Getting notifications of the tasks file

Getting notifications of the tasks file

[Víctor Fernández Martínez]

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I'm trying to use the eventfd notification API to get notified when the tasks 
file changes. This way I would like to know when child processes are spawned 
and when they exit. However, I always get EINVAL when writing to 
cgroup.event_control. Even cgroup_event_listener.c returns that error:

# cat /sys/fs/cgroup/memory/grp0/tasks 
3590
23902
# ./cgroup_event_listener /sys/fs/cgroup/memory/grp0/tasks 0
Cannot write to cgroup.event_control: Invalid argument

I have also tried to monitor cgroup.procs.

Is it possible to monitor the tasks file at all or is this a bug? If 0 is a 
wrong argument, which argument should I use instead?


Thanks.


Barracuda Networks AG
Vorsitzender des Aufsichtsrates/ Chairman of the supervisory board: Dean Drako
Vorstand/ Executive Board: Dr. Wieland Alge, Mag. Guenter Klausner
Sitz der Gesellschaft/ Registered office: 6020 Innsbruck, Austria
Handelsgericht Innsbruck Firmenbuch/ Registration Number: 184392s
UID-Nr/ VAT Number: ATU47509003

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Re: Getting notifications of the tasks file

[Kirill A. Shutemov]

On Tue, Jul 31, 2012 at 11:42:06AM +0200, Víctor Fernández Martínez wrote:
> I'm trying to use the eventfd notification API to get notified when the tasks 
> file changes. This way I would like to know when child processes are spawned 
> and when they exit. However, I always get EINVAL when writing to 
> cgroup.event_control. Even cgroup_event_listener.c returns that error:
> 
> # cat /sys/fs/cgroup/memory/grp0/tasks 
> 3590
> 23902
> # ./cgroup_event_listener /sys/fs/cgroup/memory/grp0/tasks 0
> Cannot write to cgroup.event_control: Invalid argument
> 
> I have also tried to monitor cgroup.procs.
> 
> Is it possible to monitor the tasks file at all or is this a bug? If 0 is a 
> wrong argument, which argument should I use instead?

Currently, you can only listen for events from memory.usage_in_bytes,
memory.memsw.usage_in_bytes and memory.oom_control.
It's not implemented for any other cgroup files yet.

-- 
 Kirill A. Shutemov

Re: Getting notifications of the tasks file

[Zhu Yanhai]

Did you try inotify() ?

-zyh

2012/7/31 Víctor Fernández Martínez <vfernandez@barracuda.com>:
> I'm trying to use the eventfd notification API to get notified when the tasks
> file changes. This way I would like to know when child processes are spawned
> and when they exit. However, I always get EINVAL when writing to
> cgroup.event_control. Even cgroup_event_listener.c returns that error:
>
> # cat /sys/fs/cgroup/memory/grp0/tasks
> 3590
> 23902
> # ./cgroup_event_listener /sys/fs/cgroup/memory/grp0/tasks 0
> Cannot write to cgroup.event_control: Invalid argument
>
> I have also tried to monitor cgroup.procs.
>
> Is it possible to monitor the tasks file at all or is this a bug? If 0 is a
> wrong argument, which argument should I use instead?
>
>
> Thanks.
>
>
> Barracuda Networks AG
> Vorsitzender des Aufsichtsrates/ Chairman of the supervisory board: Dean Drako
> Vorstand/ Executive Board: Dr. Wieland Alge, Mag. Guenter Klausner
> Sitz der Gesellschaft/ Registered office: 6020 Innsbruck, Austria
> Handelsgericht Innsbruck Firmenbuch/ Registration Number: 184392s
> UID-Nr/ VAT Number: ATU47509003
>
> Diese Nachricht und allfaellige angehaengte Dokumente sind vertraulich und nur fuer den/die Adressaten bestimmt. Sollten Sie nicht der beabsichtigte Adressat sein, ist jede Offenlegung, Weiterleitung oder sonstige Verwendung dieser Information nicht gestattet. In diesem Fall bitten wir, den Absender zu verstaendigen und die Information zu vernichten. Fuer Uebermittlungsfehler oder sonstige Irrtuemer bei Uebermittlung besteht keine Haftung.
>
> This message and any attached files are confidential and intended solely for the addressee(s). Any publication, transmission or other use of the information by a person or entity other than the intended addressee is prohibited. If you receive this in error please contact the sender and delete the material. The sender does not accept liability for any errors or omissions as a result of the transmission.
>
>
> 'Like' us on Facebook for exclusive content and other resources on all Barracuda Networks solutions.
> Visit http://barracudanetworks.com/facebook
>
>
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