000 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x1 \
-sandbox
on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
-msg timestamp=on
2) how much memory qemu allocates right after it started the guest? I
mean, before you start some mem stress test which causes it to
allocate the memory fully.
It starts with 300Gb. It depletes its assigned NUMA node (that has 256Gb),
then it takes ~70Gb from another NUMA node to complete the 300Gb.
Huh, than -mem-prealloc is working but something else is not. What
strikes me is that once guest starts using the memory then host kernel
kills the guest. So host kernel knows about the limits we've set but
doesn't enforce them when allocating the memory.
This means that the pseries guest is able to do mem pre-alloc. I'd
say that
there might be something missing somewhere (XML, host setup, libvirt
config ...) or perhaps even a bug that is preventing Libvirt from doing
this pre-alloc. This explains why I can't verify this patch series.
I'll see if
I dig it further to understand why when I have the time.
Yeah, I don't know Power well enough to help you. Sorry.
No problem. One question: Libvirt is supposed to let the VM do the full
allocation of its RAM using -mem-prealloc and with -realtime mlock=off,
is that correct?
-mem-prealloc should be enough. -realtime mlock is ther to lock the
allocated memory so that it doesn't get swapped out. You can enable
memory locking via:
<memoryBacking>
<locked/>
</memoryBacking>
Michal
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