Re: Memory usage with qemu-kvm-0.12.1.1

[Avi Kivity <avi@redhat.com>]

On 12/27/2009 05:51 PM, Daniel Bareiro wrote:
> Hi, all!
>
> I installed qemu-kvm-0.12.1.1 in one equipment of my house yesterday to
> test it with Linux 2.6.32 compiled by myself from the source code of
> kernel.org.
>
>  From the night of yesterday that I am observing a high use of swap. This
> is the Service Log Entries from Nagios:
>
> 12-26-2009 21:57:33     12-26-2009 23:42:33     0d 1h 45m 0s    SERVICE WARNING (HARD)  SWAP WARNING - 30% free (142 MB out of 486 MB)
> 12-26-2009 23:42:33     12-27-2009 00:00:00     0d 0h 17m 27s   SERVICE CRITICAL (HARD) SWAP CRITICAL - 9% free (41 MB out of 486 MB)
> 12-27-2009 00:00:00     12-27-2009 06:27:33     0d 6h 27m 33s   SERVICE CRITICAL (HARD) SWAP CRITICAL - 5% free (22 MB out of 486 MB)
> 12-27-2009 06:27:33     12-27-2009 12:49:51     0d 6h 22m 18s+  SERVICE WARNING (HARD)  SWAP WARNING - 14% free (67 MB out of 486 MB)
>
> The hour has been ART (GMT-3).
>
> The VMs running in this host are the following:
>
> +--------------------+----------+------------------+
> |   OS               |    RAM   |      SWAP        |
> +====================+==========+==================+
> | Debian Lenny amd64 | 512 MB   | 1 GB / 0 used    |
> | Debian Lenny amd64 | 512 MB   | 512 MB / 0 used  |
> | Debian Lenny amd64 | 512 MB   | 1 GB / 584k used |
> | Debian Lenny i386  | 512 MB   | 512 MB / 0 used  |
> | OpenBSD 4.6  i386  | 512 MB   | 1 GB / 0 used    |
> +--------------------+----------+------------------+
>
> This is what I obtain with 'free' in the host:
>
> root@ubuntu:~# free
>               total       used       free     shared    buffers     cached
> Mem:       4060340    3989512      70828          0    1804272      95212
> -/+ buffers/cache:    2090028    1970312
> Swap:       497972     415680      82292
>
>
> To what that so high use of swap can be due?
>
>    

Probably a regression in Linux swapping.  Rik, Hugh, are you aware of 
any?  Hugh posted something but it appears to be performance related, 
not causing early swap.

Try setting /proc/sys/vm/swappiness to 0, and running your guests with 
cache=none (a good idea in any case).

Also, qemu might be leaking memory.  Please post 'pmap $pid' for all of 
your guests (do that before any of the other tests, on your swapped-out 
system).

-- 
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