On Sunday, 4 December 2022 at 23:37:39 UTC, Ali Çehreli wrote:
On 12/4/22 15:25, Adam D Ruppe wrote:
> which would trigger the write barrier. The thread isn't
> allowed to complete this operation until the GC is done.
According to my limited understanding of write barriers, the
thread moving to 800 could continue because order of memory
operations may have been satisfied. What I don't see is, what
would the GC thread be waiting for about the write to 800?
I'm not a specialist but I have the impression that GC write
barrier and CPU memory ordering write barriers are 2 different
things that confusedly use the same term for 2 completely
different concepts.
Would the GC be leaving behind writes to every page it scans,
which have barriers around so that the other thread can't
continue? But then the GC's write would finish and the other
thread's write would finish.
Ok, here is the question: Is there a very long standing partial
write that the GC can perform like: "I write to 0x42, but I
will finish it 2 seconds later. So, all other writes should
wait?"
> The GC finishes its work and releases the barriers.
So, it really is explicit acquisition and releasing of these
barriers... I think this is provided by the CPU, not the OS.
How many explicit write barriers are there?
Ali
