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When a packet arrives in Rx rings, the RX descriptor moves from the used list to the free list. Then, the rxdma ring gets replenished, where the Rx descriptor again moves from the free list to the used list. At the end, the descriptor came to the used list with unnecessary list movement. The descriptor used list is maintained in the Rxdma ring structure, which creates lock contention for the list operations (add, delete) in the Rx data path. Optimize the Rx data path by removing the used list from the common Rxdma ring and maintain as a local variable in the Rx ring handler itself, which avoid lock contention. Now, to find the used list descriptor during descriptor cleanup, we need to check the in_use flag for each Rx descriptor. This is a simple UDP UL throughput test case results on x86+NUC device with QCN9274 card, which clearly shows 8% to 12% improvement in the CPU idle for the same ingress traffic. Before: Average: CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle Average: all 0.24 0.00 12.54 0.08 0.00 23.33 0.00 0.00 0.00 63.81 After: Average: CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle Average: all 0.34 0.00 4.60 0.00 0.00 19.59 0.00 0.00 0.00 75.47 Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1 Signed-off-by: Karthikeyan Periyasamy <quic_periyasa@quicinc.com> Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com> Link: https://msgid.link/20240320010615.91331-3-quic_periyasa@quicinc.com
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.