138badbc21
This driver was using the TX IRQ handler to perform all TX completion tasks. Under heavy TX network load, this can cause significant irqs-off latencies (found to be in the hundreds of microseconds using ftrace). This can cause other issues, such as overrunning serial UART FIFOs when using high baud rates with limited UART FIFO sizes. Switch to using a NAPI poll handler to perform the TX completion work to get this out of hard IRQ context and avoid the IRQ latency impact. A separate NAPI instance is used for TX and RX to avoid checking the other ring's state unnecessarily when doing the poll, and so that the NAPI budget handling can work for both TX and RX packets. A new per-queue tx_ptr_lock spinlock has been added to avoid using the main device lock (with IRQs needing to be disabled) across the entire TX mapping operation, and also to protect the TX queue pointers from concurrent access between the TX start and TX poll operations. The TX Used Bit Read interrupt (TXUBR) handling also needs to be moved into the TX NAPI poll handler to maintain the proper order of operations. A flag is used to notify the poll handler that a UBR condition needs to be handled. The macb_tx_restart handler has had some locking added for global register access, since this could now potentially happen concurrently on different queues. Signed-off-by: Robert Hancock <robert.hancock@calian.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.