Re: user space unresponsive, followup: lsf/mm congestion

[Chris Murphy <lists@colorremedies.com>]

On Fri, Jan 10, 2020 at 4:07 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> So you have redirected the output (stdout) to a file. This is less
> effective than using a file directly because the progy makes sure to
> preallocate and mlock the output file data as well. Anyway, let's have a
> look what you managed to gather

I just read the source :P and see the usage. I'll do that properly if
there's a next time. Should it be saved in /tmp to avoid disk writes
or does it not matter?


> It would interesting to see whether tuning vm_swappiness to 100 helps
> but considering how large is the anonymous active list I would be very
> skeptical.

I can try it. Is it better to capture the same amount of time as
before? Or the entire thing until it fails or is stuck for at least 30
minutes?


> So in the end it is really hard to see what the kernel should have done
> better in this overcommitted case. Killing memory hogs would likely kill
> an active workload which would lead to better desktop experience but I
> can imagine setups which simply want to have work done albeit sloooowly.

Right, so the kernel can't know and doesn't really want to know, user
intention. It's really a policy question.

But if the distribution wanted to have a policy of, the mouse pointer
always works - i.e. the user should be able to kill this process, if
they want, from within the GUI - that implies possibly a lot of work
to carve out the necessary resources for that entire stack. I have no
idea if that's possible with the current state of things.

Anyway, I see it's a difficult problem, and I appreciate the
explanations. I don't care about this particular example, my interest
is making it better for everyone - I personally run into this only
when I'm testing for it, but those who experience it, experience it
often. And they're often developers. They have no idea in advance what
the build resource requirements are, and those requirements change a
lot as the compile happens. Difficult problem.

-- 
Chris Murphy