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Many scx schedulers implement their own hard or soft-affinity rules to support topology characteristics, such as heterogeneous architectures (e.g., big.LITTLE, P-cores/E-cores), or to categorize tasks based on specific properties (e.g., running certain tasks only in a subset of CPUs). Currently, there is no mechanism that allows to use the built-in idle CPU selection policy to an arbitrary subset of CPUs. As a result, schedulers often implement their own idle CPU selection policies, which are typically similar to one another, leading to a lot of code duplication. To address this, modify scx_select_cpu_dfl() to accept an arbitrary cpumask, that can be used by the BPF schedulers to apply the existent built-in idle CPU selection policy to a subset of allowed CPUs. With this concept the idle CPU selection policy becomes the following: - always prioritize CPUs from fully idle SMT cores (if SMT is enabled), - select the same CPU if it's idle and in the allowed CPUs, - select an idle CPU within the same LLC, if the LLC cpumask is a subset of the allowed CPUs, - select an idle CPU within the same node, if the node cpumask is a subset of the allowed CPUs, - select an idle CPU within the allowed CPUs. This functionality will be exposed through a dedicated kfunc in a separate patch. Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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.