On 05/12/2023 03:37, John Hubbard wrote: > On 12/4/23 02:20, 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). > > Using a couple of Armv8 systems, I've tested this patchset. I applied it > to top of tree (Linux 6.7-rc4), on top of your latest contig pte series > [1]. > > With those two patchsets applied, the mm selftests look OK--or at least > as OK as they normally do. I compared test runs between THP/mTHP set to > "always", vs "never", to verify that there were no new test failures. > Details: specifically, I set one particular page size (2 MB) to > "inherit", and then toggled /sys/kernel/mm/transparent_hugepage/enabled > between "always" and "never". Excellent - I'm guessing this was for 64K base pages? > > I also re-ran my usual compute/AI benchmark, and I'm still seeing the > same 10x performance improvement that I reported for the v6 patchset. > > So for this patchset and for [1] as well, please feel free to add: > > Tested-by: John Hubbard <jhubbard@xxxxxxxxxx> Thanks! > > > [1] https://lore.kernel.org/all/20231204105440.61448-1-ryan.roberts@xxxxxxx/ > > > thanks,
