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

[SJ Park <sj@kernel.org>]

Hi Lance,

On Fri, 25 Sep 2026 13:44:08 +0800 Lance Yang <lance.yang@linux.dev> 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
> 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.
> 
> And it worked: time-integrated host memory use fell by 21.2%, while peak
> usage stayed about the same, with no significant CPU overhead. Pretty cool
> to see these pieces show up in another real, large-scale system :)

Thank you for sharing this, Lance!

> 
> Kernel work still changes the world. Cheers to that!

Indeed, the community is making the work a great place.

> 
> Anyhow, I still don't know DAMON and virtio-balloon as well as I should
> (mostly I just know the people who built them) :P

Please feel free to ask any question to DAMON community and me, whenever you
get :)

> 
> [1] https://arxiv.org/html/2609.22978

I only briefly read the paper.  But it looks like DeepSeek's DAMON usage is
similar to AWS' DAMON usage [1] for their serverless service.

While I was in AWS, I proposed [2] a more advanced version called
Access/Contiguity-aware Memory Autoscaling (ACMA).  After the RFC idea v2 [2],
no progress is made so far, though.  I shortly covered it in LSFMMBPF'25 [3],
but all I mentioned was that the project is suspended.  Recently a useer has
personally reached out to me asking the status of ACMA.  It is too early stage
of the discussion to say or promise something in my humble perspective, though.

[1] https://cdn.amazon.science/ee/a4/41ff11374f2f865e5e24de11bd17/resource-management-in-aurora-serverless.pdf
[2] https://lore.kernel.org/all/20240512193657.79298-1-sj@kernel.org/
[3] https://lore.kernel.org/all/20250121183103.42877-1-sj@kernel.org/


Thanks,
SJ

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