Managing memory in 4KiB pages is a serious overhead. Many benchmarks benefit from managing memory in larger chunks. As an example, an earlier iteration of this idea which used compound pages (and wasn't particularly tuned) got a 7% performance boost when compiling the kernel. Using compound pages or THPs exposes a weakness of our type system. Functions are often unprepared for compound pages to be passed to them, and may only act on PAGE_SIZE chunks. Even functions which are aware of compound pages may expect a head page, and do the wrong thing if passed a tail page. We also waste a lot of instructions ensuring that we're not looking at a tail page. Almost every call to PageFoo() contains one or more hidden calls to compound_head(). This also happens for get_page(), put_page() and many more functions. This patch series uses a new type, the struct folio, to manage memory. It provides some basic infrastructure that's worthwhile in its own right, shrinking the kernel by about 6kB of text. -- 8< -- This is the first batch of patches for the next merge window. They are identical to the ones sent yesterday to linux-kernel and the build bots didn't complain about any of these. They have been extensively reviewed. Please apply. Matthew Wilcox (Oracle) (32): mm: Convert get_page_unless_zero() to return bool mm: Introduce struct folio mm: Add folio_pgdat(), folio_zone() and folio_zonenum() mm/vmstat: Add functions to account folio statistics mm/debug: Add VM_BUG_ON_FOLIO() and VM_WARN_ON_ONCE_FOLIO() mm: Add folio reference count functions mm: Add folio_put() mm: Add folio_get() mm: Add folio_try_get_rcu() mm: Add folio flag manipulation functions mm/lru: Add folio LRU functions mm: Handle per-folio private data mm/filemap: Add folio_index(), folio_file_page() and folio_contains() mm/filemap: Add folio_next_index() mm/filemap: Add folio_pos() and folio_file_pos() mm/util: Add folio_mapping() and folio_file_mapping() mm/filemap: Add folio_unlock() mm/filemap: Add folio_lock() mm/filemap: Add folio_lock_killable() mm/filemap: Add __folio_lock_async() mm/filemap: Add folio_wait_locked() mm/filemap: Add __folio_lock_or_retry() mm/swap: Add folio_rotate_reclaimable() mm/filemap: Add folio_end_writeback() mm/writeback: Add folio_wait_writeback() mm/writeback: Add folio_wait_stable() mm/filemap: Add folio_wait_bit() mm/filemap: Add folio_wake_bit() mm/filemap: Convert page wait queues to be folios mm/filemap: Add folio private_2 functions fs/netfs: Add folio fscache functions mm: Add folio_mapped() Documentation/core-api/mm-api.rst | 4 + Documentation/filesystems/netfs_library.rst | 2 + fs/afs/write.c | 9 +- fs/cachefiles/rdwr.c | 16 +- fs/io_uring.c | 2 +- include/linux/huge_mm.h | 15 - include/linux/mm.h | 165 +++++++-- include/linux/mm_inline.h | 85 +++-- include/linux/mm_types.h | 77 ++++ include/linux/mmdebug.h | 20 + include/linux/netfs.h | 77 ++-- include/linux/page-flags.h | 247 +++++++++---- include/linux/page_ref.h | 158 +++++++- include/linux/pagemap.h | 390 +++++++++++--------- include/linux/swap.h | 7 +- include/linux/vmstat.h | 107 ++++++ mm/Makefile | 2 +- mm/filemap.c | 329 +++++++++-------- mm/folio-compat.c | 43 +++ mm/internal.h | 1 + mm/memory.c | 8 +- mm/page-writeback.c | 72 ++-- mm/page_io.c | 4 +- mm/swap.c | 30 +- mm/swapfile.c | 8 +- mm/util.c | 59 +-- 26 files changed, 1356 insertions(+), 581 deletions(-) create mode 100644 mm/folio-compat.c -- 2.30.2
