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When load balancing in a system with misfit tasks present, if we always pull a misfit task to the local group this can lead to pulling a running task from a smaller capacity CPUs to a bigger CPU which is busy. In this situation, the pulled task is likely not to get a chance to run before an idle balance on another small CPU pulls it back. This penalises the pulled task as it is stopped for a short amount of time and then likely relocated to a different CPU (since the original CPU just did a NEWLY_IDLE balance and reset the periodic interval). If we only do this unconditionally for NEWLY_IDLE balance, we can be sure that any tasks and load which are present on the local group are related to short-running tasks which we are happy to displace for a longer running task in a system with misfit tasks present. However, other balance types should only pull a task if we think that the local group is underutilized - checking the number of tasks gives us a conservative estimate here since if they were short tasks we would have been doing NEWLY_IDLE balances instead. Change-Id: I710add1ab1139482620b6addc8370ad194791beb Signed-off-by: Chris Redpath <chris.redpath@arm.com> Signed-off-by: Quentin Perret <quentin.perret@arm.com>
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.