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Affining kthreads follow either of four existing different patterns: 1) Per-CPU kthreads must stay affine to a single CPU and never execute relevant code on any other CPU. This is currently handled by smpboot code which takes care of CPU-hotplug operations. 2) Kthreads that _have_ to be affine to a specific set of CPUs and can't run anywhere else. The affinity is set through kthread_bind_mask() and the subsystem takes care by itself to handle CPU-hotplug operations. 3) Kthreads that prefer to be affine to a specific NUMA node. That preferred affinity is applied by default when an actual node ID is passed on kthread creation, provided the kthread is not per-CPU and no call to kthread_bind_mask() has been issued before the first wake-up. 4) Similar to the previous point but kthreads have a preferred affinity different than a node. It is set manually like any other task and CPU-hotplug is supposed to be handled by the relevant subsystem so that the task is properly reaffined whenever a given CPU from the preferred affinity comes up. Also care must be taken so that the preferred affinity doesn't cross housekeeping cpumask boundaries. Provide a function to handle the last usecase, mostly reusing the current node default affinity infrastructure. kthread_affine_preferred() is introduced, to be used just like kthread_bind_mask(), right after kthread creation and before the first wake up. The kthread is then affine right away to the cpumask passed through the API if it has online housekeeping CPUs. Otherwise it will be affine to all online housekeeping CPUs as a last resort. As with node affinity, it is aware of CPU hotplug events such that: * When a housekeeping CPU goes up that is part of the preferred affinity of a given kthread, the related task is re-affined to that preferred affinity if it was previously running on the default last resort online housekeeping set. * When a housekeeping CPU goes down while it was part of the preferred affinity of a kthread, the running task is migrated (or the sleeping task is woken up) automatically by the scheduler to other housekeepers within the preferred affinity or, as a last resort, to all housekeepers from other nodes. Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> |
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| .clang-format | ||
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| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.