[Info-vax] Rust as a HS language, was: Re: Quiet?

[Arne Vajhøj]

On 4/6/2022 9:56 AM, Dan Cross wrote:
> In article <624d911f$0$702$14726298 at news.sunsite.dk>,
> Arne Vajhøj  <arne at vajhoej.dk> wrote:
>> On 4/5/2022 9:30 PM, Dan Cross wrote:
>>> Eh?  It's commonly accepted that you're going to give up some
>>> percentage of your capacity for GC overhead.
>>
>> No it is not.
> 
> Sorry, but yes it is.
> 
>> With generational garbage collectors it is very fast to GC
>> short lived objects.
> 
> That does not mean that you aren't going to give up some
> percentage of your capacity for GC.  GC is not infinitely fast.

No.

But it does not need to use zero CPU.

It just need to be faster than the manual free calls.

Which it is.

>>>> The problem with GC is the poor real time characteristics.
>>>> It tend to give small pauses at non-deterministic point.
>>>
>>> That's the old style GC.  Go's concurrent GC mostly avoids that
>>> unless under severe memory pressure.
>>
>> No.
> 
> Actually, yes.
> 
>> Go GC use STW. They have managed to reduce the time but it is
>> still a STW.
> 
> Note that I said that, "Go's concurrent GC _mostly_ avoids
> that unless under severe memory pressure."

A GC STW is a GC STW.

>> The only GC I am aware of that does not do STW is Azul Zing.
> 
> The LVB in Azul is basically a localized pause.  It may be true
> that Azul doesn't STW, but that doesn't mean that it's free.

Of course it is not free.

It may likely use more CPU than a STW GC.

But it avoid STW.

(and it is Azul Zing - Azul Zulu is using traditional STW GC)

> Under severe memory pressure pretty much all of the threads will
> block in the LVB and the situation will be more or less
> indistiguishable from a STW pause.

That is not what tests show.

Tests show that Azul Zing avoid the GC pauses.

Hazelcast did a test with traditional JVM and Azul JVM.

Results showed that 99% percentile was 2 ms for both,
but 99.99% percentile was 40 ms for traditional and 8 ms
for Azul Zing.

It works.

Arne