Messages in this thread | | | Subject | Re: [PATCH v2] isolcpus: affine kernel threads to specified cpumask | From | Chris Friesen <> | Date | Tue, 24 Mar 2020 09:56:26 -0600 |
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I hadn't been keeping up with all the changes to the "isolcpus" boot arg. Given how it's been extended, I agree that it seems the logical place to deal with this. Patch seems okay to me, but I've got a couple of nits in the message portion.
If I want to specify both no_kthreads and managed_irq it then something like "isolcpus=managed_irq,no_kthreads,2-16" would work?
On 3/24/2020 9:20 AM, Marcelo Tosatti wrote: > > This is a kernel enhancement to configure the cpu affinity of kernel > threads via kernel boot option isolcpus=no_kthreads,<isolcpus_params>,<cpulist>
https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt says that "isolcpus" is deprecated. Are we un-deprecating it? Or is it only really deprecated for the "domain" option?
> When this option is specified, the cpumask is immediately applied upon > thread launch. This does not affect kernel threads that specify cpu > and node. > > This allows CPU isolation (that is not allowing certain threads > to execute on certain CPUs) without using the isolcpus=domain parameter, > making it possible to enable load balancing on such CPUs > during runtime (see
I think you're missing the rest of the sentence here.
> Note-1: this is based off on Wind River's patch at > https://github.com/starlingx-staging/stx-integ/blob/master/kernel/kernel-std/centos/patches/affine-compute-kernel-threads.patch > > Difference being that this patch is limited to modifying > kernel thread cpumask: Behaviour of other threads can > be controlled via cgroups or sched_setaffinity. > > Note-2: MontaVista's patch was based off Christoph Lameter's patch at > https://lwn.net/Articles/565932/ with the only difference being > the kernel parameter changed from kthread to kthread_cpus.
Wind River, not MontaVista. I know all us embedded linux folks look the same...
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> > > --- > > v2: use isolcpus= subcommand (Thomas Gleixner) > > Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ > include/linux/cpumask.h | 5 +++++ > include/linux/sched/isolation.h | 1 + > init/main.c | 1 + > kernel/cpu.c | 13 +++++++++++++ > kernel/kthread.c | 4 ++-- > kernel/sched/isolation.c | 6 ++++++ > 7 files changed, 36 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index c07815d230bc..7318e3057383 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1959,6 +1959,14 @@ > the CPU affinity syscalls or cpuset. > <cpu number> begins at 0 and the maximum value is > "number of CPUs in system - 1". > + When using cpusets, use the isolcpus option no_kthreads > + to avoid creation of kernel threads on isolated CPUs. > + > + no_kthreads > + Adjust the CPU affinity mask of unbound kernel threads to > + not contain CPUs on the isolated list. This complements > + the isolation provided by the cpusets mechanism described > + above.
It also complements the "managed_irq" option below. In many cases I'd expect the same set of CPUs to be isolated from both irqs and kernel threads.
Chris
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