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Jakub Kicinski 8755aae4aa Merge branch 'ipv6-misc-changes-in-output-path'
Eric Dumazet says:

====================
ipv6: misc changes in output path

Small optimizations mostly in ip6_xmit() path.

TX performance increases by about 3 %.

Patches 5-7: add dst4_mtu() and dst6_mtu() to save space.

Last patch colocates inet6_cork in inet_cork_full.

This series reduces kernel size by 494 bytes on x86_64:

scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 4/2 grow/shrink: 9/23 up/down: 665/-1159 (-494)
Function                                     old     new   delta
ip6_finish_output_gso_slowpath_drop            -     197    +197
ip6_xmit                                    1452    1595    +143
do_ipv6_getsockopt                          2855    2950     +95
kzalloc_noprof                                 -      55     +55
ip4ip6_err                                   918     955     +37
__icmp_send                                 1499    1532     +33
do_ip_getsockopt                            2573    2605     +32
__ip6_append_data                           4109    4137     +28
__pfx_kzalloc_noprof                           -      16     +16
__pfx_ip6_finish_output_gso_slowpath_drop       -      16     +16
ipmr_prepare_xmit                           1232    1238      +6
ip6_forward                                 1905    1909      +4
ip6_cork_release                             108     111      +3
ipv6_push_nfrag_opts                         489     486      -3
ipv6_push_frag_opts                           90      87      -3
ip6_finish_output2                          1446    1437      -9
ip6_tnl_xmit                                2639    2627     -12
ip6_default_advmss                           176     160     -16
__ip6_rt_update_pmtu                        1087    1071     -16
tcp_v6_syn_recv_sock                        1715    1696     -19
tcp_v4_syn_recv_sock                        1107    1088     -19
__ip_make_skb                               1339    1320     -19
ip_setup_cork                                406     385     -21
ip6_setup_cork                               732     710     -22
rawv6_push_pending_frames                    581     556     -25
ip6_push_pending_frames                      184     157     -27
udpv6_splice_eof                             203     170     -33
ip6_flush_pending_frames                     220     183     -37
ip6_append_data                              349     312     -37
udp_v6_push_pending_frames                   155     115     -40
sit_tunnel_xmit                             1957    1914     -43
__pfx_dst_mtu                                 64       -     -64
tcp_v4_mtu_reduced                           289     220     -69
tcp_v6_mtu_reduced                           209     139     -70
ip6_make_skb                                 574     484     -90
ip6_finish_output                            827     697    -130
dst_mtu                                      160       -    -160
fib6_nh_mtu_change                           511     336    -175
Total: Before=22584400, After=22583906, chg -0.00%
====================

Link: https://patch.msgid.link/20260130210303.3888261-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
History 2026-02-02 17:49:32 -08:00
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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


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



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