>> Muchun's vmemmap work is also interesting to us. My understanding is >> that it allocates private backing for struct page metadata on demand, >> which could help reduce the upfront memory overhead for large images. > > Although I haven't had a chance and time to look into that, the main > concern from me is that mmap() access will call > "dax_fault_iter->vmemmap_materialize_page()", and malicious sandbox > workloads (or not malicious, just valid mmap workloads) can cause guest > memory OOMs due to "struct page balloon" for large rootfs in the worst > cases and cause the follow-up mmap access failure, because the guest > memory size may not even fulfill "struct page" for large rootfs. > > Thanks, > Gao Xiang
Agreed, if a workload actually accesses a sufficiently large range of the image, allocating struct page metadata on demand could indeed exhaust guest memory. Best, Jialiang Huang
