[uml-devel] Re: [uml-user] UML freezes at hdd-intensive processes

[uml-devel] Re: [uml-user] UML freezes at hdd-intensive processes

[Oliver Baltz]

Hi,

my problem still exists: the UML hangs om hdd-intensive processess (like
apt-get dist-upgrade). I tried a lot of things in time:

o tried on 2 machines with different hardware, different Host- and
Guest-Kernels
o CONFIG_BLK_DEV_UBD_SYNC is not set
o tried ext2/reiserfs on the Guest-UML
o when the UML hangs, it does not respond to sysrqs
o SKAS is not patched into the Host-System
o UML has enough swap-space (tried tmpfs, too)
o did an strace: http://home.oliverbaltz.de/transfer/strace-uml-freeze.txt.gz

I followed this HOWTO: http://oliverbaltz.de/index.php?id=101

Any ideas?
Thanks in advance.

Oliver

> Thanks for all your hints but:
>
> @James:
> My UML got 32M and 256M swap. The UML-Host has 448M physical RAM - I think
> it`s enough for UML and Host. Or am I wrong?
>
> @Ginie:
> The .config of my UML says: "# CONFIG_BLK_DEV_UBD_SYNC is not set".
>
> Any other ideas?
> Olli
>
>> On Thu, 3 Mar 2005, Oliver Baltz wrote:
>>
>>> my UML hangs while intensive processes that use the HDD. For example:
>>> rgrep, upgrade,...
>>>
>>> UML-Hostsystem: 2.4.27-1-386, Intel ICH5 SATA 150-Controller
>>> UML: 2.4.26-3um-1
>>
>> I had a similar experience.  I configured the UML with 256MB RAM, and
>> put
>> the image file in /dev/shm (tmpfs).  However, the default size of tmpfs
>> is
>> half your physical memory (256 MB).  When I did a big update, I/O
>> buffers
>> went above 128MB, and UML got what it called a "kernel mode signal 7"
>> (SIGBUS).  Limiting the RAM to 120MB (leaving a little space for
>> overhead
>> and other users) cured the problem completely.  Making tmpfs bigger
>> would
>> also have helped.  But don't enlarge it above swap space plus physical
>> memory, because when you fill it up, there's no space for programs and
>> the
>> host kernel will panic.
>>
>> James F. Carter          Voice 310 825 2897    FAX 310 206 6673
>> UCLA-Mathnet;  6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA
>> 90095-1555
>> Email: jimc@math.ucla.edu    http://www.math.ucla.edu/~jimc (q.v. for
>> PGP
>> key)
>>
>
>
>
>
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Re: [uml-devel] Re: [uml-user] UML freezes at hdd-intensive processes

[Rob Landley]

On Friday 11 March 2005 09:29 am, Oliver Baltz wrote:
> Hi,
>
> my problem still exists: the UML hangs om hdd-intensive processess (like
> apt-get dist-upgrade). I tried a lot of things in time:
>
> o tried on 2 machines with different hardware, different Host- and
> Guest-Kernels
> o CONFIG_BLK_DEV_UBD_SYNC is not set
> o tried ext2/reiserfs on the Guest-UML
> o when the UML hangs, it does not respond to sysrqs
> o SKAS is not patched into the Host-System
> o UML has enough swap-space (tried tmpfs, too)
> o did an strace:
> http://home.oliverbaltz.de/transfer/strace-uml-freeze.txt.gz
>
> I followed this HOWTO: http://oliverbaltz.de/index.php?id=101
>
> Any ideas?
> Thanks in advance.

It sounds like "stick printfs into the source code" time.

It's most likely to be UBD, since A) that's not in standard linux, which 
doesn't have this problem, and B) it's what you exercise intensely when you 
see it.

Is it write-intensive, read-intensive, combination of both, or either one?

Rob


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Re: [uml-devel] Re: [uml-user] UML freezes at hdd-intensive processes

[Oliver Baltz]

Hi Rob,

> Is it write-intensive, read-intensive, combination of both, or either one?

I think it is a combination of both: When installing just one single
debian-package the UML often freezes :-(

Is there an alternative to UBD?

Oliver


> On Friday 11 March 2005 09:29 am, Oliver Baltz wrote:
>> Hi,
>>
>> my problem still exists: the UML hangs om hdd-intensive processess (like
>> apt-get dist-upgrade). I tried a lot of things in time:
>>
>> o tried on 2 machines with different hardware, different Host- and
>> Guest-Kernels
>> o CONFIG_BLK_DEV_UBD_SYNC is not set
>> o tried ext2/reiserfs on the Guest-UML
>> o when the UML hangs, it does not respond to sysrqs
>> o SKAS is not patched into the Host-System
>> o UML has enough swap-space (tried tmpfs, too)
>> o did an strace:
>> http://home.oliverbaltz.de/transfer/strace-uml-freeze.txt.gz
>>
>> I followed this HOWTO: http://oliverbaltz.de/index.php?id=101
>>
>> Any ideas?
>> Thanks in advance.





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Re: [uml-devel] Re: [uml-user] UML freezes at hdd-intensive processes

[Rob Landley]

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On Friday 11 March 2005 04:18 pm, Oliver Baltz wrote:
> Hi Rob,
>
> > Is it write-intensive, read-intensive, combination of both, or either
> > one?
>
> I think it is a combination of both: When installing just one single
> debian-package the UML often freezes :-(
>
> Is there an alternative to UBD?
>
> Oliver

Just for testing purposes, you could try hostfs and then loopback mount your 
block device.

I boot UML like this all the time, to borrow the parent's filesystem.  (It has 
a lot of downsides, and is slower than ubd, but it requires absolutely no 
setup):

./linux rootfstype=hostfs rootflags=/ rw init=/bin/sh mem=64M

Note that this works under an Xterm because you own /dev/console, but if 
you're running it from the console you either need to 
chown/chmod /dev/console or you need to be root.  I have a script that gets 
around that, lemme dig it up...  Attached.  You don't need anything _nearly_ 
that complicated, but I just thought I'd let you know what kind of abuse you 
can do with hostfs... :)

Rob

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