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4b51634cd1
linux/mm
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Hugh Dickins 4b51634cd1 mm,thp,rmap: subpages_mapcount COMPOUND_MAPPED if PMD-mapped 
Can the lock_compound_mapcount() bit_spin_lock apparatus be removed now? 
Yes.  Not by atomic64_t or cmpxchg games, those get difficult on 32-bit;
but if we slightly abuse subpages_mapcount by additionally demanding that
one bit be set there when the compound page is PMD-mapped, then a cascade
of two atomic ops is able to maintain the stats without bit_spin_lock.

This is harder to reason about than when bit_spin_locked, but I believe
safe; and no drift in stats detected when testing.  When there are racing
removes and adds, of course the sequence of operations is less well-
defined; but each operation on subpages_mapcount is atomically good.  What
might be disastrous, is if subpages_mapcount could ever fleetingly appear
negative: but the pte lock (or pmd lock) these rmap functions are called
under, ensures that a last remove cannot race ahead of a first add.

Continue to make an exception for hugetlb (PageHuge) pages, though that
exception can be easily removed by a further commit if necessary: leave
subpages_mapcount 0, don't bother with COMPOUND_MAPPED in its case, just
carry on checking compound_mapcount too in folio_mapped(), page_mapped().

Evidence is that this way goes slightly faster than the previous
implementation in all cases (pmds after ptes now taking around 103ms); and
relieves us of worrying about contention on the bit_spin_lock.

Link: https://lkml.kernel.org/r/3978f3ca-5473-55a7-4e14-efea5968d892@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-11-30 15:58:48 -08:00
..
damon mm/damon: use kstrtobool() instead of strtobool() 2022-11-30 15:58:45 -08:00
kasan memory: move hotplug memory notifier priority to same file for easy sorting 2022-11-08 17:37:17 -08:00
kfence kfence: fix stack trace pruning 2022-11-22 18:50:44 -08:00
kmsan kmsan: core: kmsan_in_runtime() should return true in NMI context 2022-11-08 15:57:24 -08:00
backing-dev.c mm: backing-dev: Remove the unneeded result variable 2022-09-11 20:26:02 -07:00
balloon_compaction.c mm: Convert all PageMovable users to movable_operations 2022-08-02 12:34:03 -04:00
bootmem_info.c bootmem: remove the vmemmap pages from kmemleak in put_page_bootmem 2022-08-28 14:02:45 -07:00
cma_debug.c mm/cma_debug: show complete cma name in debugfs directories 2022-09-11 20:25:50 -07:00
cma_sysfs.c
cma.c Revert "mm/cma.c: remove redundant cma_mutex lock" 2022-05-13 15:11:26 -07:00
cma.h mm/cma: provide option to opt out from exposing pages on activation failure 2022-03-22 15:57:09 -07:00
compaction.c mm: migrate: fix THP's mapcount on isolation 2022-11-30 14:49:41 -08:00
debug_page_ref.c
debug_vm_pgtable.c mm: debug_vm_pgtable: use VM_ACCESS_FLAGS 2022-11-08 17:37:19 -08:00
debug.c mm,thp,rmap: simplify compound page mapcount handling 2022-11-30 15:58:46 -08:00
dmapool.c mm/dmapool.c: revert "make dma pool to use kmalloc_node" 2022-01-15 16:30:28 +02:00
early_ioremap.c mm/early_ioremap: declare early_memremap_pgprot_adjust() 2022-03-22 15:57:11 -07:00
fadvise.c riscv: compat: syscall: Add compat_sys_call_table implementation 2022-04-26 13:36:25 -07:00
