在我的服务器上，我设置了多个 KVM，使用 ubuntu 上的 virsh 进行管理。一个用于 apache 的虚拟机，一个用于数据库、邮件服务器等的虚拟机。一切都运行良好，除了更大的 CMS 系统运行时存在性能问题。我把问题缩小到了数据库。但查询本身并不慢。如果我直接在数据库服务器上运行它们，它们的速度与预期的一样快。但当我从 apache VM 运行它们时则不然。如果我在本地安装这些应用程序而不使用 VM，那么一切都很快。
我构建了一个小工具进行了一些测试，并发现了 500 个不同 SQL 查询的模式： 查询运行时统计 因此，500 个查询中有 34 个比其他查询慢。但所有 34 个查询的速度大致相同。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。
每次运行此脚本时，我都会得到类似的结果。30-40 个查询明显比其他查询慢，但这 30-40 个查询的速度大致相同。
我使用本地域名访问数据库。如果我在脚本运行时监控数据库，CPU 和内存负载将大约增加 10%。
我首先猜测是网络配置存在一些问题，但我找不到任何问题。有人知道这是怎么回事吗？或者能给我一些提示吗？
数据库服务器的配置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>
答案1
您的虚拟机正在模拟 rtl8139 NIC，这是 20 世纪 90 年代中期推出的 10/100 Mbps 设备。此驱动程序的存在只是为了让 KVM 能够让老旧操作系统连接到网络。
对于现代操作系统，即目前仍然常用的任何操作系统，最好使用 virtio NIC。此半虚拟化 NIC 在 Linux 中具有内置驱动程序，并且可用于 Windows（XP/2003 及更高版本）、各种 BSD 版本以及可能的其他操作系统，并且通常是性能最高的选项，无需通过物理 NIC（或虚拟功能）传递到 VM。
对于没有 virtio 驱动程序的较新的操作系统（大约过去 20 年），下一个最佳使用的虚拟 NIC 通常是 e1000，它模拟了英特尔千兆 NIC。