I glossed over the differences between the default Solaris 8 threads MxN behavior and the Solaris 9 1:1 behavior in my
Debugging thread related hangs in the JVM writeup. Solaris 10 brings new changes in that threading has moved away from libthread and directly into libc. Phil Harman wrote a very good peice called
Multithreading in the Solaris Operating Environment[PDF] which explains in great detail the switch from MxN to 1:1 threading. Phil also posted
a very frank comment about the libthread changes in Solaris 10. This is great stuff not only for technical purposes, but also for Unix history buffs.
"Having been an advocate of MxN for many years (largely, because that was one of our differentiators), I was treading a very fine line. I think the paper makes it clear that I don't think 1:1 is superior as a _model_, but that our MxN _implementation_ was past its sell-by date. The switch was entirely pragmatic. I personally had to drag quite a few folk kicking and screaming to the right decision. We have never looked back.
Since then we've added other cool stuff like: compiler support for TLS, posix_spawn() and POSIX spin locks. But our crowning achievement is to get rid of libthread altogether by folding it into libc. None of this would have been possible in the same short time if we had persevered along the MxN route.
You can play with all* of this cool new stuff today via the Solaris Express program (which provides early access to Solaris 10 as we develop it). See www.sun.com for more details. Sorry, I didn't mean this to turn into a marketing opportunity :)
* currently, only the Forte SPARC compiler supports TLS, but we hope to fix that soon! Actually, with the right patches, TLS is available right back to /usr/lib/lwp in Solaris 8." [
Phil Harman]
