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The tickless/dynticks Linux kernel patches first appeared in 2.6.21 for the x86 platform. amd64 tickless patches appeared a bit later in 2.6.24. It isn't just a matter of changing the HZ either - it looks at what timers are set to go off and idles until the soonest timer is set to go off or an interrupt arrives rather than firing wakeup events and then realising there is nothing to do (so it's not just switching between fixed frequencies).

There may have been issues using tickless kernels with virtualisation solutions but that might have been when using tickless kernels as hosts rather than guests (it's not something I've looked at) and in all likelihood the problem has been solved by now.

The tickless/dynticks Linux kernel patches first appeared in 2.6.21 for the x86 platform. amd64 tickless patches appeared a bit later in 2.6.24. It isn't just a matter of changing the HZ either - it looks at what timers are set to go off and idles until the soonest timer is set to go off or an interrupt arrives rather than firing wakeup events and then realising there is nothing to do (so it's not just switching between fixed frequencies).

There may have been issues using tickless kernels with virtualisation solutions but that might have been when using tickless kernels as hosts rather than guests (it's not something I've looked at) and in all likelihood the problem has been solved by now.

For some reason I didn't link this correctly. The set of changes for 2.6.30 is found http://kernelnewbies.org/Linux_2_6_30.

I think this is a relatively recent addition. In the kernel as provided as the official one in both Debian/Etch and Debian/EtchAndHalf RAID1 arrays read at the speed of one drive. The change to make it try balance the reads was made a minor version or two after the version those distros use as their base so it is present in the newer Lenny (though I have not yet got round to doing any performance tests on the one Lenny box I have with a RAID1 array to see how much difference this makes).

See http://kernelnewbies.org/KernelProjects/Raid1ReadBalancing and the patch it refers to that updates the feature, http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=06386bbfd2441416875d0403d405c56822f6ebac

So for better RAID1 read performance with software RAID in Linux, make sure that your kernel is new enough (or has had that particular update back-ported and patched in.

What? Linux has had that in an officially released version for more than a year! It's called fair group scheduling. You assign processes to groups and set the cpu share for each group. Then processor time is allotted proportionally between all groups that want to run. Nice levels are only used within a group.

A nice default is grouping by uid. Then users can't hog CPU time from others by creating a ton of processes.

I graduated with a CS bachelors a few years ago thinking I would have a good shot at doing some compiler design or maybe kernel hacking..

You do have a shot:

• Contributing to GCC
• The Linux Kernel Janitor Project

If you do a good job at one of those for a while, I think there's a decent chance of turning it into a paying job eventually.

I see.. but to get all the advantages you need a costly rewrite of all files:

"All your existing files will continue using the old indirect mapping to map all the blocks of data. The online defrag tool will be able to migrate each one of those files to a extent format (using a ioctl that tells the filesystem to rewrite the file with the extent format; you can use it safely while you're using the filesystem normally)."

source: http://kernelnewbies.org/Ext4

I'll add another URL: http://kernelnewbies.org/Ext4, which summarises the online, live conversion tools available to you today. But, seeing as you're backing up your data anyway, for safety and especially with a new filesystem, you could just rsync it off to the backup disk and then rsync it back onto a reformatted ext4 partition.

Is EXT4 backwards compatible with EXT2 and EXT3?

It's partially backwards compatible. You can mount it as an ext3 filesystem up to the point you use extents.

Ext4 Features: Compatibility

if by reformat you mean fdisk followed by an explicit mkfs.ext4 after....

