Managing memory in 4KiB pages is a serious overhead. Many benchmarks benefit from a larger "page size". 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. There does not appear to be a way to tell gcc that it can cache the result of compound_head(), nor is there a way to tell it that compound_head() is idempotent. This patch series uses a new type, the struct folio, to manage memory. The first 8 patches are prep work that don't involve the folio at all but fix problems I found while working on this. Patches 9-81 introduce infrastructure (that more than pays for itself, shrinking the kernel by over 4kB of text). Patches 82-96 convert iomap (ie xfs) to use folios as an example. Git: https://git.infradead.org/users/willy/pagecache.git/shortlog/refs/tags/folio_9 v8: https://lore.kernel.org/linux-mm/20210430180740.2707166-1-willy@xxxxxxxxxxxxx/ Even more work that's not being submitted: https://git.infradead.org/users/willy/pagecache.git/shortlog/refs/heads/folio v9: - Rebase onto next-20210505 - Rename folio_test_set_foo() to folio_test_set_foo_flag() (Nick Piggin) - Rename folio_set_uptodate() to folio_mark_uptodate() - Rename trylock_folio_flag() to folio_trylock_flag() - Add all remaining supporting patches for iomap - Add iomap conversion patches Matthew Wilcox (Oracle) (96): mm: Optimise nth_page for contiguous memmap mm: Make __dump_page static mm/debug: Factor PagePoisoned out of __dump_page mm/page_owner: Constify dump_page_owner mm: Make compound_head const-preserving mm: Constify get_pfnblock_flags_mask and get_pfnblock_migratetype mm: Constify page_count and page_ref_count mm: Fix struct page layout on 32-bit systems mm: Introduce struct folio mm: Add folio_pgdat and folio_zone 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 flag manipulation functions mm: Add folio_young() and folio_idle() 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_offset and folio_file_offset mm/util: Add folio_mapping and folio_file_mapping mm: Add folio_mapcount mm/memcg: Add folio wrappers for various functions 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_lock_or_retry mm/filemap: Add folio_wait_locked 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 mm/workingset: Convert workingset_activation to take a folio mm/swap: Add folio_activate mm/swap: Add folio_mark_accessed mm/rmap: Add folio_mkclean mm: Add kmap_local_folio mm: Add flush_dcache_folio mm: Add arch_make_folio_accessible mm/memcg: Remove 'page' parameter to mem_cgroup_charge_statistics mm/memcg: Use the node id in mem_cgroup_update_tree mm/memcg: Convert commit_charge to take a folio mm/memcg: Add folio_charge_cgroup mm/memcg: Add folio_uncharge_cgroup mm/memcg: Convert mem_cgroup_track_foreign_dirty_slowpath to folio mm/writeback: Rename __add_wb_stat to wb_stat_mod flex_proportions: Allow N events instead of 1 mm/writeback: Change __wb_writeout_inc to __wb_writeout_add mm/writeback: Convert test_clear_page_writeback to __folio_end_writeback mm/writeback: Add folio_start_writeback mm/writeback: Add folio_mark_dirty mm/writeback: Use __set_page_dirty in __set_page_dirty_nobuffers mm/writeback: Add __folio_mark_dirty mm/writeback: Add filemap_dirty_folio mm/writeback: Add folio_account_cleaned mm/writeback: Add folio_cancel_dirty mm/writeback: Add folio_clear_dirty_for_io mm/writeback: Add folio_account_redirty mm/writeback: Add folio_redirty_for_writepage mm/filemap: Add i_blocks_per_folio mm/filemap: Add folio_mkwrite_check_truncate mm/filemap: Add readahead_folio block: Add bio_add_folio block: Add bio_for_each_folio_all mm/lru: Add folio_lru and folio_is_file_lru mm/workingset: Convert workingset_refault to take a folio mm/lru: Add folio_add_lru mm/page_alloc: Add __alloc_folio, __alloc_folio_node and alloc_folio mm/filemap: Add filemap_alloc_folio mm/filemap: Add folio_add_to_page_cache mm/filemap: Convert mapping_get_entry to return a folio mm/filemap: Add filemap_get_folio and find_get_folio mm/filemap: Add filemap_get_stable_folio iomap: Convert to_iomap_page to take a folio iomap: Convert iomap_page_create to take a folio iomap: Convert iomap_page_release to take a folio iomap: Convert iomap_releasepage to use a folio iomap: Convert iomap_invalidatepage to use a folio iomap: Pass the iomap_page into iomap_set_range_uptodate iomap: Use folio offsets instead of page offsets iomap: Convert bio completions to use folios iomap: Convert readahead and readpage to use a folio iomap: Convert iomap_page_mkwrite to use a folio iomap: Convert iomap_write_begin and iomap_write_end to folios iomap: Convert iomap_read_inline_data to take a folio iomap: Convert iomap_write_end_inline to take a folio iomap: Convert iomap_add_to_ioend to take a folio iomap: Convert iomap_do_writepage to use a folio Documentation/core-api/cachetlb.rst | 6 + Documentation/core-api/mm-api.rst | 4 + Documentation/filesystems/netfs_library.rst | 2 + block/bio.c | 21 + fs/afs/write.c | 9 +- fs/buffer.c | 25 - fs/cachefiles/rdwr.c | 16 +- fs/io_uring.c | 2 +- fs/iomap/buffered-io.c | 524 +++++++++----------- fs/jfs/jfs_metapage.c | 1 + include/asm-generic/cacheflush.h | 14 + include/linux/backing-dev.h | 6 +- include/linux/bio.h | 46 +- include/linux/flex_proportions.h | 9 +- include/linux/gfp.h | 22 +- include/linux/highmem-internal.h | 11 + include/linux/highmem.h | 38 ++ include/linux/iomap.h | 2 +- include/linux/memcontrol.h | 81 ++- include/linux/mm.h | 226 +++++++-- include/linux/mm_inline.h | 44 +- include/linux/mm_types.h | 75 ++- include/linux/mmdebug.h | 23 +- include/linux/netfs.h | 77 +-- include/linux/page-flags.h | 260 +++++++--- include/linux/page_idle.h | 99 ++-- include/linux/page_owner.h | 6 +- include/linux/page_ref.h | 92 +++- include/linux/pageblock-flags.h | 2 +- include/linux/pagemap.h | 467 ++++++++++++----- include/linux/rmap.h | 10 +- include/linux/swap.h | 17 +- include/linux/vmstat.h | 107 ++++ include/linux/writeback.h | 9 +- include/net/page_pool.h | 12 +- include/trace/events/writeback.h | 8 +- lib/flex_proportions.c | 28 +- mm/Makefile | 2 +- mm/debug.c | 25 +- mm/filemap.c | 509 +++++++++---------- mm/folio-compat.c | 107 ++++ mm/internal.h | 2 + mm/khugepaged.c | 32 +- mm/memcontrol.c | 100 ++-- mm/memory.c | 11 +- mm/mempolicy.c | 10 + mm/migrate.c | 56 +-- mm/page-writeback.c | 461 ++++++++++------- mm/page_alloc.c | 28 +- mm/page_io.c | 4 +- mm/page_owner.c | 2 +- mm/rmap.c | 12 +- mm/swap.c | 101 ++-- mm/swap_state.c | 2 +- mm/swapfile.c | 8 +- mm/util.c | 60 ++- mm/workingset.c | 44 +- net/core/page_pool.c | 12 +- 58 files changed, 2568 insertions(+), 1421 deletions(-) create mode 100644 mm/folio-compat.c -- 2.30.2
