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Hao Jia 873199d27b sched/core: Prioritize migrating eligible tasks in sched_balance_rq()
When the PLACE_LAG scheduling feature is enabled and
dst_cfs_rq->nr_queued is greater than 1, if a task is
ineligible (lag < 0) on the source cpu runqueue, it will
also be ineligible when it is migrated to the destination
cpu runqueue. Because we will keep the original equivalent
lag of the task in place_entity(). So if the task was
ineligible before, it will still be ineligible after
migration.

So in sched_balance_rq(), we prioritize migrating eligible
tasks, and we soft-limit ineligible tasks, allowing them
to migrate only when nr_balance_failed is non-zero to
avoid load-balancing trying very hard to balance the load.

Below are some benchmark test results. From my test results,
this patch shows a slight improvement on hackbench.

Benchmark
=========

All of the benchmarks are done inside a normal cpu cgroup in a
clean environment with cpu turbo disabled, and test machine is:

Single NUMA machine model is 13th Gen Intel(R) Core(TM)
i7-13700, 12 Core/24 HT.

Based on master b86545e02e.

Results
=======

hackbench-process-pipes
                      vanilla                  patched
Amean     1       0.5837 (   0.00%)      0.5733 (   1.77%)
Amean     4       1.4423 (   0.00%)      1.4503 (  -0.55%)
Amean     7       2.5147 (   0.00%)      2.4773 (   1.48%)
Amean     12      3.9347 (   0.00%)      3.8880 (   1.19%)
Amean     21      5.3943 (   0.00%)      5.3873 (   0.13%)
Amean     30      6.7840 (   0.00%)      6.6660 (   1.74%)
Amean     48      9.8313 (   0.00%)      9.6100 (   2.25%)
Amean     79     15.4403 (   0.00%)     14.9580 (   3.12%)
Amean     96     18.4970 (   0.00%)     17.9533 (   2.94%)

hackbench-process-sockets
                      vanilla                  patched
Amean     1       0.6297 (   0.00%)      0.6223 (   1.16%)
Amean     4       2.1517 (   0.00%)      2.0887 (   2.93%)
Amean     7       3.6377 (   0.00%)      3.5670 (   1.94%)
Amean     12      6.1277 (   0.00%)      5.9290 (   3.24%)
Amean     21     10.0380 (   0.00%)      9.7623 (   2.75%)
Amean     30     14.1517 (   0.00%)     13.7513 (   2.83%)
Amean     48     24.7253 (   0.00%)     24.2287 (   2.01%)
Amean     79     43.9523 (   0.00%)     43.2330 (   1.64%)
Amean     96     54.5310 (   0.00%)     53.7650 (   1.40%)

tbench4 Throughput
                      vanilla                  patched
Hmean     1       255.97 (   0.00%)      275.01 (   7.44%)
Hmean     2       511.60 (   0.00%)      544.27 (   6.39%)
Hmean     4       996.70 (   0.00%)     1006.57 (   0.99%)
Hmean     8      1646.46 (   0.00%)     1649.15 (   0.16%)
Hmean     16     2259.42 (   0.00%)     2274.35 (   0.66%)
Hmean     32     4725.48 (   0.00%)     4735.57 (   0.21%)
Hmean     64     4411.47 (   0.00%)     4400.05 (  -0.26%)
Hmean     96     4284.31 (   0.00%)     4267.39 (  -0.39%)

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Hao Jia <jiahao1@lixiang.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20241223091446.90208-1-jiahao.kernel@gmail.com
History 2025-01-13 14:10:23 +01:00
arch i2c-for-6.13-rc1-part3 2024-12-01 13:38:24 -08:00
block block-6.13-20242901 2024-11-30 15:47:29 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Random number generator updates for Linux 6.13-rc1. 2024-11-19 10:43:44 -08:00
Documentation docs: Update Schedstat version to 17 2024-12-20 15:31:18 +01:00
drivers i2c-for-6.13-rc1-part3 2024-12-01 13:38:24 -08:00
fs This pull request contains the following changes for UML: 2024-11-30 10:34:54 -08:00
include sched: Move sched domain name out of CONFIG_SCHED_DEBUG 2024-12-20 15:31:17 +01:00
init - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
io_uring io_uring-6.13-20242901 2024-11-30 15:43:02 -08:00
ipc - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
kernel sched/core: Prioritize migrating eligible tasks in sched_balance_rq() 2025-01-13 14:10:23 +01:00
lib vsnprintf: Removal of bprintf() 2024-12-01 13:10:51 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm Kbuild updates for v6.13 2024-11-30 13:41:50 -08:00
net 9p update for 6.13-rc1 2024-11-30 10:28:14 -08:00
rust block-6.13-20242901 2024-11-30 15:47:29 -08:00
samples TTY / Serial driver updates for 6.13-rc1 2024-11-30 09:03:16 -08:00
scripts Kbuild updates for v6.13 2024-11-30 13:41:50 -08:00
security lsm/stable-6.13 PR 20241129 2024-11-30 18:14:56 -08:00
sound sound fixes for 6.13-rc1 2024-11-29 13:01:05 -08:00
tools turbostat version 2024.11.30 2024-11-30 18:30:22 -08:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt VFIO updates for v6.13 2024-11-27 12:57:03 -08:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2024-10-07 21:39:57 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.13 2024-11-30 13:41:50 -08:00
.mailmap media updates for v6.13-rc1 2024-11-20 14:01:15 -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 cgroup: Changes for v6.13 2024-11-20 09:54:49 -08:00
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 i2c-for-6.13-rc1-part3 2024-12-01 13:38:24 -08:00
Makefile Linux 6.13-rc1 2024-12-01 14:28:56 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.