Initial commit

.gitignore

@@ -0,0 +1,3 @@
+*.swp
+*.patch
+*.bak

.luacheckrc

@@ -0,0 +1,3 @@
+read_globals = {
+	"core", "jit"
+}

LICENSE

@@ -0,0 +1,10 @@
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.

README.md

@@ -0,0 +1,47 @@
+# Tune JIT `tune_jit`
+
+A Luanti mod tuning LuaJIT parameters to improve server performance by
+preventing constant GC.
+
+
+## Wait, what does it exactly do?
+
+At a base level, this mod implements the same thing as [VoxeLibre](https://git.minetest.land/VoxeLibre/VoxeLibre/src/commit/161dbaea03a7816db1393ca767c84a5f275ef162/mods/CORE/mcl_init/tune_jit.lua)
+and [Mineclonia](https://codeberg.org/mineclonia/mineclonia/src/commit/94467d9f822ae31838e3c76d643950be2ee891f8/mods/ENTITIES/mcl_mobs/pathfinding.lua#L1627-L1636)
+but for other Luanti games, with more configurability for the server operator.
+
+[The `jit.opt.*` API](https://luajit.org/ext_jit.html) is leveraged in order to
+modify JIT compiler optimization parameters on server startup. This won't work
+with LuaJIT 1.x, but if you have a LuaJIT that ancient, most of your server-side
+performance issues should go away after you upgrade it. The coolest thing is
+that this mod doesn't have to be in the `secure.trusted_mods` list in order to
+apply the parameters.
+
+In [@halon](https://codeberg.org/halon)'s words:
+
+> Large minetest servers on stock luajit spend most of their globalsteps
+> recording and jit compiling traces that are evicted for exceeding one of the
+> minuscule limits on trace count or mcode size defined by default
+
+The specific parameters that are modified are `maxtrace`, `maxrecord`,
+`minstitch` and `maxmcode`. Please refer to this mod's `settingtypes.txt` and
+LuaJIT documentation for details.
+
+
+## Will it help with client-side lag?
+
+Unless it was the server's fault, no.
+
+For singleplayer, remember that Luanti just starts up a server under the hood
+and connects you to it, with the same server/client communication rules and
+specifics. The only difference is that both server and client are now ran on the
+same machine, though most likely in different threads.
+
+Mobs freezing and map generation suddenly stopping might get removed, but this
+won't have any effect on rendering or audio playback.
+
+
+## License
+
+The source code is licensed under 0BSD ("public domain"). See `LICENSE` file for
+details.

init.lua

@@ -0,0 +1,23 @@
+if not core.global_exists("jit") then
+	core.log("warning", "[tune_jit] Couldn't find LuaJIT, nothing to tune")
+	return
+elseif not jit.status() then
+	core.log("warning", "[tune_jit] LuaJIT is enabled but JIT compiler is disabled")
+	return
+end
+
+local PARAM_DEFAULTS = {
+	maxtrace = 24000, -- 1000 for LuaJIT; 8000 for OpenResty
+	maxrecord = 32000, -- 4000 for LuaJIT; 16000 for OpenResty
+	minstitch = 3, -- 0 for LuaJIT; 3 for OpenResty
+	maxmcode = 163840 -- 512 for LuaJIT (O_O); 40960 for OpenResty
+}
+
+local opt = {}
+for name, default_value in pairs(PARAM_DEFAULTS) do
+	local value = tonumber(core.settings:get("tune_jit."..name)) or default_value
+	table.insert(opt, name .. "=" .. value)
+end
+
+jit.opt.start(unpack(opt))
+core.log("action", "[tune_jit] Applied increased JIT compiler optimization parameters")

mod.conf

@@ -0,0 +1,3 @@
+name = tune_jit
+title = Tune JIT
+description = Tunes LuaJIT parameters to improve server performance by preventing constant GC

settingtypes.txt

@@ -0,0 +1,16 @@
+# Maximum amount of cached traces.
+# 1000 for stock, 8000 for OpenResty
+tune_jit.maxtrace (Max. # of traces in cache) int 24000 0
+
+# Maximum amount of IR (Intermediate Representation) instructions.
+# 4000 for stock, 16000 for OpenResty
+tune_jit.maxrecord (Max. # of recorded IR instructions) int 32000 0
+
+# Minimum amount of IR (Intermediate Representation) instructions to be
+# included in a stitched trace.
+# 0 for stock, 3 for OpenResty
+tune_jit.minstitch (Min. # of stitched trace IR instructions) int 3 0
+
+# Maximum total size of all machine code areas, in kilobytes.
+# 512 for stock, 40960 for OpenResty
+tune_jit.maxmcode (Max. machine code size) int 163840 0