Re: aarch64 reliability issues

[Michael van Elst <mlelstv%serpens.de@localhost>]

On Sun, May 18, 2025 at 05:41:13PM -0400, Greg Troxel wrote:
> mlelstv%serpens.de@localhost (Michael van Elst) writes:
> 
> > gdt%lexort.com@localhost (Greg Troxel) writes:
> >
> >>  There's no pressure mechanism to free vnodes from zfs under memory
> >>  pressure, and those vnodes still hold refs to other memory.
> >
> > Yes. That's also true for any other filesystem.
> 
> Agreed, but with other filesystems, it seems that the vnodes are just
> vnodes, and there are some number of them such that total RAM caused by
> vnodes is maybe 5%, waving hands wildly.

Maybe not as much as ZFS, but buffers and VM objects are also held
in memory until a vnode is removed.


> > I have a local patch to add pressure to maxvnodes when there is
> > a memory shortage. But it's a bit difficult to exercise.
> 
> That's very interesting.  I would be interested in trying it, and I
> suspect some of the other zfs-using people would too, if you are
> inclined to post it (tech-kern?).

It is unrelated to ZFS.

I keep a pressure factor on maxvnodes, so that the effective number
gets reduced whenever the pagedaemon tries to drain memory and the
pressure is relaxed in lru_requeue() when vnodes are released.

But as I said, it's difficult to exercise.


Greetings,
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."