jprof-lovr

Usually Lua programs are profiled by setting hooks using the built-in function debug.sethook, but sadly these hooks are not reliably called in luajit, which makes most profiling libraries for Lua not usable in the current version of LÖVR.

jprof-lovr is a semi-makeshift solution for profiling LÖVR applications with some extra work, but while also providing no significant slowdown while profiling.

Overview

jprof-lovr requires you to annotate your LÖVR code with "profiling zones", which form a hierarchical representation of the overall flow of your program and record time taken and memory consumption for each of these zones:

function foo()
    prof.push("do the thing")
    thething()
    prof.pop()
end

function bar()
    prof.push("foo it up in here")
    foo()
    prof.pop("foo it up in here")

    prof.push("something else")
    local baz = sum(thing, else)
    prof.pop("something else")
end

These are then saved to a file in your application's save directory, which you can analyze in the love2d-based viewer:

purple is frame time; green is memory usage

Documentation

Before you annotate your code, you need to copy (or move) lovr/jprof.lua and lovr/MessagePack.lua into your LÖVR game's directory.

The most common case does probably look somewhat like this:

PROF_NOCAPTURE = false
prof = require("jprof")

function lovr.update(dt)
    prof.pushFrame()
    prof.push("update")
    -- push and pop additional zones here
    -- also update your game if you want
    prof.pop("update")
end

function lovr.draw(pass)
    prof.push("draw")
    -- push and pop additional zones here
    prof.pop("draw")
    prof.popFrame(pass) -- optional argument for GPU profiling
end

function lovr.quit()
    prof.write("prof.mpack")
end

If PROF_NOCAPTURE evaluates to true when jprof-lovr is imported, all profiling functions are replaced with function() end i.e. do nothing, so you can leave them in even for release builds.

Also all other zones have to be pushed inside the prof.pushFrame zone and whenever prof.push or prof.pop are called outside of a frame, the viewer will not know how to interpret that data (and error).

You can pass pass to prof.popFrame to profile the GPU.

prof.pushFrame(annotation)

The annotation is optional and appears as metadata in the viewer.

prof.popFrame(pass)

The pass is optional and adds a "GPU" field in the viewer.

prof.push(name, annotation)

The annotation is optional and appears as metadata in the viewer.

prof.pop(name)

The name is optional and is only used to check if the current zone is actually the one specified as the argument. If not, somewhere before that pop-call another zone has been pushed, but not popped.

prof.popAll()

Pops all zones from the stack. You should almost never use this function, except if you want to terminate the program while having a number of zones on the zone stack (i.e. just before calling prof.write()) and cleaning up properly would be too bothersome.

prof.write(filename)

Writes the capture file to filename.

prof.enabled(enabled)

Enables capturing profiling zones (enabled = true) or disables it (enabled = false). By default, profiling is enabled.

prof.connect(saveFullProfData, port, address)

Attempts to connect to the jprof viewer to transmit realtime profiling data. If saveFullProfData is true, jprof will still save all the profiling data, so you can save it to file later using prof.write(). If it is false (default), the data is only transmitted to the viewer and prof.write() will show a notice that no profiling data was saved. The default port is 1338 and the default address is localhost.

prof.netFlush()

jprof does not send out every event by itself, but rather buffers them and sends them out, when this command is called. By default this is called when prof.pop() is called and the popped zone is "frame" (though only if you did prof.connect() earlier).

Viewer

Just start the love2d project contained in this repository like this:

love love/jprof <filepath>

With <filepath> being the path to the capture file, probably somewhere in the LÖVR project's save directory.

Realtime Profiling (untested with LÖVR)

jprof also supports realtime transmission of profiling data. To use this feature, just start the love2d viewer in listen mode:

love love/jprof listen

You may also pass an additional, optional argument to specify a port. The default port used is 1338. In the program you are profiling, call prof.connect() (see above) right after importing jprof.

Note: When realtime profiling is used, it is not as straightforward to keep track of the memory jprof is using itself, since jprof will produce garbage too. Therefore the memory values returned by jprof will be less accurate and depending on your use case the garbage generated by jprof will dominate. Make sure to capture to file first and see if the live capture looks significantly different.

Notes

Hold F1 or H to show the help overlay.

When you select a frame range, it will be averaged. Most of the time this is what you want to look at rather than individual frames.

If a single frame is selected the position of the zones in the flame graph will correspond to their relative position in time inside the frame, for averaged frames both in memory and time mode the zones will just be centered above their parent. Their size will still hold meaning though and empty space surrounding these zones implies that there was memory consumed/freed or time spent without being enclosed by a profiling zone.

The different modes (memory and time) determine whether the scale and position of the zones inside the flame graph will be derived from either memory consumption changes or time duration respectively.

The purple graph displays the total duration of the frames over time and the green graph the total memory consumption over time.

Graph Averaging Modes

• max mean is most useful for finding spikes. This is the default.
• arithmetic mean is what most people think of, when they think of an average. This is less sensitive to spikes, but still somewhat.
• harmonic mean is least sensitive to outliers and should be a bit smoother than the arithmetic mean.