source: ps/trunk/build/premake/premake5/tests/pepperfish_profiler.lua

--[[

== Introduction ==

  Note that this requires os.clock(), debug.sethook(),
  and debug.getinfo() or your equivalent replacements to
  be available if this is an embedded application.

  Example usage:

    profiler = newProfiler()
    profiler:start()

    < call some functions that take time >

    profiler:stop()

    local outfile = io.open( "profile.txt", "w+" )
    profiler:report( outfile )
    outfile:close()

== Optionally choosing profiling method ==

The rest of this comment can be ignored if you merely want a good profiler.

  newProfiler(method, sampledelay):

If method is omitted or "time", will profile based on real performance.
optionally, frequency can be provided to control the number of opcodes
per profiling tick. By default this is 100000, which (on my system) provides
one tick approximately every 2ms and reduces system performance by about 10%.
This can be reduced to increase accuracy at the cost of performance, or
increased for the opposite effect.

If method is "call", will profile based on function calls. Frequency is
ignored.


"time" may bias profiling somewhat towards large areas with "simple opcodes",
as the profiling function (which introduces a certain amount of unavoidable
overhead) will be called more often. This can be minimized by using a larger
sample delay - the default should leave any error largely overshadowed by
statistical noise. With a delay of 1000 I was able to achieve inaccuray of
approximately 25%. Increasing the delay to 100000 left inaccuracy below my
testing error.

"call" may bias profiling heavily towards areas with many function calls.
Testing found a degenerate case giving a figure inaccurate by approximately
20,000%.  (Yes, a multiple of 200.) This is, however, more directly comparable
to common profilers (such as gprof) and also gives accurate function call
counts, which cannot be retrieved from "time".

I strongly recommend "time" mode, and it is now the default.

== History ==

2008-09-16 - Time-based profiling and conversion to Lua 5.1
  by Ben Wilhelm ( zorba-pepperfish@pavlovian.net ).
  Added the ability to optionally choose profiling methods, along with a new
  profiling method.

Converted to Lua 5, a few improvements, and 
additional documentation by Tom Spilman ( tom@sickheadgames.com )

Additional corrections and tidying by original author
Daniel Silverstone ( dsilvers@pepperfish.net )

== Status ==

Daniel Silverstone is no longer using this code, and judging by how long it's
been waiting for Lua 5.1 support, I don't think Tom Spilman is either. I'm
perfectly willing to take on maintenance, so if you have problems or
questions, go ahead and email me :)
-- Ben Wilhelm ( zorba-pepperfish@pavlovian.net ) '

== Copyright ==

Lua profiler - Copyright Pepperfish 2002,2003,2004

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to
deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to
do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.

--]]


--
-- All profiler related stuff is stored in the top level table '_profiler'
--
_profiler = {}


--
-- newProfiler() creates a new profiler object for managing 
-- the profiler and storing state.  Note that only one profiler 
-- object can be executing at one time.
--
function newProfiler(variant, sampledelay)
  if _profiler.running then
    print("Profiler already running.")
    return
  end

  variant = variant or "time"

  if variant ~= "time" and variant ~= "call" then
    print("Profiler method must be 'time' or 'call'.")
    return
  end
  
  local newprof = {}
  for k,v in pairs(_profiler) do
    newprof[k] = v
  end
  newprof.variant = variant
  newprof.sampledelay = sampledelay or 100000
  return newprof
end


--
-- This function starts the profiler.  It will do nothing
-- if this (or any other) profiler is already running.
--
function _profiler.start(self)
  if _profiler.running then
    return
  end
  -- Start the profiler. This begins by setting up internal profiler state
  _profiler.running = self
  self.rawstats = {}
  self.callstack = {}
  if self.variant == "time" then
    self.lastclock = os.clock()
    debug.sethook( _profiler_hook_wrapper_by_time, "", self.sampledelay )
  elseif self.variant == "call" then
    debug.sethook( _profiler_hook_wrapper_by_call, "cr" )
  else
    print("Profiler method must be 'time' or 'call'.")
    sys.exit(1)
  end
end


--
-- This function stops the profiler.  It will do nothing 
-- if a profiler is not running, and nothing if it isn't 
-- the currently running profiler.
--
function _profiler.stop(self)
  if _profiler.running ~= self then
    return
  end
  -- Stop the profiler.
  debug.sethook( nil )
  _profiler.running = nil
end


--
-- Simple wrapper to handle the hook.  You should not
-- be calling this directly. Duplicated to reduce overhead.
--
function _profiler_hook_wrapper_by_call(action)
  if _profiler.running == nil then
    debug.sethook( nil )
  end
  _profiler.running:_internal_profile_by_call(action)
end
function _profiler_hook_wrapper_by_time(action)
  if _profiler.running == nil then
    debug.sethook( nil )
  end
  _profiler.running:_internal_profile_by_time(action)
end


