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When a user changes cpuset.cpus, each task in a v2 cpuset will be moved to one of the new cpus if it is not there already. For memory, however, they won't be migrated to the new nodes when cpuset.mems changes. This is an inconsistency in behavior. In cpuset v1, there is a memory_migrate control file to enable such behavior by setting the CS_MEMORY_MIGRATE flag. Make it the default for cpuset v2 so that we have a consistent set of behavior for both cpus and memory. There is certainly a cost to make memory migration the default, but it is a one time cost that shouldn't really matter as long as cpuset.mems isn't changed frequenty. Update the cgroup-v2.rst file to document the new behavior and recommend against changing cpuset.mems frequently. Since there won't be any concurrent access to the newly allocated cpuset structure in cpuset_css_alloc(), we can use the cheaper non-atomic __set_bit() instead of the more expensive atomic set_bit(). Signed-off-by: Waiman Long <longman@redhat.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> 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 Restructured Text 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.