On Thu, Feb 22, 2024 at 05:16:44PM -0500, Pasha Tatashin wrote: > However, we must also ensure compatibility with the interfaces and > features unique to hugetlb, such as boot-time reservation and vmemap > optimizations. Generalizing these features could potentially lead to > memory savings in THP as well. In a memdesc world, how much value is there in vmemmap? At 8 bytes per page, memmap occupies 4kB for 2MB and 2MB for 1GB. So there's no way to save memory for a 2MB allocation, and saving 2MB per 1GB page is ... not a huge win any more. Let's say you have a 64GB machine with 50GB tied up in 1GB pages, we'll end up saving 100MB on a 64GB machine which doesn't seem all that compelling? I do have a proposal for further compressing memmap, but it requires doing memdesc first, so I'm reluctant to discuss it before we've done memdescs. I have to have something to talk about at LSFMM'26 after all.
