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The 25% default imbalance threshold for DIE and NUMA domain is large enough to generate significant unfairness between threads. A typical example is the case of 11 threads running on 2x4 CPUs. The imbalance of 20% between the 2 groups of 4 cores is just low enough to not trigger the load balance between the 2 groups. We will have always the same 6 threads on one group of 4 CPUs and the other 5 threads on the other group of CPUS. With a fair time sharing in each group, we ends up with +20% running time for the group of 5 threads. Consider decreasing the imbalance threshold for overloaded case where we use the load to balance task and to ensure fair time sharing. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Phil Auld <pauld@redhat.com> Acked-by: Hillf Danton <hdanton@sina.com> Link: https://lkml.kernel.org/r/20200921072424.14813-3-vincent.guittot@linaro.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.