Libvirt Auto Memory Ballooning

auto-ballooning.py

#!/usr/bin/python3

from subprocess import Popen, PIPE

def start_monitor(domain, interval: int = 10):
    proc = Popen(['virsh','dommemstat', domain, '--period', str(interval)], 
                 stdout=PIPE)
    proc.wait()
    

def get_domains():
    proc = Popen(['virsh','list','--name'],stdout=PIPE)
    proc.wait()
    out = proc.stdout.read().decode('utf8').strip().split('\n')
    return [o for o in out if o.strip()]

def get_memory_usage(domain):
    proc = Popen(['virsh', 'dommemstat', domain], stdout=PIPE)
    proc.wait()
    out = proc.stdout.read().decode('utf8').strip().split('\n')
    res = dict([v.split() for v in out])
    for k in res:
        res[k] = int(res[k])
    return res

def get_memory_usage(domain):
    proc = Popen(['virsh', 'dommemstat', domain], stdout=PIPE)
    proc.wait()
    out = proc.stdout.read().decode('utf8').strip().split('\n')
    res = dict([v.split() for v in out])
    for k in res:
        res[k] = int(res[k])
    return res

def get_dominfo(domain):
    proc = Popen(['virsh', 'dominfo', domain], stdout=PIPE)
    proc.wait()
    out = proc.stdout.read().decode('utf8').strip().split('\n')
    res = {}
    for v in out:
        vv = v.split(':')
        res[vv[0].strip()] = ':'.join(vv[1:]).strip()
    
    return res

def balloon(domain, target):
    proc = Popen(['virsh', 'setmem', domain, '--size', str(target), '--current'], stdout=PIPE)
    proc.wait()
    out = proc.stdout.read().decode('utf8').strip().split('\n')


i1G=1048576
i512M=524288
i256M=262144

STEP=i1G


res = {}
for d in get_domains():
    start_monitor(d)
    m = get_memory_usage(d)
    if 'unused' not in m:
        continue
    dominfo = get_dominfo(d)
    available = int(dominfo['Max memory'].split()[0])
    unused = m['unused']
    actual = m['actual']
    # negative means not enough memory, positive means enough memory
    diff = (unused/available * 100)
    targets = range(i1G, available+(STEP*3), STEP)


    target = actual
    if target <= i1G:
        target = i1G

    if diff < 20:
        if actual > i1G:
            target = actual + STEP
    elif diff > 40:
        if (actual - STEP) > i1G:
            target = actual - STEP
  
    for i,t in enumerate(targets):
        next_target = target
        if i+1 < len(targets):
            next_target = targets[i+1]
        if target <= t and t <= next_target:
            target = t
            break

    if target > available:
        target = available

    if target != actual:
        print('Free Mem (%d%%) Ballooning %s %dM->%dM ' % (diff, d, actual/1024, target/1024))
        balloon(d, target)
    
    res[d] = m 

auto-ballooning.service

[Unit]
Description=Libvirt memory auto ballooning

[Service]
Type=oneshot
ExecStart=/usr/bin/python3 /opt/auto-ballooning.py

auto-ballooning.timer

# vim: set ft=ini:

[Unit]
Description=Libvirt auto memory ballooning

[Timer]
OnCalendar=*:5/10
Persistent=true

[Install]
WantedBy=timers.target