Re: Swap usage with KVM

[Daniel Bareiro <daniel-listas@gmx.net>]

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On Sunday, 11 July 2010 12:12:57 -0300,
Daniel Bareiro wrote:

> I have an installation with Debian GNU/Linux 5.0.4 amd64 with qemu-kvm
> 0.12.3 compiled with the source code obtained from the official site
> of KVM and Linux 2.6.32.12 compiled from source code of kernel.org.
> All this is installed on an HP Proliant DL380 G6 with two Xeon E5530
> quadcore processors and 16 GiB of RAM which has two VMs with the
> following configuration of memory:
> 
> Hostname       |      RAM
> ===============+===============
> Aps4           |    7 GiB
> Leela          |    7 GiB
> ===============+===============
> TOTAL          |   14 GiB
> 
> Initially the host was created with a swap partition of 1 GiB, but
> today we found that the use of swap quickly began to grow
> increasingly.  Therefore, as a contingency, we had to hot-add a
> logical volume of 1 GB of swap on the VMHost. Is 'normal' this use of
> memory?
> 
> I copy the Nagios Service Log Entries for the VMHost:
> 
> Event Start Time        Event End Time  Event Duration  Event/State Type        Event/State
> Information
> ---------------------------------------------------------------------------------------------------
> 06-07-2010 00:00:00     07-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 100% free (956 MB out of 956 MB)
> 07-07-2010 00:00:00     08-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 100% free (956 MB out of 956 MB)
> 08-07-2010 00:00:00     08-07-2010 16:41:43     0d 16h 41m 43s  SERVICE OK (HARD)       SWAP OK -
> 100% free (956 MB out of 956 MB)
> 09-07-2010 00:00:00     10-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 99% free (939 MB out of 956 MB)
> 10-07-2010 00:00:00     11-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 79% free (754 MB out of 956 MB)
> 11-07-2010 00:00:00     11-07-2010 07:08:17     0d 7h 8m 17s    SERVICE OK (HARD)       SWAP OK -
> 51% free (482 MB out of 956 MB)
> 11-07-2010 07:08:17     11-07-2010 10:41:07     0d 3h 32m 50s   SERVICE WARNING (HARD)  SWAP WARNING
> - 29% free (272 MB out of 956 MB)
> 11-07-2010 10:41:07     11-07-2010 10:45:57     0d 0h 4m 50s    SERVICE CRITICAL (HARD) SWAP
> CRITICAL - 9% free (83 MB out of 956 MB)
> ---------------------------------------------------------------------------------------------------
> 
> I'm not using qcow2 files. The /dev/cciss/c0d0p3 partition is a
> physical volume that maintains the logical volumes that are used for
> VM's disks.
> 
> The Nagios Service Log Entries for VMs shows no excessive use of swap
> in the window of time when the problem occurred in the VMHost:
> 
> Aps4:
> 
> Event Start Time        Event End Time  Event Duration  Event/State Type        Event/State
> Information
> ---------------------------------------------------------------------------------------------------
> 06-07-2010 00:00:00     07-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 100% free (2850 MB out of 2863 MB)
> 07-07-2010 00:00:00     08-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 98% free (2797 MB out of 2863 MB)
> 08-07-2010 00:00:00     08-07-2010 16:41:43     0d 16h 41m 43s  SERVICE OK (HARD)       SWAP OK -
> 99% free (2812 MB out of 2863 MB)
> 09-07-2010 00:00:00     10-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 98% free (2784 MB out of 2863 MB)
> 10-07-2010 00:00:00     11-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 97% free (2754 MB out of 2863 MB)
> 11-07-2010 00:00:00     11-07-2010 11:53:38     0d 11h 53m 38s+ SERVICE OK (HARD)       SWAP OK -
> 100% free (2839 MB out of 2863 MB)
> ---------------------------------------------------------------------------------------------------
> 
> Leela:
> 
> Event Start Time        Event End Time  Event Duration  Event/State Type        Event/State
> Information
> ---------------------------------------------------------------------------------------------------
> 06-07-2010 00:00:00     07-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 97% free (919 MB out of 956 MB)
> 07-07-2010 00:00:00     08-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 97% free (920 MB out of 956 MB)
> 08-07-2010 00:00:00     08-07-2010 16:41:43     0d 16h 41m 43s  SERVICE OK (HARD)       SWAP OK -
> 97% free (920 MB out of 956 MB)
> 08-07-2010 17:01:36     08-07-2010 17:04:16     0d 0h 2m 40s    SERVICE CRITICAL (HARD) Connection
> refused by host
> 08-07-2010 17:04:16     09-07-2010 00:00:00     0d 6h 55m 44s   SERVICE OK (HARD)       SWAP OK -
> 97% free (921 MB out of 956 MB)
> 09-07-2010 00:00:00     10-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 97% free (921 MB out of 956 MB)
> 10-07-2010 00:00:00     11-07-2010 00:00:00     1d 0h 0m 0s     SERVICE OK (HARD)       SWAP OK -
> 97% free (921 MB out of 956 MB)
> 11-07-2010 00:00:00     11-07-2010 11:58:29     0d 11h 58m 29s+ SERVICE OK (HARD)       SWAP OK -
> 97% free (921 MB out of 956 MB)
> ---------------------------------------------------------------------------------------------------
> 
> 
> 
> Unfortunately I could not take much more data because we had to act
> quickly, but if you need any additional information, please feel free to
> ask.

Has anyone experienced something like this? Avi? I remember late last
year there was a regression in Linux swapping and Rik and Hugh were
working on it. Are you aware of any?

Thanks in advance for your reply.

Regards,
Daniel
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