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Dominik Sander
Asked: 2020-09-28 07:13:44 +0800 CST

与 KVM 的数据库连接缓慢

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在我的服务器上，我有一个设置，在 ubuntu 上使用 virsh 管理多个 KVM。一个用于 apache 的 vm，一个用于数据库、邮件服务器等的 vm。一切都运行良好，除了更大的 CMS 系统在性能问题上运行。我把它缩小到数据库。但并不是查询本身很慢。如果我直接在数据库服务器上运行它们，它们的速度和预期的一样快。但不是当我从 apache VM 运行它们时。如果我在没有虚拟机的情况下在本地安装这些应用程序，那么一切都很快。

我构建了一个小工具来进行一些测试，并为 500 个不同的 SQL 查询找到了这种模式： 查询运行时统计 因此 500 个查询中的 34 个比其他查询慢。但是所有 34 个都差不多慢。如果我直接在数据库服务器上运行相同的脚本，所有 500 个查询都运行得很快。

每次我运行这个脚本时，我都会得到类似的结果。30 - 40 次查询明显慢于其他查询，但 30 - 40 次查询的速度大致相同。

我使用本地域名访问数据库。如果我在脚本运行期间监控数据库，CPU 和内存负载将大致扩展 10%。

我的第一个猜测是网络配置中的一些问题，但我在那里找不到任何问题。有人知道这里发生了什么吗？或者也许是我可以查看的提示？

配置数据库服务器的xml：

<domain type='kvm' id='4'>
  <name>sql1</name>
  <uuid>beb47f80-10a4-4687-891e-6195933d636d</uuid>
  <memory unit='KiB'>4194304</memory>
  <currentMemory unit='KiB'>4194304</currentMemory>
  <vcpu placement='static'>2</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-i440fx-2.1'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <cpu mode='custom' match='exact'>
    <model fallback='forbid'>SandyBridge</model>
  </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>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/vm/sql1.img'/>
      <backingStore/>
      <target dev='hda' bus='ide'/>
      <alias name='ide0-0-0'/>
      <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='/vm/sql1_data.img'/>
      <backingStore/>
      <target dev='hdb' bus='ide'/>
      <alias name='ide0-0-1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>
    <controller type='usb' index='0' model='ich9-ehci1'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x7'/                                                                                                                                                                                                >
    </controller>
    <controller type='usb' index='0' model='ich9-uhci1'>
      <alias name='usb'/>
      <master startport='0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'                                                                                                                                                                                                 multifunction='on'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci2'>
      <alias name='usb'/>
      <master startport='2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x1'/                                                                                                                                                                                                >
    </controller>
    <controller type='usb' index='0' model='ich9-uhci3'>
      <alias name='usb'/>
      <master startport='4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x2'/                                                                                                                                                                                                >
    </controller>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    </controller>
    <controller type='ide' index='0'>
      <alias name='ide'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/                                                                                                                                                                                                >
    </controller>
    <controller type='scsi' index='0'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/                                                                                                                                                                                                >
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:37:7d:67'/>
      <source bridge='intbr0'/>
      <target dev='vnet3'/>
      <model type='rtl8139'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/                                                                                                                                                                                                >
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/3'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/3'>
      <source path='/dev/pts/3'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <input type='mouse' bus='ps2'>
      <alias name='input0'/>
    </input>
    <input type='keyboard' bus='ps2'>
      <alias name='input1'/>
    </input>
    <graphics type='vnc' port='5903' autoport='yes' listen='0.0.0.0'>
      <listen type='address' address='0.0.0.0'/>
    </graphics>
    <video>
      <model type='cirrus' vram='16384' heads='1' primary='yes'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/                                                                                                                                                                                                >
    </video>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/                                                                                                                                                                                                >
    </memballoon>
  </devices>
  <seclabel type='none' model='none'/>
  <seclabel type='dynamic' model='dac' relabel='yes'>
    <label>+109:+117</label>
    <imagelabel>+109:+117</imagelabel>
  </seclabel>
</domain>

Web服务器的配置xml：

<domain type='kvm' id='2'>
  <name>web1</name>
  <uuid>7ac19f58-438f-4c54-b232-7acd58bb4497</uuid>
  <memory unit='KiB'>4194304</memory>
  <currentMemory unit='KiB'>4194304</currentMemory>
  <vcpu placement='static'>2</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-i440fx-2.1'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <cpu mode='custom' match='exact'>
    <model fallback='forbid'>SandyBridge</model>
  </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>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writeback'/>
      <source file='/vm/web1.img'/>
      <backingStore/>
      <target dev='hda' bus='ide'/>
      <alias name='ide0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/vm/web1_data.img'/>
      <backingStore/>
      <target dev='hdb' bus='ide'/>
      <alias name='ide0-0-1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>
    <controller type='usb' index='0' model='ich9-ehci1'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x7'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci1'>
      <alias name='usb'/>
      <master startport='0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0' multifunction='on'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci2'>
      <alias name='usb'/>
      <master startport='2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x1'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci3'>
      <alias name='usb'/>
      <master startport='4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    </controller>
    <controller type='ide' index='0'>
      <alias name='ide'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:99:65:78'/>
      <source bridge='intbr0'/>
      <target dev='vnet1'/>
      <model type='rtl8139'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/1'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/1'>
      <source path='/dev/pts/1'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <input type='mouse' bus='ps2'>
      <alias name='input0'/>
    </input>
    <input type='keyboard' bus='ps2'>
      <alias name='input1'/>
    </input>
    <graphics type='vnc' port='5901' autoport='yes' listen='0.0.0.0'>
      <listen type='address' address='0.0.0.0'/>
    </graphics>
    <video>
      <model type='cirrus' vram='16384' heads='1' primary='yes'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='none' model='none'/>
  <seclabel type='dynamic' model='dac' relabel='yes'>
    <label>+109:+117</label>
    <imagelabel>+109:+117</imagelabel>
  </seclabel>
</domain>
ubuntu kvm-virtualization virtual-machines database-performance

1 个回答

  1. Best Answer

    您的 VM 正在模拟 rtl8139 NIC，这是 1990 年代中期的 10/100 Mbps 设备。此驱动程序仅存在以便 KVM 可以允许古老的操作系统连接到网络。

    对于现代操作系统，今天仍然常用的任何东西，最好使用 virtio 网卡。这种半虚拟化 NIC 在 Linux 中具有内置驱动程序，以及适用于 Windows（XP/2003 和更高版本）、各种 BSD 风格以及可能的其他操作系统的可用驱动程序，并且通常是性能最高的选项，没有通过物理 NIC（或虚拟功能）到虚拟机。

    对于最近没有 virtio 驱动程序的操作系统（过去 20 年左右），下一个最好的虚拟 NIC 通常是 e1000，它模拟 Intel 千兆位 NIC。

    • 1

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