2024-01-10 Lumiera Developers Meeting
=====================================
:Author: Benny
:Date: 2024-01-20

Jan 10, 2024
on {l}/project/contact.html#_irc[`#lumiera`]
20:00 - 23:00 UTC +

__Participants__

 * ichthyo
 * benn

''''
Two main points of discussion:

 - Scheduler tests to examine its suitability
 - Using Gstreamer to view video for our vertical slice


Test Scheduler Suitability
--------------------------

Once the scheduler had been implemented it was necessary to subject it
to various load tests to establish its stability, and stress tests were necessary to
provide information on performance limitations so that we would be able to establish
whether these limitations met the demands required by Lumiera. 
Results were encouraging.

_Ichthyo_ reported on stress tests on the new scheduler. After resolving a series
of initial bugs, processing runs stable now, even when entering over 500 test jobs
simultaneously to the queue. Stress tests revealed typical limitations of the scheduler,
which exhibited behaviour that is well within the requirements of Lumiera. Load tests
showed that the scheduler remained stable when subjected to short heavy load bursts
within expected bounds.

Indeed performance testing is always a delicate and complex area to
investigate, as it is necessary to establish reasonable performance boundaries
of the system: we can always overload any scheduler with fanatically huge numbers
of jobs; while the scheduler is still able to process all enqueued jobs eventually,
congestion builds up and jobs start missing their deadlines. Of interest, however,
is to establish some reasonable information on the processing rate of the scheduler
which _Ichthyo_ was able to estimate statistically by carefully observing the
scheduler under a collection of pre-calibrated loads.

Some goals of the tests:

 - establish the scheduler breaking point or performance limitations
 - tests under pressure with parallelism and complex dependencies between jobs
 - demonstrate that the scheduler is stable under typical load for several seconds

Tests on a wider array of hardware constellations are not expected to reveal much
relevant information in this stage of the project and will thus be conducted later.
This kind of analytical, isolated component tests will not ultimately resolve the
issue of whether the scheduler can perform as desired, but subjecting the scheduler
to carefully selected tests can help to reduce the probability of missing serious
performance limitations inherent to the chosen design.


GStreamer Demo to Play Video
----------------------------

_Benn_ has written a simple GStreamer demo so that a video in raw format can be
displayed on the GUI for the current vertical slice. The next step in this
investigation is to identify a low-level entrance point to the functionality
provided by the GStreamer library, since for use in this vertical slice the
render engine produces a buffer filled with raw video data for each frame,
which will then be displayed in a video widget as an ongoing process.

This is a general question requiring further investigation: how to make use of
established functionality from a library to simplify our implementation task,
while retaining the full control and coordination of the rendering and playback
process and resource management within the Lumiera render engine itself.

''''

Next meeting
------------

The next Lumiera meeting is scheduled for Wednesday, Feb 14 at 20:00 UTC.
Should this be inconvenient for you, please speak up on, for example,
link:http://lists.lumiera.org/cgi-bin/mailman/listinfo/lumiera[lumiera@lists.lumiera.org]
and let us know of when you would prefer to attend.

''''

