On Fri, 5 Nov 2021 23:47:37 +1100 Gavin Shan <gs...@redhat.com> wrote:
> Hi Drew and Igor, > > On 11/2/21 6:39 PM, Andrew Jones wrote: > > On Tue, Nov 02, 2021 at 10:44:08AM +1100, Gavin Shan wrote: > >> > >> Yeah, I agree. I don't have strong sense to expose these empty nodes > >> for now. Please ignore the patch. > >> > > > > So were describing empty numa nodes on the command line ever a reasonable > > thing to do? What happens on x86 machine types when describing empty numa > > nodes? I'm starting to think that the solution all along was just to > > error out when a numa node has memory size = 0... memory less nodes are fine as long as there is another type of device that describes a node (apic/gic/...). But there is no way in spec to describe completely empty nodes, and I dislike adding out of spec entries just to fake an empty node. > Sorry for the delay as I spent a few days looking into linux virtio-mem > driver. I'm afraid we still need this patch for ARM64. I don't think x86 does it behave the same way is using pc-dimm hotplug instead of virtio-mem? CCing David as it might be virtio-mem issue. PS: maybe for virtio-mem-pci, we need to add GENERIC_AFFINITY entry into SRAT and describe it as PCI device (we don't do that yet if I'm no mistaken). > has this issue even though I didn't experiment on X86. For example, I > have the following command lines. The hot added memory is put into node#0 > instead of node#2, which is wrong. > > There are several bitmaps tracking the node states in Linux kernel. One of > them is @possible_map, which tracks the nodes available, but don't have to > be online. @passible_map is sorted out from the following ACPI table. > > ACPI_SRAT_TYPE_MEMORY_AFFINITY > ACPI_SRAT_TYPE_GENERIC_AFFINITY > ACPI_SIG_SLIT # if it exists when optional > distance map > # is provided on QEMU side. > > Note: Drew might ask why we have node#2 in "/sys/devices/system/node" again. > hw/arm/virt-acpi-build.c::build_srat() creates additional node in ACPI SRAT > table and the node's PXM is 3 ((ms->numa_state->num_nodes - 1)) in this case, > but linux kernel assigns node#2 to it. > > /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \ > -accel kvm -machine virt,gic-version=host \ > -cpu host -smp 4,sockets=2,cores=2,threads=1 \ > -m 1024M,slots=16,maxmem=64G \ > -object memory-backend-ram,id=mem0,size=512M \ > -object memory-backend-ram,id=mem1,size=512M \ > -numa node,nodeid=0,cpus=0-1,memdev=mem0 \ > -numa node,nodeid=1,cpus=2-3,memdev=mem1 \ > -numa node,nodeid=2 -numa node,nodeid=3 \ > -object memory-backend-ram,id=vmem0,size=512M \ > -device virtio-mem-pci,id=vm0,memdev=vmem0,node=2,requested-size=0 \ > -object memory-backend-ram,id=vmem1,size=512M \ > -device virtio-mem-pci,id=vm1,memdev=vmem1,node=3,requested-size=0 > : > # ls /sys/devices/system/node | grep node > node0 > node1 > node2 > # cat /proc/meminfo | grep MemTotal\: > MemTotal: 1003104 kB > # cat /sys/devices/system/node/node0/meminfo | grep MemTotal\: > Node 0 MemTotal: 524288 kB > > (qemu) qom-set vm0 requested-size 512M > # cat /proc/meminfo | grep MemTotal\: > MemTotal: 1527392 kB > # cat /sys/devices/system/node/node0/meminfo | grep MemTotal\: > Node 0 MemTotal: 1013652 kB > > Try above test after the patch is applied. The hot added memory is > put into node#2 correctly as the user expected. > > # ls /sys/devices/system/node | grep node > node0 > node1 > node2 > node3 > # cat /proc/meminfo | grep MemTotal\: > MemTotal: 1003100 kB > # cat /sys/devices/system/node/node2/meminfo | grep MemTotal\: > Node 2 MemTotal: 0 kB > > (qemu) qom-set vm0 requested-size 512M > # cat /proc/meminfo | grep MemTotal\: > MemTotal: 1527388 kB > # cat /sys/devices/system/node/node2/meminfo | grep MemTotal\: > Node 2 MemTotal: 524288 kB > > Thanks, > Gavin > > > >
