Hacker Newsnew | comments | show | ask | jobs | submit login

>I know from experience that the gc 64-bit version is production ready.

Is it really production ready though, or is it the same half-arsed implementation as the 32-bit one, just taking advantage of the larger availability of virtual memory on a 64 bit system?




On 32-bit systems, the problem is that there's a very high chance of non-pointer data looking like pointers to existing data, which, in turn might have its own pointer-like data. This means that you can end up keeping an excessive amount of unreferenced data.

However, a 64-bit address space is so much larger that you can't really suffer the same issue. Unlike on 32-bit systems, neither high entropy data nor text will look like valid pointers.

Therefore, the technique can be validly described as production-ready for 64-bit systems.

-----


Hmmmmm... I'm smelling memory-based DoS if I, say, upload carefully crafted files to a webserver. What accidentally happens in 32-bit may be deliberately triggered in 64-bit.

-----


This is impossible. I don't like to make absolute statements, but I'll stand by this one.

In order to pull of an attack, you'd need to know what address range the program in question has been allocated, then figure out the smaller range that the runtime is actively using, then give it data with integers in that range. This is impractical.

If you think you can pull it off play.golang.org lets you upload text to a Go program on Appengine, then it compiles that program and runs it. This gives you 2 programs to attack, the playground binary, and the one compiled from your source. If you can do it, you'll have a way to kill machines inside Google.

Good luck.

-----


Is it that you can't suffer the same issue, or that you can't 'really' suffer the same issue?

Even if there's a smaller chance of it happening, any language that has ANY chance of killing your system when running as expected is a language I'll never bother to learn.

Is there any sort of analysis tool they might be able to put into the compiler to tell you if a data structure you created has a high chance of looking like a pointer?

-----


Can someone help me out here with a TL;DR? This is my first exposure ever to any technical aspect of Go, and this discussion makes it sound from this discussion like it doesn't use any tag bits in its pointers, but has its garbage collector run heuristics on the data it examines to see whether it "looks like text" to decide whether to collect it? I know that can't possibly be correct.

-----


It's much simpler than that, it's called a conservative collector, It looks at every bit of data, at just pretends it is a pointer, if anything points to a valid allocated address, that address is retained. Otherwise, just like every collection when there are no references, the object is collected.

-----


Good explanation on wikipedia:

http://en.wikipedia.org/wiki/Garbage_collection_(computer_sc...

-----


If Google is, and has been for quite some time, using it for large-scale systems in production, I would call it production ready.

-----


Is there any reason to believe that Google uses Go for large-scale production systems?

-----


Yes, it's used by YouTube, in a very critical path, large scale enough :)?

https://groups.google.com/forum/#!msg/golang-nuts/U5ilNZpXzN...

http://code.google.com/p/vitess/

-----




Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | DMCA | Apply to YC | Contact

Search: