Thanks for your reply. My qemu version is qemu-kvm-rhev-0.12.The key problem is, qemu-kvm process memory usage(RSS) always increases no matter how much memory used in guset vm. for example, qemu-kvm process rss is 2.3g in host machine,  but free output in vm shows only 151MB My question is : 1. Why qemu-kvm doesn't release physical memory ?2. How to monitor real memory usage in guest vm?  Sincerely. On Thursday, September 1, 2016 11:36 PM, Patrick PICHON <patrick@pichon.me> wrote: why not using collectd with the libvirt plugin on your host. It will colect the info, and then you just have to display with rrdtool On , journey journey wrote:

Hi All

Is there a tool to monitor qemu-kvm guest vm memory usage ( free in guest vm)? Nowadays, I have already researched some methods: 1. qemu-kvm process memory usage.       Since qemu-kvm process memory usage always increases as time goes on, it will not reflect the memory usage in vm. 2. virsh dommemstat       Just as method 1. 3. virsh qemu-monitor-command --hmp [domain name] "info mem"       (1) when guest vm memory size less than 4Gbytes, it will output something like this:             7f882000-7f883000 00001000 urw             7fbf8000-7fbf9000 00001000 urw             88000000-88001000 00001000 -rw             88002000-88003000 00001000 urw             88004000-88005000 00001000 urw             c9000000-c9001000 00001000 urw             e8bfe000-e8bff000 00001000 urw             ea000000-ea001000 00001000 urw             ffbfc000-ffbfd000 00001000 -rw             ffbfe000-ffbff000 00001000 urw             it shows pde info of PG_PRESENT_MASK, maybe has some relation with guest vm memory usage.       (2) when guest vm memory size larger than 4Gbytes, it will output noting.

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