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LXer Feature: 22-Oct-2007

Welcome back! In part 4 we ranged all over the place, from how to manage and edit your photo archives with Linux, some discussion on choosing lenses, and finally getting down to the most important part of getting high-quality photographs: understanding aperture, shutter speeds, and ISO. Part 4 covered the fundamentals of aperture, so let's leap in to shutter speeds and ISO. This applies to point-and-shoot cameras as well as the fancy DSLRs with herds of different lenses; if you don't understand these three photography fundamentals, you won't understand how to get the best photos.

"Sometimes I'm tardy and miss things for weeks and need prodding, and sometimes I pull almost before you've sent the'please pull' message. I'm unpredictable. Or keeping you on your toes. Or incompetent. Pick whatever suits your mood ;)"— Linus Torvalds in anOctober 17, 2007 message to the Linux Kernel Mailing List.

To a business user of Linux, the development of its kernel may appear so Byzantine, with dozens of people maintaining different pieces and hundreds more volunteers submitting code, that it's hard to see where new features are headed.

What's Linux worth? The question has been a favorite of technology groups and cocktail party conversations ever since a character named Jeff V. Merkey offered $50,000 for a copy of Linux. The offer was a ploy. Merkey wanted it under the BSD license, which would have undermined the terms of the GPL. So he didn't get it. But we know, at least, that $50,000 proved to be a low bid.

Jeff Garzik posted a series of nine patchs to the lkml titled to "remove [the] 'irq' argument from all irq handlers", explaining, "the overwhelming majority of drivers do not ever bother with the 'irq' argument that is passed to each driver's irq handler. Of the minority of drivers that do use the arg, the majority of those have the irq number stored in their private-info structure somewhere." He noted that he had no intention to push the patches upstream anytime soon.

When asked how to best refer to kernels between official releases and release candidates, Linus Torvalds pointed to his automated git snapshots. "I still call them 'nightly snapshots', but they do in fact happen twice a day if there have been changes, so that's not technically correct," he noted. The latest snapshot is 2.6.23-git15, "this is an exact name, because you can go to kernel.org and look up the exact commit ID that was used to generate it (there's an 'ID' file associated with each snapshot there)."

LXer Feature: 21-Oct-2007

Some of the big stories this week include Linux vs. Windows Power Usage, Microsoft gets two licences approved by the OSI, Kevin Carmony switches to Ubuntu and on top of all that we have a slew of LXer features including a couple of reports from T-DOSE, Carla Schroder continues her series on Digital Photography and a reader submitted article with some advice for those trying to decide between Windows or Linux.

"Currently in mainline the balancing of multiple RT threads is quite broken. That is to say that a high priority thread that is scheduled on a CPU with a higher priority thread, may need to unnecessarily wait while it can easily run on another CPU that's running a lower priority thread," began Steven Rostedt, describing his patchset to introduce improved real time task balancing.

In a brief follow up to the earlier pluggable security discussion, Thomas Fricaccia reflected on the implications for the various security frameworks, "I noticed James Morris' proposal to eliminate the LSM in favor of ordaining SELinux as THE security framework forever and amen, followed by the definitive decision by Linus that LSM would remain."

Evgeniy Polyakov announced a new version of his distributed storage subsystem, "this release includes [a] mirroring algorithm extension, which allows [the subsystem] to store [the] 'age' of the given node on the underlying media." He went on to explain why this was useful:..

The previous 2.4 Linux kernel maintainer, Marcelo Tossati, resurrected a discussion on adding support for out of memory notifications to the Linux kernel. He explained, "AIX contains the SIGDANGER signal to notify applications to free up some unused cached memory," then noting, "there have been a few discussions on implementing such an idea on Linux, but nothing concrete has been achieved." In a request for discussion, Marcelo added, "on the kernel side Rik suggested two notification points: 'about to swap' (for desktop scenarios) and 'about to OOM' (for embedded-like scenarios)."

Ken Chen submitted a patch to reduce the memory footprint of schedstat in a thread titled, "schedstat needs a diet". He explained, "schedstat is useful in investigating CPU scheduler behavior. Ideally, I think it is beneficial to have it on all the time. However, the cost of turning it on in production system is quite high, largely due to number of events it collects and also due to its large memory footprint." His patch converted numerous unsigned long variables to unsigned int, "most of the fields probably don't need to be [a] full 64-bits on 64-bit [architectures]. Rolling over 4 billion events will most likly take a long time and user space tools can be made to accommodate that."

"This is a request to merge KGDB into the mainline kernel," Jason Wessel announced, posting a series of patches aiming toward that goal. He continued, "as of right now KGDB is comprised of 21 different patches adding in the core api and docs first and then working up to add drivers and arch specific support to KGDB. The patches were broken down into logical pieces for review and comments."

"I'm trying to keep some external drivers up to date with the kernel, and the first two weeks after the release is the worst time for me. There is no way to distinguish the current git kernel from the latest release. It's only after rc1 is released that I can use the preprocessor to check LINUX_VERSION_CODE," explained Pavel Roskin, describing the ongoing effort to keep the out of tree MadWifi driver in sync with the latest released kernel.

In How Far Behind is Linux?, WSJ writer Lee Gomes sets up a beautiful strawman about the security of GNU/Linux versus Windows and knocks it down with its own answer.

The virtual memory subsystem of a processor implements the virtual address spaces provided to each process. This makes each process think it is alone in the system. The list of advantages of virtual memory are described in detail elsewhere so they will not be repeated here. Instead this section concentrates on the actual implementation details of the virtual memory subsystem and the associated costs.

It’s been almost 200 years since Charles Babbage first started work on his difference engine, and programmable computation is fast approaching 100 years old. Over this time there has been a lot of change in software development and in this article we look at the evolutionary pressure that has shaped that.

Fred Trotter has an article in which he discusses Electronic Health Records, the Iroquois Nation's notion of considering the impact of the current generation decision 7 generations from now and Microsoft's HealthVault as well as Google's announced Personal Health Records:

All of the various clients and servers for Enemy Territory: Quake Wars (Community Site) are now available! Thanks TTimo for a job well done as always. You can find all the info you need on the ETQW GNU/Linux FAQ page.

Jaroslav Sykora posted a series of five patches to handle the kernel portion of what he described as "shadow directories", providing an example which utilized FUSE to access the contents of a compressed file from the command line.