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The linux-next integration testing tree
aa6fde93f3
wq_cpu_intensive_thresh_us is used to detect CPU-hogging per-cpu work items. Once detected, they're excluded from concurrency management to prevent them from blocking other per-cpu work items. If CONFIG_WQ_CPU_INTENSIVE_REPORT is enabled, repeat offenders are also reported so that the code can be updated. The default threshold is 10ms which is long enough to do fair bit of work on modern CPUs while short enough to be usually not noticeable. This unfortunately leads to a lot of, arguable spurious, detections on very slow CPUs. Using the same threshold across CPUs whose performance levels may be apart by multiple levels of magnitude doesn't make whole lot of sense. This patch scales up wq_cpu_intensive_thresh_us upto 1 second when BogoMIPS is below 4000. This is obviously very inaccurate but it doesn't have to be accurate to be useful. The mechanism is still useful when the threshold is fully scaled up and the benefits of reports are usually shared with everyone regardless of who's reporting, so as long as there are sufficient number of fast machines reporting, we don't lose much. Some (or is it all?) ARM CPUs systemtically report significantly lower BogoMIPS. While this doesn't break anything, given how widespread ARM CPUs are, it's at least a missed opportunity and it probably would be a good idea to teach workqueue about it. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-Tested-by: Geert Uytterhoeven <geert@linux-m68k.org> |
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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.