This looks impressive for Linux, and I’m glad FLOSS has such an impact! However, I wonder if the numbers are still this good if you consider more supercomputers. Maybe not. Or maybe yes! We’d have to see the evidence.
There's no reason to believe smaller supercomputers would have significantly different OS's.
At some point you enter the realm of mainframes and servers.
Mainframes almost all run Linux now, the last Unix's are close to EOL.
Servers have about a 75% Linux market share, with the rest mostly running Windows and some BSD.
I wonder if the numbers are still this good if you consider more supercomputers.
Great question. My guess is not terribly different.
"Top 500 Supercomputers" is arguably a self-referential term. I've seen the term "super-computer" defined whether it was among the 500 fastest computer in the world, on the day it went live.
As new super-computers come online, workloads from older ones tend to migrate to the new ones.
So there usually aren't a huge number of currently operating supercomputers outside of the top 500.
Generally a super-computer is near the top of the list the day it comes online, and it falls down the list during the years it operates.
When a super-computer falls toward the bottom of the top 500, there's a good chance it is getting turned off soon.
That said, I'm referring here only to the super-computers that spend a lot of time advertising their existence.
I suspect there's a decent number out there today that prefer not to be listed. But I have no reason to think those don't also run Linux.