ProFi, a simple lua profiler that works with LuaJIT and prints a pretty report file in columns.

ProFi.lua

--[[
	ProFi v1.3, by Luke Perkin 2012. MIT Licence http://www.opensource.org/licenses/mit-license.php.
	
	Example:
		ProFi = require 'ProFi'
		ProFi:start()
		some_function()
		another_function()
		coroutine.resume( some_coroutine )
		ProFi:stop()
		ProFi:writeReport( 'MyProfilingReport.txt' )

	API:
	*Arguments are specified as: type/name/default.
		ProFi:start( string/once/nil )
		ProFi:stop()
		ProFi:checkMemory( number/interval/0, string/note/'' )
		ProFi:writeReport( string/filename/'ProFi.txt' )
		ProFi:reset()
		ProFi:setHookCount( number/hookCount/0 )
		ProFi:setGetTimeMethod( function/getTimeMethod/os.clock )
		ProFi:setInspect( string/methodName, number/levels/1 )
]]

-----------------------
-- Locals:
-----------------------

local ProFi = {}
local onDebugHook, sortByDurationDesc, sortByCallCount, getTime
local DEFAULT_DEBUG_HOOK_COUNT = 0
local FORMAT_HEADER_LINE       = "| %-50s: %-40s: %-20s: %-12s: %-12s: %-12s|\n"
local FORMAT_OUTPUT_LINE       = "| %s: %-12s: %-12s: %-12s|\n"
local FORMAT_INSPECTION_LINE   = "> %s: %-12s\n"
local FORMAT_TOTALTIME_LINE    = "| TOTAL TIME = %f\n"
local FORMAT_MEMORY_LINE 	   = "| %-20s: %-16s: %-16s| %s\n"
local FORMAT_HIGH_MEMORY_LINE  = "H %-20s: %-16s: %-16sH %s\n"
local FORMAT_LOW_MEMORY_LINE   = "L %-20s: %-16s: %-16sL %s\n"
local FORMAT_TITLE             = "%-50.50s: %-40.40s: %-20s"
local FORMAT_LINENUM           = "%4i"
local FORMAT_TIME              = "%04.3f"
local FORMAT_RELATIVE          = "%03.2f%%"
local FORMAT_COUNT             = "%7i"
local FORMAT_KBYTES  		   = "%7i Kbytes"
local FORMAT_MBYTES  		   = "%7.1f Mbytes"
local FORMAT_MEMORY_HEADER1    = "\n=== HIGH & LOW MEMORY USAGE ===============================\n"
local FORMAT_MEMORY_HEADER2    = "=== MEMORY USAGE ==========================================\n"
local FORMAT_BANNER 		   = [[
###############################################################################################################
#####  ProFi, a lua profiler. This profile was generated on: %s
#####  ProFi is created by Luke Perkin 2012 under the MIT Licence, www.locofilm.co.uk
#####  Version 1.3. Get the most recent version at this gist: https://gist.github.com/2838755
###############################################################################################################

]]

-----------------------
-- Public Methods:
-----------------------

--[[
	Starts profiling any method that is called between this and ProFi:stop().
	Pass the parameter 'once' to so that this methodis only run once.
	Example: 
		ProFi:start( 'once' )
]]
function ProFi:start( param )
	if param == 'once' then
		if self:shouldReturn() then
			return
		else
			self.should_run_once = true
		end
	end
	self.has_started  = true
	self.has_finished = false
	self:resetReports( self.reports )
	self:startHooks()
	self.startTime = getTime()
end

--[[
	Stops profiling.
]]
function ProFi:stop()
	if self:shouldReturn() then 
		return
	end
	self.stopTime = getTime()
	self:stopHooks()
	self.has_finished = true
end

function ProFi:checkMemory( interval, note )
	local time = getTime()
	local interval = interval or 0
	if self.lastCheckMemoryTime and time < self.lastCheckMemoryTime + interval then
		return
	end
	self.lastCheckMemoryTime = time
	local memoryReport = {
		['time']   = time;
		['memory'] = collectgarbage('count');
		['note']   = note or '';
	}
	table.insert( self.memoryReports, memoryReport )
	self:setHighestMemoryReport( memoryReport )
	self:setLowestMemoryReport( memoryReport )
end

