linux下如何计算内存使用率

2.内存使用率的计算：/proc/meminfo
前面写到了在如何获得cpu使用率的问题，解决了这个问题，我们再来解决内存使用率的问题，相对来说就比较简单了，这时候我们就用到了/proc/meminfo这个文件了。先看一下这个文件中都有什么东西吧！
cat  /proc/meminfo
MemTotal:        1921916 kB
MemFree:          439180 kB
Buffers:          131680 kB
Cached:           736536 kB
SwapCached:        20404 kB
Active:           702404 kB
Inactive:         674888 kB
Active(anon):     415528 kB
Inactive(anon):   216500 kB
Active(file):     286876 kB
Inactive(file):   458388 kB
Unevictable:           0 kB
Mlocked:               0 kB
HighTotal:       1068680 kB
HighFree:          13536 kB
LowTotal:         853236 kB
LowFree:          425644 kB
SwapTotal:       7811068 kB
SwapFree:        7790572 kB
Dirty:                44 kB
Writeback:             0 kB
AnonPages:        493804 kB
Mapped:           107496 kB
Shmem:            122948 kB
Slab:              60624 kB
SReclaimable:      42576 kB
SUnreclaim:        18048 kB
KernelStack:        3048 kB
PageTables:         7496 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     8772024 kB
Committed_AS:    2533848 kB
VmallocTotal:     122880 kB
VmallocUsed:       28724 kB
VmallocChunk:      81896 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
文件中有很多的项的内容，但是在计算利用率的时候我能用到的就是前两行的内容！
mem_rate = total - free / total
怎么样很简单吧！
#include
#include
#include
using namespace std;
typedef double T;
void readToVector(vector &tvec,ifstream &in)
{
        string s;
        T temp;
        in>>s;
        in>>temp;
        tvec.push_back(temp);
        in>>s;
        in>>s;
        in>>temp;
        tvec.push_back(temp);
}
T calcMemRate(vector &tvec)
{
        T rate ;
        rate = 100 * (tvec[0] - tvec[1]) / tvec[0];
        return rate;
}
int main()
{
        vector tvec;
        T temp;
        ifstream in("/proc/meminfo");
        if(!in)
        {
                cout<<"this file can not be opened!"<        }
        else
        {
                readToVector(tvec,in);
                temp = calcMemRate(tvec);
                cout<<"the memory using rate is:"<        }
        return 0;
}