cafxx · HackerTrans

Filed a CL for this, hopefully it gets merged ~soon.

https://go-review.googlesource.com/c/go/+/729920

That's not how it's implemented (it returns false if you're inside a Do() on a unsupported platform), although I agree the wording should be clearer.

cafxx

7 ay öncediscuss

I find this example mildly infuriating/amusing:

    func Encrypt(message []byte) ([]byte, error) {
        var ciphertext []byte
        var encErr error
    
        secret.Do(func() {
            // ...
        })
        
        return ciphertext, encErr
    }

As that suggests that somehow for PFS it is critical that the ephemeral key (not the long-term one) is zeroed out, while the plaintext message - i.e. the thing that in the example we allegedly want secrecy for - is totally fine to be outside of the whole `secret` machinery, and remain in memory potentially "forever".

I get that the example is simplified (because what it should actually do is protect the long-term key, not the ephemeral one)... so, yeah, it's just a bad example.

cafxx

7 ay öncediscuss

The point is that no-one is thinking to add knobs, or allow alternative GCs.

cafxx

7 ay öncediscuss

> GOGC was introduced in Go 1.5

yes, that's quite literally what I meant by "GOGC has always been there". 1.5 was released 10 years ago, just 3 years after 1.0.

So to summarize: there is one knob (that has been there from basically the beginning), plus a second one (if you squint hard enough: GOMAXMEM), and absolutely no plans to add further ones, or to add alternative GCs.

cafxx

7 ay öncediscuss

Your previous message was referring to Go "getting" knobs, but GOGC has always been there.

The older GC algorithm won't stay, IIRC the plan is for it to be removed in 1.27 (it's kept for now just to give a fallback in case of bugs in the first release).

cafxx

7 ay öncediscuss

I still would be wary, even in that case. Go does not guarantee that the address of an allocation won't change over the lifetime of the allocation (although current implementations do not make use of this).

If you really store just references to the same arena, better to use an offset from the start of the arena. Then it does not matter whether allocations are moved around.

cafxx

7 ay öncediscuss

Not sure what you are referring to. There are no knobs involved in the things I mentioned (aside from the one to enable the experiment, but that's just temporary until the experiment completes - one way or the other).

cafxx

7 ay öncediscuss

> If you really want an arena like behavior you could allocate a byte slice and use unsafe to cast it to literally any type.

A word of caution. If you do this and then you store pointers into that slice, the GC will likely not see them (as if you were just storing them as `uintptr`s)

cafxx

7 ay öncediscuss

There's a bunch of activity ongoing to make things better for memory allocation/collection in Go. GreenTeaGC is one that has already landed, but there are others like the RuntimeFree experiment that aims at progressively reduce the amount of garbage generated by enabling safe reuse of heap allocations, as well as other plans to move more allocations to the stack.

Somehow concluding that "By killing Memory Arenas, Go effectively capped its performance ceiling" seems quite misguided.

cafxx

5 yıl öncediscuss

[nit] you should really run analyze before vacuum, not the other way around (https://github.com/segfall/static-wiki/blob/6d455de149c24e2a...)

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