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List:       fedora-devel-list
Subject:    Re: SwapOnZRAM and how it affects earlyoom thresholds
From:       Igor Raits <ignatenkobrain () fedoraproject ! org>
Date:       2020-07-13 16:44:43
Message-ID: d72d5ad6451d49af725cecd2deabef9b02d14741.camel () fedoraproject ! org
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On Tue, 2020-07-14 at 01:28 +0900, Alexey A. wrote:
> > The most
> > common value I've found over a long period of time, for swap
> > without
> > hibernation is 50% of RAM.
> 
> With low RAM (2G) it's easy to use swap on zram with disksize = 150%
> MemTotal with opening browsers.
> 
> 50% maybe OK with MemTotal=8G.
> 
> > I'd like to hear from Alexey what he thinks about further reducing
> > the
> > values in earlyoom versus possibly raising the cap in
> > zram-generator-defaults.
> 
> It may be OK to reduce mem cap to 200 MiB. This threshold also can
> work
> well and may be sufficient to prevent freezing.
> 
> I would suggest to increase zram disksize caps up to 75% and maybe to
> 6GB.

Please open ticket upstream with some more details, please.

> пт, 10 июл. 2020 г. в 01:19, Chris Murphy <lists@colorremedies.com>:
> 
> > On Thu, Jul 9, 2020 at 9:49 AM Rex Dieter <rdieter@math.unl.edu>
> > wrote:
> > > 
> > > part of some irc discussions on
> > > https://fedoraproject.org/wiki/Changes/KDEEarlyOOM
> > > 
> > > raised my attention to related item,
> > > https://fedoraproject.org/wiki/Changes/SwapOnZRAM
> > > 
> > > As it stands currently with earlyoom, it's default thresholds are
> > > 4% ram
> > and
> > > 10% swap before it acts.  That's fine and dandy.
> > > 
> > > Upon reading the SwapOnZRAM feature proposal, I see it is
> > > advocating
> > > allocating 50% of ram for swap.  I'd like folks to consider and
> > > evaluate
> > how
> > > this impacts earlyoom.  It effectively makes the earlyoom memory
> > threshold
> > > double (right?).  If so, at least think about lowering 4 to (2 or
> > > 3),
> > since
> > > that will make earlyoom's behavior closer to before swaponzram
> > > was
> > > introduced.
> > > 
> > > Thoughts?
> > 
> > The net effect is that earlyoom is more likely to trigger than with
> > a
> > disk based swap because right now disk based swap is huge by
> > default.
> > It's huge by default to accommodate a hibernation image. The most
> > common value I've found over a long period of time, for swap
> > without
> > hibernation is 50% of RAM. So this approximates those expectations.
> > 
> > I'd like to hear from Alexey what he thinks about further reducing
> > the
> > values in earlyoom versus possibly raising the cap in
> > zram-generator-defaults. I don't want to get too carried away
> > there,
> > because we are applying this to upgrades (wherever the to-be-
> > obsoleted
> > 'zram' package exists already even if not enabled). There is an
> > opportunity, of course, right now and through beta testing, to keep
> > on
> > testing variations on both the size of the zram device used for
> > swap
> > and for earlyoom. But we also have another Fedora release, Fedora
> > 34.
> > So I'm more inclined to go conservative so long as that itself
> > isn't
> > causing problems.
> > 
> > One thing I'm a bit skeptical of with reducing earlyoom's triggers
> > is
> > that free memory is needed for the recovery from an actual kill.
> > Usually this is just sigterm. That's the first attempt. If that
> > doesn't work then earlyoom issues sigkill, which is at a lower
> > threshold already.
> > 
> > 
> > --
> > Chris Murphy
> > _______________________________________________
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- -- 
Igor Raits <ignatenkobrain@fedoraproject.org>
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