You should be doing the following:
http://kernelnewbies.org/Ext4#head-3891522e0601162aab24c73c1f148a1e28c6a9d4

http://kernelnewbies.org/Linux_2_6_24
http://kernelnewbies.org/Linux_2_6_25
http://kernelnewbies.org/Linux_2_6_26
http://kernelnewbies.org/Linux_2_6_27
http://kernelnewbies.org/Linux_2_6_28

Those are the 2008 kernel releases. They look exciting to me...

http://kernelnewbies.org/Linux_2_6_24
http://kernelnewbies.org/Linux_2_6_25
http://kernelnewbies.org/Linux_2_6_26
http://kernelnewbies.org/Linux_2_6_27
http://kernelnewbies.org/Linux_2_6_28

Those are the 2008 kernel releases. They look exciting to me...

http://kernelnewbies.org/Linux_2_6_24
http://kernelnewbies.org/Linux_2_6_25
http://kernelnewbies.org/Linux_2_6_26
http://kernelnewbies.org/Linux_2_6_27
http://kernelnewbies.org/Linux_2_6_28

Those are the 2008 kernel releases. They look exciting to me...

http://kernelnewbies.org/Linux_2_6_24
http://kernelnewbies.org/Linux_2_6_25
http://kernelnewbies.org/Linux_2_6_26
http://kernelnewbies.org/Linux_2_6_27
http://kernelnewbies.org/Linux_2_6_28

Those are the 2008 kernel releases. They look exciting to me...

http://kernelnewbies.org/Linux_2_6_24
http://kernelnewbies.org/Linux_2_6_25
http://kernelnewbies.org/Linux_2_6_26
http://kernelnewbies.org/Linux_2_6_27
http://kernelnewbies.org/Linux_2_6_28

Those are the 2008 kernel releases. They look exciting to me...

Your question feels a bit of strange question to ask as surely anyone who has looked would notice a huge difference between the latest 2.6 (2.6.28) and the latest 2.4 (2.4.37).

Preemptible kernel (so lower latencies are possible)
Far more devices supported (both in terms of architectures and additional add on devices e.g. SATA support)
Better scheduler (initially made O(1) scales better under load and then fairer with CFS)
Task Control Groups
Better support for threads (schedules them in a more intelligent fashion)
Strict overcommit
Massive VM changes
Tickless/dynticks support
Asynchronous I/O support
Introduction of different I/O schedulers (deadline, cfq
Network stack improvements (faster, better under load e.g. NAPI support)
epoll support
Improved ACPI support
Network filesystem improvements
Initramfs support

There is a huge list of Linux kernel changes that happened between 2.4 and 2.5. There is also a good Linux kernel 2.5 changes page on IBM's developerworks. Kernelnewbies has an excellent summary of changes for each of the 2.6 kernels and a 2.5 changes page. LWN is also excellent for kernel news.

I hate it when people don't bother to state exactly the points they object to. What other changes (not listed above) do you think the question poster wouldn't benefit from? Follow the links to the full lists (don't just use the ones off the top of your head)...

Your question feels a bit of strange question to ask as surely anyone who has looked would notice a huge difference between the latest 2.6 (2.6.28) and the latest 2.4 (2.4.37).

Preemptible kernel (so lower latencies are possible)
Far more devices supported (both in terms of architectures and additional add on devices e.g. SATA support)
Better scheduler (initially made O(1) scales better under load and then fairer with CFS)
Task Control Groups
Better support for threads (schedules them in a more intelligent fashion)
Strict overcommit
Massive VM changes
Tickless/dynticks support
Asynchronous I/O support
Introduction of different I/O schedulers (deadline, cfq
Network stack improvements (faster, better under load e.g. NAPI support)
epoll support
Improved ACPI support
Network filesystem improvements
Initramfs support

There is a huge list of Linux kernel changes that happened between 2.4 and 2.5. There is also a good Linux kernel 2.5 changes page on IBM's developerworks. Kernelnewbies has an excellent summary of changes for each of the 2.6 kernels and a 2.5 changes page. LWN is also excellent for kernel news.

I hate it when people don't bother to state exactly the points they object to. What other changes (not listed above) do you think the question poster wouldn't benefit from? Follow the links to the full lists (don't just use the ones off the top of your head)...

Your question feels a bit of strange question to ask as surely anyone who has looked would notice a huge difference between the latest 2.6 (2.6.28) and the latest 2.4 (2.4.37).

