Re: [Tarantool-patches] [PATCH luajit] build: provide LUAJIT_USE_PERFTOOLS option

[Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

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Hi, Sergey,

thanks for the patch!

On 6/3/25 20:35, Sergey Kaplun wrote:
> This patch provides the LUAJIT_USE_PERFTOOLS flag via the CMake build
> system. It allows you to avoid the definition of the cognominal macro

it's better to write impersonally: It allows avoiding the definition of ...

Feel free to ignore.


> definition via CMAKE_C_FLAGS to use integration with the Linux perf
> tools interface [1] to resolve symbols for traces generated by a JIT.
>
> It may be used like the following:
>
> | perf record script -f luajit test.lua

seems command is incorrect, because it does not work for me:

<snipped>

script: unexpected number of arguments
Try 'script --help' for more information.
<snipped>

I've used instead:

$ sudo perf record -F 2000 ./build/src/luajit fib.lua
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.024 MB perf.data (8 samples) ]

> | perf report -s symbol
>
and "perf report /tmp/perf-1699839.map" to check that luajit report 
symbols in map file.
> [1]:https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jit-interface.txt
>
> Resolves tarantool/tarantool#11300
> ---
>
> Branch:https://github.com/tarantool/luajit/tree/skaplun/gh-11300-use-perftools-flag
> Issue:https://github.com/tarantool/tarantool/issues/11300
>
>   CMakeLists.txt | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/CMakeLists.txt b/CMakeLists.txt
> index 854b3613..c0da4362 100644
> --- a/CMakeLists.txt
> +++ b/CMakeLists.txt
> @@ -259,6 +259,14 @@ if(LUAJIT_USE_VALGRIND)
>     AppendFlags(TARGET_C_FLAGS -DLUAJIT_USE_VALGRIND)
>   endif()
>   
> +# This creates a symbol table of the JIT-compiled code in
> +# a </tmp/perf-%d.map> (%d = pid of process) file. It should be
> +# used with Linux perf tools. See <src/lj_trace.c> for details.
> +option(LUAJIT_USE_PERFTOOLS "Linux perf JIT support" OFF)
> +if(LUAJIT_USE_PERFTOOLS)
> +  AppendFlags(TARGET_C_FLAGS -DLUAJIT_USE_PERFTOOLS)
> +endif()

Adding a CMake flag means that we support it in our fork (users will 
rely on this functionality).

Do want a regression test for this option?

> +
>   # This is the client for the GDB JIT API. GDB 7.0 or higher is
>   # required to make use of it. See lj_gdbjit.c for details.
>   # Enabling this causes a non-negligible overhead, even when not

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