[ltt-dev] LTTng Patch set against 2.6.33.7 and Prempt-RT?

[Mathieu Desnoyers]

* Jesse Keller (Jesse.Keller at spacex.com) wrote:
> It looks like development of the PREEMPT_RT patch set
> (https://rt.wiki.kernel.org/index.php/CONFIG_PREEMPT_RT_Patch) has
> calmed down in recent months. Last patch is against 2.6.33.7 and was
> released in December 2010.   A kernel with those patches seems to work
> fine for my application, but I'd like to be able to use LTTng as well.
> Unfortunately, patch-2.6.33.4-lttng-0.216.tar.gz doesn't seem to apply
> cleanly to an -rt patched kernel.
> 
> What would it take to get an LTTng patchset that works on
> 2.6.33.7-rt30?  While I can see that LTTng doesn't normally track the
> -rt tree, I have seen at least one other person asking about this and
> it would be helpful to me to do a one-off sync.
> 
> If I were to tackle this myself, how would I identify the changes made
> between r217 (the last 2.6.33 LTTng release) and r245 that would be
> critical to include in such a patch?

This first thing you want to look at is the compatibility list:

http://git.lttng.org/?p=lttv.git;a=blob_plain;f=doc/developer/lttng-lttv-compatibility.html;hb=HEAD

You'll notice that LTTng 0.227 reintroduced the external lttng-modules
package, which is a very large code-base change. So incrementally moving
from 217 to 0.245 is not really recommended.

So either you start from 217 and pick the fixes you can from the
compatibility list, added patches at each version, and changes you can
spot between releases (using git diff between branches can be good for
this), or you try to backport a more recent LTTng version.

If I were you, I'd try backporting a more recent LTTng version, because
then you get a lot of fixes, and you'll also notice that the size of the
patchset have shrinked from about 400 patches down to 200 between 227
and 245. (thanks to exporting most of the tracer code into a stand-alone
module package)

Hoping this helps,

Mathieu

> 
> -Jesse Keller
> 
> 
> 
> 
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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com