--
-- This is the main by-function-call function of the profiler and should not
-- be called except by the hook wrapper
--
function _profiler._internal_profile_by_call(self,action)
  -- Since we can obtain the 'function' for the item we've had call us, we
  -- can use that...
  local caller_info = debug.getinfo( 3 )
  if caller_info == nil then
    print "No caller_info"
    return
  end
  
  --SHG_LOG("[_profiler._internal_profile] "..(caller_info.name or "<nil>"))

  -- Retrieve the most recent activation record...
  local latest_ar = nil
  local callstackLen = #self.callstack
  if callstackLen > 0 then
    latest_ar = self.callstack[callstackLen]
  end
  
  -- Are we allowed to profile this function?
  local should_not_profile = 0
  for k,v in pairs(self.prevented_functions) do
    if k == caller_info.func then
      should_not_profile = v
    end
  end
  -- Also check the top activation record...
  if latest_ar then
    if latest_ar.should_not_profile == 2 then
      should_not_profile = 2
    end
  end

  -- Now then, are we in 'call' or 'return' ?
  -- print("Profile:", caller_info.name, "SNP:", should_not_profile,
  --       "Action:", action )
  if action == "call" then
    -- Making a call...
    local this_ar = {}
    this_ar.should_not_profile = should_not_profile
    this_ar.parent_ar = latest_ar
    this_ar.anon_child = 0
    this_ar.name_child = 0
    this_ar.children = {}
    this_ar.children_time = {}
    this_ar.clock_start = os.clock()
    -- Last thing to do on a call is to insert this onto the ar stack...
    table.insert( self.callstack, this_ar )
  else
    local this_ar = latest_ar
    if this_ar == nil then
      return -- No point in doing anything if no upper activation record
    end

    -- Right, calculate the time in this function...
    this_ar.clock_end = os.clock()
    this_ar.this_time = this_ar.clock_end - this_ar.clock_start

    -- Now, if we have a parent, update its call info...
    if this_ar.parent_ar then
      this_ar.parent_ar.children[caller_info.func] =
        (this_ar.parent_ar.children[caller_info.func] or 0) + 1
      this_ar.parent_ar.children_time[caller_info.func] =
        (this_ar.parent_ar.children_time[caller_info.func] or 0 ) +
        this_ar.this_time
      if caller_info.name == nil then
        this_ar.parent_ar.anon_child =
          this_ar.parent_ar.anon_child + this_ar.this_time
      else
        this_ar.parent_ar.name_child =
          this_ar.parent_ar.name_child + this_ar.this_time
      end
    end
    -- Now if we're meant to record information about ourselves, do so...
    if this_ar.should_not_profile == 0 then
      local inforec = self:_get_func_rec(caller_info.func,1)
      inforec.count = inforec.count + 1
      inforec.time = inforec.time + this_ar.this_time
      inforec.anon_child_time = inforec.anon_child_time + this_ar.anon_child
      inforec.name_child_time = inforec.name_child_time + this_ar.name_child
      inforec.func_info = caller_info
      for k,v in pairs(this_ar.children) do
        inforec.children[k] = (inforec.children[k] or 0) + v
        inforec.children_time[k] =
          (inforec.children_time[k] or 0) + this_ar.children_time[k]
      end
    end

    -- Last thing to do on return is to drop the last activation record...
    local callstackLen = #self.callstack
    table.remove( self.callstack, callstackLen )
  end
end


--
-- This is the main by-time internal function of the profiler and should not
-- be called except by the hook wrapper
--
function _profiler._internal_profile_by_time(self,action)
  -- we do this first so we add the minimum amount of extra time to this call
  local timetaken = os.clock() - self.lastclock
  
  local depth = 3
  local at_top = true
  local last_caller
  local caller = debug.getinfo(depth)
  while caller do
    if not caller.func then caller.func = "(tail call)" end
    if self.prevented_functions[caller.func] == nil then
      local info = self:_get_func_rec(caller.func, 1, caller)
      info.count = info.count + 1
      info.time = info.time + timetaken
      if last_caller then
        -- we're not the head, so update the "children" times also
        if last_caller.name then
          info.name_child_time = info.name_child_time + timetaken
        else
          info.anon_child_time = info.anon_child_time + timetaken
        end
        info.children[last_caller.func] =
          (info.children[last_caller.func] or 0) + 1
        info.children_time[last_caller.func] =
          (info.children_time[last_caller.func] or 0) + timetaken
      end
    end
    depth = depth + 1
    last_caller = caller
    caller = debug.getinfo(depth)
  end
  
  self.lastclock = os.clock()
end


--
-- This returns a (possibly empty) function record for 
-- the specified function. It is for internal profiler use.
--
function _profiler._get_func_rec(self,func,force,info)
  -- Find the function ref for 'func' (if force and not present, create one)
  local ret = self.rawstats[func]
  if ret == nil and force ~= 1 then
    return nil
  end
  if ret == nil then
    -- Build a new function statistics table
    ret = {}
    ret.func = func
    ret.count = 0
    ret.time = 0
    ret.anon_child_time = 0
    ret.name_child_time = 0
    ret.children = {}
    ret.children_time = {}
    ret.func_info = info
    self.rawstats[func] = ret
  end
  return ret
end


