Do we need to compile lua-resty-core to *.luac in order to benefit from LuaJIt ?

ddragosd · 2014-01-19T23:34:49+00:00

Thanks!I have reported this issue to the nginx mailing list. Meanwhile could you suggest any alternate solution(if any) to handle this?Regards,MakailolOn Mon...

Do we need to compile lua-resty-core to *.luac in order to benefit from LuaJIt ?

ddragosd

Hi, I've built the latest Openresty 1.5.8.1 and I'm trying to understand how to benefit from the optimisations provided by lua-resty-core.

After building Openresty I've tried to find some *.luac, or *.a, or *.o files somewhere in /usr/local/* but I didn't find any file pointing to lua-resty-core; instead I was able to find the *.lua files in /usr/local/openresty/lualib/resty/core/* .

So my question is when is lua-resty-core compiled to LuaJIT ? At build time, or at runtime ?

Reading on the thread at [1], I see that we need to define a block:

init_by_lua '
require "resty.core"
';

And in the lua-resty-core code - [2] I'm reading that: "..."

So my question is if we need to compile this module before hand, or if it get compiled at runtime. If we have to compile it before hand, is the "statically link" described at [3] the only way to link the lua module ?

Thanks,

Dragos Dascalita Haut

[1] - https://groups.google.com/forum/#!searchin/openresty-en/lua-resty-core/openresty-en/KJq6IWzGcnY/FkdBy3SZxiEJ

[2] - https://github.com/agentzh/lua-resty-core

[3] - https://github.com/chaoslawful/lua-nginx-module#statically-linking-pure-lua-modules

agentzh

Hello!

On Sun, Jan 19, 2014 at 7:34 AM, Dragos Dascalita Haut wrote:
> So my question is when is lua-resty-core compiled to LuaJIT ? At build time,
> or at runtime ?
>

Basically you load lua-resty-core via require() in the phase of
init_by_lua or init_by_lua_file. And Lua code gets compiled at
runtime.

> Reading on the thread at [1], I see that we need to define a block:
>     init_by_lua '
>         require "resty.core"
>     ';

Yeah, just put the snippet above in the http {} block in your nginx.conf.

> So my question is if we need to compile this module before hand, or if it
> get compiled at runtime.

You cannot compile your Lua code to native machine code manually. The
compilation (to native code) only happens at runtime, or to be more
specific, happens when LuaJIT's interpreter finds a code path "hot"
enough. You can see the process happen by means of the jit.dump or
jit.v modules shipped (and installed by default) with LuaJIT.

> If we have to compile it before hand, is the
> "statically link" described at [3] the only way to link the lua module ?
>

No, the "statically linking" thing is just for compiling Lua source to
LuaJIT bytecode. It has nothing to do with compiling the LuaJIT
bytecode further down to native machine code.

The Lua source code will always be compiled to LuaJIT bytecode before
executing (by the interpreter). So pre-compiling Lua source code to
bytecode will only reduce the Lua code loading time and will not help
your Lua code's execution speed at all. They're cleanly separate
compilation phases.

Usually the Lua source code will experience the following two
transformation paths:

    Lua source --> LuaJIT bytecode --> [run by the LuaJIT interpreter]

    Lua source --> LuaJIT bytecode --> LuaJIT IR code --> machine code
--> [run by the CPU directly]

The LuaJIT JIT compiler is involved only in the second path. And for a
typical Lua app, these two paths are massively interleaved. Usually we
can get more and more speed if more and more hot Lua code paths can
take the second transformation path (that is, getting JIT compiled to
native machine code).

Best regards,
-agentzh

ddragosd

Hi,

Thanks for clearing this picture for me.

I will follow the lua-resty-core model to create another "core" module for what I need to expose my APIs.

Thanks again,

Dragos Dascalita Haut