Kvm-Virtualization
如何在 kvm 來賓上啟用 L3 記憶體？
我在 Intel 機器（centos6.5）上啟動了一個 kvm guest（centos6.5），使用 libvirt，guest 的 xml 如下
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'> <name>test-1</name> <uuid>9377bce1-ae83-e356-ed15-919c8625fb4b</uuid> <memory unit='KiB'>8388608</memory> <currentMemory unit='KiB'>4194304</currentMemory> <vcpu placement='static' current='2'>8</vcpu> <os> <type arch='x86_64' machine='rhel6.5.0'>hvm</type> <boot dev='hd'/> <boot dev='cdrom'/> <bootmenu enable='yes'/> <bios useserial='yes' rebootTimeout='0'/> </os> <features> <acpi/> <apic/> <pae/> </features> <cpu mode='host-passthrough'> </cpu> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/data/vhosts//test-1.disk'/> <target dev='vda' bus='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> </disk> <controller type='ide' index='0'> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> </controller> <controller type='virtio-serial' index='0'> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> </controller> <controller type='usb' index='0'> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/> </controller> <interface type='bridge'> <mac address='52:54:00:ea:12:d9'/> <source bridge='br-ex'/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> <serial type='pty'> <target port='0'/> </serial> <console type='pty'> <target type='serial' port='0'/> </console> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'> <listen type='address' address='0.0.0.0'/> </graphics> <video> <model type='cirrus' vram='9216' heads='1'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </video> <memballoon model='virtio'> <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/> </memballoon> </devices> <qemu:commandline> <qemu:env name='SPICE_DEBUG_ALLOW_MC' value='1'/> </qemu:commandline> </domain>現在我很困惑，儘管使用了“host-passthrough”，我仍然看不到guest中的L3記憶體，只有L1，L2記憶體，如下
[root@vm-kvm-115 results]# lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 2 On-line CPU(s) list: 0,1 Thread(s) per core: 1 Core(s) per socket: 1 Socket(s): 2 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 26 Stepping: 5 CPU MHz: 2266.746 BogoMIPS: 4533.49 Hypervisor vendor: KVM Virtualization type: full L1d cache: 32K L1i cache: 32K L2 cache: 4096K NUMA node0 CPU(s): 0,1以下是我的物理機資訊
[root@host-kvm-22 linux]# rpm -qa | grep libvirt libvirt-client-0.10.2-54.el6_7.2.x86_64 libvirt-0.10.2-54.el6_7.2.x86_64 libvirt-devel-0.10.2-54.el6_7.2.x86_64 libvirt-python-0.10.2-54.el6_7.2.x86_64 [root@host-kvm-22 linux]# rpm -qa | grep qemu qemu-img-0.12.1.2-2.479.el6_7.2.x86_64 gpxe-roms-qemu-0.9.7-6.14.el6.noarch qemu-kvm-0.12.1.2-2.479.el6_7.2.x86_64 [root@host-kvm-22 linux]# uname -r 2.6.32-573.8.1.el6.x86_64 [root@host-kvm-22 linux]# lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 16 On-line CPU(s) list: 0-15 Thread(s) per core: 2 Core(s) per socket: 4 Socket(s): 2 NUMA node(s): 2 Vendor ID: GenuineIntel CPU family: 6 Model: 26 Stepping: 5 CPU MHz: 2266.743 BogoMIPS: 4532.68 Virtualization: VT-x L1d cache: 32K L1i cache: 32K L2 cache: 256K L3 cache: 8192K NUMA node0 CPU(s): 0-3,8-11 NUMA node1 CPU(s): 4-7,12-15誰能告訴我如何在來賓上啟用 L3 記憶體？
FWIW，您誤解了主機直通 CPU 模型的範圍。它僅控制 CPU 及其功能標誌的辨識 - CPU 的某些方面仍未向來賓公開。例如，使用您那裡的 XML，所有 8 個 CPU 作為同一 NUMA 節點中的單獨套接字公開給來賓。相反，您的主機有 2 個 NUMA 節點，每個節點有兩個插槽，每個插槽有四個核心。僅此一項可能就足以使主機中的 L3 記憶體概念無法很好地映射到客戶機中。
您可以在 XML 中設置虛擬 CPU 拓撲，但我仍然認為它不會使 L3 記憶體出現。這也無關緊要，因為您允許 8 個虛擬 CPU 在所有 16 個主機 CPU 上浮動。由於您的主機 CPU 分佈在 2 個 NUMA 節點上，因此您將在大部分時間獲得跨 NUMA 節點記憶體訪問，這會帶來很高的延遲損失，這將消除記憶體的任何好處。IOW，您最好專注於更有效的 VM 放置，通過使用 CPU 固定將來賓限製到單個主機 NUMA 節點。