Preemptible kernel (so lower latencies are possible)
Far more devices supported (both in terms of architectures and additional add on devices e.g. SATA support)
Better scheduler (initially made O(1) scales better under load and then fairer with CFS)
Task Control Groups
Better support for threads (schedules them in a more intelligent fashion)
Strict overcommit
Massive VM changes
Tickless/dynticks support
Asynchronous I/O support
Introduction of different I/O schedulers (deadline, cfq
Network stack improvements (faster, better under load e.g. NAPI support)
epoll support
Improved ACPI support
Network filesystem improvements
Initramfs support

There is a huge list of Linux kernel changes that happened between 2.4 and 2.5. There is also a good Linux kernel 2.5 changes page on IBM's developerworks. Kernelnewbies has an excellent summary of changes for each of the 2.6 kernels and a 2.5 changes page. LWN is also excellent for kernel news.

I hate it when people don't bother to state exactly the points they object to. What other changes (not listed above) do you think the question poster wouldn't benefit from? Follow the links to the full lists (don't just use the ones off the top of your head)...

Your question feels a bit of strange question to ask as surely anyone who has looked would notice a huge difference between the latest 2.6 (2.6.28) and the latest 2.4 (2.4.37).

Preemptible kernel (so lower latencies are possible)
Far more devices supported (both in terms of architectures and additional add on devices e.g. SATA support)
Better scheduler (initially made O(1) scales better under load and then fairer with CFS)
Task Control Groups
Better support for threads (schedules them in a more intelligent fashion)
Strict overcommit
Massive VM changes
Tickless/dynticks support
Asynchronous I/O support
Introduction of different I/O schedulers (deadline, cfq
Network stack improvements (faster, better under load e.g. NAPI support)
epoll support
Improved ACPI support
Network filesystem improvements
Initramfs support

There is a huge list of Linux kernel changes that happened between 2.4 and 2.5. There is also a good Linux kernel 2.5 changes page on IBM's developerworks. Kernelnewbies has an excellent summary of changes for each of the 2.6 kernels and a 2.5 changes page. LWN is also excellent for kernel news.

I hate it when people don't bother to state exactly the points they object to. What other changes (not listed above) do you think the question poster wouldn't benefit from? Follow the links to the full lists (don't just use the ones off the top of your head)...

Your question feels a bit of strange question to ask as surely anyone who has looked would notice a huge difference between the latest 2.6 (2.6.28) and the latest 2.4 (2.4.37).

Preemptible kernel (so lower latencies are possible)
Far more devices supported (both in terms of architectures and additional add on devices e.g. SATA support)
Better scheduler (initially made O(1) scales better under load and then fairer with CFS)
Task Control Groups
Better support for threads (schedules them in a more intelligent fashion)
Strict overcommit
Massive VM changes
Tickless/dynticks support
Asynchronous I/O support
Introduction of different I/O schedulers (deadline, cfq
Network stack improvements (faster, better under load e.g. NAPI support)
epoll support
Improved ACPI support
Network filesystem improvements
Initramfs support

There is a huge list of Linux kernel changes that happened between 2.4 and 2.5. There is also a good Linux kernel 2.5 changes page on IBM's developerworks. Kernelnewbies has an excellent summary of changes for each of the 2.6 kernels and a 2.5 changes page. LWN is also excellent for kernel news.

I hate it when people don't bother to state exactly the points they object to. What other changes (not listed above) do you think the question poster wouldn't benefit from? Follow the links to the full lists (don't just use the ones off the top of your head)...

With the addition of uvcvideo and gpsca usb webcam drivers most webcams should be supported in Linux distros released in the past 4 or so months. Assuming you tried an extremely new distro which webcam was not working?

With the addition of uvcvideo and gpsca usb webcam drivers most webcams should be supported in Linux distros released in the past 4 or so months. Assuming you tried an extremely new distro which webcam was not working?

Really? And they are fixing the hard coded locking mechanism when again? They are abandoning the frame buffer video when?