--[[
	Writes the profile report to a file.
	Param: [filename:string:optional] defaults to 'ProFi.txt' if not specified.
]]
function ProFi:writeReport( filename )
	if #self.reports > 0 or #self.memoryReports > 0 then
		filename = filename or 'ProFi.txt'
		self:sortReportsWithSortMethod( self.reports, self.sortMethod )
		self:writeReportsToFilename( filename )
		print( string.format("[ProFi]\t Report written to %s", filename) )
	end
end

--[[
	Resets any profile information stored.
]]
function ProFi:reset()
	self.reports = {}
	self.reportsByTitle = {}
	self.memoryReports  = {}
	self.highestMemoryReport = nil
	self.lowestMemoryReport  = nil
	self.has_started  = false
	self.has_finished = false
	self.should_run_once = false
	self.lastCheckMemoryTime = nil
	self.hookCount = self.hookCount or DEFAULT_DEBUG_HOOK_COUNT
	self.sortMethod = self.sortMethod or sortByDurationDesc
	self.inspect = nil
end

--[[
	Set how often a hook is called.
	See http://pgl.yoyo.org/luai/i/debug.sethook for information.
	Param: [hookCount:number] if 0 ProFi counts every time a function is called.
	if 2 ProFi counts every other 2 function calls.
]]
function ProFi:setHookCount( hookCount )
	self.hookCount = hookCount
end

--[[
	Set how the report is sorted when written to file.
	Param: [sortType:string] either 'duration' or 'count'.
	'duration' sorts by the time a method took to run.
	'count' sorts by the number of times a method was called.
]]
function ProFi:setSortMethod( sortType )
	if sortType == 'duration' then
		self.sortMethod = sortByDurationDesc
	elseif sortType == 'count' then
		self.sortMethod = sortByCallCount
	end
end

--[[
	By default the getTime method is os.clock (CPU time),
	If you wish to use other time methods pass it to this function.
	Param: [getTimeMethod:function]
]]
function ProFi:setGetTimeMethod( getTimeMethod )
	getTime = getTimeMethod
end

--[[
	Allows you to inspect a specific method.
	Will write to the report a list of methods that
	call this method you're inspecting, you can optionally
	provide a levels parameter to traceback a number of levels.
	Params: [methodName:string] the name of the method you wish to inspect.
	        [levels:number:optional] the amount of levels you wish to traceback, defaults to 1.
]]
function ProFi:setInspect( methodName, levels )
	if self.inspect then
		self.inspect.methodName = methodName
		self.inspect.levels = levels or 1
	else
		self.inspect = {
			['methodName'] = methodName;
			['levels'] = levels or 1;
		}
	end
end

-----------------------
-- Implementations methods:
-----------------------

function ProFi:shouldReturn( )
	return self.should_run_once and self.has_finished
end

function ProFi:getFuncReport( funcInfo )
	local title = self:getTitleFromFuncInfo( funcInfo )
	local funcReport = self.reportsByTitle[ title ]
	if not funcReport then
		funcReport = self:createFuncReport( funcInfo )
		self.reportsByTitle[ title ] = funcReport
		table.insert( self.reports, funcReport )
	end
	return funcReport
end

function ProFi:getTitleFromFuncInfo( funcInfo )
	local name        = funcInfo.name or 'anonymous'
	local source      = funcInfo.short_src or 'C_FUNC'
	local linedefined = funcInfo.linedefined or 0
	linedefined = string.format( FORMAT_LINENUM, linedefined )
	return string.format(FORMAT_TITLE, source, name, linedefined)
end

