linux-kernel - Re: [PATCHSET v6] sched: Implement BPF extensible scheduler class

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Date: Fri, 10 May 2024 20:24:26 +0200
From: Peter Jung <ptr1337@...hyos.org>
To: Tejun Heo <tj@...nel.org>, torvalds@...ux-foundation.org,
 mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
 vincent.guittot@...aro.org, dietmar.eggemann@....com, rostedt@...dmis.org,
 bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com,
 vschneid@...hat.com, ast@...nel.org, daniel@...earbox.net,
 andrii@...nel.org, martin.lau@...nel.org, joshdon@...gle.com,
 brho@...gle.com, pjt@...gle.com, derkling@...gle.com, haoluo@...gle.com,
 dvernet@...a.com, dschatzberg@...a.com, dskarlat@...cmu.edu,
 riel@...riel.com, changwoo@...lia.com, himadrics@...ia.fr, memxor@...il.com,
 andrea.righi@...onical.com, joel@...lfernandes.org
Cc: linux-kernel@...r.kernel.org, bpf@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCHSET v6] sched: Implement BPF extensible scheduler class

Hi everyone,

We (CachyOS [0]) want to support to proposal of sched_ext.
CachyOS is an archlinux based distribution, which improves the performance,
throughput and interactivity for the desktop but also on servers. We 
have a big
community, which likes testing new features on the kernel, GPU drivers,
frequency drivers, new locking technologies and schedulers.

[0]: https://cachyos.org/

For CachyOS, schedulers have always been a key matter. We have numerous
variants of kernels with different schedulers so that everyone can be
satisfied. So far, schedulers in the kernel have faced one problem, 
namely: 1
kernel = 1 scheduler. It was impossible to change the CPU scheduler without
restarting the computer and booting another kernel. scx-scheduler simply and
extremely successfully changes this approach and allows you to change
schedulers at runtime. The approach with a single default scheduler in the
kernel also leads to a problematic situation, because in our opinion it is
impossible to develop a single scheduler that is the optimal solution 
for all
possible tasks. Again, and in this case, scx-scheds makes this problem
obsolete.

The EEVDF Scheduler gives a good overall experience, but it currently lacks
good interactivity under load, specific scenarios like gaming and also the
latency. Rusty gives CachyOS currently a very good replacement for desktop
usage. We are planning to provide the Rusty Scheduler in the future as 
default.
The interactivity of Rusty is dramatically better than EEVDF, especially 
when a
heavy workload is running in the background, e.g. during compilation. 
Using the
desktop under such a workload can be very challenging for the default 
scheduler
and at rusty it is not even noticeable that during compilation is 
running. Also
in gaming scenarios rusty seems to provide excellent performance.

The LAVD Scheduler is integrated as default in our handheld variant and 
shows
very good impressive results in frame times as well as 1% lows. This 
gives our
user on the Handheld Edition a better experience.

It is also worth mentioning that our community takes an active part in
sched-ext testing and regularly reports bugs and suggestions for changes.
Cooperation with developers is also perfect - they immediately make 
corrections
if there are any regressions.

Regards,

Peter Jung
CachyOS