Re: [uml-devel] uml crashes when producing large files

[Blaisorblade <blaisorblade@yahoo.it>]

On giovedì 26 aprile 2007, Herbert Volkmann wrote:
> Hi List,
>
> i ran in the following problem:
Very strange...
> when i produce files (with dd) or copy files to or from the uml machine,
Which filesystems are involved? Can you give a sample command?

> i can see (with top),
Run on the guest (i.e. UML) I guess, right?
> that the used memory and the cached things 
> increases, while the unused memory will go down.
That is reasonable, but the cache should not make the system stop.
> shortly before memory 
> will come to zero, the uml stops working completely without any messages
> in the /var/log/* files on uml or host system.
>
> if i do in between a "echo 3 > /proc/sys/vm/drop_caches"
On the guest (i.e. UML) I assume, right?
>
> it cleans caches, frees memory and works fine! but i have to do this all
> 10 seconds when i use dd for producing large files ;-(
>
> these are the components i use:
> - debian etch on host with debian kernel patched with skas3 from debian
32bit system, right?
> - 1024 MB RAM on host
> - RAID5 System with 3ware Controller (5x2G) almost 1 TB
> - on uml i use debian etch, with bridged networking, 512MB RAM for uml
Which UML kernel release? That's the most important thing.
> - 6G root_fs for uml and 256M swap
>
> here is the command with which i start the uml:
> sudo -u uml /usr/bin/linux.uml umid=uml mem=512M eth0=tuntap,tap1
> ubd0=/usr/media/uml-linux/root_fs_2007_04_23
> ubd1=/usr/media/uml-linux/swap_fs con=null root=/dev/ubda uml_dir=/tmp/
>
> I would be really happy if someone could tell me what i can test more to
> find out why this system is instable with i/o operations and caches.

I have only a doubt: if you are filling a shmfs/tmpfs filesystem (which is 
backed by ram), that's an almost normal behaviour, and can happen even on 
host systems.

> thanx for any reply,
> Herbert

-- 
Inform me of my mistakes, so I can add them to my list!
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade

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