FileDescriptor.sync isn't using Blocker

[Brian S O'Neill]

I don't think changing the behavior is a priority, but I'm concerned 
about all the legacy libraries out there making use of `sync` which work 
just fine. They shouldn't have to be updated just because they appear to 
be causing issues when used with virtual threads. The temporary pinning 
due to a sync operation isn't that temporary when a lot of dirty pages 
need to be flushed out.

On 2023-07-13 02:29 AM, Alan Bateman wrote:
> 
> 
> You shouldn't need to worry about it, it will run just fine in a virtual 
> thread, it just doesn't currently compensate so doesn't smooth over the 
> temporary pinning. A static analysis of 485k libraries didn't find a lot 
> of usage, at least not compared to all the other blocking I/O, probably 
> not too surprising as the FileDescriptor can only be obtained from a 
> small number of APIs (those that date from early JDK releases). We can 
> include it in the next update but eventually it will be replaced as we 
> want operations like this to release the carrier to do other work.
> 
> -Alan