RFR: 8300926: Several startup regressions ~6-70% in 21-b6 all platforms [v7]

[Robbin Ehn]

> Hi all, please consider.
> 
> The original issue was when thread 1 asked to deopt nmethod set X and thread 2 asked for the same or a subset of X.
> All method will already be marked, but the actual deoptimizing, not entrant, patching PC on stacks and patching post call nops, was not done yet. Which meant thread 2 could 'pass' thread 1.
> Most places did deopt under Compile_lock, thus this is not an issue, but WB and clearCallSiteContext do not.
> 
> Since a handshakes may take long before completion and Compile_lock is used for so much more than deopts.
> The fix in https://bugs.openjdk.org/browse/JDK-8299074 instead always emitted a handshake even when everything was already marked. (instead of adding Compile_lock to all places)
> 
> This turnout to be problematic in the startup, for example the number of deopt handshakes in jetty dry run startup went from 5 to 39 handshakes.
> 
> This fix first adds a barrier for which you do not pass until the requested deopts have happened and it coalesces the handshakes.
> Secondly it moves handshakes part out of the Compile_lock where it is possible.
> 
> Which means we fix the performance bug and we reduce the contention on Compile_lock, meaning higher throughput in compiler and things such as class-loading.
> 
> It passes t1-t7 with flying colours! t8 still not completed and I'm redoing some testing due to last minute simplifications.
> 
> Thanks, Robbin

Robbin Ehn has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains ten additional commits since the last revision:

 - Merge branch 'master' into 8300926
 - Comment fixes
 - Include/fwd fixes
 - More review fixes
 - Coleen fix
 - Review fixes 2
 - Review fixes
 - Fixed WS
 - Deopt scopes

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/12585/files
  - new: https://git.openjdk.org/jdk/pull/12585/files/e1162979..16732f1d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12585&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12585&range=05-06

  Stats: 36623 lines in 1278 files changed: 23503 ins; 7075 del; 6045 mod
  Patch: https://git.openjdk.org/jdk/pull/12585.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12585/head:pull/12585

PR: https://git.openjdk.org/jdk/pull/12585