the system monitor shows only 4GB memory when running 'free'

[myarice]

dear all:
有个问题求助大家：
4G*2的内存，查看时只有4G，但系统提示已经认到8G，不知道下面这句话是什么意思？什么原因呢？

The machine has totally 8GB memory (four X 2GB) however the system monitor shows only 4GB memory when running 'free' , it gives the message :
>
> total used free shared buffers cached
> Mem: 3959 3847 111 0 353 2479
> -/+ buffers/cache: 1014 2945
> Swap: 31996 140 31855

[枫叶饭团]

意思是系统监视器在玩你？

[myarice]

意思是系统监视器在玩你？

我晕

[myarice]

没人帮忙一下吗？