function ProFi:createFuncReport( funcInfo )
	local name = funcInfo.name or 'anonymous'
	local source = funcInfo.source or 'C Func'
	local linedefined = funcInfo.linedefined or 0
	local funcReport = {
		['title']         = self:getTitleFromFuncInfo( funcInfo );
		['count'] = 0;
		['timer']         = 0;
	}
	return funcReport
end

function ProFi:startHooks()
	debug.sethook( onDebugHook, 'cr', self.hookCount )
end

function ProFi:stopHooks()
	debug.sethook()
end

function ProFi:sortReportsWithSortMethod( reports, sortMethod )
	if reports then
		table.sort( reports, sortMethod )
	end
end

function ProFi:writeReportsToFilename( filename )
	local file, err = io.open( filename, 'w' )
	assert( file, err )
	self:writeBannerToFile( file )
	if #self.reports > 0 then
		self:writeProfilingReportsToFile( self.reports, file )
	end
	if #self.memoryReports > 0 then
		self:writeMemoryReportsToFile( self.memoryReports, file )
	end
	file:close()
end

function ProFi:writeProfilingReportsToFile( reports, file )
	local totalTime = self.stopTime - self.startTime
	local totalTimeOutput =  string.format(FORMAT_TOTALTIME_LINE, totalTime)
	file:write( totalTimeOutput )
	local header = string.format( FORMAT_HEADER_LINE, "FILE", "FUNCTION", "LINE", "TIME", "RELATIVE", "CALLED" )
	file:write( header )
 	for i, funcReport in ipairs( reports ) do
		local timer         = string.format(FORMAT_TIME, funcReport.timer)
		local count         = string.format(FORMAT_COUNT, funcReport.count)
		local relTime 		= string.format(FORMAT_RELATIVE, (funcReport.timer / totalTime) * 100 )
		local outputLine    = string.format(FORMAT_OUTPUT_LINE, funcReport.title, timer, relTime, count )
		file:write( outputLine )
		if funcReport.inspections then
			self:writeInpsectionsToFile( funcReport.inspections, file )
		end
	end
end

function ProFi:writeMemoryReportsToFile( reports, file )
	file:write( FORMAT_MEMORY_HEADER1 )
	self:writeHighestMemoryReportToFile( file )
	self:writeLowestMemoryReportToFile( file )
	file:write( FORMAT_MEMORY_HEADER2 )
	for i, memoryReport in ipairs( reports ) do
		local outputLine = self:formatMemoryReportWithFormatter( memoryReport, FORMAT_MEMORY_LINE )
		file:write( outputLine )
	end
end

function ProFi:writeHighestMemoryReportToFile( file )
	local memoryReport = self.highestMemoryReport
	local outputLine   = self:formatMemoryReportWithFormatter( memoryReport, FORMAT_HIGH_MEMORY_LINE )
	file:write( outputLine )
end

function ProFi:writeLowestMemoryReportToFile( file )
	local memoryReport = self.lowestMemoryReport
	local outputLine   = self:formatMemoryReportWithFormatter( memoryReport, FORMAT_LOW_MEMORY_LINE )
	file:write( outputLine )
end

function ProFi:formatMemoryReportWithFormatter( memoryReport, formatter )
	local time       = string.format(FORMAT_TIME, memoryReport.time)
	local kbytes     = string.format(FORMAT_KBYTES, memoryReport.memory)
	local mbytes     = string.format(FORMAT_MBYTES, memoryReport.memory/1024)
	local outputLine = string.format(formatter, time, kbytes, mbytes, memoryReport.note)
	return outputLine
end

function ProFi:writeBannerToFile( file )
	local banner = string.format(FORMAT_BANNER, os.date())
	file:write( banner )
end

