It was observed, that the Valhalla specific compiler tests are slow and increase overall execution time of the lower tiers significantly. We should evaluate if we can improve the tests (see, for example JDK-8369437) or if we need to move some of them into higher tiers.

Top offenders at tier1:
- compiler/valhalla/inlinetypes/TestFieldNullMarkers.java 31m 19s
- compiler/valhalla/inlinetypes/TestArrayNullMarkers.java 20m 30s
- compiler/valhalla/inlinetypes/TestVirtualThreads.java 16m 55s
- compiler/valhalla/inlinetypes/TestNullableInlineTypes.java 15m 45s
- compiler/valhalla/inlinetypes/TestTearing.java#tiered 11m 49s

The top three tests try to trigger concurrency issues and therefore need quite a large number of iterations.