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The current driver attempts to allocate an interrupt vector per cpu using the systems managed IRQ allocator (flag PCI_IRQ_AFFINITY). The system IRQ allocator will either provide the per-cpu vector, or return fewer vectors. When fewer vectors, they are evenly spread between the numa nodes on the system. When run on an AMD architecture, if interrupts occur to a cpu that is not in the same numa node as the adapter generating the interrupt, there are extreme costs and overheads in performance. Thus, if 1:1 vector allocation is used, or the "balanced" vectors in the other numa nodes, performance can be hit significantly. A much more performant model is to allocate interrupts only on the cpus that are in the numa node where the adapter resides. I/O completion is still performed by the cpu where the I/O was generated. Unfortunately, there is no flag to request the managed IRQ subsystem allocate vectors only for the CPUs in the numa node as the adapter. On AMD architecture, revert the irq allocation to the normal style (non-managed) and then use irq_set_affinity_hint() to set the cpu affinity and disable user-space rebalancing. Tie the support into CPU offline/online. If the cpu being offlined owns a vector, the vector is re-affinitized to one of the other CPUs on the same numa node. If there are no more CPUs on the numa node, the vector has all affinity removed and lets the system determine where it's serviced. Similarly, when the cpu that owned a vector comes online, the vector is reaffinitized to the cpu. Link: https://lore.kernel.org/r/20191105005708.7399-10-jsmart2021@gmail.com Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com> Signed-off-by: James Smart <jsmart2021@gmail.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.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.