"BootUtils is a collection of utilities to facilitate booting of modern Kernel 2.6 based systems. BootUtils is designed for initramfs, although volunteers to add support for initrd are welcome. The process of finding the root volume either by label or explicit label= on the kernel command line, mounting it and 'switchroot'ing is automated. BootUtils can also drop to emergency shell if the root volume cannot be mounted. Why not even start sshd and allow admin login if the box is in a remote location?"
With the release of the 2.6.18-rc3-mm1 kernel, Andrew Morton [interview] included a brief note stating, "fwiw, I recently took a position with Google." He then linked to a Linux Today article which details the reasons behind his recent move. The article begins, "Andrew Morton has started working for a new company, but his day job as the Linux 2.6 kernel maintainer will remain exactly the same." In the article, Andrew discusses one of the reasons Google was a good fit, "in my position as kernel maintainer I feel that I should not be employed by a company which has a direct interest in the kernel.org kernel because this would put me in a position of making decisions which are commercially significant to my employer's competitors. As Google maintains their own kernel variant for internal use, their interests are largely decoupled from what happens in the kernel.org kernel."
Hans Reiser formed Namesys and began the development of Reiserfs ten years ago. The first release of the filesystem, Reiser3, is part of the mainline 2.4 and 2.6 Linux kernels. The more recent Reiser4 is a complete redesign and reimplementation of Reiserfs, aiming to soon be merged into the mainline 2.6 Linux kernel.
In this interview, Hans discusses his background and how he came to create Namesys and Reiserfs. He looks back at Reiser3, describing the advantages it had over other filesystems when it was released and its current state. He then explores the many improvements currently in Reiser4, describing the plugin architecture and its exciting potential for future semantic enhancements.
At the July 2004 kernel summit, it was decided that there was no need to fork a 2.7 kernel [forum] to introduce new functionality into the Linux kernel. Instead, the decision was made that it was possible for Andrew Morton [interview] and Linus Torvalds to continue working together to first merge things into Andrew's -mm tree, and then after testing the changes to merge them into Linus' mainline tree [story]. This of course led to discussion, with some confusion as to how the 2.6 kernel [forum] could be considered stable while new features were still being merged in [story]. During another short discussion nine months after this decision, Rik van Riel [interview] offered some insight into why the new development model works:
"Things get merged one change at a time, and stabilised one change at a time. This is a big change from the even/odd numbered kernel series, where sometimes a bug crops up without anybody knowing exactly what change introduced it. The current development model seems to go much smoother than anything I've seen before."
An interesting thread on the lkml began when Greg KH submitted a patch for the 2.6 kernel saying, "Ok, to test out the new development model, here's a nice patch that simply removes the devfs code." This was quickly followed with a comment by Oliver Neukum who said, "may I point out that 2.6 is supposed to be a _stable_ series?" In one branch of the thread, the usefulness of devfs was examined.
In another thread, discussion was focused on this "new development model". Jonathan Corbet explained that Linus Torvalds and Andrew Morton [interview] were very happy with the results of their recent teamwork, and saw no immediate pressure to fork a 2.7 development branch. On the contrary, they intend to keep at it as they've been, with things first going into Andrew's -mm patchset [story] for testing, then eventually being merged into the mainline 2.6 kernel. Jonathan went on to explain, "Andrew stated his willingness to consider, for example, four-level page tables, MODULE_PARM removal, API changes, and more. 2.7 will only be created when it becomes clear that there are sufficient patches which are truly disruptive enough to require it. When 2.7 *is* created, it could be highly experimental, and may turn out to be a throwaway tree." And he summarized:
"Andrew's vision, as expressed at the summit, is that the mainline kernel will be the fastest and most feature-rich kernel around, but not, necessarily, the most stable. Final stabilization is to be done by distributors (as happens now, really), but the distributors are expected to merge their patches quickly."
Continuing the earlier discussion about low latency and Ingo Molnar [interview]'s voluntary kernel preemption patch [story], the conversation moved onto the affect a filesystem can have on latency. Specifically, 2.6 maintainer Andrew Morton [interview] noted that ReiserFS was known to have some latency issues in both the 2.4 and 2.6 Linux kernels, "resierfs: yes, it's a problem. I 'fixed' it multiple times in 2.4, but the fixes ended up breaking the fs in subtle ways and I eventually gave up." However, he did go on to note, "actually, the 2.4 low-latency patch does still have some reiserfs fixes, so it's probably better than reiserfs in 2.6."
When asked if ext3 was a better choice for low latency work, Andrew Morton replied, "ext3 is certainly better than [reiserfs], but still has a couple of potential problem spots. ext2 is probably the best at this time." Data is continuing to be collected and reviewed by a number of kernel developers, so the more noticeable latency issues in the 2.6 kernel will likely be addressed soon.
Anyone who's been following Linux kernel development for the past several months has heard about one exciting feature after another being merged into the still un-released 2.6 kernel. New features that noticeably affect user experience include Robert Love's [interview] preemptible kernel work [story], Ingo Molnar's [interview] O(1) Scheduler [story], Rik Van Riel's [interview] reverse mapping VM [story], Nick Piggins' [interview] Anticipatory I/O scheduler [story], and much, much more...
Having some spare time a few nights ago, I decided to give the latest kernel, 2.6.0-test4, a trial run on my aging 550Mhz PIII desktop computer, and the result was nothing short of spectacular. As the final 2.6.0 release approaches, it is important that an increasing number of users (aka testers) give this kernel a try, especially as currently it's still a sexy task for developers to track down kernel bugs and stabalize their work. Once work starts on the 2.7 development tree, inevitably much talent will again be focusing on new features.
The purpose of this document is to provide some helpful tips to readers that currently compile their own 2.4 kernels, but haven't yet made the leap to 2.6. This is still a development kernel, so you may run into problems, but overall stability and performance is quite impressive and I can't recommend enough that you try it today.
A recent lkml thread explored an interesting tangent when Jeff Garzik asked about what was to follow the 2.5 development kernel, "is it definitely to be named 2.6? Maybe it's just my impression from development speed, but it felt more like a 3.0 to me :)". Linux creator Linus Torvalds first suggested that there was no reason to skip from 2.5 to 3.0, qualifying it with, "But hey, it's just a number. I don't feel that strongly either way."
Ingo Molnar reflected on the significant improvements we've seen to the VM and the IO subsystem, going so far as to say, "I think due to these improvements if we dont call the next kernel 3.0 then probably no Linux kernel in the future will deserve a major number. In 2-4 years we'll only jump to 3.0 because there's no better number available after 2.8."
Linus agreed that if the VM is as good as it seems to be, indeed the upcoming release deserves to be called 3.0. But he also pointed out that there are many silent users who tend not to speak up until there is an official release. He asks, "people who are having VM trouble with the current 2.5.x series, please _complain_, and tell what your workload is. Don't sit silent and make us think we're good to go.. And if Ingo is right, I'll do the 3.0.x thing."