> > > > Adds two new per-node fields, namely nr_page_metadata and > > nr_page_metadata_boot, to /sys/devices/system/node/nodeN/vmstat and a > > global PageMetadata field to /proc/meminfo. This information can be used > > by users to see how much memory is being used by per-page metadata, which > > can vary depending on build configuration, machine architecture, and > > system use. > > /me wonders what page metadata is. > > > Per-page metadata is the amount of memory that Linux needs in order to > > manage memory at the page granularity. The majority of such memory is > > used by "struct page" and "page_ext" data structures. > > The term for this in Linux MM is "memmap". > > That's what's used throughout the code, in Kconfig options, and it > shows up in the documentation as well. It's in the names of most files > and functions that adjust your new counters. The new name is > unnecessary, and frankly it's quite vague and nondescript. > > Also no reason to keep the stat name intentionally "open ended". As > became clear from the side discussions on MemTotal, all proposals to > change the semantics of counters later on will be nacked on the basis > of established user expectations. So just call it what it is now. I am not closely following this series, but I just wanted to point out that this is not always true. We are actively extending NR_SECONDARY_PAGETABLE to add IOMMU page tables in addition to KVM page tables [1]. In that case as well, the name was left open-ended exactly for this purpose [2]. [1]https://lore.kernel.org/lkml/20240207174102.1486130-11-pasha.tatashin@xxxxxxxxxx/ [2]https://lore.kernel.org/lkml/20220823004639.2387269-2-yosryahmed@xxxxxxxxxx/
