On Tue Nov 12, 2024 at 8:45 AM CET, Baolin Wang wrote: > Traditionally, tmpfs only supported PMD-sized huge folios. However nowadays Nitpick: We are mixing here folios/page, PMD-size huge. For anyone not aware of Memory Folios conversion in the kernel I think this makes it confusing. Tmpfs has never supported folios so, this is not true. Can we rephrase it? Below you are also mixing terms huge/large folios etc. Can we be consistent? I'd stick with folios (for order-0), and large folios (! order-0). I'd use huge term only when referring to PMD-size pages. > with other file systems supporting any sized large folios, and extending > anonymous to support mTHP, we should not restrict tmpfs to allocating only > PMD-sized huge folios, making it more special. Instead, we should allow Again here. > tmpfs can allocate any sized large folios. > > Considering that tmpfs already has the 'huge=' option to control the huge > folios allocation, we can extend the 'huge=' option to allow any sized huge 'huge=' has never controlled folios. > folios. The semantics of the 'huge=' mount option are: > > huge=never: no any sized huge folios > huge=always: any sized huge folios > huge=within_size: like 'always' but respect the i_size > huge=advise: like 'always' if requested with fadvise()/madvise() > > Note: for tmpfs mmap() faults, due to the lack of a write size hint, still > allocate the PMD-sized huge folios if huge=always/within_size/advise is set. > > Moreover, the 'deny' and 'force' testing options controlled by > '/sys/kernel/mm/transparent_hugepage/shmem_enabled', still retain the same > semantics. The 'deny' can disable any sized large folios for tmpfs, while > the 'force' can enable PMD sized large folios for tmpfs. > > Any comments and suggestions are appreciated. Thanks. > > Changes from v1: > - Add reviewed tag from Barry and David. Thanks. > - Fix building warnings reported by kernel test robot. > - Add a new patch to control the default huge policy for tmpfs. > > Changes from RFC v3: > - Drop the huge=write_size option. > - Allow any sized huge folios for 'hgue' option. > - Update the documentation, per David. > > Changes from RFC v2: > - Drop mTHP interfaces to control huge page allocation, per Matthew. > - Add a new helper to calculate the order, suggested by Matthew. > - Add a new huge=write_size option to allocate large folios based on > the write size. > - Add a new patch to update the documentation. > > Changes from RFC v1: > - Drop patch 1. > - Use 'write_end' to calculate the length in shmem_allowable_huge_orders(). > - Update shmem_mapping_size_order() per Daniel. > > Baolin Wang (4): > mm: factor out the order calculation into a new helper > mm: shmem: change shmem_huge_global_enabled() to return huge order > bitmap > mm: shmem: add large folio support for tmpfs > mm: shmem: add a kernel command line to change the default huge policy > for tmpfs > > David Hildenbrand (1): > docs: tmpfs: update the huge folios policy for tmpfs and shmem > > .../admin-guide/kernel-parameters.txt | 7 + > Documentation/admin-guide/mm/transhuge.rst | 64 ++++++-- > include/linux/pagemap.h | 16 +- > mm/shmem.c | 148 ++++++++++++++---- > 4 files changed, 183 insertions(+), 52 deletions(-)