--
-- This writes a profile report to the output file object.  If
-- sort_by_total_time is nil or false the output is sorted by
-- the function time minus the time in it's children.
--
function _profiler.report( self, outfile, sort_by_total_time )

  outfile:write
    [[Lua Profile output created by profiler.lua. Copyright Pepperfish 2002+

]]

  -- This is pretty awful.
  local terms = {}
  if self.variant == "time" then
    terms.capitalized = "Sample"
    terms.single = "sample"
    terms.pastverb = "sampled"
  elseif self.variant == "call" then
    terms.capitalized = "Call"
    terms.single = "call"
    terms.pastverb = "called"
  else
    assert(false)
  end
  
  local total_time = 0
  local ordering = {}
  for func,record in pairs(self.rawstats) do
    table.insert(ordering, func)
  end

  if sort_by_total_time then
    table.sort( ordering, 
      function(a,b) return self.rawstats[a].time > self.rawstats[b].time end
    )
  else
    table.sort( ordering, 
      function(a,b)
        local arec = self.rawstats[a] 
        local brec = self.rawstats[b]
        local atime = arec.time - (arec.anon_child_time + arec.name_child_time)
        local btime = brec.time - (brec.anon_child_time + brec.name_child_time)
        return atime > btime
      end
    )
  end

  local len = #ordering
  for i=1,len do
    local func = ordering[i]
    local record = self.rawstats[func]
    local thisfuncname = " " .. self:_pretty_name(func) .. " "
    if string.len( thisfuncname ) < 42 then
      local nameLen = math.ceil((42 - string.len(thisfuncname))/2)
      thisfuncname =
        string.rep( "-", nameLen) .. thisfuncname
      thisfuncname =
        thisfuncname .. string.rep( "-", 42 - string.len(thisfuncname) )
    end

    total_time = total_time + ( record.time - ( record.anon_child_time +
      record.name_child_time ) )
    outfile:write( string.rep( "-", 19 ) .. thisfuncname ..
      string.rep( "-", 19 ) .. "\n" )
    outfile:write( terms.capitalized.." count:         " ..
      string.format( "%4d", record.count ) .. "\n" )
    outfile:write( "Time spend total:       " ..
      string.format( "%4.3f", record.time ) .. "s\n" )
    outfile:write( "Time spent in children: " ..
      string.format("%4.3f",record.anon_child_time+record.name_child_time) ..
      "s\n" )
    local timeinself =
      record.time - (record.anon_child_time + record.name_child_time)
    outfile:write( "Time spent in self:     " ..
      string.format("%4.3f", timeinself) .. "s\n" )
    outfile:write( "Time spent per " .. terms.single .. ":  " ..
      string.format("%4.5f", record.time/record.count) ..
      "s/" .. terms.single .. "\n" )
    outfile:write( "Time spent in self per "..terms.single..": " ..
      string.format( "%4.5f", timeinself/record.count ) .. "s/" ..
      terms.single.."\n" )

    -- Report on each child in the form
    -- Child  <funcname> called n times and took a.bs
    local added_blank = 0
    for k,v in pairs(record.children) do
      if self.prevented_functions[k] == nil or
         self.prevented_functions[k] == 0
      then
        if added_blank == 0 then
          outfile:write( "\n" ) -- extra separation line
          added_blank = 1
        end
        outfile:write( "Child " .. self:_pretty_name(k) ..
          string.rep( " ", 41-string.len(self:_pretty_name(k)) ) .. " " ..
          terms.pastverb.." " .. string.format("%6d", v) )
        outfile:write( " times. Took " ..
          string.format("%4.2f", record.children_time[k] ) .. "s\n" )
      end
    end

    outfile:write( "\n" ) -- extra separation line
    outfile:flush()
  end
  outfile:write( "\n\n" )
  outfile:write( "Total time spent in profiled functions: " ..
                 string.format("%5.3g",total_time) .. "s\n" )
  outfile:write( [[

