We need to revisit the tiered compilation thread ergonomics:
1) The default number of compiler threads is too high:
JDK-8027168 shows that the default number of compiler threads can cause a performance regression for short-running applications on some system. We should investigate the performance impact of the number of compiler threads and try to find a heuristic that does not cause a performance regression.
2) Remove the distinction between C1 and C2 compiler threads for TieredCompilation:
While discussing options to smoothen out the tiered compilation thread ergonomics, Nils raised the concern that keeping two distinct set of threads for C1 and C2 compilation jobs might be a historical accident which contributes to the need to have more compiler threads for tiered than C1 or C2 alone to achieve good startup and time-to-performance characteristics. Removing the distinction and moving to a more direct priority and/or FIFO queue should be evaluated.