Messages in this thread | | | Date | Tue, 31 Mar 2020 02:57:08 +0200 | From | Frederic Weisbecker <> | Subject | Re: [patch 2/3] isolcpus: affine kernel threads to specified cpumask |
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On Sat, Mar 28, 2020 at 12:21:19PM -0300, 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> > > 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 kernel-parameters.txt). > > 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: Wind River'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. > > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> > > --- > Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ > include/linux/sched/isolation.h | 1 + > kernel/kthread.c | 6 ++++-- > kernel/sched/isolation.c | 6 ++++++ > 4 files changed, 19 insertions(+), 2 deletions(-) > > Index: linux-2.6/Documentation/admin-guide/kernel-parameters.txt > =================================================================== > --- linux-2.6.orig/Documentation/admin-guide/kernel-parameters.txt > +++ linux-2.6/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 "kthread" > + to avoid creation of kernel threads on isolated CPUs. > + > + kthread > + 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 and by managed_irq option.
So, what about what I suggested with having "unbound" instead, which includes all the CPU-unbound work?
HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC | HK_FLAG_KTHREAD | HK_FLAG_SCHED
(and yes your suggestion of including HK_FLAG_SCHED is good).
Because I don't see the point of exposing kthread isolation alone as an ABI so far.
Later I suspect I'll turn all these flags into a single HK_FLAG_UNBOUND.
Thanks.
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