Trace compilation from embedded LuaJIT

[Douglas Creager <dcreager@...>]

Hi all,

I have a quick question about how much hot JIT action you'll get when embedding LuaJIT within another application.  My understanding is that LuaJIT's heuristics look for hot traces by identifying loops within the Lua code.  But what happens if the loop is in the host C application?  So for instance, I've got a data processing app where I'm allowing the user to do some custom processing by providing a Lua function.  That's going to be a hot function, since I'm processing many many records, so I'd like to have that function trace-compiled down into machine code.  [As an aside, this is a good use case for a possible lua_pushcdata function on the C side of things, to get a nice FFI cdata object into the Lua code from the host app.  But I digress.]

Are there any constructs that would let me accomplish this?  In stock Lua I'd just call the user's customization function using lua_pcall, but then there's no Lua loop to cause LuaJIT to start recording traces.

I've also tried using a coroutine, where I pass in each record using lua_resume:

  while true do
    local more, record = coroutine.yield()
    if not more then return end
    process(record)
  end

This gives me a loop, which will be executed once per record.  But unfortunately coroutine.yield is NYI, so I don't get a nice tasty compiled trace.

Any other things I can try?  Or is this too far outside of LuaJIT's intended use cases?

Thanks in advance,
—
Douglas Creager
<dcreager@dcreager.net>