[lttng-dev] Is there a way to make LTTng use the same subbuffers for multiple processes?

[Amit Margalit]

Security trumps most things, IMHO, so for me this is (one of the few) 
valid reasons to change backward compatibility.

An environment variable is a good solution to allow controlling this. 
Thank you.

Amit Margalit
IBM XIV - Storage Reinvented
XIV-NAS Development Team
Tel. 03-689-7774
Fax. 03-689-7230



From:   Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
To:     Amit Margalit/Israel/IBM at IBMIL
Cc:     lttng-dev at lists.lttng.org, Michel Dagenais 
<michel.dagenais at polymtl.ca>
Date:   05/10/2013 05:50 PM
Subject:        Re: [lttng-dev] Is there a way to make LTTng use the same 
subbuffers for multiple processes?



I expect we could let an environment variable control this.

I would be tempted to make the default behavior switch to the new user
ID buffers in the future though, for security reasons.

Thoughts ?

Thanks,

Mathieu

* Amit Margalit (AMITM at il.ibm.com) wrote:
> This (current) behavior you describe is very suitable for our needs.
> 
> Is there an intention to insert a hook into setuid() in the future?
> If yes - will the existing behavior remain as a default and the hook be 
> used only if I choose to use it?
> 
> Thanks,
> 
> Amit Margalit
> IBM XIV - Storage Reinvented
> XIV-NAS Development Team
> Tel. 03-689-7774
> Fax. 03-689-7230
> 
> 
> 
> From:   Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> To:     Amit Margalit/Israel/IBM at IBMIL
> Cc:     Michel Dagenais <michel.dagenais at polymtl.ca>, 
> lttng-dev at lists.lttng.org
> Date:   04/29/2013 07:27 PM
> Subject:        Re: [lttng-dev] Is there a way to make LTTng use the 
same 
> subbuffers for multiple processes?
> 
> 
> 
> * Amit Margalit (AMITM at il.ibm.com) wrote:
> > Another 2.2 question -
> > 
> > What if I have a single process, that forks, and each child process 
then 
> 
> > changes its own UID. Will the tracing continue on the parent UID 
> buffers?
> 
> Yes, we indeed currently keep the user ID that was effective at process
> creation or last exec() encountered, because we don't have hooks in
> libc's setuid() at the moment.
> 
> Thanks,
> 
> Mathieu
> 
> > 
> > Thanks,
> > 
> > Amit Margalit
> > IBM XIV - Storage Reinvented
> > XIV-NAS Development Team
> > Tel. 03-689-7774
> > Fax. 03-689-7230
> > 
> > 
> > 
> > From:   Michel Dagenais <michel.dagenais at polymtl.ca>
> > To:     Amit Margalit/Israel/IBM at IBMIL
> > Cc:     lttng-dev at lists.lttng.org
> > Date:   04/29/2013 04:32 AM
> > Subject:        Re: [lttng-dev] Is there a way to make LTTng use the 
> same 
> > subbuffers for multiple processes?
> > 
> > 
> > 
> > 
> > > Our system is a 12-core x86 (6-core + HT). If I take 4 subbuffers of 

> > 1MB, this means 4MB per
> > > process. As the number of processes rises, this becomes prohibitive. 

> > > For example, we may need to support > 500 sub-processes ==> 500 * 
4MB 
> = 
> > 2GB - 
> > > which is a bit too much.  Is there a way to tell LTTng to share the 
> > sub-buffers with forked processes? 
> > 
> > This is the number one feature listed in the changelog for lttng-tools 

> and 
> > UST for version 2.2. The first release candidate is out so you can try 

> the 
> > feature, and the final 2.2 version should not be too far away.
> > 
> > http://lttng.org/lttng-tools-220-rc1
> > - Add UST per UID buffers support
> > 
> 
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev at lists.lttng.org
> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> 
> 
> -- 
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> 
> 

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


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