The per-thread performance counters for compiler threads have relatively little value in the presence of more fine-grained and precise compilation events and should be considered for removal. A quick survey indicates there is little or no usage of these counters:

sun.ci.compilerThread.#.compiles
sun.ci.compilerThread.#.method
sun.ci.compilerThread.#.time
sun.ci.compilerThread.#.type

Removing these counters would ensure that the number of perf counters which write to the PerfData memory buffer is invariant with JVM scale factors (#CPU, #threads etc)