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Khazhismel Kumykov f20426056f dm mpath selector: more evenly distribute ties
Move the last used path to the end of the list (least preferred) so that
ties are more evenly distributed.

For example, in case with three paths with one that is slower than
others, the remaining two would be unevenly used if they tie. This is
due to the rotation not being a truely fair distribution.

Illustrated: paths a, b, c, 'c' has 1 outstanding IO, a and b are 'tied'
Three possible rotations:
(a, b, c) -> best path 'a'
(b, c, a) -> best path 'b'
(c, a, b) -> best path 'a'
(a, b, c) -> best path 'a'
(b, c, a) -> best path 'b'
(c, a, b) -> best path 'a'
...

So 'a' is used 2x more than 'b', although they should be used evenly.

With this change, the most recently used path is always the least
preferred, removing this bias resulting in even distribution.
(a, b, c) -> best path 'a'
(b, c, a) -> best path 'b'
(c, a, b) -> best path 'a'
(c, b, a) -> best path 'b'
...

Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Reviewed-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2018-01-29 13:44:58 -05:00
Documentation dm thin: extend thinpool status format string with omitted fields 2018-01-17 09:16:12 -05:00
arch Merge branch 'fixes' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-12-03 10:51:08 -05:00
block Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-12-01 08:05:45 -05:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-11-28 16:22:10 -08:00
drivers dm mpath selector: more evenly distribute ties 2018-01-29 13:44:58 -05:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs NFS client fixes for Linux 4.15-rc2 2017-12-01 20:04:20 -05:00
include dm mpath: delay the retry of a request if the target responded as busy 2018-01-29 13:44:54 -05:00
init EXPERT Kconfig menu: fix broken EXPERT menu 2017-11-17 16:10:05 -08:00
ipc Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
kernel Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-12-01 08:05:45 -05:00
lib RISC-V Cleanups and ABI Fixes for 4.15-rc2 2017-12-01 19:39:12 -05:00
mm Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-12-01 08:05:45 -05:00
net NFS client fixes for Linux 4.15-rc2 2017-12-01 20:04:20 -05:00
samples kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
scripts Merge branch 'akpm' (patches from Andrew) 2017-11-29 19:12:44 -08:00
security bug fixes: 2017-11-30 18:56:41 -05:00
sound Revert "ALSA: usb-audio: Fix potential zero-division at parsing FU" 2017-11-28 09:34:36 -08:00
tools Power management fixes for v4.15-rc2 2017-11-30 18:45:55 -05:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt * x86 bugfixes: APIC, nested virtualization, IOAPIC 2017-11-30 08:15:19 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild misc updates for v4.15 2017-11-17 17:51:33 -08:00
.mailmap Add Jason Gunthorpe as co-maintainer of the RDMA stack 2017-11-17 09:36:18 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS hwmon fixes for v4.15-rc2 2017-12-03 10:46:16 -05:00
Makefile Linux 4.15-rc2 2017-12-03 11:01:47 -05:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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.