profiler

profiler.lua

@@ -0,0 +1,59 @@
+-- Developer-only CPU sampler. It is inert until F9 is pressed.
+--
+-- On stop it writes `chroma-solstice.folded` in LÖVE's save directory. The
+-- file uses Brendan Gregg's folded-stack format and can be given directly to
+-- FlameGraph's flamegraph.pl.
+PerfProfiler = {
+	active = false,
+	samples = {},
+	status = "F9: start CPU profile",
+}
+
+local ok, profile = pcall(require, "jit.profile")
+PerfProfiler.available = ok
+if not ok then
+	PerfProfiler.status = "LuaJIT sampler unavailable"
+end
+
+local function sample(thread, count, vmstate)
+	-- Negative depth produces caller -> callee order, which is what folded
+	-- flamegraphs expect. Function-level samples keep the output compact.
+	local stack = profile.dumpstack(thread, "pF;", -64):gsub(";$", "")
+	if stack ~= "" then
+		PerfProfiler.samples[stack] = (PerfProfiler.samples[stack] or 0) + count
+	end
+end
+
+function PerfProfiler:toggle()
+	if not self.available then return false end
+	if not self.active then
+		self.samples = {}
+		profile.start("fi2", sample)
+		self.active = true
+		self.status = "CPU profile recording (F9 to write)"
+		return true
+	end
+
+	profile.stop()
+	self.active = false
+	local lines, sampleCount = {}, 0
+	for stack, count in pairs(self.samples) do
+		table.insert(lines, stack .. " " .. count)
+		sampleCount = sampleCount + count
+	end
+	table.sort(lines)
+	local path = "chroma-solstice.folded"
+	local saved = love.filesystem.write(path, table.concat(lines, "\n") .. "\n")
+	local directory = love.filesystem.getSaveDirectory()
+	self.status = saved and ("CPU profile saved (" .. sampleCount .. " samples); see terminal")
+		or "Could not write CPU profile"
+	if saved then print("CPU profile: " .. directory .. "/" .. path) else print(self.status) end
+	return saved
+end
+
+function PerfProfiler:draw()
+	if not self.active and self.status == "F9: start CPU profile" then return end
+	love.graphics.setColor(self.active and 1 or 0.6, self.active and 0.75 or 1, self.active and 0.2 or 0.6, 1)
+	love.graphics.print(self.active and "PROFILING: F9 to save flamegraph data" or self.status, 10, 28)
+	love.graphics.setColor(1, 1, 1, 1)
+end