Reducing Memory Usage in Ruby | Hacker News Reader

Reducing Memory Usage in Ruby

tenderlovemaking.com

222 pointscraigkerstiens56 comments

What I'm really keen to see is truffleruby receiving a lot of community support.

The underlying JVM and the Truffle/Graal/SubstrateVM is the product of millions of man hours of research - and for the very first time, you have a compiler framework on top of that.

The Truffle framework also brings in a lot of support that all languages get for free, like zero overhead profiling https://twitter.com/nirvdrum/status/948333404122214401

Truffleruby is already in the running in benchmarks, and it will be awesome to see how far it can be pushed . http://nirvdrum.com/2017/02/15/truffleruby-on-the-substrate-...

The major obstacle right now is C extension, which I think Sulong [1] is suppose to solve.

It seems right now, TruffleRuby 99% of Ruby code without much problem. C Extension may be the key to wide spread adoption.

[1] https://github.com/graalvm/sulong

I am so happy that Github have hired Tenderlove to go nuts with these type of projects. His talks are always extremely fun and interesting.

I run Ruby with jemalloc, and I know that samsaffron have tried to include it within the Ruby releases (like Redis does), but progress seems to have been stalled https://bugs.ruby-lang.org/issues/9113

I thought he was nuts already. (Smiley thing here.)

This is orthogonal to tenderlove's GC work, but if you're using MRI and want an easy memory usage/performance win, swap out the standard glibc malloc for jemalloc: https://www.levups.com/en/blog/2017/optimize_ruby_memory_usa...

Kind of a tangent, but does anyone know why glibc’s allocator loses to jemalloc on common workloads? I would expect that would be something worth rectifying unless other requirements tie their hands.

Quite a few complaints about jemalloc from Rust, where people wonder about higher than necessary memory usage

jemalloc likely wins more for the kinds of allocations you find in scripting language runtimes, which also happens to be similar to a browser given DOM & JS

> Kind of a tangent, but does anyone know why glibc’s allocator loses to jemalloc on common workloads?

Jemalloc implements more complex strategies (per-thread caches learned from tcmalloc, preallocated arenas, …).

It tends to have a somewhat higher memory use than simpler allocators, but have faster throughput and less fragmentation (the latter is why Firefox switched to jemalloc by default IIRC).

> I would expect that would be something worth rectifying unless other requirements tie their hands.

Why? If they consider ptmalloc good enough for their purpose, replacing it would be very low priority, and they may value e.g. code simplicity higher.

Incidentally, there was talk at one point to replace glibc's ptmalloc: https://sourceware.org/ml/libc-alpha/2014-10/msg00419.html

What I'd like to be able to do is load ActiveRecord (or any other v. heavy lib) asynchronously in non web-based apps so that I can paint the UI quicker. By the time the user will do/need anything db-related a proxy object should be swapped out for an actual ActiveRecord object. Using Rails' ORM is so nice and ergonomic but it kills start-up time with all the file requires, Bootsnap helps a bit but I'd prefer not to have to use it as it is yet one other moving part to consider.

I don’t quite understand why this is a problem. You pay the ActiveRecord boot time once, at app start, and then it’s no longer an issue.

I am actually facing a similar problem. I also find that Rails just creates a db connection everytime I do Model.new even though I have not yet saved it.

This is because active record models learn their attributes by querying the database scheme. I haven’t tried it but there appears to be a way to cache this information in the local file system which would likely avoid the early dB connect if you really needed to do that. Also avoids querying the scheme on processs boot entirely if you are willing to trust the cached scheme matches the. database scheme. See https://github.com/rails/rails/issues/24133 for discussion

Ruby seems to have a footprint on Hacker News disproportionate to its general popularity and TIOBE index. Why?

> Ruby seems to have a footprint on Hacker News disproportionate to its general popularity and TIOBE index.

TIOBE index is a junk metric (I'm surprised so many technical people seem to buy into it; it's the worst kind of easy to get a precise number, hard to demonstrate that that number has any more than a very distant relationship to anything meaningful, kind of metric that, IME, tech people mock bad managers for buying into.)

That said, Ruby’s got (via Rails and other web frameworks, and via various testing and admin tools) a very strong footprint in use even if it's no longer the hype-of-the-month.

Rails, and possibly 37signals, was very influential to many folks about a decade ago, especially in the startup community, where Rails was seen as especially useful for prototyping or rapid, test-driven web app development. https://www.quora.com/Why-do-so-many-startups-use-Ruby-on-Ra...

