Linus Torvalds announced the first release candidate for the upcoming 2.6.21 kernel, ending the two-week merge window [story [1]], "there's a lot of changes, as is usual for an -rc1 thing, but at least so far it would seem that 2.6.20 has been a good base, and I don't think we have anything *really* scary here." Linus noted that the tickless kernel patch [story [2]] was finally merged into the mainline kernel, "the most interesting core change may be the dyntick/nohz one, where timer ticks will only happen when needed. It's been brewing for a _loong_ time, but it's in the standard kernel now as an option." Thomas Gleixner explained a year ago how this could result in cooler CPUs and power savings, "the tickless kernel feature (CONFIG_NO_HZ) enables 'on-demand' timer interrupts: if there is no timer to be expired for say 1.5 seconds when the system goes idle, then the system will stay totally idle for 1.5 seconds."

As for the rest of the changes, Linus added, "there's a ton of architecture updates (arm, mips, powerpc, x86, you name it), ACPI updates, and lots of driver work. And just a lot of cleanups." Release candidate kernels can be downloaded from your nearest kernel.org mirror [3]. You can browse through all the changes using the gitweb interface [4]. Kernel Newbiews maintains a useful summary [5] of all the changes going into the latest version of the Linux kernel.

From: Linus Torvalds [email blocked]
To: Linux Kernel Mailing List [email blocked]
Subject: Linux 2.6.21-rc1
Date:	Tue, 20 Feb 2007 20:53:45 -0800 (PST)


Ok, the merge window for 2.6.21 has closed, and -rc1 is out there.

There's a lot of changes, as is usual for an -rc1 thing, but at least so 
far it would seem that 2.6.20 has been a good base, and I don't think we 
have anything *really* scary here.

The most interesting core change may be the dyntick/nohz one, where timer 
ticks will only happen when needed. It's been brewing for a _loong_ time, 
but it's in the standard kernel now as an option. 

But there's a ton of architecture updates (arm, mips, powerpc, x86, you 
name it), ACPI updates, and lots of driver work. And just a lot of 
cleanups.

Have fun,

			Linus

• Archive of above thread [6]