Linus Torvalds e2457a664e Merge tag 'sched-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
 "Load-balancing updates:

   - 'flatten the pick': improve cgroup scheduling, which has always
     been problematic and painful, which has caused various scheduling
     misbehavior such as the mishandling of reniced tasks et al.

     Add various cgroup weight distribution methods via cgroup_mode:
     'up', 'max', 'concur' and 'tasks' - with the default being 'concur'
     which is the most precise yet also most expensive version.

     Finally, change cgroup scheduling to a single runqueue (Peter
     Zijlstra)

   - Series to improve the scheduling latency of short slice tasks
     (Vincent Guittot)

   - Series to fix cluster scheduling in the presence of asymmetric
     capacity (Ricardo Neri)

   - Prefer fully idle cores for NOHZ balancing (Andrea Righi)

   - Don't trigger active load-balancing if src_rq->curr is not on_rq
     (Xin Zhao)

  PSI updates:

   - Skip irqtime accounting when no new irq time has elapsed (Usama
     Arif)

  Scheduler debugging updates:

   - Remove unused schedstats (Shrikanth Hegde)

   - Defer freeing of cpumask memblock memory to initcall (Waiman Long)

  Misc fixes and updates by Yu C Chen, K Prateek Nayak, Peter Zijlstra,
  Vincent Guittot, Xin Zhao, Yury Norov, Zhan Xusheng"

* tag 'sched-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
  sched/fair: Fix flat hierarchy
  sched/isolation: Defer freeing of cpumask memblock memory to initcall
  sched/topology: Restore SD_PREFER_SIBLING in domains with asymmetric capacity
  sched/fair: Allow load balancing between CPUs of identical capacity
  sched/fair: Skip misfit load accounting when the destination CPU cannot help
  sched/fair: Check CPU capacity before comparing group types during load balance
  sched/fair: Also gate overloaded status update for SD_ASYM_CPUCAPACITY
  sched/fair: Do not skip CPUs of similar capacity with busy SMT siblings
  sched/fair: Prefer fully idle cores for NOHZ balancing
  stop_machine: Make stop_one_cpu_nowait() return void
  sched/eevdf: Delayed dequeue task can't preempt
  sched/fair: Fix stale comments referring to removed CFS concepts
  sched/debug: Remove unused schedstats
  sched/psi: skip irqtime accounting when no new irq time has elapsed
  sched/fair: Reflow sched_balance_rq()
  sched/fair: Simplify balance_interval reset logic in sched_balance_rq()
  sched/fair: Don't trigger active lb if src_rq->curr is not on_rq
  sched/eevdf: Speedup short slice task scheduling
  sched/eevdf: Always update slice protection
  sched/eevdf: Cancel slice protection if short slice task is eligible
  ...
2026-08-18 13:39:48 -07:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2026-07-14 16:34:04 +02:00
2025-02-19 14:53:27 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst
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