最後更新: 2017-01-23

介紹

• memtune
• dommemstat
• dominfo
• setmaxmem
• setmem

memtune (Get or set domain memory parameters)

i.e.

virsh memtune centos6.3

hard_limit     : unlimited
soft_limit     : unlimited
swap_hard_limit: unlimited

以下 unit 都是 kilobytes, -1 => unlimited

• --hard-limit                    <-- The maximum memory the guest can use.
• --soft-limit
• --swap-hard-limit           <-- maximum memory plus swap the guest can use

其他 Opts:

• --live
• --config

XML:

<memtune>
  <hard_limit>131072</hard_limit>
  <soft_limit>65536</soft_limit>
  <swap_hard_limit>262144</swap_hard_limit>
</memtune>

Prevents the the guest swapping out

XML:

<memoryBacking>
    <locked/>
</memoryBacking>

memory usage (active domain 的 memory 情況)

dommemstat

virsh dommemstat centos6.3

actual 512000  <-- Used memory
swap_in 0
rss 61476      <-- ps aux 時見到的 rss

dominfo

virsh dominfo centos6.3

Id:             -
Name:           centos6.3
UUID:           d161d64e-ccc0-3774-4907-e6be57089a49
OS Type:        hvm
State:          shut off
CPU(s):         2
Max memory:     512000 kB          <-- setmaxmem    
Used memory:    512000 kB          <-- setmem
Persistent:     yes
Autostart:      disable
Managed save:   no
Security model: apparmor
Security DOI:   0

setmaxmem 與 setmem

setmaxmem

i.e.

setmaxmem centos6.3 --size 700m

• --live                       # KVM 不支援 live config
• --config                   # take effect affect next boot

Check Guest 支不支援 ballooning:

# Centos 7

ps aux | grep vballoon

root       443  0.0  0.0      0     0 ?        S    16:33   0:00 [vballoon]

setmem (即時改變 guest 的 ram 的 total) <-- perform a memory balloon of a running guest

# setmem unit: kilobytes

i.e. 512 Mbyte

setmem  centos6.3  524288

• --live           # perform a memory balloon of a running guest (Default, reboot 後無效)
• --config       # next boot of a persistent guest

check guest memory usage

free -m

升 ram 前:

              total        used        free      shared  buff/cache   available
Mem:            482          81         338           3          62         296
Swap:          1023           2        1021

升 ram 後: "virsh setmem --size 780m centos7"

              total        used        free      shared  buff/cache   available
Mem:            750          81         606           3          62         564
Swap:          1023           2        1021

 * 如果有用 HugePage, 當 VM start 時, HugePage 會根據 "Max memory" 去食走