Hi,
As painfully found out by mono team, if big/little cores have different cache line sizes, __clear_cache doesn't work as expected. This affects any home-grown cache flushing mechanism as well.
http://www.mono-project.com/news/2016/09/12/arm64-icache/
protip, if you suspect your application issues might related to big.LITTLE, use taskset(1) or hwloc-bind(1) to tie the process to either big or little cluster (or just a single core).