Re: [PATCH v21 1/4] mm: add VM_DROPPABLE for designating always lazily freeable mappings

[David Hildenbrand]

On 10.07.24 05:34, Jason A. Donenfeld wrote:
> On Wed, Jul 10, 2024 at 05:05:06AM +0200, David Hildenbrand wrote:
> > On 09.07.24 04:17, Jason A. Donenfeld wrote:
> > > Hi David,
> > >
> > > On Mon, Jul 08, 2024 at 10:21:09PM +0200, David Hildenbrand wrote:
> > > > BTW, I was just trying to understand how MADV_FREE + MAP_DROPPABLE would
> > > > behave without any swap space around.
> > > >
> > > > Did you experiment with that?
> > >
> > > You mean on a system without any swap configured? That's actually my
> > > primary test environment for this. It behaves as expected: when ram
> > > fills up and the scanner is trying to reclaim what it can,
> > > folio_test_swapbacked(folio) is false, and the memory gets freed. After,
> > > reads fault in a zero page. So it's working as expected.
> >
> > Okay, just to be clear: no swap/zram/zswap. The reclaim code regarding
> > not scanning anonymous memory without swap was a bit confusing.
>
> Right, no swap, as boring a system as can be. I've experimented with
> that behavior on my swap-less 64GB thinkpad, as well as on little
> special purpose VMs, where I hacked the VM_DROPPABLE test code into the
> wireguard test suite.

Great, thanks!

--
Cheers,

David / dhildenb