[PAPPPmAc]

I was mixing up where the big multiprocessor changes that went into the 2.5 series in that 2000-2005 era came from.

I was thinking of the the basic kernel preemption stuff and sched_setaffinity syscall + userspace plumbing like taskset that is _extremely_ consequential on little multicore/SMT machines, but the prominent name on a lot of that was Robert Love and he was at MontaVista at the time.

The Dynix parts that arrived via IBM were, as you say, mostly NUMA and RCU stuff based on Paul McKenney's work, which also went in in the same major overhaul during the 2.5 series but weren't quite so immediately consequential to smaller systems.

I hadn't heard that anecdote, but that is a neat tale of IBM using their gravitas at the time to legitimize Linux.

[jabl]

SGI also did a lot of scalability work in that time frame, as part of their migration from MIPS+Irix to Itanium+Linux. In the end they got Linux working on IIRC up to 4096 processors.