END
]] )
  outfile:flush()
end


--
-- This writes the profile to the output file object as 
-- loadable Lua source.
--
function _profiler.lua_report(self,outfile)
  -- Purpose: Write out the entire raw state in a cross-referenceable form.
  local ordering = {}
  local functonum = {}
  for func,record in pairs(self.rawstats) do
    table.insert(ordering, func)
    local len = #ordering
    functonum[func] = len
  end

  outfile:write(
    "-- Profile generated by profiler.lua Copyright Pepperfish 2002+\n\n" )
  outfile:write( "-- Function names\nfuncnames = {}\n" )
  local len = #ordering
  for i=1,len do
    local thisfunc = ordering[i]
    outfile:write( "funcnames[" .. i .. "] = " ..
      string.format("%q", self:_pretty_name(thisfunc)) .. "\n" )
  end
  outfile:write( "\n" )
  outfile:write( "-- Function times\nfunctimes = {}\n" )

  local len = #ordering
  for i=1,len do
    local thisfunc = ordering[i]
    local record = self.rawstats[thisfunc]
    outfile:write( "functimes[" .. i .. "] = { " )
    outfile:write( "tot=" .. record.time .. ", " )
    outfile:write( "achild=" .. record.anon_child_time .. ", " )
    outfile:write( "nchild=" .. record.name_child_time .. ", " )
    outfile:write( "count=" .. record.count .. " }\n" )
  end
  outfile:write( "\n" )
  outfile:write( "-- Child links\nchildren = {}\n" )

  local len = #ordering
  for i=1,len do
    local thisfunc = ordering[i]
    local record = self.rawstats[thisfunc]
    outfile:write( "children[" .. i .. "] = { " )
    for k,v in pairs(record.children) do
      if functonum[k] then -- non-recorded functions will be ignored now
        outfile:write( functonum[k] .. ", " )
      end
    end
    outfile:write( "}\n" )
  end
  outfile:write( "\n" )
  outfile:write( "-- Child call counts\nchildcounts = {}\n" )
 
  local len = #ordering 
  for i=1,len do
    local thisfunc = ordering[i]
    local record = self.rawstats[thisfunc]
    outfile:write( "children[" .. i .. "] = { " )
    for k,v in record.children do
      if functonum[k] then -- non-recorded functions will be ignored now
        outfile:write( v .. ", " )
      end
    end
    outfile:write( "}\n" )
  end
  outfile:write( "\n" )
  outfile:write( "-- Child call time\nchildtimes = {}\n" )
  local len = #ordering
  for i=1,len do
    local thisfunc = ordering[i]
    local record = self.rawstats[thisfunc];
    outfile:write( "children[" .. i .. "] = { " )
    for k,v in pairs(record.children) do
      if functonum[k] then -- non-recorded functions will be ignored now
        outfile:write( record.children_time[k] .. ", " )
      end
    end
    outfile:write( "}\n" )
  end
  outfile:write( "\n\n-- That is all.\n\n" )
  outfile:flush()
end

-- Internal function to calculate a pretty name for the profile output
function _profiler._pretty_name(self,func)

  -- Only the data collected during the actual
  -- run seems to be correct.... why?
  local info = self.rawstats[ func ].func_info
  -- local info = debug.getinfo( func )

  local name = ""
  if info.what == "Lua" then
    name = "L:"
  end
  if info.what == "C" then
    name = "C:"
  end
  if info.what == "main" then
    name = " :"
  end
  
  if info.name == nil then
    name = name .. "<"..tostring(func) .. ">"
  else
    name = name .. info.name
  end

  if info.source then
    name = name .. "@" .. info.source
  else
    if info.what == "C" then
      name = name .. "@?"
    else
      name = name .. "@<string>"
    end
  end
  name = name .. ":"
  if info.what == "C" then
    name = name .. "?"
  else
    name = name .. info.linedefined
  end

  return name
end


--
-- This allows you to specify functions which you do
-- not want profiled.  Setting level to 1 keeps the
-- function from being profiled.  Setting level to 2
-- keeps both the function and its children from
-- being profiled.
--
-- BUG: 2 will probably act exactly like 1 in "time" mode.
-- If anyone cares, let me (zorba) know and it can be fixed.
--
function _profiler.prevent(self, func, level)
  self.prevented_functions[func] = (level or 1)
end


_profiler.prevented_functions = {
  [_profiler.start] = 2,
  [_profiler.stop] = 2,
  [_profiler._internal_profile_by_time] = 2,
  [_profiler._internal_profile_by_call] = 2,
  [_profiler_hook_wrapper_by_time] = 2,
  [_profiler_hook_wrapper_by_call] = 2,
  [_profiler.prevent] = 2,
  [_profiler._get_func_rec] = 2,
  [_profiler.report] = 2,
  [_profiler.lua_report] = 2,
  [_profiler._pretty_name] = 2
}