[lttng-dev] Is LTTng self-conscious?

[Mathieu Desnoyers]

----- On Jul 14, 2016, at 5:10 PM, Thibault, Daniel Daniel.Thibault at drdc-rddc.gc.ca wrote:

>> De : Mathieu Desnoyers [mailto:mathieu.desnoyers at efficios.com]
>> Envoyé : 13 juillet 2016 13:44
>>
>> However, if we were to implement a "blocking" mode as an alternative to the
>> "discard" and "overwrite" modes of lttng when dealing with buffer full
>> conditions,
>> we would need to be very cautious not to deadlock the system in such situation.
>> With both "discard" and "overwrite" buffering strategies, we cannot cause system
>> hang even in such extreme situations.
>>
>> Mathieu
> 
>   Couldn't lttng-untrack be used to fix this?  I was thinking of automatically
>   untracking all instances of lttng-sessiond, lttng-consumerd, and lttng-runas.

That could remove the system calls and actions directly performed by those
processes, but what would you do about RCU callbacks, timers, interrupts and
block I/O requests at the disk driver level ? The link with the associated
process that triggered those is typically lost at that level.

Thanks,

Mathieu

> 
> Daniel U. Thibault, M.Sc.²
> 
> Informaticien scientifique, CME-PSC, Centre de recherches de Valcartier
> Recherche et développement pour la défense Canada / Gouvernement du Canada
> daniel.thibault at drdc-rddc.gc.ca / Tél: 418-844-4000x4245 Téléc: 418-844-4538
> daniel.thibault at forces.gc.ca / Tél: 418-844-4000x4245 Téléc: 418-844-4538
> 
> Computer Scientist, MCCS-SPC, Valcartier Research Centre
> Defence Research and Development Canada / Government of Canada
> daniel.thibault at drdc-rddc.gc.ca / Tel: 418-844-4000x4245 Fax: 418-844-4538
> daniel.thibault at forces.gc.ca / Tel: 418-844-4000x4245 Fax: 418-844-4538
> 
> DRDC is an agency of the Department of National Defence / RDDC est une agence du
> ministère de la Défense nationale

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com