使用libvirt技术监控虚拟机资源利用情况
（一）计算资源与内存资源的监控
libvirt中提供virDomainGetInfo方法可以将一个domain的计算资源和内存资源的使用情况封装在一个结构体中，如下：
- struct virDomainInfo{
- unsigned char state : //the running state, one of virDomainState
- unsigned long maxMem :// the maximum memory in KBytes allowed
- unsigned long memory :// the memory in KBytes used by the domain
- unsigned short nrVirtCpu :// the number of virtual CPUs for the domain
- unsigned long long cpuTime : //the CPU time used in nanoseconds
- }
获取内存资源和计算资源监控信息并打印的方法如下：
- virDomainInfoPtr domaininfo;
- domaininfo = malloc(sizeof(virDomainInfo)* 1);
- m = virDomainGetInfo(allDomains[numOfDom] , domaininfo);
- printf("状态:%d ",(*domaininfo).state);
- printf("最大内存:%ld ",((*domaininfo).maxMem)/1024);
- printf("内存:%ld ",((*domaininfo).memory)/1024);
- printf("虚拟cpu个数:%d ",(*domaininfo).nrVirtCpu);
- printf("cpu时间:%lld ",(*domaininfo).cpuTime);
libvirt中并不能直接获取到虚拟机的CPU使用率，但是可以通过CPUTIME来计算出实际使用率。计算的公式为：
首先得到一个周期差：cpu_time_diff = cpuTimenow — cpuTimet seconds ago
然后根据这个差值计算实际使用率：%CPU = 100 × cpu_time_diff / (t × nr_cores × 109)
cpuTime可以通过virDomainGetInfo(C)和virDomain::info()(Python)获得
#include <stdio.h>
#include <sys/time.h>
#include <libvirt/libvirt.h>
#include <libvirt/virterror.h>
int main(int argc, char ** argv) { virConnectPtr conn = virConnectOpen("qemu:///system"); if(conn == NULL) { printf("error connecting qemu driver\n"); exit(1); } virDomainPtr vm_ptr = virDomainLookupByName(conn, "1"); if(vm_ptr == NULL) { printf("error finding domain\n"); virConnectClose(conn); exit(1); } virDomainInfo info_s,info_e; struct timeval real_time_s, real_time_e; int cpu_diff, real_diff; float usage; while(true){ if(virDomainGetInfo(vm_ptr, &info_s) !=0) { printf("error get domain info\n"); virDomainFree(vm_ptr); virConnectClose(conn); exit(1); } if(gettimeofday(&real_time_s, NULL) == -1) { printf("error get time of day\n"); virDomainFree(vm_ptr); virConnectClose(conn); exit(1); } sleep(1); if(virDomainGetInfo(vm_ptr, &info_e) !=0) { printf("error get domain info\n"); virDomainFree(vm_ptr); virConnectClose(conn); exit(1); } if(gettimeofday(&real_time_e, NULL) == -1) { printf("error get time of day\n"); virDomainFree(vm_ptr); virConnectClose(conn); exit(1); }//转换成微秒 cpu_diff = (info_e.cpuTime - info_s.cpuTime) / 1000; //转换成微秒 real_diff = 1000000 * (real_time_e.tv_sec - real_time_s.tv_sec) + (real_time_e.tv_usec - real_time_s.tv_usec);
//是否要考虑多核的情况？
usage = cpu_diff / (float) (real_diff); printf("cpu_diff:%d, real_diff:%d, cpu usage:%f\n", cpu_diff, real_diff, usage); } virDomainFree(vm_ptr); virConnectClose(conn); return 0;
#include <stdio.h>
#include <sys/time.h>
#include <libvirt/libvirt.h>
#include <libvirt/virterror.h>
int main(int argc, char ** argv) { virConnectPtr conn = virConnectOpen("qemu:///system"); if(conn == NULL) { printf("error connecting qemu driver\n"); exit(1); } virDomainPtr vm_ptr = virDomainLookupByName(conn, "1"); if(vm_ptr == NULL) { printf("error finding domain\n"); virConnectClose(conn); exit(1); } virTypedParameter par_s, par_e; struct timeval real_time_s, real_time_e; int cpu_diff, real_diff; float usage; while(true){ if(gettimeofday(&real_time_s, NULL) == -1) { printf("error get time of day\n"); virDomainFree(vm_ptr); virConnectClose(conn); exit(1); } virDomainGetCPUStats(vm_ptr, &par_s, 1, -1, 1, 0); sleep(1); if(gettimeofday(&real_time_e, NULL) == -1) { printf("error get time of day\n"); virDomainFree(vm_ptr); virConnectClose(conn); exit(1); virDomainGetCPUStats(vm_ptr, &par_e, 1, -1, 1, 0); cpu_diff = (par_e.value.ul - par_s.value.ul) / 1000; real_diff = 1000000 * (real_time_e.tv_sec - real_time_s.tv_sec) + (real_time_e.tv_usec - real_time_s.tv_usec); usage = cpu_diff / (float)(real_diff); printf("cpu_diff:%d, real_diff:%d, cpu usage:%f\n", cpu_diff, real_diff, usage); } virDomainFree(vm_ptr); virConnectClose(conn); return 0; }
这两个接口的结果差不多，利用率与top命令输出一致，但是与虚拟机内部使用率不一致。如将结果除以vcpu个数，则cpu利用率更接近虚拟机内部的虚拟机使用率。
对于memory利用率，windows需要安装 virtio memory balloon drivers for Windows guests，这样 memory/MaxMemory就是正确的内存利用率。如果不安装，那么这个比例始终为1。
（二）获得网络流量信息
可以使用 virDomainInterfaceStats方法，将一个domain的网络流量信息封装在一个virDomainInterfaceStatsStruct结构体中，该方法需要传递一个虚拟网卡接口的参数，这个参数可以通过XML文件取得：
<interface type='bridge'>
<mac address='00:16:3e:74:03:53'/>
<source bridge='xenbr0'/>
<script path='vif-bridge'/>
<target dev='vif1.0 '/> /*这个就是需要的参数*/
</interface>
具体代码如下：
-
- virDomainInterfaceStatsPtr interfacestats;
- interfacestats = malloc(sizeof(virDomainInterfaceStatsStruct)* 10);
- m = virDomainInterfaceStats(allDomains[numOfDom], i_path, interfacestats, 10);
- printf("rx字节数:%ld ",(*interfacestats).rx_bytes);
- printf("tx字节数:%ld ",(*interfacestats).tx_bytes);
- printf("rx丢包:%ld ",(*interfacestats).rx_drop);
- printf("tx丢包:%ld\n",(*interfacestats).tx_drop);
