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

[Yilei Zheng]

> What's the size of the roots image? And I just want to know how much
> memory this series could save in your workload.

In our setup, the rootfs is an EROFS image exported from the OCI
container image, so the pmem device size follows the image size.

Most of our workloads are simple today, with images around 1 to 2 GiB,
which means 16 to 32 MiB of vmemmap overhead per guest. And we expect
the average image size to reach about 5 GiB as we add heavier desktop
and agentic RL environments. That would save roughly 80 MiB per guest.

At our target density of about 200 sandboxes per node, this adds up
to around 16 GiB of guest RAM saved per node. Memory is what caps
density here, so this saving helps a lot.