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Triggering RX interrupt for every byte defeats the purpose of aging timer and leads to interrupt storm at high baud rates. The interrupt storm can starve line discipline worker and prevent tty throttling, rendering hardware/software flow control useless. Increase receiver trigger level to 8 to increase the minimum period between RX interrupts to 8 characters time. The tradeoff is increased latency. Aging timer resets with every received character. Worst case scenario happens when RX data intercharacter delay is slightly less than the aging timer timeout (8 characters time). The upper bound of the time a character can wait in RxFIFO before interrupt is raised is: (RXTL - 1) * (8 character time timeout + received 1 character time) Usually the data is received in frames, with low intercharacter delay. In such case the latency increase is 8 characters time at the end of the frame with probability (RXTL - 1) / RXTL. Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Tomasz Moń <tomasz.mon@camlingroup.com> Link: https://lore.kernel.org/r/20220117060417.624613-1-tomasz.mon@camlingroup.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.