Re: [FYI] DAMON and virtio-balloon in DeepSeek's DSec paper

["David Hildenbrand (Arm)" <david@kernel.org>]

On 9/25/26 07:44, Lance Yang wrote:
> Hi all,
> 
> I was reading DeepSeek's new DSec paper[1] and found a nice use of DAMON
> and virtio-balloon:
> 
> With this kind of workload, an agent may read a file once and never touch
> it again, while those pages remain in the guest page cache. Without memory
> pressure in the guest, they can stay cached even though the host would
> like that memory back ...
> 
> The trick is DAMON + virtio-balloon free-page reporting :) DAMON reclaims

Heh, I read "virtio-balloon" and thought "balloon inflation/deflation, what year
is it?!". Free-page reporting makes much more sense.

> cold file pages from the guest page cache; buddy gets a chance to coalesce
> them into reportable blocks, and virtio-balloon passes those blocks to
> Firecracker. Firecracker can then drop the host backing with MADV_DONTNEED.

When I was at RH we were looking at this issue as well. virtio-pmem was one way
of avoiding the page cache in VM entirely. But it has its own limitations.

Thanks for sharing!

-- 
Cheers,

David