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Vincent Guittot 6cf82d559e sched/cfs: fix spurious active migration
The load balance can fail to find a suitable task during the periodic check
because  the imbalance is smaller than half of the load of the waiting
tasks. This results in the increase of the number of failed load balance,
which can end up to start an active migration. This active migration is
useless because the current running task is not a better choice than the
waiting ones. In fact, the current task was probably not running but
waiting for the CPU during one of the previous attempts and it had already
not been selected.

When load balance fails too many times to migrate a task, we should relax
the contraint on the maximum load of the tasks that can be migrated
similarly to what is done with cache hotness.

Before the rework, load balance used to set the imbalance to the average
load_per_task in order to mitigate such situation. This increased the
likelihood of migrating a task but also of selecting a larger task than
needed while more appropriate ones were in the list.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/1575036287-6052-1-git-send-email-vincent.guittot@linaro.org
2019-12-17 13:32:48 +01:00
arch ARM fixes for 5.5-rc: 2019-12-06 16:12:39 -08:00
block block: fix memleak of bio integrity data 2019-12-05 11:38:36 -07:00
certs
crypto
Documentation powerpc updates for 5.5 #2 2019-12-06 13:36:31 -08:00
drivers Thermal material for -rc2 2019-12-09 10:59:00 -08:00
fs sched/cputime, proc/stat: Fix incorrect guest nice cpustat value 2019-12-11 07:09:58 +01:00
include pr_warning() removal for 5.5 2019-12-09 11:48:21 -08:00
init init/Kconfig: fix indentation 2019-12-04 19:44:13 -08:00
ipc
kernel sched/cfs: fix spurious active migration 2019-12-17 13:32:48 +01:00
lib lib/: fix Kconfig indentation 2019-12-07 11:00:19 -08:00
LICENSES
mm Merge branch 'akpm' (patches from Andrew) 2019-12-05 09:46:26 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
samples samples/bpf: Fix broken xdp_rxq_info due to map order assumptions 2019-12-04 17:54:15 -08:00
scripts pr_warning() removal for 5.5 2019-12-09 11:48:21 -08:00
security + Features 2019-12-03 12:51:35 -08:00
sound sound updates #2 for 5.5-rc1 2019-12-06 13:06:14 -08:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-08 13:28:11 -08:00
usr arch: sembuf.h: make uapi asm/sembuf.h self-contained 2019-12-04 19:44:14 -08:00
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore
.mailmap Merge mainline/master into arm/fixes 2019-12-05 13:18:54 -08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Thermal material for -rc2 2019-12-09 10:59:00 -08:00
Makefile Linux 5.5-rc1 2019-12-08 14:57:55 -08:00
README

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.