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Pierre Gondois 390eb5433e sched/fair: Check if prev_cpu has highest spare cap in feec()
[ Upstream commit ad841e569f ]

When evaluating the CPU candidates in the perf domain (pd) containing
the previously used CPU (prev_cpu), find_energy_efficient_cpu()
evaluates the energy of the pd:
- without the task (base_energy)
- with the task placed on prev_cpu (if the task fits)
- with the task placed on the CPU with the highest spare capacity,
  prev_cpu being excluded from this set

If prev_cpu is already the CPU with the highest spare capacity,
max_spare_cap_cpu will be the CPU with the second highest spare
capacity.

On an Arm64 Juno-r2, with a workload of 10 tasks at a 10% duty cycle,
when prev_cpu and max_spare_cap_cpu are both valid candidates,
prev_spare_cap > max_spare_cap at ~82%.
Thus the energy of the pd when placing the task on max_spare_cap_cpu
is computed with no possible positive outcome 82% most of the time.

Do not consider max_spare_cap_cpu as a valid candidate if
prev_spare_cap > max_spare_cap.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20221006081052.3862167-2-pierre.gondois@arm.com
Stable-dep-of: e26fd28db8 ("sched/uclamp: Fix a uninitialized variable warnings")
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-02-01 08:34:36 +01:00
Documentation docs: Fix path paste-o for /sys/kernel/warn_count 2023-01-24 07:24:41 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
arch arm64: efi: Account for the EFI runtime stack in stack unwinder 2023-02-01 08:34:35 +01:00
block block: mq-deadline: Rename deadline_is_seq_writes() 2023-01-24 07:24:44 +01:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto crypto: tcrypt - Fix multibuffer skcipher speed test mem leak 2022-12-31 13:32:34 +01:00
drivers drm/amdgpu: complete gfxoff allow signal during suspend without delay 2023-02-01 08:34:35 +01:00
fs btrfs: zoned: enable metadata over-commit for non-ZNS setup 2023-02-01 08:34:34 +01:00
include wifi: mac80211: Proper mark iTXQs for resumption 2023-02-01 08:34:35 +01:00
init gcc: disable -Warray-bounds for gcc-11 too 2023-01-14 10:33:43 +01:00
io_uring io_uring/msg_ring: fix remote queue to disabled ring 2023-02-01 08:34:35 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel sched/fair: Check if prev_cpu has highest spare cap in feec() 2023-02-01 08:34:36 +01:00
lib lockref: stop doing cpu_relax in the cmpxchg loop 2023-02-01 08:34:34 +01:00
mm panic: Consolidate open-coded panic_on_warn checks 2023-01-24 07:24:41 +01:00
net wifi: mac80211: Fix iTXQ AMPDU fragmentation handling 2023-02-01 08:34:36 +01:00
rust Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
samples samples: vfio-mdev: Fix missing pci_disable_device() in mdpy_fb_probe() 2022-12-31 13:32:42 +01:00
scripts - Handle different output of readelf on different distros running 2022-11-27 12:08:17 -08:00
security tomoyo: fix broken dependency on *.conf.default 2023-02-01 08:34:06 +01:00
sound ASoC: fsl-asoc-card: Fix naming of AC'97 CODEC widgets 2023-02-01 08:34:31 +01:00
tools Revert "selftests/bpf: check null propagation only neither reg is PTR_TO_BTF_ID" 2023-02-01 08:34:34 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt Merge branch 'kvm-dwmw2-fixes' into HEAD 2022-11-23 18:59:45 -05:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS panic: Expose "warn_count" to sysfs 2023-01-24 07:24:41 +01:00
Makefile kbuild: fix 'make modules' error when CONFIG_DEBUG_INFO_BTF_MODULES=y 2023-02-01 08:34:08 +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.