[Bug]: jemalloc does not support setting malloc_conf

[stevebarrau]

What happened?

First off, thanks @sallustfire for the jemalloc module!

I am trying to migrate our http_archive+rules_foreign_cc from the WORKSPACE world to using this module and I feel we are so close. This is our configure options and what I understand the replacements are:

Configure Options	Replacement
--disable-cxx	@jemalloc//settings/flags:enable_cxx=false
--enable-doc=no	?
--enable-shared=no	not required
--with-jemalloc-prefix=_rjem_	@jemalloc//settings/flags:jemalloc_prefix=_rjem_
--with-malloc-conf=metadata_thp:auto,narenas:128,prof:true	?
--with-private-namespace=_rjem_	?

IIUC we need code changes to support passing down a malloc-conf; correct?

Version

Output of bazel --version: bazel 7.6.1

Version of relevant rules from the WORKSPACE or MODULE.bazel file: jemalloc@5.3.0-bcr.alpha.2

Language(s) and/or frameworks involved: C++ for jemalloc, and rust wrapping it in tikv-jemalloc-sys.

[sallustfire]

@stevebarrau Thanks. Glad to hear that others are finding this work potentially useful!

We will need code changes to support the combination of flags you're using. Fortunately, they are pretty easy to make. It should be a matter of adding:

--@jemalloc//settings/flags:private_namespace=_rjem_
--@jemalloc//settings/flags:malloc_conf=metadata_thp:auto,narenas:128,prof:true

However, to enable prof via malloc_conf I believe the library has to be compiled with profiling support. Not something I've personally used, but as of alpha.3 that can be done with the various --@jemalloc//settings/flags:enable_prof flags.

We don't build the docs, and if they ever were built they'd be a separate target.

You're welcome to take a stab at this with a PR against https://github.com/sallustfire/jemalloc where the overlay is currently maintained. Otherwise, I can try to get to it within the next day or two.

[sallustfire]

I had 15 min to kill and added the flags to the repo where the overlay comes from: jemalloc/jemalloc@76176f6

Next week I'll look at publishing to BCR. You can try it out sooner if you like and let me know.