Before joining PAE (Performance and Availabilty Engineering), I worked with a major european database vendor on their kernel scalability (on behalf of a mutual customer, a leading media company). We were fighting limitations in an aging implementation of Sun’s pioneering two-level thread model (something which became known as “old and broken libthread”). During one of my OS Ambassador trips, I visited Bryan Cantrill and Roger Faulker, and discovered that Bryan had sketched and Roger had prototyped a new implementation based on a one-level model. I then used the customer as the business case for introducing the one level “alternate” implementation in Solaris 8 (under /usr/lib/lwp).
By the time I joined PAE, the new implementation had gained quite a reputation for fixing scalability and stability problems with many multithreaded applications. PAE had many fans of the two-level concept, so I found myself immediately in conflict with some of my new colleagues. But I stuck to my guns and was able to win most of them over to the one-level model. I then worked with Roger, Bart Smaalders and others to have make the one-level model the only implementation in Solaris 9. Part of my contribution to this effort was to write the technical whitepaper Multithreading in the Solaris Operating Environment:
This paper has become a widely quoted document of how we do multithreading, and is still relevant today. Of course, the new thread implementation paved the way for Roger’s 1600 file putback to unify the Solaris process model, making threads first class citizens in Solaris – something Linux may actually never achieve!