Tracking down a memory leak

[Tim Müller]

On Sat, 2014-03-08 at 17:37 +0000, Chris Tapp wrote:

Hi Chris,

> I've got a pipeline that's used to play audio and feed video to a
> fakesink so that I can grab the latest frame when I want it (for
> rendering in a GLES app).
> 
> This works fine on my development system (Ubuntu 12.04, AMD video
> card), but when I run it on the target hardware there is a small memory
> leak related to running the pipeline. I've found this when running some
> long-term robustness tests, and it takes many, many days of looping
> playback for the leak to get to the point where the application gets
> terminated. This isn't ideal, as the app is expected to run for months
> at a time. As I said, this leak does not happen on the development
> system.
> 
> The target is an Intel Cedartrail platform with the PVR drivers (needed
> for acceleration), and I suspect that the memory leak is related to
> these drivers and/or their interaction with GStreamer.
> 
> Are there any recommend techniques that I can use to try and get an
> idea of where the problem lies?

I would start with the usual tools: run your test case / app in valgrind
(--leak-check=yes, initially with--show-reachable=no); you can also use
valgrind's massif tool to track memory allocation over time to see which
functions are responsible for increasing the usage.

Alternatively, try to narrow down if any particular type of object or
mini object is being leaked (e.g. caps or events or so). If you don't
mind modifying gstreamer itself, you could use the internal alloc trace
stuff and regularly dump the list (counter) of allocated objects. Once
you know that you can look at the code. This assumes it's in GStreamer
though.

I would try valgrind first. Note that you don't have to run it until it
aborts of course, just run it for a while (the longer, the more likely
the leak is to stand out). Could also try running it for an hour and for
two hours to see if any particular leaked/reachable allocations
increase/double.

If valgrind is too slow or makes it change behaviour, there are
LD_PRELOAD type memory alloc/free trackers as well if I remember
correctly.

 Cheers
  -Tim

-- 
Tim Müller, Centricular Ltd - http://www.centricular.com