Re: Periodic rant about SCHED_ULE

From: Konstantin Belousov <>
Date: Thu, 23 Mar 2023 20:54:07 UTC
On Thu, Mar 23, 2023 at 05:42:22PM +0100, Mateusz Guzik wrote:
> On 3/23/23, Konstantin Belousov <> wrote:
> > On Thu, Mar 23, 2023 at 04:15:21AM +0100, Mateusz Guzik wrote:
> >> So I also ran the following setup: 8 core vm doing -j 8 buildkernel,
> >> while 8 nice -n 20 processes are cpu-bound. After the build ends
> >> workers report how many ops they did in that time.
> > Why nice?  Did you tried with the idle class instead?
> >
> The original message reported numbers with -n 20 and it is not
> particularly unusual.
I do not think we should target this level of feature compatibility with
the historic behavior.  nice -20 was not guaranteed to behave the way it
is requested in this thread ("only use CPU when no other threads are
runnable").  Instead, it is the declared behavior of the idle class.

If idle class is broken, then it is indeed should be fixed.  But not
nice -20, IMO.