e5e678e4fe
The try_to_wake_up function has an optimization where it can queue a task for wakeup on its previous CPU, if the task is still in the middle of going to sleep inside schedule(). Once schedule() re-enables IRQs, the task will be woken up with an IPI, and placed back on the runqueue. If we have such a wakeup pending, there is no need to search other CPUs for runnable tasks. Just skip (or bail out early from) newidle balancing, and run the just woken up task. For a memcache like workload test, this reduces total CPU use by about 2%, proportionally split between user and system time, and p99 and p95 application response time by 10% on average. The schedstats run_delay number shows a similar improvement. Signed-off-by: Rik van Riel <riel@surriel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Acked-by: Mel Gorman <mgorman@suse.de> Link: https://lkml.kernel.org/r/20210422130236.0bb353df@imladris.surriel.com |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| 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 | ||
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.