tech-kern archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: UVM behavior under memory pressure

On Thu, Apr 01, 2021 at 01:13:05PM -0700, Greg A. Woods wrote:
> At Thu, 1 Apr 2021 21:03:37 +0200, Manuel Bouyer <> wrote:
> Subject: UVM behavior under memory pressure
> >
> > Of course the system is very slow
> > Shouldn't UVM choose, in this case, to reclaim pages from the file cache
> > for the process data ?
> > I'm using the default vm.* sysctl values.
> I almost never use the default vm.* values.
> I would guess the main problem for your system's memory requirements, at
> the time you showed it, is that the default for vm.anonmin is way too
> low and so raising vm.anonmin might help.  If vm.anonmin isn't high
> enough then the pager won't sacrifice other requirements already in play
> for anon pages.

Yes, I understand this. But, in an emergency situation like this one (there
is no free ram, swap is full, openscad eventually gets killed),
I would expect the pager to reclaim pages where it can;
like file cache (down to vm.filemin, I agree it shouldn't go down to 0).

In my case, vm.anonmax is at 80%, and I suspect it was not reached
(I tried to increase it to 90% but this didn't change anything).

I don't know what was in the file cache; in the mean time, its usage is down
to 39M. Maybe firefox was had some background maintenance running ...
And now openscad can complete its rendering :)

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference

Home | Main Index | Thread Index | Old Index