inspector: split --cpu-prof-path to --cpu-prof-dir and --cpu-prof-name

[joyeecheung]

To improve the integration of --cpu-prof with workers, this patch
splits --cpu-prof-path into --cpu-prof-dir and --cpu-prof-name,
so when a worker is launched from a thread that enables
--cpu-prof, if the parent thread sets --cpu-prof-dir, then the
profile of both thread would be generated to the specified directory.
If they end up specifying the same --cpu-prof-name the behavior
is undefined - the last profile will overwritten the first one.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[joyeecheung]

cc @nodejs/workers @nodejs/performance @nodejs/process

[mcollina]

LGTM

[mscdex]

Why --prof-dir instead of something more specific like --cpu-prof-dir ? Having non-V8 --prof-* options is confusing because we already have --prof and --prof-process for V8.

[mscdex]

I prefer keeping the specific directory prefix in the flag names for clarity. If we support more profile types in the future it just gives more flexibility.

[joyeecheung]

I prefer keeping the specific directory prefix in the flag names for clarity. If we support more profile types in the future it just gives more flexibility.

How would that gives more flexibility? If the whole path is specified in the flag, how would --cpu-prof-path work with workers? With --cpu-prof-path, you either hard-code the entire path, or nothing at all. With --prof-dir and --cpu-prof-name you can just hard-code the directory but let Node.js generate the file name for you, which I believe is the more common use case.

BTW, this is also closer to how the reports are generated. I think it's better to have a consistent style to generate these files.

[joyeecheung]

Moved the directory initialization to env.cc and renamed --prof-dir to --node-prof-dir to avoid the ambiguity. @mcollina @addaleax @mscdex PTAL, thanks!

[mscdex]

With --cpu-prof-path, you either hard-code the entire path, or nothing at all.

I was referring to having individual profile type directory prefix flags like --cpu-prof-dir vs a --prof-dir for all profile types.

[joyeecheung]

I was referring to having individual profile type directory prefix flags like --cpu-prof-dir vs a --prof-dir for all profile types.

I see, that makes sense to me, I'll switch to that instead, thanks!

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/22594/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/22617/

[joyeecheung]

If there are no more reviews, I'd like to land this later today.

[joyeecheung]

Landed in 49d3d11