Joseph Myers announced the availability of GCC 4.2.4 saying, "GCC 4.2.4 is a bug-fix release, containing fixes for regressions in GCC 4.2.3 relative to previous GCC releases." He adds, "as always, a vast number of people contributed to this GCC release -- far too many to thank individually!"

GCC is the GNU Compiler Collection which includes C, C++, Objective-C, Fortran, Java, and Ada compilers. Download GCC 4.2.4 from your nearest gcc.gnu.org mirror.

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"Is there a write up of what you consider the 'proper' git workflow?" Theodore Ts'o asked Linux creator Linus Torvalds, "why do you consider rebasing topic branches a bad thing?" Linus replied, "rebasing branches is absolutely not a bad thing for individual developers. But it *is* a bad thing for a subsystem maintainer." He went on to differentiate between 'grunts' who write the code and 'managers' who primarily collect other people's code, "a grunt should use 'git rebase' to keep his own work in line. A technical manager, while he hopefully does some useful work on his own, should strive to make _others_ do as much work as possible, and then 'git rebase' is the wrong thing, because it will always make it harder for the people around you to track your tree and to help you update your tree." Linus compared his own patch management style and productivity from over six years ago before he started using BK and git, to his current style using git:

"You can either try to drink from the firehose and inevitably be bitched about because you're holding something up or not giving something the attention it deserves, or you can try to make sure that you can let others help you. And you'd better select the 'let other people help you', because otherwise you _will_ burn out. It's not a matter of 'if', but of 'when'. [...] And when you're in that kind of ballpark, you should at least think of yourself as being where I was six+ years ago before BK. You should really seriously try to make sure that you are *not* the single point of failure, and you should plan on doing git merges. [...] I think a lot of people are a lot happier with how I can take their work these days than they were six+ years ago."

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"This time around, we have 60+% of the changes in drivers, notably drives/video and drivers/media, with some infiniband, networking and usb lovin' to fill things out," began Linux creator Linus Torvalds, announcing the 2.6.26-rc3 kernel. "The rest is (as usual) mostly arch updates," he continued, "this time mostly mips, m68k and uml." Linus noticed that Linux kernel development has been managed with git now as long as it was managed with BitKeeper, a little over three years for both tools. He explained, "the most striking difference has nothing to do with git or BK (the switch-over timing was just the reason I decided to take a look), but with the fact that we're not just continuing to develop, but we're developing faster and with more people," adding:

"So during the three years 2002->2005, we had 63,428 commits, attributed to 1,560 different authors (caveat: misspellings etc will mean that some people get counted more than once). During the last three years, we've had 96,885 attributed to 4,068 distinct authors (with the same caveat, obviously).

"I didn't do a lot of per-commit statistics yet, but from the little I've done it also seems like we've gotten increasingly better at doing small commits (which is probably one of the reasons we have a larger number of them, but also why we have more authors - small commits is how people get into doing kernel development)."

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Leslie Hawthorn, a Program Manager in Google's Open Source team, gave a talk at BSDCAN 2008 on Google's ongoing Summer of Code project. She started by explaining what the open source team does, including enforcing license compliance, hosting over 700,000 open source projects with Google Code, academic research, funding open source development, and community outreach including the sponsorship of conferences such as BSDCan. She went on to discuss how she got started running the project after its initial launch in 2005.

Having sponsored four summer of code's now, Leslie noted that Google has had over 1,500 "graduates" and over 2,000 mentors involved, coming from over 98 countries and working with over 175 open source projects. By the end of the currently in progress 2008 Summer of Code, the project will have provided over 10 million US dollars in funding, generating over 6 million lines of code.

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Randall Stewart of Cisco Systems gave a talk titled SCTP, what it is and how to use it, discussing the Stream Control Transmission Protocol (SCTP). A paper that was displayed on the overhead projecter before the talk began summarized:

"Integrated into FreeBSD 7.0 -- first standardized by the Internet Engineering Task force (IETF) in October of 2000, in RFC 2960 and later updated by RFC 4960. SCTP is a message oriented protocol providing reliable end to end communication between two peers in an IP network."

Randall explained that SCTP is an alternative protocol to TCP, UDP. To describe SCTP, he suggested you start with TCP features, including: reliable retransmission, congestion control, flow control, connection oriented, and selective acknowledgements. You then add to it more features, including: "association" 4-way handshake, framing and ordered service, multistreaming, multihoming, and reachability.

