Often Update RS is quite high, and there is desire to push more work into the concurrent phase.

There is G1UpdateRSTimePercent (or so) that should actually help with this, but many times it is ineffective. The only thing you can do, if still possible, is increasing heap region size.

Often however, at the heap sizes Update RS becomes a problem, heap region size is already maxed out.

Investigate on how to give the user a tool to reduce update rs time.