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Cheng Jian a25ae55390 sched/fair: Optimize select_idle_cpu
commit 60588bfa22 upstream.

select_idle_cpu() will scan the LLC domain for idle CPUs,
it's always expensive. so the next commit :

	1ad3aaf3fc ("sched/core: Implement new approach to scale select_idle_cpu()")

introduces a way to limit how many CPUs we scan.

But it consume some CPUs out of 'nr' that are not allowed
for the task and thus waste our attempts. The function
always return nr_cpumask_bits, and we can't find a CPU
which our task is allowed to run.

Cpumask may be too big, similar to select_idle_core(), use
per_cpu_ptr 'select_idle_mask' to prevent stack overflow.

Fixes: 1ad3aaf3fc ("sched/core: Implement new approach to scale select_idle_cpu()")
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20191213024530.28052-1-cj.chengjian@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-05 16:43:48 +01:00
Documentation kbuild: remove header compile test 2020-03-05 16:43:47 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch KVM: SVM: Override default MMIO mask if memory encryption is enabled 2020-03-05 16:43:48 +01:00
block block, bfq: do not plug I/O for bfq_queues with no proc refs 2020-02-24 08:36:31 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: rename sm3-256 to sm3 in hash_algo_name 2020-02-28 17:22:26 +01:00
drivers mwifiex: delete unused mwifiex_get_intf_num() 2020-03-05 16:43:48 +01:00
fs namei: only return -ECHILD from follow_dotdot_rcu() 2020-03-05 16:43:48 +01:00
include kbuild: remove header compile test 2020-03-05 16:43:47 +01:00
init kbuild: remove header compile test 2020-03-05 16:43:47 +01:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-28 17:22:20 +01:00
kernel sched/fair: Optimize select_idle_cpu 2020-03-05 16:43:48 +01:00
lib kbuild: move headers_check rule to usr/include/Makefile 2020-03-05 16:43:47 +01:00
mm mm: Avoid creating virtual address aliases in brk()/mmap()/mremap() 2020-02-28 17:22:21 +01:00
net net/smc: no peer ID in CLC decline for SMCD 2020-03-05 16:43:47 +01:00
samples samples/bpf: Set -fno-stack-protector when building BPF programs 2020-02-24 08:36:36 +01:00
scripts kbuild: move headers_check rule to usr/include/Makefile 2020-03-05 16:43:47 +01:00
security selinux: ensure we cleanup the internal AVC counters on error in avc_update() 2020-02-24 08:36:39 +01:00
sound ASoC: SOF: Intel: hda: Add iDisp4 DAI 2020-02-28 17:22:29 +01:00
tools selftests: Install settings files to fix TIMEOUT failures 2020-03-05 16:43:47 +01:00
usr kbuild: move headers_check rule to usr/include/Makefile 2020-03-05 16:43:47 +01:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-05 16:43:48 +01:00
.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 ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
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 MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 17:22:19 +01:00
Makefile kbuild: make single target builds even faster 2020-03-05 16:43:48 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.