It’s popularity at this may have diminished with the rise of JavaScript, Go and alternatives but many folks still like and use Ruby, or at least would like to see it continue to improve and thrive.

Ruby has one of the better communities among programming languages - disproportionate to its popularity. I wish more languages had that quality of discourse.

Ruby and Rails have been around for about 10 years at this point. It is stable and for most websites it just works (up to a certain size). It is not as exciting as JS is now but people are using it to get things done since it is relatively mature and used a lot in startups. Likely why you see it referenced a lot here.

From a different perspective, having worked on numerous Ruby projects for years across the private (startups to Fortune 500), nonprofit, and government sectors, spanning many locations with worldwide team members, I don’t see where Ruby/Rails isn't at this point—it’s seemingly all-pervasive.

Similar to general hiring/salary surveys, I’m not sure that the referenced index is accurate.

Not only due to the popularity of Rails, Ruby has become popular for sysadmins as config management solutions such as puppet and chef are built on top of it. The resulting syntax is very ruby like, and in some cases you are even required to write a few ruby blocks here and there.

It also has an amazing testing framework in the form of rspec, which can be used for much more than just testing Ruby code.

Yeah, and i use Selenium with Ruby as well.

Do you Watir Webdriver, much nicer Ruby wrapper, or straight up Selenium?

Straight up Selenium.

HN is not at all representative of the wider programming community. HN attracts a lot of people working for trendy startup companies and is very silicon valley centric, but that is a tiny portion of the programmers world wide who are much more likely to be working on a java project for a generic business than using the latest fad.

TIOBE has it's issues but as a rough guide to what the industry is actually using I think it's in the ballpark.

Because Ruby has a footprint in the startup community that is disproportionate to its general popularity and TIOBE index.

Is there any effort to make WASM run under Ruby? Seems like easy work to get high performance without bespoke work on Ruby's VM.

Or just use Crystal https://crystal-lang.org XD

Crystal is not a replacement for Ruby. In the same way that many Algol-like languages are not a straight swap for each other. Don't get me wrong, Crystal is a nice idea but say goodbye to all that yummy Ruby meta-programming which is one of the key things what makes the language so appealing in the first place.

Exactly. As a Ruby developer, Crystal makes me itch. It jettisons exactly what Ruby is valuable to me for: quickly and dynamically building fluent-feeling libraries and tools. It's fast, but I don't need fast--if I don't need Ruby's metaprogramming, I have other, better, established languages to use for those tasks. (Kotlin, C#, Rust, whatever.)

Elixir is kind-of in the same boat for me. I think it's neat and has its place, and BEAM is really cool, but it doesn't scratch the Ruby itch for me. I just don't care about it looking vaguely like Ruby if it's not actually gonna be Ruby.

Have you used a recent (2017) version of Crystal? Quickly building fluent-feeling libraries and tools is exactly my use case for Crystal.

For me, everything that Ruby is valuable for is retained. I'm able to do all the things I did in Ruby just fine, and it prevents me from doing a lot of things I shouldn't have been doing.

We recently migrated our app from Rails to Crystal (using the Amber framework) and our code base is now 2/3rds the size and we eliminated hundreds of bugs in the process simply from static typing and explicit nil handling. Our response times are also now all under 30ms where we were at 100ms+ before.

Until I can perform runtime define_method calls and dynamically construct classes, it doesn't matter what Crystal does. It's fundamentally antithetical to my needs. (JavaScript isn't, but JavaScript is kind of clunky.)

I have Kotlin, C#, C++, and Rust if I need static typing. Ruby is for when I don't.

People think "oh, it's compiled, so I can't have dynamic methods" but that couldn't be more far from the truth. You can do all of that at compile time, and Crystal provides an excellent way of doing so. E.g.: https://github.com/sam0x17/crystal-mongo-orm/blob/master/src...

How late at runtime do these dynamic definitions need to be possible? Just at startup or also after the program has been running for a while?

I occasionally wonder whether it might be possible to accommodate more dynamic language features with a compiler that treats them like a macro system that is expanded statically, such that no actual dynamicism is necessary at runtime.

This is exactly what crystal does

Reading well written source code creates a more efficient workflow than reading api docs. For me, the fact that Crystal is written in Crystal gives it a far greater advantage.

Plus it is faster than Go/Java/Elixir. As others have pointed out, Crystal does have meta programming capabilities.

You can do all of that with really easy to write crystal macros.

You can dynamically build at runtime an HTTP client from an OpenAPI spec (unavailable until runtime, to be clear), method-by-method, using macros? Tell me more.

