As my Lua game got more complex, I noticed that the game was slowing down over tme. My hunch was that this was a memory "leak". So I decided to track memory usage to see if my code was behaving itself...
It wasn't. I was losing 32KB of memory every level load and this turned out to be of my own making.
Simulator
Use Simulator > Window > Lua Memory
pros
- sortable
- displays everything
cons
- game paused while displayed
- does not update live
Also be wary that memory allocations are different on Simulator and Device.
Device & Simulator
There's a Lua command called collectgarbage("count") that when called with the count parameter reports memory, which is ideal to print as debug logging.
I used a call to remember the inital memory usage, and then additional calls to it at the end of each of my methods as below
Note: you may have to drill in to more places to lock on to where exactly your memory being allocated and never freed.
There may be better ways to do this, but this was enough for me.
I hope this is a useful guide to others.
pros
- displays whilst game runs
- updates live
cons
- not sortable
- displays specifics
function game:init()
...
if debug == true then
self.memoryInit = collectgarbage("count")*1024
self.memoryUsed = self.memoryInit
print( string.format("initial memory usage (%d bytes)", self.memoryInit) )
end
end
function game:levelLoad()
...
if debug == true then
self:memoryCheck()
end
end
function game:memoryCheck()
local new <const> = collectgarbage("count")*1024
local diff <const> = new - self.memoryUsed
-- still making large numbers of allocations
if diff > self.memoryInit then
self.memoryUsed = new
return
end
-- fine grained memory changes
if diff > 0 then
print(string.format("memory use\t+%dKB (%d bytes)", diff//1024, new - self.memoryInit))
elseif diff < 0 then
print(string.format("memory free\t%dKB (%d bytes)", diff//1024, new - self.memoryInit))
end
self.memoryUsed = new
end