RFR: Remove safepoint-cleanup piggybacking code

[Aleksey Shipilev]

On 09/17/2018 11:04 AM, Roman Kennke wrote:
> The code that attempts to piggy-back monitor deflation and nmethod
> marking on thread scanning requires quite a lot of changes against
> upstream. To my knowledge, it has not worked very reliably, and hasn't
> provided a very significant benefit either. It has also bitrotten a bit
> because we never enabled it by default and therefore it's never been
> part of our testing.
> 
> I have asked if upstream has interest in accepting it and the reply has
> been that monitor deflation is being worked on to be done concurrently
> (and probably there's ways to come up with a deflation scheme such that
> it doesn't become a problem to begin with), and nmethod marking should
> not be done in safepoints to begin with, but instead use thread local
> handshakes.
> 
> I propose to remove/revert this stuff:
> 
> http://cr.openjdk.java.net/~rkennke/remove-sp-cleanup/webrev.00/

Yes, let's remove it.

The patch looks good.

-Aleksey