Multi-core network packet steering: Difference between revisions

Revision as of 10:22, 10 July 2025

Revision as of 10:28, 10 July 2025

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For this reason many techniques, both in hardware and in software, are leveraged in order to distribute the incoming load of [[Network_packet|packets]] across the cores of the processor.<br>

As shown by the figure beside, packets coming into the [[Network_interface_controller|network interface card (NIC)]] are processed and loaded to the receiving queues managed by the cores (which are usually implemented as [[Circular buffer|ring buffers]] within the [[User space and kernel space|kernel space]]).

The main objective is being able to leverage all the cores available within the CPU to process incoming packets, while also improving performances like [[Latency (engineering)|latency]] and [[Network throughput|throughput]].<ref name="RSS kernel linux docs">{{Cite web|title=RSS kernel linux docs|url=https://www.kernel.org/doc/html/v5.1/networking/scaling.html#rss-receive-side-scaling|access-date=2025-07-08|website=kernel.org|publisher=The Linux Kernel documentation|language=en-US}}</ref><ref name="RFS by redhat">{{Cite web|title=RFS by redhat|url=https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/6/html/performance_tuning_guide/network-rfs|access-date=2025-07-08|website=docs.redhat.com|publisher=Red Hat Documentation|language=en-US}}</ref><ref name="RFS by nvidea">{{Cite web|title=RFS by nvidea|url=https://docs.nvidia.com/networking/display/mlnxofedv23070512/flow+steering|access-date=2025-07-08|website=docs.nvidia.com|publisher=NVIDIA Documentation Hub|language=en-US}}</ref><ref name="RSS overview by microsoft">{{Cite web|title=RSS overview by microsoft|url=https://learn.microsoft.com/en-us/windows-hardware/drivers/network/introduction-to-receive-side-scaling|access-date=2025-07-08|website=learn.microsoft.com|language=en-US}}</ref><ref name="RSS++">{{Cite journal |last=Barbette |first=Tom |last2=Katsikas |first2=Georgios P. |last3=Maguire |first3=Gerald Q. |last4=Kostić |first4=Dejan |date=2019-12-03 |title=RSS++: load and state-aware receive side scaling |url=https://dl.acm.org/doi/10.1145/3359989.3365412 |journal=Proceedings of the 15th International Conference on Emerging Networking Experiments And Technologies |series=CoNEXT '19 |___location=New York, NY, USA |publisher=Association for Computing Machinery |doi=10.1145/3359989.3365412 |isbn=978-1-4503-6998-5}}</ref><ref name="General intro">{{Citation |last=Madden |first=Michael M. |title=Challenges Using the Linux Network Stack for Real-Time Communication |date=2019-01-06 |work=AIAA Scitech 2019 Forum |url=https://arc.aiaa.org/doi/10.2514/6.2019-0503 |access-date=2025-07-10 |series=AIAA SciTech Forum |publisher=American Institute of Aeronautics and Astronautics |doi=10.2514/6.2019-0503 |pages=9-11}}</ref><ref>{{Cite web |last=Herbert |first=Tom |date=2025-02-24 |title=The alphabet soup of receive packet steering: RSS, RPS, RFS, and aRFS |url=https://medium.com/@tom_84912/the-alphabet-soup-of-receive-packet-steering-rss-rps-rfs-and-arfs-c84347156d68 |access-date=2025-07-10 |website=Medium |language=en}}</ref><ref>{{Cite journal |last=Wu |first=Wenji |last2=DeMar |first2=Phil |last3=Crawford |first3=Matt |date=2011-02-01 |title=Why Can Some Advanced Ethernet NICs Cause Packet Reordering? |url=https://ieeexplore.ieee.org/document/5673999/ |journal=IEEE Communications Letters |doi=10.1109/LCOMM.2011.122010.102022 |issn=1558-2558}}</ref>

== Hardware techniques ==

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To do this, after having computed the hash of the header fields for the current packet, the result is used to index a lookup table.

This table is managed by the scheduler, which updates its entries when the application processes are moved between the cores.

The overall CPU load distribution is balanced as long as the applications in [[User space and kernel space|user-space]] are evenly distributed across the multiple cores.<ref name="RFS by redhat">{{Cite web|title=RFS by redhat|url=https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/6/html/performance_tuning_guide/network-rfs|access-date=2025-07-08|website=docs.redhat.com|publisher=Red Hat Documentation|language=en-US}}</ref><ref name="RFS by nvidea">{{Cite web|title=RFS by nvidea|url=https://docs.nvidia.com/networking/display/mlnxofedv23070512/flow+steering|access-date=2025-07-08|website=docs.nvidia.com|publisher=NVIDIA Documentation Hub|language=en-US}}</ref><ref>{{Cite web|title=RFS kernel linux docs|url=https://www.kernel.org/doc/html/v5.1/networking/scaling.html#rfs-receive-flow-steering|access-date=2025-07-08|website=kernel.org|publisher=The Linux Kernel documentation|language=en-US}}</ref>

=== XPS (in transmission) ===