Code cache sweeper must yield to safepoint. With high numbers of methods sweeping can block the safepoint from happening. Synchronization times on the order of 200ms are observed on T4 with AccountSOA benchmark.
JDK-2221479Code cache sweeper must cooperate with safepoints
JDK-2221517Code cache sweeper must cooperate with safepoints
JDK-7143341+TieredCompilation regression on 7u4-b10 on Solaris