On 05/12/2023 17:21, David Hildenbrand wrote: > On 04.12.23 11:20, Ryan Roberts wrote: >> Hi All, >> >> A new week, a new version, a new name... This is v8 of a series to implement >> multi-size THP (mTHP) for anonymous memory (previously called "small-sized THP" >> and "large anonymous folios"). Matthew objected to "small huge" so hopefully >> this fares better. >> >> The objective of this is to improve performance by allocating larger chunks of >> memory during anonymous page faults: >> >> 1) Since SW (the kernel) is dealing with larger chunks of memory than base >> pages, there are efficiency savings to be had; fewer page faults, batched PTE >> and RMAP manipulation, reduced lru list, etc. In short, we reduce kernel >> overhead. This should benefit all architectures. >> 2) Since we are now mapping physically contiguous chunks of memory, we can take >> advantage of HW TLB compression techniques. A reduction in TLB pressure >> speeds up kernel and user space. arm64 systems have 2 mechanisms to coalesce >> TLB entries; "the contiguous bit" (architectural) and HPA (uarch). >> >> This version changes the name and tidies up some of the kernel code and test >> code, based on feedback against v7 (see change log for details). >> >> By default, the existing behaviour (and performance) is maintained. The user >> must explicitly enable multi-size THP to see the performance benefit. This is >> done via a new sysfs interface (as recommended by David Hildenbrand - thanks to >> David for the suggestion)! This interface is inspired by the existing >> per-hugepage-size sysfs interface used by hugetlb, provides full backwards >> compatibility with the existing PMD-size THP interface, and provides a base for >> future extensibility. See [8] for detailed discussion of the interface. >> >> This series is based on mm-unstable (715b67adf4c8). > > I took a look at the core pieces. Some things might want some smaller tweaks, > but nothing that should stop this from having fun in mm-unstable, and replacing > the smaller things as we move forward. > Thanks! I'll address your comments and see if I can post another (final??) version next week.
