Linux kernel source tree
Find a file
Srinivas Pandruvada 1a4fe38add cpufreq: intel_pstate: Remove max/min fractions to limit performance
In the current model the max/min perf limits are a fraction of current
user space limits to the allowed max_freq or 100% for global limits.
This results in wrong ratio limits calculation because of rounding
issues for some user space limits.

Initially we tried to solve this issue by issue by having more shift
bits to increase precision. Still there are isolated cases where we still
have error.

This can be avoided by using ratios all together. Since the way we get
cpuinfo.max_freq is by multiplying scaling factor to max ratio, we can
easily keep the max/min ratios in terms of ratios and not fractions.

For example:
if the max ratio = 36
cpuinfo.max_freq = 36 * 100000 = 3600000

Suppose user space sets a limit of 1200000, then we can calculate
max ratio limit as
= 36 * 1200000 / 3600000
= 12
This will be correct for any user limits.

The other advantage is that, we don't need to do any calculation in the
fast path as ratio limit is already calculated via set_policy() callback.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2017-06-24 01:48:12 +02:00
arch x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz" 2017-06-24 01:45:47 +02:00
block
certs
crypto
Documentation mm: larger stack guard gap, between vmas 2017-06-19 21:50:20 +08:00
drivers cpufreq: intel_pstate: Remove max/min fractions to limit performance 2017-06-24 01:48:12 +02:00
firmware
fs mm: larger stack guard gap, between vmas 2017-06-19 21:50:20 +08:00
include mm: larger stack guard gap, between vmas 2017-06-19 21:50:20 +08:00
init
ipc
kernel
lib
mm mm: larger stack guard gap, between vmas 2017-06-19 21:50:20 +08:00
net
samples
scripts
security
sound
tools
usr
virt
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 4.12-rc6 2017-06-19 22:19:37 +08:00
README

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.