These changes are specific to this context and are unlikely to be accepted into the more generalised Ruby core.
Same team as Phusion Passenger, so excellent background.
I also spoke to Matz during EuRuKo 2019. And this is the impression I got.
Also found a discussion on jemalloc https://bugs.ruby-lang.org/issues/14718
- Shyouhei Urabe did a marvelous job of resisting pressure from several well-known developers representing multiple high profile ruby companies/projects.
- Everyone eventually came to their senses in https://bugs.ruby-lang.org/issues/14718#note-89, and concluded that the best way forward is to use glibc with MALLOC_ARENA_MAX=2.
My personal feeling is that while the "Jemalloc FTW" section in http://oldblog.antirez.com/post/everything-about-redis-24.ht... might have been correct back in the jemalloc 3.x days, a lot has changed on both jemalloc and glibc since then. Furthermore, there is also musl in the equation these days.
I actually have a mention of this in my book on deploying Rails (https://deploymentfromscratch.com/). Here's a one liner with ruby-install:
$ sudo dnf install -y jemalloc-devel
$ ruby-install 3.0.0 -- --with-jemalloc
Then check you have it:
$ ruby -r rbconfig -e "puts RbConfig::CONFIG['LIBS']"
... -ljemalloc
Furthermore, it's not just "dnf install jemalloc-devel". The Jemalloc version matters a lot. For reasons that are not yet clear, significant memory savings are only achieved with Jemalloc 3, not with Jemalloc 5. And your distribution only ships 1 Jemalloc version. So likely you need to compile Jemalloc 3 yourself.
But Jemalloc 3 no longer compiles by default on some modern distributions, such as Debian 10. Fullstaq Ruby fixes this by patching Jemalloc: https://github.com/fullstaq-labs/fullstaq-ruby-server-editio...
Another caveat is that LD_PRELOADing Jemalloc is more effective than compiling with --with-jemalloc.
Furthermore, installing Ruby is one thing. Keeping it security-patched without having to constantly monitor things, is a whole other can of worms. Here's where Fullstaq Ruby's second value proposition comes in: we supply DEB/RPMs and do the tiny version patching for you, you don't have to go through the whole compilation process and gem migration process every time there's a new Ruby tiny version.
See also this FAQ entry, "Fullstaq Ruby vs LD_PRELOADing Jemalloc yourself": https://github.com/fullstaq-labs/fullstaq-ruby-server-editio...
Sam Saffron: "After spending a bit too much time thinking about this, I would like to recommend against any jemalloc related changes " https://bugs.ruby-lang.org/issues/14718#note-89
Besides being the author of Fullstaq Ruby, I am also the author of the first copy-on-write-GC-friendliness patch for Ruby. Consider the fact that it took ~5 years for the copy-on-write-friendly-GC feature to find its way back to upstream Ruby.
If you lived in 2008, would you be willing to wait 5 years in order to save 33% memory?
Your original statement basically equates quality with authority: you believe a project is qualitatively good if and only if it's officially blessed by an authority you trust. And that belief is fine. Most people either aren't able to, or don't care enough to, verify quality themselves, so we defer to trusted authorities. Nothing wrong with that approach in general.
The thing I'm trying to tell you though, is that in case of MRI, there have been multiple past cases when the lack of official authority blessing did not in fact mean a lack of quality. This isn't hypothetical: there's a proven track record. My own track record is proven as well.
What is in it for you? Well, reduced memory usage, improved performance, faster and lower-hassle installation and security patching!
There is always a risk, yes. But all I'm trying to say is that the equation "lack of authority blessing == lack of quality" is proven not to be true for a Ruby project such as this. Whether you want to take the risk of trying it out, that's entirely up to you.
There has been 8 - 10 glibc release since then I am not sure if things have improved or not.
> Wow, a lot of comments. What Fullstaq Ruby is doing is difficult to add into mainline, so my overall impression is I'm thankful someone's going to the trouble of doing it themselves.
> It's not quite right to say that on Linux with jemalloc it uses less memory. In reality, it would be more correct to say that using a super-old version of jemalloc that for some reason used less memory leads to reduced memory usage (for unknown reasons). So it can't go into mainline.
> That said, I can understand that some people are just happy to see reduced memory usage, so if those people want to keep using the super-old version of jemalloc with reduced memory usage, I have no objection. Go for it, is my feeling.
Why MRI ruby likes to keep unused memory pages around is only, that they don't like to add that compile-time option and probe for jemalloc. It's too trivial to worry