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Odin Ugedal 1c35b07e6d sched/fair: Ensure _sum and _avg values stay consistent
The _sum and _avg values are in general sync together with the PELT
divider. They are however not always completely in perfect sync,
resulting in situations where _sum gets to zero while _avg stays
positive. Such situations are undesirable.

This comes from the fact that PELT will increase period_contrib, also
increasing the PELT divider, without updating _sum and _avg values to
stay in perfect sync where (_sum == _avg * divider). However, such PELT
change will never lower _sum, making it impossible to end up in a
situation where _sum is zero and _avg is not.

Therefore, we need to ensure that when subtracting load outside PELT,
that when _sum is zero, _avg is also set to zero. This occurs when
(_sum < _avg * divider), and the subtracted (_avg * divider) is bigger
or equal to the current _sum, while the subtracted _avg is smaller than
the current _avg.

Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Link: https://lore.kernel.org/r/20210624111815.57937-1-odin@uged.al
2021-06-28 15:42:24 +02:00
arch sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
block sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto async_xor: check src_offs is not NULL before updating it 2021-06-10 19:40:14 -07:00
Documentation sched/doc: Update the CPU capacity asymmetry bits 2021-06-24 09:07:51 +02:00
drivers sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
fs sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
include sched/core: Introduce SD_ASYM_CPUCAPACITY_FULL sched_domain flag 2021-06-24 09:07:50 +02:00
init sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel sched/fair: Ensure _sum and _avg values stay consistent 2021-06-28 15:42:24 +02:00
lib sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm sched: Introduce task_is_running() 2021-06-18 11:43:07 +02:00
net sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
samples VFIO fixes for v5.13-rc5 2021-06-03 11:52:24 -07:00
scripts kbuild: Quote OBJCOPY var to avoid a pahole call break the build 2021-05-27 11:32:56 -07:00
security trusted-keys: match tpm_get_ops on all return paths 2021-05-12 22:36:37 +03:00
sound sound fixes for 5.13-rc6 2021-06-11 10:47:10 -07:00
tools Merge branch 'sched/urgent' into sched/core, to resolve conflicts 2021-06-18 11:31:25 +02:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt sched,perf,kvm: Fix preemption condition 2021-06-18 11:43:07 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: use private address for Michel Lespinasse 2021-06-05 08:58:12 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS USB fixes for 5.13-rc6 2021-06-12 12:34:49 -07:00
Makefile Linux 5.13-rc6 2021-06-13 14:43:10 -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.