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Pawel Dawidek first ported ZFS to FreeBSD from OpenSolaris in April of 2007. He continues to actively port new ZFS features from OpenSolaris, and focuses on improving overall ZFS stability. During the introduction to his talk at BSDCan, he explained that his goal was to offer an accessible view of ZFS internals. His discussion was broken into three sections, a review of the layers ZFS is built from and how they work together, a look at unique features found in ZFS and how they work internally, and a report on the current status of ZFS in FreeBSD.

The BSDCan website notes that Pawel is a FreeBSD committer, adding:

"In the FreeBSD project, he works mostly in the storage subsystems area (GEOM, file systems), security (disk encryption, opencrypto framework, IPsec, jails), but his code is also in many other parts of the system. Pawel currently lives in Warsaw, Poland, running his small company."

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BSDCan 2008 officially started this morning at 9AM with an opening talk by the event's organizer, Dan Langille. However, in reality the event has already been running for two days, with the FreeBSD tutorials having started on the 14'th. After arriving in Ottawa yesterday afternoon and finding my room in a 20 story University of Ottawa residence, I wandered down to the Royal Oak Pub for early registration, meeting several dozen BSD hackers from all over the world.

This morning's opening talk was well attended, filling up first with clusters of laptop users around the power outlets along both walls. By 15 minutes after the hour, the room was completely full, and Dan started with a humorous slideshow of example letters he's been receiving ever since posting the words "letter of invitation" somewhere on the BSDCan website two year back. Coming primarily from Nigeria, the letter's authors often claim to represent large groups of developers, yet always coming from "disposable" email addresses. After some laughs, he launched into his opening keynote.

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"As some of the latency junkies on lkml already know, commit 8e3e076 in v2.6.26-rc2 removed the preemptible BKL feature and made the Big Kernel Lock a spinlock and thus turned it into non-preemptible code again. This commit returned the BKL code to the 2.6.7 state of affairs in essence," began Ingo Molnar. He noted that this had a very negative effect on the real time kernel efforts, adding that Linux creator Linus Torvalds indicated the only acceptable way forward was to completely remove the BKL. Ingo explained:

"This task is not easy at all. 12 years after Linux has been converted to an SMP OS we still have 1300+ legacy BKL using sites. There are 400+ lock_kernel() critical sections and 800+ ioctls. They are spread out across rather difficult areas of often legacy code that few people understand and few people dare to touch. It takes top people like Alan Cox to map the semantics and to remove BKL code, and even for Alan (who is doing this for the TTY code) it is a long and difficult task."

Ingo went on to describe how the BKL works, how it differs from other locking mechanisms, and why this complicates removing it permanently from the kernel. He noted that the various dependencies of the lock are lost in the haze of 15 years of code changes, "all this has built up to a kind of Fear, Uncertainty and Doubt about the BKL: nobody really knows it, nobody really dares to touch it and code can break silently and subtly if BKL locking is wrong." He then suggested "changing the rules of the game", creating a "kill-the-BKL" branch which "turns the BKL into an ordinary albeit somewhat big mutex, with a quirky lock/unlock interface called 'lock_kernel()' and 'unlock_kernel()'."

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KernelTrap is excited to be able to offer live coverage of this year's BSDCan 2008 in Ottawa, Canada on May 16th and 17th. The two day conference takes place at the University of Ottawa, and was organized for the fifth consecutive year by Dan Langille who has also made it possible for me to attend and cover the event on KernelTrap. I spoke with Dan to get some background information on the conference, and learn about some of the upcoming highlights.

The event's webpage explains:

"BSDCan, a BSD conference held in Ottawa, Canada, has quickly established itself as the technical conference for people working on and with 4.4BSD based operating systems and related projects. The organizers have found a fantastic formula that appeals to a wide range of people from extreme novices to advanced developers."

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"I'm please to announce [the] POHMEL high performance network filesystem. POHMELFS stands for Parallel Optimized Host Message Exchange Layered File System," began Evgeniy Polyakov, explaining:

"This is a high performance network filesystem with local coherent cache of data and metadata. Its main goal is distributed parallel processing of data. Network filesystem is a client transport. POHMELFS protocol was proven to be superior to NFS in lots (if not all, then it is in a roadmap) operations."

This latest release prompted Jeff Garzik to reply, "this continues to be a neat and interesting project :)" New features include fast transactions, round-robin failover, and near-wire limit performance. This adds to existing features which include a local coherent data and metadata cache, async processing of most events, and a fast and scalable multi threaded user space server. Planned features include a server extension to allow mirroring data across multiple devices, strong authentication, and possible data encryption when transferring data over the network. Evgeniy linked to several benchmarks in his blog.

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