Yeah use Ruby. I prefer to have well defined interfaces for the objects I use. I love Ruby to death, but it's frustrating to encounter code like this:

  [:thing, :other_thing].each do |msg|
    define_method(msg) do
      @json[msg].to_s
    end
  end

When this is far more clear and, for me, aesthetically pleasing:

  def thing
    @json[:thing].to_s
  end

  def other_thing
    @json[:other_thing].to_s
  end

I'm not sure how you'd use a ruby object that maps to an OpenAPI spec if you don't know what's in the API response until runtime... surely you or the user of your library has an idea what's in the API they are consuming?

You may have an idea, sure, but the alternative is to codegen a new instance of the client library any time anything changes rather than keeping up to date with the API as it evolves and exists. (The moral equivalent is pulling a WSDL during app startup and making sure that you're presenting a correct interface to it.)

I full-stop don't do codegen in any project under any circumstance that is not done strictly within the workflow of a build tool (i.e., a Maven generated-sources gizmo). OpenAPI's options are pretty much all exactly not that: all the codegen options's happy paths seem to be vendoring generated code. And that makes me itch, too.

The example in question is perfectly possible to do in Crystal during compile-time, using macros. What isn't possible is to create a new class on the fly as a sort of magic lookup table that magic methods is called upon. Good riddance, for that functionality.

For the sake of this example, consider [:thing, :other_thing] to be dynamically created at runtime.

Although it probably does not fit your use case something like Common Lisp would shine in a situation like this.

You can build your code at runtime from the spec and then compile it at runtime to get pretty good performance.

Sure. Or I get effectively the same thing with JavaScript. (I just don't much like Node--it's not bad but it's not great--and the dev experience for specifying something like a DSL is a bummer.)

Got me there. First time I've ever in my life heard of a legitimate example where you really do need dynamic methods.

If you're doing stuff with OpenAPI (as I've been doing over the last few weeks), it becomes a pressing thing. =( Generated clients usually are pretty awful, you usually have to generate your own (because they don't publish gems when their APIs change, which is why I've written online-generated ones!), and once you've completed the bootstrap process for an HTTP client, it's as fast as any other Ruby thing. Which is not the fastest out there by a long shot--though JRuby helps--but is Fast Enough for most stuff.

I'm also not sure Crystal can implement an active record pattern off of a database? (Though I am not personally the type to go with that, I prefer row mappers.)

See GraniteORM or my crystal-mongo-orm. You just have to specify your fields at compile time and you are good-to-go. It works just like active record.

https://github.com/amberframework/granite-orm https://github.com/sam0x17/crystal-mongo-orm

"You have to specify your fields at compile time" is exactly not like ActiveRecord, though. That's exactly the downside to it for doing ActiveRecord.

At that point, you may (should) just use an object mapper like ROM that has no model-class hooks at all. (Which I actually like. But the Rails world disagrees.)

You effectively do specify your fields before runtime in Rails, though, in the form of your migrations. Furthermore all of the associations (belongs_to, etc), are arguably also specified before runtime since those helpers run when the class is parsed.

I frequently don't use Ruby-based migrations. I use datastores defined elsewhere and use Sequel as a convenient and easy interface for tasks against those datastores.

You're trying to slice too fine. Crystal can't do this. That's OK. Own it, don't try to hide it.

If the problem is stated as you want a dynamic class to create instances where you call dynamic methods, then yes you need Ruby.

However, that is basically a lookup table using string based dispatch to decide what to execute, and such a lookup table can be done in anything.

Crystal "does" have dynamic methods if you are willing to override method_missing.

No, the dispatch is still decided during compilation.

Wow. I've been checking in on the Crystal ecosystem every few weeks, but I somehow missed Amber. It feels like someone has finally cracked the code that made Rails great.

Elixir is, in my view, an even-more-awesome Erlang with an unfortunate and distracting cosmetic resemblance to Ruby.

Ruby is awesome, as is Elixir, but very different awesome.

Agreed, to be clear. I think Elixir is cool. It just keeps getting framed as a "better Ruby"--though Phoenix might be (probably is) a better Rails.

Take a look at macros in crystal and I promise you 99% of the time you will be able to do what you did in Ruby. Practically everything people do that is "necessarily dynamic" could be done with macros at compile-time. You CAN do things like define the behavior for when a method name is unmatched on an Object or (at compile time) do some string processing and define a bunch of methods based on the results.

Meta-programming in Crystal exists through Macros.

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