我试图确定为什么我的 KVM 主机显示特定来宾的系统 CPU 使用率很高。
我已经设置了一个 KVM 主机（Ubuntu 20.04）来托管一个来宾 VM（Ubuntu 20.04）。我将客户机配置为使用来自套接字 1 中处理器的内核（通过 vcpu / vcpupin / emulatorpin），内存（通过 numatune）连接到套接字 1 中处理器上的通道，并且 NIC（通过接口/地址源）连接到插槽 1 中处理器上的通道，以确保 VM 以最佳状态运行。即使我已经完成了配置 IOMMU、SR-IOV 和 Intel VF 以将 NIC 的虚拟功能 PCI 设备直接传递到 VM 的过程，主机实例仍然看到来宾停放的内核上的系统 cpu 使用率很高这是网卡中断。
我无法弄清楚为什么涉及主机系统，因为 PCI 设备与主机断开连接并直接连接到来宾。这会导致巨大的性能问题。有没有人经历过这个？我这边有配置错误吗？请参阅下面的配置和 mpstat 数据：
<vcpu placement='static' cpuset='0,2,4,6,8,10,12,14,16,18,20,22,24,52,54,56,58,60,62,64,66,68,70,72,74,76'>26</vcpu>
<cputune>
<vcpupin vcpu='0' cpuset='0'/>
<vcpupin vcpu='1' cpuset='2'/>
<vcpupin vcpu='2' cpuset='4'/>
<vcpupin vcpu='3' cpuset='6'/>
<vcpupin vcpu='4' cpuset='8'/>
<vcpupin vcpu='5' cpuset='10'/>
<vcpupin vcpu='6' cpuset='12'/>
<vcpupin vcpu='7' cpuset='14'/>
<vcpupin vcpu='8' cpuset='16'/>
<vcpupin vcpu='9' cpuset='18'/>
<vcpupin vcpu='10' cpuset='20'/>
<vcpupin vcpu='11' cpuset='22'/>
<vcpupin vcpu='12' cpuset='24'/>
<vcpupin vcpu='13' cpuset='52'/>
<vcpupin vcpu='14' cpuset='54'/>
<vcpupin vcpu='15' cpuset='56'/>
<vcpupin vcpu='16' cpuset='58'/>
<vcpupin vcpu='17' cpuset='60'/>
<vcpupin vcpu='18' cpuset='62'/>
<vcpupin vcpu='19' cpuset='64'/>
<vcpupin vcpu='20' cpuset='66'/>
<vcpupin vcpu='21' cpuset='68'/>
<vcpupin vcpu='22' cpuset='70'/>
<vcpupin vcpu='23' cpuset='72'/>
<vcpupin vcpu='24' cpuset='74'/>
<vcpupin vcpu='25' cpuset='76'/>
<emulatorpin cpuset='0,2,4,6,8,10,12,14,16,18,20,22,24,52,54,56,58,60,62,64,66,68,70,72,74,76'/>
</cputune>
<numatune>
<memory mode='strict' nodeset='0'/>
</numatune>
<cpu mode='host-passthrough' check='none'/>
<interface type='hostdev' managed='yes'>
<mac address='52:54:08:06:48:01'/>
<driver name='vfio'/>
<source>
<address type='pci' domain='0x0000' bus='0x19' slot='0x02' function='0x0'/>
</source>
<address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
</interface>
<interface type='hostdev' managed='yes'>
<mac address='52:54:08:06:48:01'/>
<driver name='vfio'/>
<source>
<address type='pci' domain='0x0000' bus='0x19' slot='0x0a' function='0x0'/>
</source>
<address type='pci' domain='0x0000' bus='0x08' slot='0x00' function='0x0'/>
</interface>
<interface type='hostdev' managed='yes'>
<mac address='52:54:08:06:48:02'/>
<driver name='vfio'/>
<source>
<address type='pci' domain='0x0000' bus='0x19' slot='0x02' function='0x1'/>
</source>
