Thomas Gleixner ae67badaa1 hrtimer: Optimize the hrtimer code by using static keys for migration_enable/nohz_active
The hrtimer_cpu_base::migration_enable and ::nohz_active fields
were originally introduced to avoid accessing global variables
for these decisions.

Still that results in a (cache hot) load and conditional branch,
which can be avoided by using static keys.

Implement it with static keys and optimize for the most critical
case of high performance networking which tends to disable the
timer migration functionality.

No change in functionality.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: keescook@chromium.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1801142327490.2371@nanos
Link: https://lkml.kernel.org/r/20171221104205.7269-2-anna-maria@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-01-16 02:35:44 +01:00
2017-12-20 11:10:17 -07:00
2017-12-31 14:47:43 -08:00

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.
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