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

[Amit Margalit]

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?

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

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