<address type='pci' domain='0x0000' bus='0x09' slot='0x00' function='0x0'/>
</interface>
<interface type='hostdev' managed='yes'>
<mac address='52:54:08:06:48:02'/>
<driver name='vfio'/>
<source>
<address type='pci' domain='0x0000' bus='0x19' slot='0x0a' function='0x1'/>
</source>
<address type='pci' domain='0x0000' bus='0x0a' slot='0x00' function='0x0'/>
</interface>
22:26:38 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle
22:26:43 all 0.00 0.00 3.39 0.00 0.00 0.09 0.00 7.30 0.00 89.22
22:26:43 0 0.00 0.00 7.30 0.00 0.00 0.00 0.00 26.57 0.00 66.13
22:26:43 1 0.00 0.00 0.00 0.00 0.00 8.43 0.00 0.00 0.00 91.57
22:26:43 2 0.00 0.00 10.38 0.00 0.00 0.00 0.00 29.34 0.00 60.28
22:26:43 4 0.00 0.00 8.69 0.00 0.00 0.00 0.00 29.09 0.00 62.22
22:26:43 6 0.00 0.00 5.00 0.00 0.00 0.00 0.00 23.20 0.00 71.80
22:26:43 8 0.20 0.00 39.31 0.00 0.00 0.00 0.00 35.03 0.00 25.46
22:26:43 10 0.00 0.00 6.96 0.00 0.00 0.00 0.00 31.21 0.00 61.83
22:26:43 12 0.00 0.00 44.90 0.00 0.00 0.00 0.00 35.31 0.00 19.80
22:26:43 14 0.00 0.00 13.18 0.00 0.00 0.00 0.00 32.05 0.00 54.77
22:26:43 16 0.20 0.00 5.31 0.00 0.00 0.00 0.00 26.12 0.00 68.37
22:26:43 18 0.00 0.00 15.95 0.00 0.00 0.20 0.00 30.47 0.00 53.37
22:26:43 20 0.00 0.00 7.04 0.00 0.00 0.00 0.00 26.16 0.00 66.80
22:26:43 22 0.00 0.00 15.76 0.00 0.00 0.00 0.00 31.92 0.00 52.32
22:26:43 24 0.00 0.00 7.35 0.00 0.00 0.00 0.00 27.96 0.00 64.69
22:26:43 52 0.00 0.00 10.46 0.00 0.00 0.00 0.00 29.78 0.00 59.76
22:26:43 54 0.00 0.00 7.35 0.00 0.00 0.00 0.00 26.12 0.00 66.53
22:26:43 56 0.00 0.00 6.91 0.00 0.00 0.00 0.00 29.67 0.00 63.41
22:26:43 58 0.00 0.00 7.82 0.00 0.00 0.00 0.00 29.42 0.00 62.76
22:26:43 60 0.00 0.00 37.17 0.00 0.00 0.00 0.00 35.15 0.00 27.68
22:26:43 62 0.00 0.00 14.99 0.00 0.00 0.00 0.00 28.54 0.00 56.47
22:26:43 64 0.00 0.00 37.50 0.00 0.00 0.00 0.00 33.53 0.00 28.97
22:26:43 66 0.00 0.00 7.30 0.00 0.00 0.00 0.00 29.61 0.00 63.08
22:26:43 68 0.00 0.00 8.08 0.00 0.00 0.00 0.00 27.88 0.00 64.04
22:26:43 70 0.00 0.00 7.09 0.00 0.00 0.00 0.00 24.49 0.00 68.42
22:26:43 72 0.20 0.00 6.94 0.00 0.00 0.00 0.00 29.96 0.00 62.90
22:26:43 74 0.00 0.00 7.63 0.00 0.00 0.00 0.00 27.91 0.00 64.46
22:26:43 76 0.00 0.00 8.63 0.00 0.00 0.00 0.00 29.32 0.00 62.05
22:26:43 98 0.00 0.00 0.20 0.00 0.00 0.00 0.00 0.00 0.00 99.80
22:26:43 100 0.00 0.00 0.20 0.00 0.00 0.00 0.00 0.00 0.00 99.80
有谁知道什么配置不正确或为什么 %sys 在核心 8、12、60、64 上如此之高？