Re: [PATCH 3/4] mm: add shared read-only vmemmap support for FS-DAX

[Muchun Song]

> On Oct 29, 2026, at 15:12, Yilei Zheng <trilith.zheng@xxxxxxxxx> wrote:
> 
> I forgot to mention the tool execution case in my last mail. Those
> microVMs start, run a small task, and exit. DAX is there to save
> memory, but the vmemmap is allocated for the whole image. A 2 GiB
> image pays 32 MiB of vmemmap even if a microVM only reads a few MB, so
> for those microVMs the DAX setup can use more memory than the same
> image on virtio-blk. That is also a case this series fixes for us.

Thanks for sharing. I think in this scenario it also saves boot time.
I'm not sure how significant that is, though, since the number of
vmemmap pages isn't large enough to be noticeable.

Thanks.