Linaro Releases

The Linaro Networking Group (LNG) is pleased to announce the
2016.03 release of the Linaro Networking Kernel.

Interesting changes include:

• No changes since last month’s release due to focus on isolation support for Open Data Plane and regressions seen after adding subsequent kernel patches.

• LNG intends to discontinue separate kernel releases in the near future, and to focus on upstreaming patches to the mainline kernel. Expectations are to maintain LNG-specific config fragments for enabling network-centric features in other kernels.

The release is also available via tags in the LNG git repository:

git://git.linaro.org/kernel/linux-linaro-lng.git linux-lng-4.1.14-2016.03
git://git.linaro.org/kernel/linux-linaro-lng.git linux-lng-preempt-rt-4.1.14-2016.03

More information on Linaro Networking Group Kernels is available at
http://wiki.linaro.org/LNG/Engineering/Foundational

Fixed in this release

Known issues

NO_HZ_FULL isolation is not fully functional in the LNG v4.1 ‘RT’ kernel.
Upstream developers are focusing on correcting this with the next stable
kernel release (V4.4) and its corresponding RT patch set.

Extended periods of isolation presently come at the expense of CPU accounting accuracy on the isolated cores while running in ‘full tickless’ mode.

CPU cores designated for use as ‘full tickless’ isolated cores are excluded from CPU load balancing, so CPU load balancing is effectively disabled on the LNG 3.18 kernels as currently configured. This is due to the compile-time configuration setting of CONFIG_NO_HZ_FULL_ALL=y, coupled with the fact that the allocation of CPUs as either ‘nohz_full’ or ‘housekeeping’ cores is statically defined at boot time. A work-around would be to configure the kernel with CONFIG_NO_HZ_FULL=y and CONFIG_NO_HZ_FULL_ALL=n, and then to use boot command line “nohz_full=…” CPU list parameter to apportion CPU resources appropriately. But for testing purposes the most convenient NO_HZ_FULL configuration is the one used in our kernel builds.

Feedback and Support

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• Linaro Networking Development mailing list
• Linaro Networking IRC channel on irc.freenode.net at #linaro-networking

• Bug reports should be filed in the Linaro Bug Tracking System against “LNG Kernel” product and “General” component: https://bugs.linaro.org
• Questions? ask Linaro.
• Interested in commercial support? inquire at Linaro support