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When running workloads heavy unbalanced towards TX (high TX, low RX traffic), sfc driver can retain the CPU during too long times. Although in many cases this is not enough to be visible, it can affect performance and system responsiveness. A way to reproduce it is to use a debug kernel and run some parallel netperf TX tests. In some systems, this will lead to this message being logged: kernel:watchdog: BUG: soft lockup - CPU#12 stuck for 22s! The reason is that sfc driver doesn't account any NAPI budget for the TX completion events work. With high-TX/low-RX traffic, this makes that the CPU is held for long time for NAPI poll. Documentations says "drivers can process completions for any number of Tx packets but should only process up to budget number of Rx packets". However, many drivers do limit the amount of TX completions that they process in a single NAPI poll. In the same way, this patch adds a limit for the TX work in sfc. With the patch applied, the watchdog warning never appears. Tested with netperf in different combinations: single process / parallel processes, TCP / UDP and different sizes of UDP messages. Repeated the tests before and after the patch, without any noticeable difference in network or CPU performance. Test hardware: Intel(R) Xeon(R) CPU E5-1620 v4 @ 3.50GHz (4 cores, 2 threads/core) Solarflare Communications XtremeScale X2522-25G Network Adapter Fixes: |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| 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.