[lttng-dev] [tracecompass-dev] Scalability

Matthew Khouzam matthew.khouzam at ericsson.com
Wed Mar 13 08:12:55 EDT 2019

Hi Doug & Efficios,

I suspect the issue is with libbabeltrace-ctf. When opening the trace in Trace Compass, it failed saying the sequence was 2gb big. When opening in babeltrace, it OOMed with 2gb allocations. When opening with a hex editor, I saw 2gb allocations.

On another subject, fixing the trace made it scale well in both babeltrace and Trace Compass.

I don't know why, data_length writes the wrong data. Hope this helps all parties.



From: tracecompass-dev-bounces at eclipse.org <tracecompass-dev-bounces at eclipse.org> on behalf of Doug Schaefer <dschaefer at blackberry.com>
Sent: Tuesday, March 12, 2019 2:50:29 PM
To: jonathan.rajotte-julien at efficios.com
Cc: lttng-dev at lists.lttng.org; tracecompass-dev at eclipse.org
Subject: Re: [tracecompass-dev] [lttng-dev] Scalability

I have attached the C file for a generator that creates a trace that reproduces the memory issue with babeltrace. The same issue happens with a custom program in the call to add a trace to a context.

I am using babeltrace that I get from my Ubuntu 18.04 distro. It has the version number 1.5.5.

Thanks for the help!

On Tue, 2019-03-12 at 15:47 +0000, Doug Schaefer wrote:
In the thread on the tracecompass list, I also mentioned that the babeltrace utility itself ran out of memory when reading the file. That's actually my biggest worry. I got around the generator issue by flushing every 100K events.

I'll create a quick generator that shows the same issue and post it in a bit.


On Tue, 2019-03-12 at 11:34 -0400, Jonathan Rajotte-Julien wrote:

On Tue, Mar 12, 2019 at 03:23:23PM +0000, Doug Schaefer wrote:

It should be easy to generate a random one with the class I mentioned below

and fill it with 16 million events.

Not if the problem is in the generator code ;).

BTW, two of the int fields are 5 and 10

bits respectively, but I'm not sure that matters (or at least it shouldn't).

Make sure to check the endian-ness of those fields.

What class? Not sure I see any reference to any.

Since you are generating CTF the error can be in the generator code. Please

provide either a trace reproducing the issue or a base reproducer. It will be

much easier overall than us trying to reproduce it blindly.



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