Your answer:

There has been a lot of work in the latest years to modernize the Linux graphics stack so that it's both well designed and also ready to use the full power of modern and future GPUs. In 2.6.28, Linux is adding one of the most important pieces of the stack: A memory manager for the GPU memory, called GEM ("Graphic Execution Manager"). The purpose is to have a central manager for buffer object placement, caching, mapping and synchronization. On top of GEM are being built a lot of improvementes to the graphic stack: Kernel Modesetting, DRI2, UXA (a EXA implementation based in GEM). The Linux/FOSS graphics stack will be finally unified and optimally coupled. -- Kernel Newbie on 2.6.28

I agree that MS has done some pretty cool stuff recently, but the main achievement is trying to improve whiile retaining complete backward compatibility.

OS X also has a great developer stack, I understand, which exposes all the important functionality in the OS elegantly. Linux + Gnome (or KDE) is also moving forward really well. Vala promises to make developing for Gnome a much nicer process. GStreamer + Telepathy is going to make things really nice.

The changelog is available aswell...you might aswell have waited a bit to the final release!

If you haven't been following every commit's short log, you may find http://kernelnewbies.org/Linux_2_6_28 useful. I for one, would like 2.6.28 for Christmas.

As per Linus' email, the list of changes in a human-readable format can be accessed:
here

http://janitor.kernelnewbies.org/

Maybe this will answer some of your questions. But yes, and it's good that the linux kernel doesn't operate like wikipedia, for obvious reasons.

The RepRap is a truly awesome piece of equipment. For those who are not able to expend the time or energy to check it out, I'll explain it here as briefly as I can. It's kinda like a 3D printer; It generates physical objects by extruding a polymer resin, based on a 3-dimensional model (think CAD/CAM). You can use it to make things, including making another one, and it's completely open source.

The free government project looks pretty neat, although I only gave it a quick once-over. I've bookmarked it for later perusal, when I have more time. Open-source governance is a great concept, I'm looking forward to seeing what becomes of it.

The idea of mesh networking is still in its infancy, but is another wonderful concept. Basically, it takes the idea of the internet, and rips off all the ugly wiring. This gives us a reliable, global, mobile structure of communication anywhere, everywhere, whenever. Imagine every electrical device being a wireless access point. The basic framework for supporting mesh networking was added to the linux kernel in the latest release, so this may actually have enough steam to start getting underway.

The surveillance state is already the here and now. Releasing that information to the public at large is the only way to make certain it is not abused, and I like where you were headed with that.

In short, sign me up.

"Server virtualization" is an admission that system administration is badly designed. After all, you're not going to get any more work out of the machine than you would running multiple processes. Usually, you get less. Part of the problem is that Linux is still locked into the old UNIX user/group/everybody model of security, with an all-powerful "root". Virtualization is a way of working around that limitation.

OpenVZ and Linux-VServer are efforts to get around this problem by adding another level of administrative containerization. The performance is better, since you're not going through two layers of operating systems.

Many of the problems come from the fact that some major applications are coded as singletons. For example, Apache assumes there is only one instance of itself per machine. (Yes, this can be worked around, but it's not easy.) So do most mail handling programs. If you can install and run an application without running as "root", it probably doesn't need virtualization.

"Server virtualization" is an admission that system administration is badly designed. After all, you're not going to get any more work out of the machine than you would running multiple processes. Usually, you get less. Part of the problem is that Linux is still locked into the old UNIX user/group/everybody model of security, with an all-powerful "root". Virtualization is a way of working around that limitation.

OpenVZ and Linux-VServer are efforts to get around this problem by adding another level of administrative containerization. The performance is better, since you're not going through two layers of operating systems.

Many of the problems come from the fact that some major applications are coded as singletons. For example, Apache assumes there is only one instance of itself per machine. (Yes, this can be worked around, but it's not easy.) So do most mail handling programs. If you can install and run an application without running as "root", it probably doesn't need virtualization.

1.3. Improved webcam support, 2.6.26 includes a driver that supports video input devices compliant with the USB Video Class specification. This means lots of currently manufactured webcams, and probably most of the future ones (commit)

You mean like that?

KernelNewbies is your friend.

You're looking for this: http://kernelnewbies.org/LinuxChanges

In case you meant 2.6.26 and not 2.2.26, you can get the old changes at http://kernelnewbies.org/Linux26Changes. This has been done for a few years now. lwn.net provides good info on what has changed as well, if you want more in depth info on some specific change.

