Bruce, Yocto kernel folks, Here are backports for an ease-of-use enhancement, aimed at people doing multiple identical Yocto image deployments on a group of systems with possibly varying CPU counts.
To steal from the description in the mainline/lkml posting... The basic objective here was to add support for "nohz_full=8-last" and/or "rcu_nocbs="4-last" -- essentially introduce "last" as a portable reference evaluated at boot/runtime for anything using a CPU list. The thinking behind this, is that people carve off a few early CPUs to support housekeeping tasks, and perhaps dedicate one to a busy I/O peripheral, and then the remaining pool of CPUs out to the end are a part of a commonly configured pool used for the real work the user cares about. Extend that logic out to a fleet of machines - some new, and some nearing EOL, and you've probably got a wide range of core counts to contend with - even though the early number of cores dedicated to the system overhead probably doesn't vary. This change would enable sysadmins to have a common bootarg across all such systems, and would also avoid any off-by-one fencepost errors that happen for users who might briefly forget that core counts start at zero. https://lore.kernel.org/r/[email protected]/ As one can see from the above link, these commits were OK'd early November and are well on their way to mainline via the RCU --> tip path. But of course that doesn't help us with the v5.10 kernel that we'll be using in Yocto probably on into the year 2022. So, here is a set of commits tested on v5.10.1 of standard/base in -dev, and since the same commits apply "hands-free" to the v5.4.83 of the standard/base in linux-yocto and pass testing there as well - we might as well enable this administrative helper on that widely used version too. Thanks, Paul. -- Paul Gortmaker (4): cpumask: Un-inline cpulist_parse for SMP; prepare for ascii helpers cpumask: Make "all" alias global and not just RCU cpumask: Add a "none" alias to complement "all" cpumask: Add "last" alias for cpu list specifications .../admin-guide/kernel-parameters.rst | 20 +++ .../admin-guide/kernel-parameters.txt | 4 +- include/linux/cpumask.h | 8 ++ kernel/rcu/tree_plugin.h | 13 +- lib/cpumask.c | 132 ++++++++++++++++++ 5 files changed, 165 insertions(+), 12 deletions(-) -- 2.17.1
-=-=-=-=-=-=-=-=-=-=-=- Links: You receive all messages sent to this group. View/Reply Online (#9283): https://lists.yoctoproject.org/g/linux-yocto/message/9283 Mute This Topic: https://lists.yoctoproject.org/mt/79068035/21656 Group Owner: [email protected] Unsubscribe: https://lists.yoctoproject.org/g/linux-yocto/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
