首先需求了解基本的信息

1 宿主机CPU特性查看

使用virsh nodeinfo可以看到一些基本信息

复制代码代码如下:virsh nodeinfo
CPU model: x86_64
CPU(s): 32
CPU frequency: 1200 MHz
CPU socket(s): 1
Core(s) per socket: 8
Thread(s) per core: 2
NUMA cell(s): 2
Memory size: 132119080 KiB

使用virsh capabilities可以查看物理机CPU的详细信息，包括物理CPU个数，每个CPU的核数，是否开了超线程。
 
复制代码代码如下:</p> <p>virsh capabilities
<capabilities>
<host>
<uuid>36353332-3030-3643-5534-3235445a564a</uuid>
<cpu>
<arch>x86_64</arch>
<model>SandyBridge</model>
<vendor>Intel</vendor>
<topology sockets='1' cores='8' threads='2'/>
<feature name='erms'/>
<feature name='smep'/>
...
</cpu>
<power_management>
<suspend_disk/>
</power_management>
<migration_features>
<live/>
<uri_transports>
<uri_transport>tcp</uri_transport>
</uri_transports>
</migration_features>
<topology>
<cells num='2'>
<cell id='0'>
<cpus num='16'>
<cpu id='0' socket_id='0' core_id='0' siblings='0,16'/>
...
<cpu id='23' socket_id='0' core_id='7' siblings='7,23'/>
</cpus>
</cell>
<cell id='1'>
<cpus num='16'>
<cpu id='8' socket_id='1' core_id='0' siblings='8,24'/>
...
<cpu id='31' socket_id='1' core_id='7' siblings='15,31'/>
</cpus>
</cell>
</cells>
</topology>
<secmodel>
<model>none</model>
<doi>0</doi>
</secmodel>
<secmodel>
<model>dac</model>
<doi>0</doi>
</secmodel>
</host>
...
</capabilities>

使用virsh freecell命令查看可以当前空闲内存
 
复制代码代码如下:
virsh freecell --all
0: 787288 KiB
1: 94192 KiB
--------------------
Total: 881480 KiB

物理CPU的特性也可以通过/proc/cpuinfo查看
 
cat /proc/cpuinfo
rocessor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 62
model name : Intel(R) Xeon(R) CPU E5-2640 v2 @ 2.00GHz
stepping : 4
cpu MHz : 1200.000
cache size : 20480 KB
physical id : 0
siblings : 16
core id : 0
cpu cores : 8
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid fsgsbase smep erms
bogomips : 3990.67
clflush size : 64
cache_alignment : 64
address sizes : 46 bits physical, 48 bits virtual
power management:
...

综合上面的信息，我们可以得出以下信息：

1) 物理CPU为 E5-2640V2，为8核2颗，开启了超线程，在物理机系统上可以看到32个CPU；

2) 物理机内存为128G 

2 虚拟机CPU使用情况查看

可以使用virsh vcpuinfo命令查看虚拟机vcpu和物理CPU的对应关系
 

复制代码代码如下:virsh vcpuinfo 21
VCPU: 0
CPU: 25
State: running
CPU time: 10393.0s
CPU Affinity: --------yyyyyyyy--------yyyyyyyy
VCPU: 1
CPU: 8
State: running
CPU time: 7221.2s
CPU Affinity: --------yyyyyyyy--------yyyyyyyy
...

可以看到vcpu0被调度到物理机CPU25上，目前是使用状态，使用时间是10393.0s
 
CPU Affinity: --------yyyyyyyy--------yyyyyyyy

yyyyyyy表示可以使用的物理CPU内部的逻辑核，可以看到这台虚拟机可以在8-15， 24-31这些cpu之间调度，为什么不能使用0-7，16-23这些CPU呢，是因为系统的自动numa平衡服务在发生作用，一个虚拟机默认只能使用同一颗物理CPU内部的逻辑核。

使用emulatorpin可以查看虚拟机可以使用那些物理逻辑CPU
 

复制代码代码如下:virsh # emulatorpin 21
emulator: CPU Affinity
----------------------------------
*: 0-31

