VM Slowness

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I hope this in the right list, but I was wondering if someone could help me with a VM I have that has lately started having problems. It had been running for years without problems. It’s possible an update is causing this, but I can’t say.

The VM is running CentOS 5.8 and after a time, the machine begins to slow down. Things like pings or running commands lag. If I reboot the VM, it runs normally for at least a few hours, but it eventually slows again.

I’ve tried changing the VM’s virtio devices to standard devices like IDE and e1000, but it makes no difference. Currently its running virtio.

Top shows that nothing is taking up significant cpu time, but even running top takes several seconds for it to open. The system is slow now, but top shows:

top – 21:39:48 up 1 day, 5:27, 1 user, load average: 0.93, 1.37, 1.12
Tasks: 177 total, 1 running, 176 sleeping, 0 stopped, 0 zombie Cpu(s): 0.3%us, 0.3%sy, 0.0%ni, 98.6%id, 0.9%wa, 0.0%hi, 0.0%si,
0.0%st Mem: 2075016k total, 1484624k used, 590392k free, 64336k buffers Swap: 4128760k total, 12k used, 4128748k free, 981368k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

4124 root 20 0 2444 1080 812 R 0.1 0.1 0:00.03 top

1 root 15 0 2176 692 604 S 0.0 0.0 0:02.46 init

2 root RT -5 0 0 0 S 0.0 0.0 0:00.39 migration/0

3 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0

Any ideas what to look for? Any information I can provide?

Thanks

4 thoughts on - VM Slowness

  • How about a top on the host? Could the virtual machine be getting swapped out on the host?

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  • Good question. There is another VM on the host without this issue, but here’s top from the host:

    top – 22:11:52 up 1 day, 6:00, 1 user, load average: 0.67, 0.34, 0.29
    Tasks: 175 total, 3 running, 172 sleeping, 0 stopped, 0 zombie Cpu(s): 4.3%us, 0.9%sy, 0.0%ni, 94.5%id, 0.3%wa, 0.0%hi, 0.0%si,
    0.0%st Mem: 8001476k total, 7794800k used, 206676k free, 284212k buffers Swap: 10620924k total, 156k used, 10620768k free, 4390824k cached

    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

    2983 libvirt- 20 0 4373m 2.0g 7392 R 33 26.1 626:39.45 kvm

    3385 libvirt- 20 0 3405m 574m 6868 S 15 7.4 263:01.62 kvm

    36 root 25 5 0 0 0 S 1 0.0 19:24.48 ksmd

  • Is the one that is slow the one that has 2g resident?

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