On Thu, Jan 9, 2020 at 5:58 AM Benjamin Berg <bberg(a)redhat.com> wrote:
On Wed, 2020-01-08 at 12:24 -0700, Chris Murphy wrote:
> On Mon, Jan 6, 2020 at 11:09 AM Lennart Poettering <mzerqung(a)0pointer.de>
> > - 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
> > 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.
> Looks like PSI based oom killing doesn't work without swap. Therefore
> oomd can't be considered a universal solution. Quite a lot of
> developers have workstations with quite a decent amount of RAM,
> ~64GiB, and do not use swap at all. Server baremetal are likewise
> mixed, depending on workloads, and in cloud it's rare for swap to
> We think earlyoom can be adjusted to work well for both the swap and
> no swap use cases.
But so can oomd, after all, they are willing to implement a plugin that
uses the MaxAvailable heuristic. It just won't be available in the
In principle, I think what we are trying to achieve here is to keep the
system mostly responsive from a user perspective. This seems to imply
keeping pages in main memory that belong to "important" processes.
Right, not merely clobbering a process the user ostensibly wants to
run and complete. The just don't want it to take over.
Should oomd not manage to do this well enough out of the box, then I
see two main methods we have to improve things:
* Aggressively kill when we think important pages might get evicted
- earlyoom does this based on MemAvailable
- oomd plugin could do the same if deemed the right thing
* Actively protect important processes:
- set MemoryMin, MemoryLow on important units
- limit "normal" processes more e.g. MemoryHigh for applications
- in the long run: adjust the OOMScore/MemoryHigh dynamically based
on whether the user is interacting with an application at the time
earlyoom does the first and has the big advantage that it can be
shipped in F32. However, it is not clear to me that this aggressive
heuristic is actually better overall. And even if it is, we would
likely still move it into oomd in the long run.
I agree, although the decisions made in this release cycle can really
only be made based on what we know now. Earlyoom has a chance of
making this a better experience in the case where something really
should be OOM killed, just sooner than the kernel's oom-killer would
have. It doesn't solve the unresponsiveness problem that happens once
RAM is full, but before swap reaches 10%. In any case, it's not going
on a process kill spree. It's not going to magically free up a system
every time its under swap duress.
I've got cases where a system is under significant duress with only
50% swap use - earlyoom does nothing for that.
Finally, for F32 we might already be able to improve things quite a lot
simply by setting a few configuration options in GNOME systemd units.
Maybe. What are the risks? Is it fair to characterize this as more of
optimization of existing functionality, than it is a feature? That's a
technical question. Of course, if this improves responsivity of the
system while under swap thrashing, it's definitely a marketable