可以看到0-31我们都可以使用，意味这我们也可以强制将CPU调度到任何CPU上。

3 在线pinning虚拟机的cpu

强制让虚拟机只能在26-31这些cpu之间调度
 
复制代码代码如下:
virsh emulatorpin 21 26-31 --live

查看结果
 

复制代码代码如下:virsh emulatorpin 21
emulator: CPU Affinity
----------------------------------
*: 26-31

查看vcpu info
 
复制代码代码如下:
virsh vcpuinfo 21
VCPU: 0
CPU: 28
State: running
CPU time: 10510.5s
CPU Affinity: --------------------------yyyyyy
VCPU: 1
CPU: 28
State: running
CPU time: 7289.7s
CPU Affinity: --------------------------yyyyyy
...</p> <p>
查看xml文件
 
复制代码代码如下:
virsh # dumpxml 21
<domain type='kvm' id='21'>
<name>cacti-230</name>
<uuid>23a6455c-5cd1-20cd-ecfe-2ba89be72c41</uuid>
<memory unit='KiB'>4194304</memory>
<currentMemory unit='KiB'>4194304</currentMemory>
<vcpu placement='static'>4</vcpu>
<cputune>
<emulatorpin cpuset='26-31'/>
</cputune>

我们也可以强制vcpu和物理机cpu一对一的绑定

强制vcpu 0和物理机cpu 28绑定

强制vcpu 1和物理机cpu 29绑定

强制vcpu 2和物理机cpu 30绑定

强制vcpu 3和物理机cpu 31绑定

复制代码代码如下:
virsh vcpupin 21 0 28
virsh vcpupin 21 1 29
virsh vcpupin 21 2 30
virsh vcpupin 21 3 31

查看xml文件，生效了
 
复制代码代码如下:
virsh # dumpxml 21
<domain type='kvm' id='21'>
<name>cacti-230</name>
<uuid>23a6455c-5cd1-20cd-ecfe-2ba89be72c41</uuid>
<memory unit='KiB'>4194304</memory>
<currentMemory unit='KiB'>4194304</currentMemory>
<vcpu placement='static'>4</vcpu>
<cputune>
<vcpupin vcpu='0' cpuset='28'/>
<vcpupin vcpu='1' cpuset='29'/>
<vcpupin vcpu='2' cpuset='30'/>
<vcpupin vcpu='3' cpuset='31'/>
<emulatorpin cpuset='26-31'/>
</cputune>

是vcpuino命令查看，可以看到配置生效了
 
复制代码代码如下:
virsh vcpuinfo 22
VCPU: 0
CPU: 28
State: running
CPU time: 1.8s
CPU Affinity: ----------------------------y---
VCPU: 1
CPU: 29
State: running
CPU time: 0.0s
CPU Affinity: -----------------------------y--
...

