Linked by Thom Holwerda on Tue 30th Jan 2007 21:36 UTC, submitted by David Dengg
BSD and Darwin derivatives DragonFly 1.8.0 has been released. The biggest kernel change in this release is the addition of virtual kernel support and a virtual kernel build target. The biggest user-visible changes include updates to third party applications included in the base system, a major rewrite of NULLFS which removes all directory recursion restrictions from mount_null and removes nearly all the kernel resource overhead when using such mounts, and a multi-ip feature for jails.
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In addition, it is very hard to fault the FreeBSD team for making the decision to which way to go. What Matt wanted to do is rather revolutionary and is rather risky for a product lots of companies use for production purposes. While there is the potential of a huge payoff, there is a certain amount of risk involved with it. The FreeBSD project would be rather self-centered and careless to try such a revolutionary path without some alternate "safe" path to fall back to if it fails. In a way, the way Solaris, HPUX, AIX, and Linux chose to scale was the only safe and reasonable choice for such a large project.

FreeBSD took pretty much the same approach as Linux to address SMP, at about the same time. They both introduced big kernel locks and planned on phasing in finer-grained locking in the future. Linux also experimented with M:N threading at about the same time as FreeBSD implemented it. The difference is that FreeBSD just doesn't have the same resources. Linux was able to implement fine-grained locking, per-cpu runqueues, and a vast array of threading and process scheduling experiments while FreeBSD seemed stuck in the mud.

Everybody and their dog is prototyping some new theory on Linux, and often it pays off. The kernel maintainers honestly thought IBM's NGPT model would be the next-gen thread model for 2.6, but Ingo Molnar did some quick hacks. Whoa! That simple, unsophisticated 1:1 model rocks IBM's fancy-shmancy implementation. Nicksched or staircase, anticipatory or CFQ... Linux doesn't need to pick a path to pursue, it just picks whatever proves most successful.

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