Click the link in the story: http://kernelnewbies.org/Linux_2_6_26

and it explains it all there

Um, did you try clicking on the link?

http://kernelnewbies.org/Linux_2_6_26

That's a pretty highlevel featurelist

Any word on when they're going to fix the even older "Too many arguments" bug?

Use linux instead.
CHANGELOG
git commit

It is a kernel option called fair group scheduling. If you could recompile your kernel you can change that. I know I had huge issues with this where any disk intensive operation would slow the machine to a halt. That said, the last time I used Ubuntu was years ago and the developers on the forum told me I should never compile my own kernel on Ubuntu, maybe that has changed by now, but it was easy on Gentoo to fix.

GREAT article - it is interesting for a non-programmer to read this type of technical detail, presented in an understandable way. For me, right at the edge of my theoretical-only knowledge. A detailed summary, I guess. (oxymoron)

Similar article on NetBSD: Waving the flag: NetBSD developers speak about version 4.0 (1/30/2008)

Linux focused links:

Current discussion:
LWN: Kernel
KernelTrap
KernelNewbies: Summary of Linux Changes
---
The Wonderful World of Linux series are excellent history - in-depth for outsiders:
WWOL 2.2
WWOL 2.4
WWOL 2.6
---
Towards Linux 2.6 - A look into the workings of the next new kernel(2003)
Kernel Comparison: Linux (2.6.22) versus Windows (Vista)(2007)

From Google cache (of http://kernelnewbies.org/Linux_2_6_24): ...
  In Linux 2.6.22, the mac80211 (formerly d80211) wireless stack was
      merged, but not many drivers that use this new stack have been merged
      (only one). Linux 2.6.24 will have a lot of new wireless drivers using
      the new stack; 2.3 MB of source files in total:
          * iwlwifi driver for the Intel PRO/Wireless 3945ABG/BG Network
              Connection and Intel Wireless Wifi Link AGN (4965) adapters
              (commit)
          * rt2x00 driver for Ralink wireless hardware (rt2400 pci/pcmcia,
              rt2500 pci/pcmcia, rt61 pci/pcmcia, rt2500 usb, rt73 usb). Check
              the hardware matrix (commit)
          * adm8211 driver for the ADMtek ADM8211x based wireless cards. These
              are PCI/mini-PCI/Cardbus 802.11b chips found in cards such as:
              Xterasys Cardbus XN-2411b, Blitz Netwave Point PC, Trendnet 221pc,
              Belkin F5d6001, SMC 2635W, Linksys WPC11 v1, Fiberline FL-WL-200X,
              3com Office Connect (3CRSHPW796), Corega WLPCIB-11, SMC 2602W V2
              EU, D-Link DWL-520 Revision C (commit)
          * b43 driver for modern BCM43xx devices. This driver supports the
              new BCM43xx IEEE 802.11G devices, but not the old IEEE 802.11B
              devices - those are supported by the b43legacy driver. This driver
            uses V4 firmware, which must be installed separately using
              b43-fwcutter (commit)
          * b43legacy driver for legacy BCM43xx devices from Broadcom (BCM4301
              and BCM4303) and early model 802.11g chips (BCM4306 Ver. 2) used
              in the Linksys WPC54G V1 PCMCIA devices. Newer 802.11g and 802.11a
              devices need the b43 driver. This driver uses V3 firmware, which
              must be installed separately using b43-fwcutter (commit)
          * p54 driver for prism54 softmac pci/usb hardware (commit)
          * Driver for Marvell Libertas 8385 Compactflash 802.11b/g cards
              (commit)
          * Libertas sdio driver (commit)

      There're also a lot of network (non-wireless) drivers being merged,
      look at the section 2.14, "new drivers" ...

Did you RTFM? It's all there in the link to kernelnewbies.

btw, for 'things to come' in a near future kernelnewbies changelogs were great. unfortunately, it seems that one for 2.6.23 is pretty much abandoned...
http://kernelnewbies.org/LinuxChanges

Well, the upcoming sister-raping feature could qualify as "major".

