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Nadav noticed that the cpumask allocations in native_send_call_func_ipi() are noticeable in microbenchmarks. Use the new cpumask_or_equal() function to simplify the decision whether the supplied target CPU mask is either equal to cpu_online_mask or equal to cpu_online_mask except for the CPU on which the function is invoked. cpumask_or_equal() or's the target mask and the cpumask of the current CPU together and compares it to cpu_online_mask. If the result is false, use the mask based IPI function, otherwise check whether the current CPU is set in the target mask and invoke either the send_IPI_all() or the send_IPI_allbutselt() APIC callback. Make the shorthand decision also depend on the static key which enables shorthand mode. That allows to remove the extra cpumask comparison with cpu_callout_mask. Reported-by: Nadav Amit <namit@vmware.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190722105220.768238809@linutronix.de
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.