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Christian Loehle b39b62075a cpuidle: menu: Remove iowait influence 
[ Upstream commit 38f83090f5 ]

Remove CPU iowaiters influence on idle state selection.

Remove the menu notion of performance multiplier which increased with
the number of tasks that went to iowait sleep on this CPU and haven't
woken up yet.

Relying on iowait for cpuidle is problematic for a few reasons:

 1. There is no guarantee that an iowaiting task will wake up on the
    same CPU.

 2. The task being in iowait says nothing about the idle duration, we
    could be selecting shallower states for a long time.

 3. The task being in iowait doesn't always imply a performance hit
    with increased latency.

 4. If there is such a performance hit, the number of iowaiting tasks
    doesn't directly correlate.

 5. The definition of iowait altogether is vague at best, it is
    sprinkled across kernel code.

Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20240905092645.2885200-2-christian.loehle@arm.com
[ rjw: Minor edits in the changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Stable-dep-of: 779b1a1cb1 ("cpuidle: governors: menu: Avoid selecting states with too much latency")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-08-28 16:31:08 +02:00
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README 

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 reStructuredText 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.