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Felix Fietkau b1103d2567 mac80211: minstrel_ht: replace rate stats ewma with a better moving average
Rate success probability usually fluctuates a lot under normal conditions.
With a simple EWMA, noise and fluctuation can be reduced by increasing the
window length, but that comes at the cost of introducing lag on sudden
changes.

This change replaces the EWMA implementation with a moving average that's
designed to significantly reduce lag while keeping a bigger window size
by being better at filtering out noise.

It is only slightly more expensive than the simple EWMA and still avoids
divisions in its calculation.

The algorithm is adapted from an implementation intended for a completely
different field (stock market trading), where the tradeoff of lag vs
noise filtering is equally important. It is based on the "smoothing filter"
from http://www.stockspotter.com/files/PredictiveIndicators.pdf.

I have adapted it to fixed-point math with some constants so that it uses
only addition, bit shifts and multiplication

To better make use of the filtering and bigger window size, the update
interval time is cut in half.

For testing, the algorithm can be reverted to the older one via debugfs

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20191008171139.96476-2-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
History 2019-10-11 10:31:32 +02:00
arch powerpc fixes for 5.4 #2 2019-09-28 13:43:00 -07:00
block block: fix null pointer dereference in blk_mq_rq_timed_out() 2019-09-27 07:01:25 -06:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
Documentation dt-bindings: sh_eth convert bindings to json-schema 2019-10-01 15:31:33 -07:00
drivers mac80211: simplify TX aggregation start 2019-10-04 13:58:13 +02:00
fs Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-09-28 12:39:07 -07:00
include mac80211: simplify TX aggregation start 2019-10-04 13:58:13 +02:00
init init: Support mounting root file systems over SMB 2019-10-02 12:15:15 -04:00
ipc ipc/sem.c: convert to use built-in RCU list checking 2019-09-25 17:51:41 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-09-28 17:47:33 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-09-28 17:47:33 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'hugepage-fallbacks' (hugepatch patches from David Rientjes) 2019-09-28 14:26:47 -07:00
net mac80211: minstrel_ht: replace rate stats ewma with a better moving average 2019-10-11 10:31:32 +02:00
samples rpmsg updates for v5.4 2019-09-22 10:58:15 -07:00
scripts Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2019-09-27 19:37:27 -07:00
security net: rtnetlink: add linkprop commands to add and delete alternative ifnames 2019-10-01 14:47:19 -07:00
sound sound fixes for 5.4-rc1 2019-09-24 16:46:16 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-09-28 17:47:33 -07:00
usr Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-09-28 17:47:33 -07:00
virt * s390: ioctl hardening, selftests 2019-09-18 09:49:13 -07:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2019-09-18 12:34:53 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS CREDITS: Update email address 2019-09-13 17:21:38 +03:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS dt-bindings: sh_eth convert bindings to json-schema 2019-10-01 15:31:33 -07:00
Makefile Modules updates for v5.4 2019-09-22 10:34:46 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.