Linux Kernel 2.6.21 Released

diegocgteleline.es writes "Linus Torvalds has released Linux 2.6.21 after months of development. This release improves the virtualization with VMI, a paravirtualization interface that will be used by Vmware. KVM does get initial paravirtualization support along with live migration and host suspend/resume support. 2.6.21 also gets a tickless idle loop mechanism called 'Dynticks', built in top of 'clockevents', another feature that unifies the timer handling and brings true high-resolution timers. Other features are: bigger kernel parameter-line, support for the PA SEMI PWRficient CPU and for the Cell-based 'celleb' Toshiba architecture, NFS IPv6 support, IPv4 IPv6 IPSEC tunneling, UFS2 write, kprobes for PPC32, kexec and oprofile for ARM, public key encryption for ecryptfs, Fcrypt and Camilla cipher algorithms, NAT port randomization, audit lockdown mode, some new drivers and many other small improvements."

Comments

Damnit!

[FunWithKnives]

And I just upgraded to 2.6.20-15! (Kubuntu Feisty Fawn)

Tickless only for x86 now, still good news

[MarcQuadra]

I follow prerelease kernels and I've been waiting for this. I've found that running my VMWare hosts and guests with tickless, low-HZ, voluntary-preempted kernels is seriously reducing the overhead you get when you run more virtual CPUs than real ones in your box.

I can't wait for it to mature on PPC, MIPS, and x86_64! Right now it's 32-bit x86 only.

Re:Tickless only for x86 now, still good news

[AaronW]

It means that they were able to successfully remove the blood sucking parasites from the kernel.

Most kernels use a periodic system timer tick to do various housekeeping chores, like rescheduling tasks, sending packets, flushing files from the cache, etc. Usually this occurs at some periodic rate, i.e. every 1-10ms for Linux and every 10-15ms for Windows (according to this article.

This is a bit wasteful of CPU resources, since the kernel might not need to do anything for quite a while, or it might want a high resolution timer with higher accuracy than normal system timer. For example, when the system is idle, the CPU still must wake up and process a timer interrupt for every timer tick, and if it's set to 1ms there are 1000 interrupts per second.

A tickless kernel instead only schedules the next tick for when it is needed, so if the system is idle and nothing needs to happen for 50ms, then the next tick will be scheduled 50ms later. On the other hand, if a timer needs to go off in 750 microseconds, the kernel can schedule the next interrupt to go off then, giving much higher accuracy.

Another solution to a timeless problem!

[iamacat]

Once again, it took many months of work to optimize an idle loop.

You joke,

[StarKruzr]

but I wonder if we're ever going to see 2.8 at this rate. The current kernel revision is MILES away in technology from 2.6.0. What will it take to move to 2.8, or (dare I say it?) 3.0? What qualifies as a major enough change?

Re:You joke,

[Anonymous Coward]

I wonder if we're ever going to see 2.8 at this rate

Linux 2.8 will compete with SunOS 6.0 as the best platform for running Duke Nukem Forever.

Re:Does it still crash after 49.7 days??

[Cro Magnon]

497 day wrap around? You should switch to Windows. I'm sure no such problem has ever been reported on that OS.