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Íñigo Huguet says: ==================== sfc: optimize RXQs count and affinities In sfc driver one RX queue per physical core was allocated by default. Later on, IRQ affinities were set spreading the IRQs in all NUMA local CPUs. However, with that default configuration it result in a non very optimal configuration in many modern systems. Specifically, in systems with hyper threading and 2 NUMA nodes, affinities are set in a way that IRQs are handled by all logical cores of one same NUMA node. Handling IRQs from both hyper threading siblings has no benefit, and setting affinities to one queue per physical core is neither a very good idea because there is a performance penalty for moving data across nodes (I was able to check it with some XDP tests using pktgen). This patches reduce the default number of channels to one per physical core in the local NUMA node. Then, they set IRQ affinities to CPUs in the local NUMA node only. This way we save hardware resources since channels are limited resources. We also leave more room for XDP_TX channels without hitting driver's limit of 32 channels per interface. Running performance tests using iperf with a SFC9140 device showed no performance penalty for reducing the number of channels. RX XDP tests showed that performance can go down to less than half if the IRQ is handled by a CPU in a different NUMA node, which doesn't happen with the new defaults from this patches. ==================== Link: https://lore.kernel.org/r/20220228132254.25787-1-ihuguet@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
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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 Restructured Text 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.