Project Loom VirtualThreads hang

[Alan Bateman]

On 03/01/2023 14:03, Robert Engels wrote:
> :
>
> A virtual thread should be far more efficient in regards to user space 
> locking/blocking/wake-up - my tests show only a few % system cpu time. 
> To do this well though the vthread scheduler needs to be super 
> efficient and the locking constructs rewritten knowing they’re on 
> green threads - because the spin time/block decisions are much 
> different (eg upwards of 16 microseconds to perform an os switch to 
> another thread on the cpu vs a few hundred nanoseconds for a green 
> thread switch).

Yes, the cost model is different so the use of spin loops to reduce 
parking has to looked at in several places. So what are you testing, is 
a  j.u.concurrent API or something else? There is some spinning and 
yield once in APIs such as SQ and LTQ that do need to be re-examined.

-Alan