systemd-oomd issues on desktop

[Ernst Sjöstrand]

Den fre 10 juni 2022 kl 07:36 skrev Olivier Tilloy <
olivier.tilloy at canonical.com>:

>
>
> On Fri, Jun 10, 2022 at 1:49 AM Steve Langasek <steve.langasek at ubuntu.com>
> wrote:
>
>> On Thu, Jun 09, 2022 at 01:00:45PM -0400, Nick Rosbrook wrote:
>> > In the reports I refer to above, applications are being killed due to
>> > (1). In practice, the SwapUsedLimit might be too easy to reach on
>> > Ubuntu, largely because Ubuntu provides just 1GB of swap. Since we
>> > follow the suggestion of setting ManagedOOMSwap=kill on the root slice
>> > [7], every cgroup is eligible for swap kill. When this condition is
>> > met, user applications like browsers are going to be killed first.
>>
>> In terms of behavior that we want to see, this last sentence sets off red
>> flags for me.  There are times when, due to memory pressure, killing
>> processes to reclaim memory is the right answer; and it is likely that the
>> process using the most memory on a desktop system is the browser.  But in
>> terms of how a modern desktop is used, it's also quite likely that the
>> browser is the most important process to the user experience on a
>> desktop.
>> (Cf. the Chromebook experience, where the browser effectively *is* the
>> desktop.)
>>
>> I understand how we've arrived at the situation that browsers are the
>> processes likely to be killed first when there's memory pressure; but
>> separately from the question of what we should do for systemd-oomd
>> overall,
>> are there configuration changes we could make to lower the priority of the
>> browser as a candidate for oom killing, and would those be reasonable
>> configuration changes to make?
>>
>
> Also note that modern browsers (at least firefox and chrom{e,ium}) have
> built-in mechanisms to discard/unload tabs they consider inactive to
> reclaim memory, and these mechanisms are enabled by default. See
> about:unloads in firefox, and chrome://discards in chromium. So it really
> shouldn't be necessary to kill browsers the hard way.
>

Yeah Firefox tracks memory pressure like this:
https://hg.mozilla.org/mozilla-central/rev/267c8b31a3633ddfb4d7e29af56c82fc8745c0d0

So systemd-oomd should trigger later than the Firefox memory pressure
system.

Regards
//Ernst
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