function ProFi:writeInpsectionsToFile( inspections, file )
	local inspectionsList = self:sortInspectionsIntoList( inspections )
	file:write('\n==^ INSPECT ^======================================================================================================== COUNT ===\n')
	for i, inspection in ipairs( inspectionsList ) do
		local line 			= string.format(FORMAT_LINENUM, inspection.line)
		local title 		= string.format(FORMAT_TITLE, inspection.source, inspection.name, line)
		local count 		= string.format(FORMAT_COUNT, inspection.count)
		local outputLine    = string.format(FORMAT_INSPECTION_LINE, title, count )
		file:write( outputLine )
	end
	file:write('===============================================================================================================================\n\n')
end

function ProFi:sortInspectionsIntoList( inspections )
	local inspectionsList = {}
	for k, inspection in pairs(inspections) do
		inspectionsList[#inspectionsList+1] = inspection
	end
	table.sort( inspectionsList, sortByCallCount )
	return inspectionsList
end

function ProFi:resetReports( reports )
	for i, report in ipairs( reports ) do
		report.timer = 0
		report.count = 0
		report.inspections = nil
	end
end

function ProFi:shouldInspect( funcInfo )
	return self.inspect and self.inspect.methodName == funcInfo.name
end

function ProFi:getInspectionsFromReport( funcReport )
	local inspections = funcReport.inspections
	if not inspections then
		inspections = {}
		funcReport.inspections = inspections
	end
	return inspections
end

function ProFi:getInspectionWithKeyFromInspections( key, inspections )
	local inspection = inspections[key]
	if not inspection then
		inspection = {
			['count']  = 0;
		}
		inspections[key] = inspection
	end
	return inspection
end

function ProFi:doInspection( inspect, funcReport )
	local inspections = self:getInspectionsFromReport( funcReport )
	local levels = 5 + inspect.levels
	local currentLevel = 5
	while currentLevel < levels do
		local funcInfo = debug.getinfo( currentLevel, 'nS' )
		if funcInfo then
			local source = funcInfo.short_src or '[C]'
			local name = funcInfo.name or 'anonymous'
			local line = funcInfo.linedefined
			local key = source..name..line
			local inspection = self:getInspectionWithKeyFromInspections( key, inspections )
			inspection.source = source
			inspection.name = name
			inspection.line = line
			inspection.count = inspection.count + 1
			currentLevel = currentLevel + 1
		else
			break
		end
	end
end

function ProFi:onFunctionCall( funcInfo )
	local funcReport = ProFi:getFuncReport( funcInfo )
	funcReport.callTime = getTime()
	funcReport.count = funcReport.count + 1
	if self:shouldInspect( funcInfo ) then
		self:doInspection( self.inspect, funcReport )
	end
end

function ProFi:onFunctionReturn( funcInfo )
	local funcReport = ProFi:getFuncReport( funcInfo )
	if funcReport.callTime then
		funcReport.timer = funcReport.timer + (getTime() - funcReport.callTime)
	end
end

function ProFi:setHighestMemoryReport( memoryReport )
	if not self.highestMemoryReport then
		self.highestMemoryReport = memoryReport
	else
		if memoryReport.memory > self.highestMemoryReport.memory then
			self.highestMemoryReport = memoryReport
		end
	end
end

function ProFi:setLowestMemoryReport( memoryReport )
	if not self.lowestMemoryReport then
		self.lowestMemoryReport = memoryReport
	else
		if memoryReport.memory < self.lowestMemoryReport.memory then
			self.lowestMemoryReport = memoryReport
		end
	end
end

-----------------------
-- Local Functions:
-----------------------

getTime = os.clock

onDebugHook = function( hookType )
	local funcInfo = debug.getinfo( 2, 'nS' )
	if hookType == "call" then
		ProFi:onFunctionCall( funcInfo )
	elseif hookType == "return" then
		ProFi:onFunctionReturn( funcInfo )
	end
end

sortByDurationDesc = function( a, b )
	return a.timer > b.timer
end

sortByCallCount = function( a, b )
	return a.count > b.count
end

-----------------------
-- Return Module:
-----------------------

ProFi:reset()
return ProFi

what about tail return?