player/lua/defaults: add LuaJIT profiling support

[N-R-K]

gives us a way to properly profile the lua scripts to get some verifiable way to test which "optimizations" work and which don't.

currently only supports LuaJIT but the cli option is generically named in case support for profiling other scripts is added in the future.

[N-R-K]

Pretty rudimentary right now. Just dumps to a file/stdout. Maybe makes sense to display it in somewhere in the stat page? Open to suggestion on how the interface should be like.

[kasper93]

Just dumps to a file/stdout.

I think we could just print it into the log.

Maybe makes sense to display it in somewhere in the stat page?

I think it's too much info to fit info stat page. Technically with some preprocessing we could show some info. Similar to perf top, but not sure it's really that critical.

[github-actions]

Download the artifacts for this pull request:

Windows

• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-aarch64-pc-windows-msvc
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-aarch64-pc-windows-msvc-pdb
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-i686-w64-mingw32
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-x86_64-pc-windows-msvc
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-x86_64-pc-windows-msvc-pdb
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-x86_64-w64-mingw32

macOS

• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-macos-14-arm
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-macos-15-arm
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-macos-15-intel
• mpv-v0.41.0-dev-gf627256bd-pr17785-24777402281-macos-26-arm

[N-R-K]

What feedback is needed exactly? I don't see any questions. And the patch was updated to print it via mpv's logging system by default if no path was given like requested.

[kasper93]

What feedback is needed exactly? I don't see any questions. And the patch was updated to print it via mpv's logging system by default if no path was given like requested.

Keep it simple, you can grep the log if you need profile in another file, there is no need to NIH file writing.

[N-R-K]

there is no need to NIH file writing.

It's just standard lua io, what's NIH here?

you can grep the log if you need profile in another file

Very common case is to have a base profile and then make change and collect another profile. Yes, you can just grep the log and extract it manually, but if we're going to add a cli option it should at least make the common cases easy to handle. Otherwise, you can also argue "KISS, just let users do their own luajit markup themselves".

[kasper93]

Otherwise, you can also argue "KISS, just let users do their own luajit markup themselves".

I agree with you. If the main feature of this integration is saving to external text file, than indeed it's best to not include it in the mpv core.

[kasper93]

Also if you prefer more native interface, you could bring up the changes from @avih d708977

[N-R-K]

If the main feature of this integration is saving to external text file

Interesting. The ~8 loc saving the profiling report to a file is the main feature and not the other ~100 loc to collect and format the profiling information?

indeed it's best to not include it in the mpv core

Almost entirety of the added code lives in defaults.lua, not mpv core. Only thing added to mpv core was the cli flag. If that's a problem, maybe some kind of script-opt can be used instead.

[kasper93]

Interesting. The ~8 loc saving the profiling report to a file is the main feature and not the other ~100 loc to collect and format the profiling information?

Out of the 106 added lines in default.lua, 44 are only related to saving the profiling report to a file. Don't be disingenuous by saying it's ~8 loc. It's not about loc.

I noticed that almost half of the PR is about saving file, and I suggested to keep it simple and log it through our existing log code, that can also save to file.

It can be 1000 loc, if there is a value it that, you can draw graphs, flame graphs, whatever, I don't mind.

Almost entirety of the added code lives in defaults.lua, not mpv core.

default.lua is very much mpv core, it's embedded and used for every script.