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List:       fedora-devel-list
Subject:    Re: Fedora 32 System-Wide Change proposal (late): Enable EarlyOOM
From:       Chris Murphy <lists () colorremedies ! com>
Date:       2020-01-07 15:55:53
Message-ID: CAJCQCtQyghxvBYjLg2mNW=cO3b+1eaDke70ug=h-TQK8m8gauQ () mail ! gmail ! com
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On Mon, Jan 6, 2020 at 10:28 PM Mark Otaris <mark@net-c.com> wrote:
> 
> > For now, kernel developers have made it clear they do not care about
> > user space responsiveness. At all. Their concern with kernel
> > oom-killer is strictly with keeping the kernel functioning.
> 
> This is false. The stated purpose of the OOM killer is not only to keep the
> kernel alive.

https://lore.kernel.org/linux-fsdevel/20200104090955.GF23195@dread.disaster.area/T/#m8b25fd42501d780d8053fc7aa9f4e3a28a19c49f



> Nor does the fact the kernel has not solved userspace
> responsiveness yet imply that kernel folks do not care. Rather, it means that
> they will not solve it on their own because the kernel does not have all the
> information it needs. Kernel folks do care, or we wouldn't have PSI or cgroups.

OK.


> > Can it be done with cgroupv2 and PSI alone? Unclear.
> 
> Of course it can. Just run 100 instances of every stress-ng memory worker in
> a podman container with a cgroup memory limit. The system will not hang.

a. Not everything is running or will run in a container;
b. To what degree cgroups and PSI, making no other changes,
solves/avoids the problem under discussion is workload dependent.
That's stated in the last part of the email response I reference
above.

Of course, Fedora Workstation is a general purpose operating system.
It's untenable to have workload specific operating systems. By what
mechanism is the workload categorized? And by what mechanism is the
system dynamical (re)configured?


> Try it. With a memory limit,
> 
> podman run --rm -it --memory=1G fedora bash -c 'dnf install -y stress-ng && \
> stress-ng --malloc 100 --memcpy 100 --mmap 100 --vm 100'

When I ask the question "can it be done" I'm asking for cake and
eating it too. I'm not asking for an example of running something that
doesn't implode the system, I know about that. I want to compile
something, and have the system figure out the resources it can give to
that task, without killing it, and without impacting the responsivity
of my computer.


-- 
Chris Murphy
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