Another side effect of focusing on (b) is that it frees up the resources someone else (a runtime implementer) has to focus on (a) independently. This is just another corollary of "build it, build it right, build it fast".
In particular, consider the new MIO IO manager included in Haskell GHC 7.8. It's increasing performance of IO-bound lightweight threading by orders of magnitude... all performance provided completely for free to consumers of these abstract threading services who've spent all their time making their algorithms correct, not fast.
In particular, consider the new MIO IO manager included in Haskell GHC 7.8. It's increasing performance of IO-bound lightweight threading by orders of magnitude... all performance provided completely for free to consumers of these abstract threading services who've spent all their time making their algorithms correct, not fast.