4 cpu pinning简单的性能测试

cpu pinning到底对cpu的性能影响有多大，进行了一个简单的测试。

测试环境

硬件

ntel(R) Xeon(R) CPU X5650 @ 2.67GHz 2颗

软件

centos 7 update到内核 3.10.0-123.8.1.el7.x86_64

虚拟机

centos 7 update到内核 3.10.0-123.8.1.el7.x86_64

虚拟机 cpu 1颗

测试工具

unixbench 5.1.2

测试结果

不做cpu绑定
 
1 CPU in system; running 1 parallel copy of tests
Dhrystone 2 using register variables       28890881.0 lps   (10.0 s, 7 samples)
Double-Precision Whetstone                     3880.4 MWIPS (9.0 s, 7 samples)
Execl Throughput                               4146.3 lps   (30.0 s, 2 samples)
File Copy 1024 bufsize 2000 maxblocks       1051084.3 KBps  (30.0 s, 2 samples)
File Copy 256 bufsize 500 maxblocks          286552.2 KBps  (30.0 s, 2 samples)
File Copy 4096 bufsize 8000 maxblocks       2142638.4 KBps  (30.0 s, 2 samples)
Pipe Throughput                             1726807.0 lps   (10.0 s, 7 samples)
Pipe-based Context Switching                 322865.5 lps   (10.0 s, 7 samples)
Process Creation                              13662.4 lps   (30.0 s, 2 samples)
Shell Scripts (1 concurrent)                   5955.4 lpm   (60.0 s, 2 samples)
Shell Scripts (8 concurrent)                    713.1 lpm   (60.0 s, 2 samples)
System Call Overhead                        2138318.1 lps   (10.0 s, 7 samples)
System Benchmarks Index Values               BASELINE       RESULT    INDEX
Dhrystone 2 using register variables         116700.0   28890881.0   2475.7
Double-Precision Whetstone                       55.0       3880.4    705.5
Execl Throughput                                 43.0       4146.3    964.2
File Copy 1024 bufsize 2000 maxblocks          3960.0    1051084.3   2654.3
File Copy 256 bufsize 500 maxblocks            1655.0     286552.2   1731.4
File Copy 4096 bufsize 8000 maxblocks          5800.0    2142638.4   3694.2
Pipe Throughput                               12440.0    1726807.0   1388.1
Pipe-based Context Switching                   4000.0     322865.5    807.2
Process Creation                                126.0      13662.4   1084.3
Shell Scripts (1 concurrent)                     42.4       5955.4   1404.6
Shell Scripts (8 concurrent)                      6.0        713.1   1188.4
System Call Overhead                          15000.0    2138318.1   1425.5
                                                                   ========
System Benchmarks Index Score                                        1444.7

做了cpu绑定

 
1 CPU in system; running 1 parallel copy of tests
Dhrystone 2 using register variables       29812559.6 lps   (10.0 s, 7 samples)
Double-Precision Whetstone                     3928.7 MWIPS (8.9 s, 7 samples)
Execl Throughput                               4314.4 lps   (30.0 s, 2 samples)
File Copy 1024 bufsize 2000 maxblocks       1068627.9 KBps  (30.0 s, 2 samples)
File Copy 256 bufsize 500 maxblocks          291834.2 KBps  (30.0 s, 2 samples)
File Copy 4096 bufsize 8000 maxblocks       2052612.8 KBps  (30.0 s, 2 samples)
Pipe Throughput                             1737466.2 lps   (10.0 s, 7 samples)
Pipe-based Context Switching                 326839.9 lps   (10.0 s, 7 samples)
Process Creation                              14234.5 lps   (30.0 s, 2 samples)
Shell Scripts (1 concurrent)                   6040.8 lpm   (60.0 s, 2 samples)
Shell Scripts (8 concurrent)                    717.4 lpm   (60.1 s, 2 samples)
System Call Overhead                        2149194.4 lps   (10.0 s, 7 samples)
System Benchmarks Index Values               BASELINE       RESULT    INDEX
Dhrystone 2 using register variables         116700.0   29812559.6   2554.6
Double-Precision Whetstone                       55.0       3928.7    714.3
Execl Throughput                                 43.0       4314.4   1003.4
File Copy 1024 bufsize 2000 maxblocks          3960.0    1068627.9   2698.6
File Copy 256 bufsize 500 maxblocks            1655.0     291834.2   1763.3
File Copy 4096 bufsize 8000 maxblocks          5800.0    2052612.8   3539.0
Pipe Throughput                               12440.0    1737466.2   1396.7
Pipe-based Context Switching                   4000.0     326839.9    817.1
Process Creation                                126.0      14234.5   1129.7
Shell Scripts (1 concurrent)                     42.4       6040.8   1424.7
Shell Scripts (8 concurrent)                      6.0        717.4   1195.7
System Call Overhead                          15000.0    2149194.4   1432.8
                                                                   ========
System Benchmarks Index Score                                        1464.1

比较

综合得分

绑定 1464.1  不绑定 1444.7

综合得分 性能提升 1.34%

浮点运算

绑定 3928.7  不绑定  3880.4

浮点运算 性能提升 1.24%