Details:
"The features are tested in the -mm tree, but be warned, it can crash your machine, eat your data (unlikely but not impossible) or rape your sister (just because it has never happened it doesn't means you're safe):"

Here.

From http://kernelnewbies.org/Linux_2_6_20 (raw copy and paste -- didn't fix the formatting) since the site is getting hammered:

Short overview (for news sites, etc)

2.6.20 makes linux join to the virtualization trends. This release adds two virtualization implementations: A full-virtualization implementation that uses Intel/AMD hardware virtualization capabilities called KVM (http://kvm.sourceforge.net) and a paravirtualization implementation (http://lwn.net/Articles/194543) that can be used by different hypervisors (Rusty's lguest; Xen and Vmware in the future, etc),. But this release also adds initial Sony Playstation 3 support, a fault injection debugging feature (http://lwn.net/Articles/209257), UDP-lite support, better per-process IO accounting, relative atime, support for using swap files for suspend users, relocatable x86 kernel support for kdump users, small microoptimizations in x86 (sleazy FPU, regparm, support for the Processor Data Area, optimizations for the Core 2 platform), a generic HID layer, DEEPNAP power savings for PPC970, lockless radix-tree readside, shared pagetables for hugetbl, ARM support for the AT91 and iop13xx processors, full NAT for nf_conntrack and many other things.

Important things (AKA: ''the cool stuff'')

Sony Playstation 3 support

You may like the Wii or the 360 more, but only the PS3 is gaining official Linux support, written by Sony engineers. Notice that the support at this time is incomplete (apparently enabling it will not boot on a stock PS3) and it doesn't support the devices included like the graphics card, etc. (commit 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)

Virtualization support through KVM

KVM (project page) adds a driver for Intel's and AMD's hardware virtualization extensions to the x86 architecture (KVM will not work in CPUs without virtualization capabilities). See the Virtualization wiki for more information about virtualization in Linux

The driver adds a character device (/dev/kvm) that exposes the virtualization capabilities to userspace. Using this driver, a process can run a virtual machine (a "guest") in a fully virtualized PC containing its own virtual hard disks, network adapters, and display. Each virtual machine is a process on the host; a virtual cpu is a thread in that process. kill(1), nice(1), top(1) work as expected. In effect, the driver adds a third execution mode to the existing two: we now have kernel mode, user mode, and guest mode. Guest mode has its own address space mapping guest physical memory (which is accessible to user mode by mmap()ing /dev/kvm). Guest mode has no access to any I/O devices; any such access is intercepted and directed to user mode for emulation.

32 and 64 bits guests are supported (but not x86-64 guests on x86-32 hosts!). For i386 guests and hosts, both pae and non-pae paging modes are supported. SMP hosts and UP guests are supported, SMP guests aren't (support will be added in the future). You also can start multiple virtual machines in a host. Performance currently is non-stellar, it will be improved by a lot with the future inclusion of KVM paravirtualization KVM support.

The Windows install currently bluescreens due to a problem with the virtual APIC, a fix is being worked on and will be added in future releases. A temporary workaround is to use an existing image or install through qemu - Windows 64-bit does not work either (commit)

Paravirtualization support for i386

Paravirtualization is the act of running a guest operating system, under control of a host system, where the guest has been ported to a virtual architecture which is almost like the hardware it is actually running on. This technique allows full guest systems to be run in a relatively efficient manner (continue reading this LWN article for more information). This allows to link different hypervisors (lguest/lhype/rustyvisor implements a hypervisor in 6.000 lines; Xen and Vmware will be probably ported to th

CFQ is default since 2.6.18, released back in September 2006.

I've tried to put together an easy to understand overview of the various Linux virtualization technologies, at http://virt.kernelnewbies.org/TechComparison

Has anyone read that changes document yet?
First item under USB is Add Playstation 2 Trance Vibrator driver

Is this the first sex toy to be officially supported by the Linux kernel?! Surely that's enough for front page news.

Sorry dude, but the Kernelnewbies wiki runs at my home :)

Having said that, Greg-KH is one of the largest contributors on the kernelnewbies mailing list...