On Mon, Jan 6, 2020 at 11:09 AM Lennart Poettering <mzerqung@xxxxxxxxxxx> wrote:
>
> On Mo, 06.01.20 11:22, Michael Catanzaro (mcatanzaro@xxxxxxxxx) wrote:
>
> So I talked to Tejun Heo about this (kernel cgroups maintainer,
> working for facebook with the people who did the PSI stuff, kernel mm
> guy). Here's the gist:
>
> - earlyoom might be OK as short time stopgap if people really want to
> hurry something, as long as it watches only swap depletion (which it
> pretty much does already). But it should then also determine what
> to kill taking the swap use into account and little else (which it
> apparently does not). This doesn't make any sense to have though if
> there is no swap.
>
> - Don't bother with the OOM score the kernel calculates for processes,
> it doesn't take the swap use into account. That said, do take the
> configurable OOM score *adjustment* into account, so that processes
> which set that are respected, i.e. journald, udevd, and such. (or in
> otherwords, ignore /proc/$PID/oom_score, but respect
> /proc/PID/oom_score_adj).
>
> - going down to 100ms poll intervals is a bad idea, 1s is sufficient,
> maybe higher.
>
> - facebook is working on making oomd something that just works for
> everyone, they are in the final rounds of canonicalizing the
> configuration so that it can just work for all workloads without
> tuning. The last bits for this to be deployable are currently being
> done on the kernel side ("iocost"), when that's in, they'll submit
> oomd (or simplified parts of it) to systemd, so that it's just there
> and works. It's their expressive intention to make this something
> that also works for desktop stuff and requires no further
> tuning. they also will do the systemd work necessary. time frame:
> half a year, maybe one year, but no guarantees.
>
> - oomd currently polls some parameters in time intervals too,
> still. They are working on getting rid of that too, so that
> everything is event based via PSI. Given their own focus on servers
> it's not a primary goal, but still a goal.
>
> Or in other words: oomd is the way to go in the long run, developed
> alongside the kernel features backing it. You can use it already if
> you like, but there are still too many knobs for generic
> deployment. earlyoom might be a valid temporary stopgap if you want to
> hurry this.
>
> (And now I hope I paraphrased everything he said more or less
> correctly...)
Thanks for all of that, and it's consistent with the research and
discussion the working group have done in the past 6 months on this
subject. What I can't estimate is whether oomd or lmm will be better
long term for Fedora Workstation, or if there's an advantage of them
co-existing.
And yes the idea is to go a little faster. Earlyoom is easy to take
out. And I have no problem with it coming out in fc33 if oomd or (more
likely) lmm are ready by then.
--
Chris Murphy
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