Messages in this thread | | | Date | Tue, 24 Mar 2020 13:50:36 -0300 | From | Marcelo Tosatti <> | Subject | Re: [PATCH v2] isolcpus: affine kernel threads to specified cpumask |
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On Tue, Mar 24, 2020 at 09:56:26AM -0600, Chris Friesen wrote: > 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?
Yes.
> 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?
I don't think its deprecated (see the recent inclusion of managed_irq, and the suggestion from Thomas to extend it).
Will send another patch to remove that sentence.
> > 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.
Right.
> > 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...
Doh^2.
> > > > > 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
Agree, will fix in -v3.
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