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A mirror of the official Linux kernel repository just in case
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Mike and others noticed that EEVDF does like to over-schedule quite a bit -- which does hurt performance of a number of benchmarks / workloads. In particular, what seems to cause over-scheduling is that when lag is of the same order (or larger) than the request / slice then placement will not only cause the task to be placed left of current, but also with a smaller deadline than current, which causes immediate preemption. [ notably, lag bounds are relative to HZ ] Mike suggested we stick to picking 'current' for as long as it's eligible to run, giving it uninterrupted runtime until it reaches parity with the pack. Augment Mike's suggestion by only allowing it to exhaust it's initial request. One random data point: echo NO_RUN_TO_PARITY > /debug/sched/features perf stat -a -e context-switches --repeat 10 -- perf bench sched messaging -g 20 -t -l 5000 3,723,554 context-switches ( +- 0.56% ) 9.5136 +- 0.0394 seconds time elapsed ( +- 0.41% ) echo RUN_TO_PARITY > /debug/sched/features perf stat -a -e context-switches --repeat 10 -- perf bench sched messaging -g 20 -t -l 5000 2,556,535 context-switches ( +- 0.51% ) 9.2427 +- 0.0302 seconds time elapsed ( +- 0.33% ) Suggested-by: Mike Galbraith <umgwanakikbuti@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20230816134059.GC982867@hirez.programming.kicks-ass.net |
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| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
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| samples | ||
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| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
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| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
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| 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.