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Tejun Heo 7cd806a9a9 iocost: improve nr_lagging handling
Some IOs may span multiple periods.  As latencies are collected on
completion, the inbetween periods won't register them and may
incorrectly decide to increase vrate.  nr_lagging tracks these IOs to
avoid those situations.  Currently, whenever there are IOs which are
spanning from the previous period, busy_level is reset to 0 if
negative thus suppressing vrate increase.

This has the following two problems.

* When latency target percentiles aren't set, vrate adjustment should
  only be governed by queue depth depletion; however, the current code
  keeps nr_lagging active which pulls in latency results and can keep
  down vrate unexpectedly.

* When lagging condition is detected, it resets the entire negative
  busy_level.  This turned out to be way too aggressive on some
  devices which sometimes experience extended latencies on a small
  subset of commands.  In addition, a lagging IO will be accounted as
  latency target miss on completion anyway and resetting busy_level
  amplifies its impact unnecessarily.

This patch fixes the above two problems by disabling nr_lagging
counting when latency target percentiles aren't set and blocking vrate
increases when there are lagging IOs while leaving busy_level as-is.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-09-26 01:12:00 -06:00
arch Merge branch 'akpm' (patches from Andrew) 2019-09-24 16:10:23 -07:00
block iocost: improve nr_lagging handling 2019-09-26 01:12:00 -06:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto - crypto and DM crypt advances that allow the crypto API to reclaim 2019-09-21 10:40:37 -07:00
Documentation The highlights are: 2019-09-25 10:21:13 -07:00
drivers The highlights are: 2019-09-25 10:21:13 -07:00
fs The highlights are: 2019-09-25 10:21:13 -07:00
include The highlights are: 2019-09-25 10:21:13 -07:00
init mm: use CPU_BITS_NONE to initialize init_mm.cpu_bitmask 2019-09-24 15:54:10 -07:00
ipc Merge branch 'work.mount-base' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-09-18 13:15:58 -07:00
kernel Merge branch 'akpm' (patches from Andrew) 2019-09-24 16:10:23 -07:00
lib mm: remove quicklist page table caches 2019-09-24 15:54:09 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/zsmalloc.c: fix a -Wunused-function warning 2019-09-24 15:54:12 -07:00
net The highlights are: 2019-09-25 10:21:13 -07:00
samples rpmsg updates for v5.4 2019-09-22 10:58:15 -07:00
scripts Modules updates for v5.4 2019-09-22 10:34:46 -07:00
security KEYS: trusted: correctly initialize digests and fix locking issue 2019-09-25 02:43:53 +03:00
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tools tpmdd fixes for Linux v5.4 2019-09-25 09:40:24 -07:00
usr kbuild: clean compressed initramfs image 2019-09-24 15:54:07 -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
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.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 tpmdd fixes for Linux v5.4 2019-09-25 09:40:24 -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.