[Xenomai-help] VM killer

[Xenomai-help] VM killer

[Daniel Schnell]

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Hi,
 
I know this is somewhat not related to Xenomai. But as I encountered
this while actually testing the memory allocation with Xenomai, maybe
there is some common sense here, as there are many people having to do
with embedded systems, where something like that matters.
 
Everytime the system comes to its limits and some process uses up all
the memory the vm systems kills (more or less randomly) one or more
processes. Even system processes. I would really like to get rid of this
behaviour, but having disabled CONFIG_OOM_KILLER inside the linux kernel
doesn't help.
 
I use ELDK4.0 with 2.4.25 Denx Kernel.
 
Any hints ?
 
 
Best regards,
 
Daniel.

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Re: [Xenomai-help] VM killer

[Gilles Chanteperdrix]

Daniel Schnell wrote:
> Hi,
>  
> I know this is somewhat not related to Xenomai. But as I encountered
> this while actually testing the memory allocation with Xenomai, maybe
> there is some common sense here, as there are many people having to do
> with embedded systems, where something like that matters.
>  
> Everytime the system comes to its limits and some process uses up all
> the memory the vm systems kills (more or less randomly) one or more
> processes. Even system processes. I would really like to get rid of this
> behaviour, but having disabled CONFIG_OOM_KILLER inside the linux kernel
> doesn't help.
>  
> I use ELDK4.0 with 2.4.25 Denx Kernel.
>  
> Any hints ?

There is no way the system can run properly if there is not enough RAM.
Add some RAM to your board, or decrease the memory used by applications.

-- 
                                                 Gilles Chanteperdrix

Re: [Xenomai-help] VM killer

[Jan Kiszka]

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Gilles Chanteperdrix wrote:
> Daniel Schnell wrote:
>> Hi,
>>  
>> I know this is somewhat not related to Xenomai. But as I encountered
>> this while actually testing the memory allocation with Xenomai, maybe
>> there is some common sense here, as there are many people having to do
>> with embedded systems, where something like that matters.
>>  
>> Everytime the system comes to its limits and some process uses up all
>> the memory the vm systems kills (more or less randomly) one or more
>> processes. Even system processes. I would really like to get rid of this
>> behaviour, but having disabled CONFIG_OOM_KILLER inside the linux kernel
>> doesn't help.
>>  
>> I use ELDK4.0 with 2.4.25 Denx Kernel.
>>  
>> Any hints ?
> 
> There is no way the system can run properly if there is not enough RAM.
> Add some RAM to your board, or decrease the memory used by applications.

Having a means to avoid that your critical process gets killed
accidentally because some uncritical one decided to suck up all system
resources is, IMO, a very legitimate use case. On 2.6, where there is no
CONFIG_OOM_KILLER, you can play with /proc/<pid>/oom_adj and make your
process "unattractive" to the OOM killer (set to -17). On older kernels
you also had to include any parent processes in this protection. I think
this was fixed meanwhile.

But I wonder why there should be no effect of CONFIG_OOM_KILLER on 2.4.
Forgot to replay the updated kernel binaries?

Jan


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RE: [Xenomai-help] VM killer

[Daniel Schnell]

jan.kiszka@domain.hid wrote:
 
> Having a means to avoid that your critical process gets killed
> accidentally because some uncritical one decided to suck up all
> system resources is, IMO, a very legitimate use case. On 2.6, where
> there is no CONFIG_OOM_KILLER, you can play with /proc/<pid>/oom_adj
> and make your process "unattractive" to the OOM killer (set to -17).
> On older kernels you also had to include any parent processes in this
> protection. I think this was fixed meanwhile.      
> 
> But I wonder why there should be no effect of CONFIG_OOM_KILLER on
> 2.4. 
> Forgot to replay the updated kernel binaries?

Well double checked: no. At least if my .config in the linux kernel
directory is not magically updated after compiling the kernel. BTW: I
could not find that option in the make menuconfig configuration. Maybe
it is hidden somewhere in a submenu, but at least in the .config file it
is definetly disabled.


Best regards,

Daniel Schnell.

Re: [Xenomai-help] VM killer

[Philippe Gerum]

On Fri, 2006-11-17 at 18:15 +0000, Daniel Schnell wrote:
> Hi,
>  
> I know this is somewhat not related to Xenomai. But as I encountered
> this while actually testing the memory allocation with Xenomai, maybe
> there is some common sense here, as there are many people having to do
> with embedded systems, where something like that matters.
>  
> Everytime the system comes to its limits and some process uses up all
> the memory the vm systems kills (more or less randomly) one or more
> processes. Even system processes. I would really like to get rid of
> this behaviour, but having disabled CONFIG_OOM_KILLER inside the linux
> kernel doesn't help.

What does the following say on your board?
cat /proc/sys/vm/overcommit_memory

>  
> I use ELDK4.0 with 2.4.25 Denx Kernel.
>  
> Any hints ?
>  
>  
> Best regards,
>  
> Daniel.
> _______________________________________________
> Xenomai-help mailing list
> Xenomai-help@domain.hid
> https://mail.gna.org/listinfo/xenomai-help
-- 
Philippe.

Re: [Xenomai-help] VM killer

[Wolfgang Grandegger]

Daniel Schnell wrote:
> Hi,
>  
> I know this is somewhat not related to Xenomai. But as I encountered 
> this while actually testing the memory allocation with Xenomai, maybe 
> there is some common sense here, as there are many people having to do 
> with embedded systems, where something like that matters.
>  
> Everytime the system comes to its limits and some process uses up all 
> the memory the vm systems kills (more or less randomly) one or more 
> processes. Even system processes. I would really like to get rid of this 
> behaviour, but having disabled CONFIG_OOM_KILLER inside the linux kernel 
> doesn't help.
>  
> I use ELDK4.0 with 2.4.25 Denx Kernel.

For 2.4 kernels you should use ELDK 3.1.1. Wolfgang, can you confirm that?

Wolfgang.

RE: [Xenomai-help] VM killer

[Daniel Schnell]

Wolfgang Grandegger wrote:
 
> For 2.4 kernels you should use ELDK 3.1.1. Wolfgang, can you confirm
> that? 

I have heard that, but actually did not have any hint that something
wouldn't work. Also I like the gcc-4 provided here. I have both setups
running and can not make up a lot of differences.

But maybe there is a clear reason not to use, it. Would be interesting
to hear.


Best regards,

Daniel Schnell.

Re: [Xenomai-help] VM killer

[Wolfgang Denk]

In message <455E16DD.4090804@domain.hid> you wrote:
> 
> > I use ELDK4.0 with 2.4.25 Denx Kernel.
> 
> For 2.4 kernels you should use ELDK 3.1.1. Wolfgang, can you confirm that?

If you wan to be on the safe side: indeed.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@domain.hid
Life would be so much easier if everyone read the manual.