VFSForGit VS Graal

It's not only Windows that uses Git at Microsoft, but Sharepoint and Office (which includes the on-prem version of SharePoint). In terms of repo size Windows and Office are similar. I was part of the team that migrated Sharepoint from a Perforce clone to Git and helped build the tooling to allow Office to move as well. VFS for Git [1] and Scalar [2] are really good pieces of software.

[1] - https://github.com/microsoft/VFSForGit

[2] - https://github.com/microsoft/scalar

Congratulations! That means you basically figured out how the clone procedure works and found a way to do so just in a partial way (also in an unsafe way). But it is a cool idea, nonetheless.

Also check out the Scalar [1] project and its predecessor, GVFS [2], both from Microsoft to manage their monorepo via a VFS layer.

[1]: https://github.com/microsoft/scalar

[2]: https://github.com/microsoft/VFSForGit

VFS for Git is still Open Source: https://github.com/microsoft/VFSForGit

Microsoft's blog posts have indicated a move to use something as close to off-the-shelf git as possible, though. They say they've stopped using VFS much and are instead more often relying on sparse checkouts. They've upstreamed a lot of patches into git itself, and maintain their own git fork but the fork distance is generally shrinking as those patches upstream.

https://github.com/microsoft/VFSForGit

better than it used to, with the caveat that git in particular is not and has never claimed to be good at versioning blobs.

Oh dear you're not going to like this.

It’s virtualised file system: https://github.com/microsoft/VFSForGit, only downloads what you actually use. Same thing in every large company, but different implementations.

This is where something like VFSForGit[0] helps out. Instead of cloning the entire repo, it creates a virtual file system and fetches objects on demand. MSFT uses it internally for the Windows source tree (which now exceeds 300GB).

[0]: https://github.com/microsoft/VFSForGit

There's also a performance consideration. Not excluding /bin/ or /obj/ folders means dependencies are being tracked as well, and sometimes dependencies themselves are bigger than the program's source code itself. This is commonly the case with node projects, as the node_modules folder can balloon to hundreds of megabytes. They should never be tracked in git due to the nature of how git's internal database works. For e.g. if you delete a dependency because it's no longer needed, you can never fully reclaim that disk space (at least for the master branch) as git will need to keep the binary data stored in its internal tracking database because a previous commit in the master branch has captured the data. As you make more branches, git needs to store the data required to reconstruct your repo to a different state when you switch branches. When a branch has changes measured in the kilobytes, check out is very manageable, but when the differences balloon to many MBs due to the presence of heavy binary files, then checkout between different branches/commits can get very slow. Though, this happens anyway when source code data eventually reaches a certain threshold, beyond the hundreds of megabytes, it's made unnecessarily worse by including any binary files. It's one of the reasons Microsoft created VFS for git: https://github.com/microsoft/VFSForGit.

You mean like VFSforGit? Or the successor for that called Scalar? This has been a solved problem. Microsoft moved their entire Windows codebase to git. There have been a ton of huge improvements to performance as a result of that. And the above two plugins are easily better ways to deal with what you're referring to without resulting to dead tech.

Contrary to what vocal Kotlin advocates might believe, Kotlin only matters on Android, and that is thanks to Google pushing it no matter what.

https://spectrum.ieee.org/the-top-programming-languages-2023

https://snyk.io/reports/jvm-ecosystem-report-2021/

And even so, they had to conceed Android and Kotlin on their own, without the Java ecosystem aren't really much useful, thus ART is now updatable via Play Store, and currently supports OpenJDK 17 LTS on Android 12 and later devices.

As for your question regarding numbers, mostly Java 74.6%, C++ 13.7%, on the OpenJDK, other JVM implementations differ, e.g. GraalVM is mostly Java 91.8%, C 3.6%.

https://github.com/openjdk/jdk

https://github.com/oracle/graal

Two examples from many others, https://en.wikipedia.org/wiki/List_of_Java_virtual_machines

Pkl was built using the GraalVM Truffle framework. So it supports runtime compilation using Futurama Projections. We have been working with Apple on this for a while, and I am quite happy that we can finally read the sources!

https://github.com/oracle/graal/tree/master/truffle

Disclaimer: graalvm dev here.

That's pretty interesting. It's not as aggressive as Bee sounds, but the Espresso JVM is somewhat similar in concept. It's a full blown JVM written in Java with all the mod cons, which can either be compiled ahead of time down to memory-efficient native code giving something similar to a JVM written in C++, or run itself as a Java application on top of another JVM. In the latter mode it obviously doesn't achieve top-tier performance, but the advantage is you can easily hack on it using all the regular Java tools, including hotswapping using the debugger.

When run like this, the bytecode interpreter, runtime system and JIT compiler are all regular Java that can be debugged, edited, explored in the IDE, recompiled quickly and so on. Only the GC is provided by the host system. If you compile it to native code, the GC is also written in Java (with some special conventions to allow for convenient direct memory access).

What's most interesting is that Espresso isn't a direct translation of what a classical C++ VM would look like. It's built on the Truffle framework, so the code is extremely high level compared to traditional VM code. Details like how exactly transitions between the interpreter/compiled code happen, how you communicate pointer maps to the GC and so on are all abstracted away. You don't even have to invoke the JIT compiler manually, that's done for you too. The only code Espresso really needs is that which defines the semantics of the Java bytecode language and associated tools like the JDWP debugger protocol.

https://github.com/oracle/graal/tree/master/espresso

This design makes it easy to experiment with new VM features that would be too difficult or expensive to implement otherwise. For example it implements full hotswap capability that lets you arbitrarily redefine code and data on the fly. Espresso can also fully self-host recursively without limit, meaning you can achieve something like what's described in the paper by running Espresso on top of Espresso.

I'm also using GraalVM if that's of any help.

Quarkus is one of Java frameworks for microservices development and cloud-native deployment. It is developed as container-first stack and working with GraalVM and HotSpot virtual machines (VM).

Apologies, I didn't mean to imply DCEVM went poof, just that I was sad it didn't make it into OpenJDK so one need not do JDK silliness between the production one and the "debugging one" since my experience is that's an absolutely stellar way to produce Heisenbugs

And I'll be straight: Graal scares me 'cause Oracle but I just checked and it looks to the casual observer that it's straight-up GPLv2 now so maybe my fears need revisiting: https://github.com/oracle/graal/blob/vm-23.1.0/LICENSE

> to be compiled to a single executable is a strength that Java does not have

I think this is very outdated claim: https://www.graalvm.org/

https://github.com/oracle/graal/issues/7182