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manual_gc cleanup/clarification and default arguments

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This commit is contained in:
Max Cahill 2021-07-23 10:53:29 +10:00
parent 6d0f21a7c0
commit 3b739380e4
1 changed files with 33 additions and 18 deletions
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51
manual_gc.lua
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@ -4,28 +4,43 @@
specify a time budget and a memory ceiling per call.
called once per frame, this will spread any big collections
over a couple of frames, and "catch up" when there is. This
keeps GC burden much more predictable.
over several frames, and "catch up" when there is too much
work to do.
The memory ceiling provides some level of "relief valve" - if
exceeded it will trigger a "full" collection, but this is
likely to hurt performance. If you hit the ceiling, it
indicates you likely need to either generate less garbage
or spent more time each frame collecting.
This keeps GC time burden much more predictable.
1ms (1e-3) is a good place to start for the budget, adjust
down or up as needed. games that generate more garbage will
need to spend longer on gc each frame.
The memory ceiling provides a safety backstop.
if exceeded it will trigger a "full" collection, and this will
hurt performance - you'll notice the hitch. If you hit your ceiling,
it indicates you likely need to either find a way to generate less
garbage, or spend more time each frame collecting.
64mb is a good place to start for the memory ceiling, though
some games will need much more.
the function instructs the garbage collector only as small a step
as possible each iteration. this prevents the "spiky" collection
patterns, though with particularly large sets of tiny objects,
the start of a collection can still take longer than you might like.
the function steps the garbage collector only do a small step
each time. this prevents the start of collection from "spiking",
though it still causes some with particularly large sets
default values:
time_budget - 1ms (1e-3)
adjust down or up as needed. games that generate more garbage
will need to spend longer on gc each frame.
memory_ceiling - 64mb
a good place to start, though some games will need much more.
remember, this is lua memory, not the total memory consumption
of your game.
disable_otherwise - false
disabling the gc completely is dangerous - any big allocation
event (eg - level gen) could push you to an out of memory
situation and crash your game. test extensively before you
ship a game with this set true.
]]
return function(time_budget, safetynet_megabytes, disable_otherwise)
return function(time_budget, memory_ceiling, disable_otherwise)
time_budget = time_budget or 1e-3
memory_ceiling = memory_ceiling or 64
local max_steps = 1000
local steps = 0
local start_time = love.timer.getTime()
@ -37,11 +52,11 @@ return function(time_budget, safetynet_megabytes, disable_otherwise)
steps = steps + 1
end
--safety net
if collectgarbage("count") / 1024 > safetynet_megabytes then
if collectgarbage("count") / 1024 > memory_ceiling then
collectgarbage("collect")
end
--don't collect gc outside this margin
if disable_otherwise then
collectgarbage("stop")
end
end
end