failslab.c mm: fix unexpected changes to {failslab|fail_page_alloc}.attr 2022-11-22 18:50:44 -08:00
filemap.c filemap: find_get_entries() now updates start offset 2022-11-08 17:37:12 -08:00
folio-compat.c mm,thp,rmap: simplify compound page mapcount handling 2022-11-30 15:58:46 -08:00
frontswap.c frontswap: don't call ->init if no ops are registered 2022-09-26 12:14:34 -07:00
gup_test.c mm/gup_test: start/stop/read functionality for PIN LONGTERM test 2022-11-08 17:37:15 -08:00
gup_test.h mm/gup_test: start/stop/read functionality for PIN LONGTERM test 2022-11-08 17:37:15 -08:00
gup.c hugetlb: simplify hugetlb handling in follow_page_mask 2022-11-08 17:37:10 -08:00
highmem.c highmem: fix kmap_to_page() for kmap_local_page() addresses 2022-10-12 18:51:51 -07:00
hmm.c mm/swap: add swp_offset_pfn() to fetch PFN from swap entry 2022-09-26 19:46:05 -07:00
huge_memory.c mm,thp,rmap: subpages_mapcount of PTE-mapped subpages 2022-11-30 15:58:47 -08:00
hugetlb_cgroup.c mm/hugeltb_cgroup: convert hugetlb_cgroup_commit_charge*() to folios 2022-11-30 15:58:43 -08:00
hugetlb_vmemmap.c mm/hugetlb_vmemmap: remap head page to newly allocated page 2022-11-30 15:58:47 -08:00
hugetlb_vmemmap.h mm: hugetlb_vmemmap: improve hugetlb_vmemmap code readability 2022-08-08 18:06:43 -07:00
hugetlb.c mm,thp,rmap: simplify compound page mapcount handling 2022-11-30 15:58:46 -08:00
hwpoison-inject.c mm/hwpoison: add __init/__exit annotations to module init/exit funcs 2022-10-03 14:03:05 -07:00
init-mm.c mm: remove rb tree. 2022-09-26 19:46:16 -07:00
internal.h mm/hwpoison: introduce per-memory_block hwpoison counter 2022-11-08 17:37:22 -08:00
interval_tree.c
io-mapping.c
ioremap.c mm: ioremap: Add ioremap/iounmap_allowed() 2022-06-27 12:22:31 +01:00
Kconfig mm,hugetlb: use folio fields in second tail page 2022-11-30 15:58:46 -08:00
Kconfig.debug Two followon fixes for the post-5.19 series "Use pageblock_order for cma 2022-05-27 11:40:49 -07:00
khugepaged.c mm,thp,rmap: simplify compound page mapcount handling 2022-11-30 15:58:46 -08:00
kmemleak.c mm/kmemleak: prevent soft lockup in kmemleak_scan()'s object iteration loops 2022-10-28 13:37:22 -07:00
ksm.c memory: move hotplug memory notifier priority to same file for easy sorting 2022-11-08 17:37:17 -08:00
list_lru.c mm: kmem: make mem_cgroup_from_obj() vmalloc()-safe 2022-06-16 19:48:31 -07:00
maccess.c asm-generic updates for 5.18 2022-03-23 18:03:08 -07:00
madvise.c madvise: use zap_page_range_single for madvise dontneed 2022-11-30 14:49:40 -08:00
Makefile mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol 2022-10-03 14:03:36 -07:00
mapping_dirty_helpers.c mm: move tlb_flush_pending inline helpers to mm_inline.h 2022-01-15 16:30:27 +02:00
memblock.c mm: add pageblock_align() macro 2022-10-03 14:03:04 -07:00
memcontrol.c mm: vmscan: split khugepaged stats from direct reclaim stats 2022-11-30 15:58:41 -08:00
memfd.c memfd: fix F_SEAL_WRITE after shmem huge page allocated 2022-03-05 11:08:32 -08:00
memory_hotplug.c mm: add pageblock_aligned() macro 2022-10-03 14:03:04 -07:00
memory-failure.c mm,hugetlb: use folio fields in second tail page 2022-11-30 15:58:46 -08:00
