Whenever I am asked whether Linux is trustworthy or not for critical applications I cite statistics from top500.org. That’s a list of the top 500 commercial supercomputers that are known. Every six months the list is updated and the Linux share of supercomputers keeps growing.
I recall that during the LUGM Linux Festival of 2013 I presented stats from top500.org and people were astounded to find only two supercomputers that actually ran Windows while the majority ran a Linux variant.
However, the latest statistics, i.e as of June 2017, show that Linux is close to reaching 100% of the Top 500 list. Currently, Linux runs on 498 supercomputers out of the top 500.