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jabley : kernel   75

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This article is intended to serve as an introduction to the newest Linux IO interface, io_uring, and compare it to the
existing offerings. We'll go over the reasons for its existence, inner workings of it, and the user visible interface. The
article will not go into details about specific commands and the likes, as that would just be duplicating the information
available in the associated man pages. Rather, it will attempt to provide an introduction to io_uring and how it works,
with the goal hopefully being that the reader will have gained a deeper understanding of how it all ties together. That
said, there will be some overlap between this article and the man pages. It's impossible to provide a description of
io_uring without including some of those details.
linux  kernel  io  async  io_uring  data-structures  performance  overview  design  filetype:pdf 
7 weeks ago by jabley
The Battle of the Schedulers: FreeBSD ULE vs. Linux CFS
This paper analyzes the impact on application performance
of the design and implementation choices made
in two widely used open-source schedulers: ULE, the
default FreeBSD scheduler, and CFS, the default Linux
scheduler. We compare ULE and CFS in otherwise identical
circumstances. We have ported ULE to Linux, and
use it to schedule all threads that are normally scheduled
by CFS. We compare the performance of a large suite
of applications on the modified kernel running ULE and
on the standard Linux kernel running CFS. The observed
performance differences are solely the result of scheduling
decisions, and do not reflect differences in other subsystems
between FreeBSD and Linux.
There is no overall winner. On many workloads the
two schedulers perform similarly, but for some workloads
there are significant and even surprising differences.
ULE may cause starvation, even when executing
a single application with identical threads, but this
starvation may actually lead to better application performance
for some workloads. The more complex load balancing
mechanism of CFS reacts more quickly to workload
changes, but ULE achieves better load balance in
the long run.
freebsd  linux  kernel  scheduling  comp-sci  comparison  paper  filetype:pdf 
september 2018 by jabley

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