In message: [PATCH 0/4] support for global CPU list abbreviations on 18/12/2020 Paul Gortmaker wrote:
> 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, This looks sane to me, and I've merged it to the v5.10 branches of linux-yocto (i.e. the ones that will be the reference kernel shortly). I held back on v5.4 for the moment, since that gets pulled back into the LTS dunfell releases and I want things to soak in my builds before moving it into that version. Bruce > > 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 >
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