Re: "failed to reclaim memory" with much free physmem

On Fri, Sep 12, 2025 at 8:58 AM Garrett Wollman <wollman@bimajority.org> wrote:
>
> <<On Fri, 12 Sep 2025 08:50:10 -0700, Rick Macklem <rick.macklem@gmail.com> said:
>
> > Ok, but don't we want something that prevents the arc from taking all
> > the memory? (It seems like 932Gbytes should be close to a hard
> > upper bound for a system with 1Tbyte of ram?)
>
> Presently it says:
>
> kstat.zfs.misc.arcstats.c_max: 1098065367040
>
> That's 1 TiB less 1379 MiB.  Which in all honesty *ought to be enough*
> for munin-node, nrpe, ntpd, sendmail, inetd, lldpd, nslcd, sshd, syslogd,
> mountd, and nfsuserd.
If you look at arc_default_max() in
sys/contrib/openzfs/module/os/freebsd/arc_os.c
you'll see it returns "allmem - 1Gbyte".
This may make sense for a machine with a few Gbytes of ram, but I'd bump it
up for machines like you have. (As I noted, a system that boots with
128Gbyte->1Tbyte
of ram is going to size things a lot larger and "allmem" looks like
the total ram in the
system. They haven't even subtracted out what the kernel uses.)
(Disclaimer: I know nothing about ZFS, so the above may be crap!!)

It's a trivial function to patch, rick

>
> -GAWollman
>