Dragos Tatulea df5135fced net/mlx5e: SHAMPO, Allow high order pages in zerocopy mode
Allow high order pages only when SHAMPO mode is enabled (hw-gro) and the
queue is used for zerocopy (has memory provider ops set). The limit is
128K and it was chosen for the following reasons:
- 256K size requires a special case during MTT calculation to split the
  page in two. That's because two MTTs are needed to form an octword.
- Higher sizes require increasing WQE size and/or reducing the number
  of WQEs.
- Having the RQ lined with too few large pages can lead to refill
  issues.

Results show an increase in BW and a decrease in CPU usage.
The benchmark was done with the zcrx samples from liburing [0].

rx_buf_len=4K, oncpu [1]:
packets=3358832 (MB=820027), rps=55794 (MB/s=13621)
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle
Average:       9    1.56    0.00   18.09   13.42    0.00   66.80    0.00    0.00    0.00    0.12

rx_buf_len=128K, oncpu [2]:
packets=3781376 (MB=923187), rps=62813 (MB/s=15335)
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle
Average:       9    0.33    0.00    7.61   18.86    0.00   73.08    0.00    0.00    0.00    0.12

rx_buf_len=4K, offcpu [3]:
packets=3460368 (MB=844816), rps=57481 (MB/s=14033)
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle
Average:       9    0.00    0.00    0.26    0.00    0.00   92.63    0.00    0.00    0.00    7.11
Average:      11    3.04    0.00   68.09   28.87    0.00    0.00    0.00    0.00    0.00    0.00

rx_buf_len=128K, offcpu [4]:
packets=4119840 (MB=1005820), rps=68435 (MB/s=16707)
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle
Average:       9    0.00    0.00    0.87    0.00    0.00   63.77    0.00    0.00    0.00   35.36
Average:      11    1.96    0.00   43.68   54.37    0.00    0.00    0.00    0.00    0.00    0.00

[0] https://github.com/isilence/liburing/tree/zcrx/rx-buf-len

[1] commands:
  $> taskset -c 9 ./zcrx 6 -i eth2 -q 9 -A 1 -B 4096 -S 33554432
  $> ./send-zerocopy tcp -6 -D 2001:db8::1 -t 60 -C 0 -l 1 -b 1 -n 1 -z 1 -d -s 256000

[2] commands:
  $> taskset -c 9 ./zcrx 6 -i eth2 -q 9 -A 1 -B 131072 -S 33554432
  $> ./send-zerocopy tcp -6 -D 2001:db8::1 -t 60 -C 0 -l 1 -b 1 -n 1 -z 1 -d -s 256000

[3] commands:
  $> taskset -c 11 ./zcrx 6 -i eth2 -q 9 -A 1 -B 4096 -S 33554432
  $> ./send-zerocopy tcp -6 -D 2001:db8::1 -t 60 -C 0 -l 1 -b 1 -n 1 -z 1 -d -s 256000

[4] commands:
  $> taskset -c 11 ./zcrx 6 -i eth2 -q 9 -A 1 -B 131072 -S 33554432
  $> ./send-zerocopy tcp -6 -D 2001:db8::1 -t 60 -C 0 -l 1 -b 1 -n 1 -z 1 -d -s 256000

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260223204155.1783580-16-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2026-02-26 10:54:24 +01:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +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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