memory-tiers.c memory: move hotplug memory notifier priority to same file for easy sorting 2022-11-08 17:37:17 -08:00
memory.c mm: use pte markers for swap errors 2022-11-30 15:58:46 -08:00
mempolicy.c mm/mempolicy: fix mbind_range() arguments to vma_merge() 2022-10-20 21:27:21 -07:00
mempool.c mempool: do not use ksize() for poisoning 2022-11-30 15:58:41 -08:00
memremap.c mm/memremap.c: map FS_DAX device memory as decrypted 2022-11-08 15:57:23 -08:00
memtest.c
migrate_device.c mm/migrate_device: return number of migrating pages in args->cpages 2022-11-22 18:50:43 -08:00
migrate.c mm/hugetlb: convert move_hugetlb_state() to folios 2022-11-30 15:58:43 -08:00
mincore.c mm: convert find_get_incore_page() to filemap_get_incore_folio() 2022-11-08 17:37:18 -08:00
mlock.c mm/mlock: drop dead code in count_mm_mlocked_page_nr() 2022-09-26 19:46:27 -07:00
mm_init.c memory: move hotplug memory notifier priority to same file for easy sorting 2022-11-08 17:37:17 -08:00
mm_slot.h mm: introduce common struct mm_slot 2022-10-03 14:02:43 -07:00
mmap_lock.c
mmap.c Merge branch 'mm-hotfixes-stable' into mm-stable 2022-11-30 14:58:42 -08:00
mmu_gather.c mm/khugepaged: fix GUP-fast interaction by sending IPI 2022-11-30 14:49:42 -08:00
mmu_notifier.c mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() 2022-04-21 20:01:10 -07:00
mmzone.c mm: multi-gen LRU: groundwork 2022-09-26 19:46:09 -07:00
mprotect.c Revert "mm/uffd: fix warning without PTE_MARKER_UFFD_WP compiled in" 2022-11-08 17:37:21 -08:00
mremap.c mm: add merging after mremap resize 2022-09-26 19:46:28 -07:00
msync.c mm/msync: use vma_find() instead of vma linked list 2022-09-26 19:46:25 -07:00
nommu.c mm: remove the vma linked list 2022-09-26 19:46:26 -07:00
oom_kill.c mm: reduce noise in show_mem for lowmem allocations 2022-09-26 19:46:29 -07:00
page_alloc.c mm,thp,rmap: subpages_mapcount COMPOUND_MAPPED if PMD-mapped 2022-11-30 15:58:48 -08:00
page_counter.c mm: page_counter: remove unneeded atomic ops for low/min 2022-09-11 20:26:01 -07:00
page_ext.c Merge branch 'mm-hotfixes-stable' into mm-stable 2022-11-30 14:58:42 -08:00
page_idle.c mm: don't be stuck to rmap lock on reclaim path 2022-05-19 14:08:54 -07:00
page_io.c swap: convert swap_writepage() to use a folio 2022-10-03 14:02:52 -07:00
page_isolation.c mm/page_isolation: fix clang deadcode warning 2022-10-28 13:37:22 -07:00
page_owner.c mm: reuse pageblock_start/end_pfn() macro 2022-10-03 14:03:03 -07:00
page_poison.c
page_reporting.c
page_reporting.h
page_table_check.c mm: use kstrtobool() instead of strtobool() 2022-11-30 15:58:45 -08:00
page_vma_mapped.c mm/swap: add swp_offset_pfn() to fetch PFN from swap entry 2022-09-26 19:46:05 -07:00
page-writeback.c mm: export balance_dirty_pages_ratelimited_flags() 2022-09-26 12:28:07 +02:00
pagewalk.c - Yu Zhao's Multi-Gen LRU patches are here. They've been under test in 2022-10-10 17:53:04 -07:00
percpu-internal.h percpu: improve percpu_alloc_percpu event trace 2022-05-13 07:20:18 -07:00
percpu-km.c
percpu-stats.c mm: use vmalloc_array and vcalloc for array allocations 2022-03-08 09:30:46 -05:00
percpu-vm.c
percpu.c mm: percpu: use kmemleak_ignore_phys() instead of kmemleak_free() 2022-07-17 17:14:47 -07:00
pgalloc-track.h
