On Sunday, 6 December 2020 at 07:45:17 UTC, Bruce Carneal wrote:
GCs scan memory, sure. Lots of variations. Not germane. Not a rationale.
We need to freeze the threads when collecting stacks/globals.
D is employed at multiple "levels". Whatever level you call it, Go and modern JVMs employ low latency GCs in multi-threaded environments. Some people would like to use D at that "level".
Yes, but they don't allow low level programming. Go also freeze to sync threads this has a rather profound impact on code generation. They have spent a lot of effort on sync instructions in code gen to lower the latency AFAIK.
My question remains: how difficult would it be to bring such technology to D as a GC option? Is it precluded somehow by the language? Is it doable but quite a lot of effort because ...? Is it no big deal once you have the GC itself because you only need xyz hooks? Is it ...?
Get rid of the system stack and globals. Use only closures and put in a restrictive memory model. Then maybe you can get a fully no freeze multi threaded GC. That would be a different language.
Also, I think Walter may have been concerned about read barrier overhead but, again, I'm looking for feasibility information. What would it take to get something that we could compare?
Just add ARC + single threaded GC. And even that is quite expensive.
