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我在同一台主机上构建了一个macOS虚拟机和一个ubuntu虚拟机。两个虚拟机的配置几乎一样。但是当我使用sysbench测试我的两台 VM 的性能时，我发现当读/写块大小小于L3 缓存大小时，macOS VM 的内存读/写速度比 Ubuntu VM 慢。所以，我认为 macOS VM 中 L1/L2/L3 缓存的读/写速度比 Ubuntu VM 慢。但是，我不知道为什么会这样。

我的 macOS 虚拟机的 xml 文件如下：

<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <name>mac_os_catalina</name>
  <memory unit='KiB'>16777216</memory>
  <currentMemory unit='KiB'>16777216</currentMemory>
  <vcpu placement='static'>12</vcpu>
  <memoryBacking>
    <hugepages/>
    <nosharepages/>
  </memoryBacking>
  <cputune>
    <vcpupin vcpu="0" cpuset="6"/>
    <vcpupin vcpu="1" cpuset="30"/>
    <vcpupin vcpu="2" cpuset="8"/>
    <vcpupin vcpu="3" cpuset="32"/>
    <vcpupin vcpu="4" cpuset="10"/>
    <vcpupin vcpu="5" cpuset="34"/>
    <vcpupin vcpu="6" cpuset="12"/>
    <vcpupin vcpu="7" cpuset="36"/>
    <vcpupin vcpu="8" cpuset="14"/>
    <vcpupin vcpu="9" cpuset="38"/>
    <vcpupin vcpu="10" cpuset="16"/>
    <vcpupin vcpu="11" cpuset="40"/>
    <emulatorpin cpuset="2,26,4,28"/>
  </cputune>
  <numatune>
    <memory mode='preferred' nodeset='0'/>
  </numatune>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-q35-2.11'>hvm</type>
    <loader readonly='yes' type='pflash'>OVMF_CODE.fd</loader>
    <nvram>OVMF_VARS-1024x768.fd</nvram>
  </os>
  <features>
    <acpi/>
    <apic/>
      <kvm>
        <hidden state='on'/>
      </kvm>
    <vmport state='off'/>
  </features>
  <cpu>
    <topology sockets='12' cores='1' threads='1'/>
    <cpu mode='host-model'/>
    <cache level='3' mode='emulate'/>
    <numa>
      <cell id='0' cpus='0-11' memory='16777216' unit='KiB'/>
    </numa>
  </cpu>
  <clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='writeback'/>
      <source file='ESP.qcow2'/>
      <target dev='sda' bus='sata'/>
      <alias name='sata-disk0'/>
      <boot order='1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writeback'/>
      <source file='BaseSystem.img'/>
      <target dev='sdb' bus='sata'/>
      <alias name='sata-disk1'/>
      <boot order='2'/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='writeback'/>
      <source file='mac_hdd.qcow2'/>
      <target dev='sdc' bus='sata'/>
      <alias name='sata-disk2'/>
      <boot order='3'/>
      <address type='drive' controller='0' bus='0' target='0' unit='2'/>
    </disk>
  </devices>
  <qemu:commandline>
    <qemu:arg value='-cpu'/>
    <qemu:arg value='Penryn,vendor=GenuineIntel,kvm=on,+sse3,+sse4.2,+aes,+xsave,+avx,+xsaveopt,+xsavec,+xgetbv1,+avx2,+bmi2,+smep,+bmi1,+fma,+movbe,+invtsc'/>
    <qemu:arg value='-device'/>
    <qemu:arg value='isa-applesmc,osk=ourhardworkbythesewordsguardedpleasedontsteal(c)AppleComputerInc'/>
    <qemu:arg value='-smbios'/>
    <qemu:arg value='type=2'/>
    <qemu:arg value='-nographic'/>
  </qemu:commandline>
</domain>

Ubuntu VM的xml文件如下：

<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <name>ubuntu</name>
  <memory unit='KiB'>16777216</memory>
  <currentMemory unit='KiB'>16777216</currentMemory>
  <vcpu placement='static'>12</vcpu>
  <cputune>
    <vcpupin vcpu="0" cpuset="6"/>
    <vcpupin vcpu="1" cpuset="30"/>
    <vcpupin vcpu="2" cpuset="8"/>
    <vcpupin vcpu="3" cpuset="32"/>
    <vcpupin vcpu="4" cpuset="10"/>
    <vcpupin vcpu="5" cpuset="34"/>
    <vcpupin vcpu="6" cpuset="12"/>
    <vcpupin vcpu="7" cpuset="36"/>
    <vcpupin vcpu="8" cpuset="14"/>
    <vcpupin vcpu="9" cpuset="38"/>
    <vcpupin vcpu="10" cpuset="16"/>
    <vcpupin vcpu="11" cpuset="40"/>
    <emulatorpin cpuset="2,26,4,28"/>
  </cputune>
  <numatune>
    <memory mode='preferred' nodeset='0'/>
  </numatune>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-q35-2.11'>hvm</type>
  </os>
  <features>
    <acpi/>
    <apic/>
<!--    <kvm>-->
<!--      <hidden state='on'/>-->
<!--    </kvm>-->
    <vmport state='off'/>
  </features>
  <cpu>
    <topology sockets='1' cores='12' threads='1'/>
    <cache level='3' mode='emulate'/>
    <numa>
      <cell id='0' cpus='0-11' memory='16777216' unit='KiB'/>
    </numa>
  </cpu>
  <clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writeback'/>
      <source file='hdd.img'/>
      <target dev='sda' bus='sata'/>
      <alias name='sata-disk0'/>
      <boot order='1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
  </devices>
  <qemu:commandline>
    <qemu:arg value='-cpu'/>
    <qemu:arg value='Penryn,kvm=on,l3-cache=on,vendor=GenuineIntel,+invtsc,vmware-cpuid-freq=on,+pcid,+ssse3,+sse4.2,+popcnt,+avx,+aes,+xsave,+xsaveopt,check'/>
    <qemu:arg value='-device'/>
    <qemu:arg value='isa-applesmc,osk=ourhardworkbythesewordsguardedpleasedontsteal(c)AppleComputerInc'/>
    <qemu:arg value='-smbios'/>
    <qemu:arg value='type=2'/>
    <qemu:arg value='-nographic'/>
  </qemu:commandline>
</domain>

如上所示，我只为不同的虚拟机更改了 xml 中的磁盘配置。

RAM读取速度的数据如下，'seq'代表顺序读取，'rnd'代表随机读取。

随机读取速度

顺序读取速度

我在网上找了很久。但是没有用。请帮助或尝试提供一些解决此问题的想法。提前致谢。

4

1 回答 1

0

由于您询问的是两个 VM 之间的性能差异，因此实际提供两个 VM 的配置会很有用。通常，正确配置的 Ubuntu 客户机将使用 virtio-blk 作为磁盘，这将在 I/O 性能方面轻松击败模拟的 sata 控制器。我在这里看不到你的 Ubuntu 来宾配置，所以无法确认这是否真的是原因。

于 2020-06-10T12:37:11.900 回答