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Building a Minimalistic Virtual Machine

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Re: Building a Minimalistic Virtual Machine

#41

Post by kaba0 »

maxime_cb wrote: post #40
kaba0 wrote: post #29

Earlier quoted context omitted.

> Implementing a good GC is incredibly hard If you are interpreting instructions a simple one will be more than enough. Classes are its primitives, you just create a basic runtime representation for them with name, superclass, implemented interfaces and the methods’ bytecodes. Then an object can be as simple as a header containing a pointer to the class’s representation and then a listing of its fields, which can all…

> With all due respect, you ain’t going to beat the JVM with your UVM’s JIT compiler, not even close. I think I may be able to get very close to native performance. I don't want to sound like an asshole by appealing to authority, but you aren't talking to a teenager writing an interpreter from their parent's basement. I have 21 years of programming experience, a PhD in compiler design and multiple published papers. I…

I eagerly await your results, and didn’t want to sound condescending at all, sorry if it came across like that. I was just genuinely interested in a - to me - more understandable difference.

Also, what does “native performance” even mean here? Only removing the interpreter overhead?

Re: Building a Minimalistic Virtual Machine

#43

Post by maxime_cb »

efficax wrote: post #42

the jvm already exists and you can run ancient compiled class files with it.

The level of cynicism on HN is sometimes really depressing.

> the jvm already exists and you can run [some] ancient compiled class files with it [but many won't work correctly].

FTFY.

Re: Building a Minimalistic Virtual Machine

#45

Post by maxime_cb »

narag wrote: post #39
maxime_cb wrote: post #38

Earlier quoted context omitted.

I could actually use some feedback when it comes to the design of the parallelism model for UVM. I have a few ideas but it's not my area of expertise, so I would welcome feedback and suggestions.

I have experience as a user, implementation is way over my head. Depending on the minimum host supported, you could only use lightweight threads or write a scheduler. IIRC, JVM started using its own thread implementation and later used the one provided by the host OS, when available. Best of luck!

At the moment I have an event-driven system where you can set up callbacks and timers. It's not green threads but it makes it easy to have multiple different update events running at different rates, for example: https://github.com/maximecb/uvm/blob/main/ncc/examples/attac...

Re: Building a Minimalistic Virtual Machine

#46

Post by maxime_cb »

kaba0 wrote: post #41
maxime_cb wrote: post #40

Earlier quoted context omitted.

> With all due respect, you ain’t going to beat the JVM with your UVM’s JIT compiler, not even close. I think I may be able to get very close to native performance. I don't want to sound like an asshole by appealing to authority, but you aren't talking to a teenager writing an interpreter from their parent's basement. I have 21 years of programming experience, a PhD in compiler design and multiple published papers. I…

I eagerly await your results, and didn’t want to sound condescending at all, sorry if it came across like that. I was just genuinely interested in a - to me - more understandable difference. Also, what does “native performance” even mean here? Only removing the interpreter overhead?

Thanks for clarifying. Tone is sometimes ambiguous via text.

At the moment I'm in no rush to actually write the JIT compiler because I think it's faster to iterate with an interpreter. I want to flesh out the VM and its APIs, test the hell out of everything and develop the system a bit more first.

The interpreter runs at something ~400 million instructions per second on my laptop, which is probably close to the performance of an old school Pentium 2 chip, so it's actually fast enough to run a lot of non-trivial software. With even a really basic JIT I should be able to hit 10x that throughput. I've benchmarked code out of GCC and it runs about 27 times faster (on a microbenchmark).

Re: Building a Minimalistic Virtual Machine

#47

Post by tambourine_man »

maxime_cb wrote: post #37
tambourine_man wrote: post #30

Earlier quoted context omitted.

That’s one of the many advantages of building for the web. It won’t ever be unsupported (for some reasonable definition of never). You get text rendering, canvas, audio, webgl… it’s a pretty wide platform.

Except that's just not true. It's already broken/incompatible in many places across browsers. You may not notice if you're just doing basic HTML/CSS, but if you do anything slightly more dynamic, you're going to notice. An ever-expanding set of complex APIs also makes it more and more likely that bugs will go unseen and unfixed. See two examples I detailed in the blog post.

Sorry, I was reading the comments before reading your article.

Getting around pointer events inconsistencies is a lot easier than building your own cross-platform VM, of course. But the project looks awesome and seems like a great initiative.

I imagine there will also be differences in the way macOS, Linux and Windows handle graphics, IO, audio, etc, that will eventually leak to UVM, it's just the nature of the challenge.

Re: Building a Minimalistic Virtual Machine

#48

Post by chc4 »

maxime_cb wrote: post #38
narag wrote: post #35

Very interesting for embedded or kiosk. Or in general, if the VM is run as a server inside a host: encryption in a box, instead of a library. Curious about what kind of multitask will be added.

I could actually use some feedback when it comes to the design of the parallelism model for UVM. I have a few ideas but it's not my area of expertise, so I would welcome feedback and suggestions.

For parallelism I'd expect something like Cilk (or Rayon, which was inspired by it), where there's some syscalls for spawning and then joining on tasks, but the VM handles starting and managing the thread pool.

For concurrency it's a lot harder to make a good interface

Re: Building a Minimalistic Virtual Machine

#49

Post by maxime_cb »

tambourine_man wrote: post #47
maxime_cb wrote: post #37

Earlier quoted context omitted.

Except that's just not true. It's already broken/incompatible in many places across browsers. You may not notice if you're just doing basic HTML/CSS, but if you do anything slightly more dynamic, you're going to notice. An ever-expanding set of complex APIs also makes it more and more likely that bugs will go unseen and unfixed. See two examples I detailed in the blog post.

Sorry, I was reading the comments before reading your article. Getting around pointer events inconsistencies is a lot easier than building your own cross-platform VM, of course. But the project looks awesome and seems like a great initiative. I imagine there will also be differences in the way macOS, Linux and Windows handle graphics, IO, audio, etc, that will eventually leak to UVM, it's just the nature of the chall…

> Getting around pointer events inconsistencies is a lot easier than building your own cross-platform VM

For sure, and I did. I wrote some code that makes an invisible fullscreen div appear just at the right time to prevent pointer events being triggered when they shouldn't be #cleancode. It's just frustrating that things like that need to be done, and how often they might need to be done.

> I imagine there will also be differences in the way macOS, Linux and Windows handle graphics, IO, audio, etc, that will eventually leak to UVM, it's just the nature of the challenge.

At the moment you can create a window with one function call, and you have another function call to copy one frame's worth of pixels into the window. The pixel format is in BGRA byte order, 32-bits per pixel, and that's the only option. I'm going with really basic, low-level APIs like that because they're harder to get wrong.

Audio is going to be equally simple. There could be cross-platform differences in things like the amount of latency to write audio, but I'll do my best to make the APIs extremely portable and hard to get wrong.

Re: Building a Minimalistic Virtual Machine

#50

Post by maxime_cb »

chc4 wrote: post #48
maxime_cb wrote: post #38

Earlier quoted context omitted.

I could actually use some feedback when it comes to the design of the parallelism model for UVM. I have a few ideas but it's not my area of expertise, so I would welcome feedback and suggestions.

For parallelism I'd expect something like Cilk (or Rayon, which was inspired by it), where there's some syscalls for spawning and then joining on tasks, but the VM handles starting and managing the thread pool. For concurrency it's a lot harder to make a good interface

> For concurrency it's a lot harder to make a good interface

Can you elaborate?

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