pgtable-generic.c mm: avoid unnecessary flush on change_huge_pmd() 2022-05-13 07:20:05 -07:00
process_vm_access.c
ptdump.c mm: pagewalk: Fix race between unmap and page walker 2022-09-03 10:13:13 -07:00
readahead.c mm: add PSI accounting around ->read_folio and ->readahead calls 2022-09-20 08:24:38 -06:00
rmap.c mm,thp,rmap: subpages_mapcount COMPOUND_MAPPED if PMD-mapped 2022-11-30 15:58:48 -08:00
rodata_test.c mm/rodata_test: use PAGE_ALIGNED() helper 2022-10-03 14:03:05 -07:00
secretmem.c mm/secretmem: remove reduntant return value 2022-10-03 14:03:36 -07:00
shmem.c mm: use pte markers for swap errors 2022-11-30 15:58:46 -08:00
shrinker_debug.c mm: shrinkers: fix double kfree on shrinker name 2022-07-29 18:07:13 -07:00
shuffle.c mm/shuffle: convert module_param_call to module_param_cb 2022-10-03 14:03:07 -07:00
shuffle.h
slab_common.c - Yu Zhao's Multi-Gen LRU patches are here. They've been under test in 2022-10-10 17:53:04 -07:00
slab.c Random number generator fixes for Linux 6.1-rc1. 2022-10-16 15:27:07 -07:00
slab.h - Yu Zhao's Multi-Gen LRU patches are here. They've been under test in 2022-10-10 17:53:04 -07:00
slob.c Merge branch 'slab/for-6.1/kmalloc_size_roundup' into slab/for-next 2022-09-29 11:30:55 +02:00
slub.c mm/slub.c: use hotplug_memory_notifier() directly 2022-11-08 17:37:16 -08:00
sparse-vmemmap.c mm: hugetlb_vmemmap: move vmemmap code related to HugeTLB to hugetlb_vmemmap.c 2022-08-08 18:06:42 -07:00
sparse.c mm/hwpoison: introduce per-memory_block hwpoison counter 2022-11-08 17:37:22 -08:00
swap_cgroup.c mm: memcontrol: don't allocate cgroup swap arrays when memcg is disabled 2022-10-03 14:03:36 -07:00
swap_slots.c mm/swap: convert put_swap_page() to put_swap_folio() 2022-10-03 14:02:46 -07:00
swap_state.c mm: convert find_get_incore_page() to filemap_get_incore_folio() 2022-11-08 17:37:18 -08:00
swap.c swap: add a limit for readahead page-cluster value 2022-11-08 17:37:22 -08:00
swap.h mm: convert find_get_incore_page() to filemap_get_incore_folio() 2022-11-08 17:37:18 -08:00
swapfile.c mm: use pte markers for swap errors 2022-11-30 15:58:46 -08:00
truncate.c filemap: find_get_entries() now updates start offset 2022-11-08 17:37:12 -08:00
usercopy.c mm: use kstrtobool() instead of strtobool() 2022-11-30 15:58:45 -08:00
userfaultfd.c mm/shmem: use page_mapping() to detect page cache for uffd continue 2022-11-08 15:57:23 -08:00
util.c mm,thp,rmap: simplify compound page mapcount handling 2022-11-30 15:58:46 -08:00
vmalloc.c mm: vmalloc: use trace_free_vmap_area_noflush event 2022-11-08 17:37:17 -08:00
vmpressure.c
vmscan.c mm: vmscan: split khugepaged stats from direct reclaim stats 2022-11-30 15:58:41 -08:00
vmstat.c mm: vmscan: split khugepaged stats from direct reclaim stats 2022-11-30 15:58:41 -08:00
workingset.c mm: vmscan: make rotations a secondary factor in balancing anon vs file 2022-11-08 17:37:11 -08:00
z3fold.c mm: Convert all PageMovable users to movable_operations 2022-08-02 12:34:03 -04:00
zbud.c
zpool.c zpool: remove the list of pools_head 2022-01-15 16:30:31 +02:00
zsmalloc.c zsmalloc: replace IS_ERR() with IS_ERR_VALUE() 2022-11-30 15:58:46 -08:00
zswap.c mm/swap: remove the end_write_func argument to __swap_writepage 2022-09-11 20:25:50 -07:00