[PATCH v2 0/4] mm: split the file's i_mmap tree for NUMA

[Huang Shijie]

  In NUMA, there are maybe many NUMA nodes and many CPUs.
For example, a Hygon's server has 12 NUMA nodes, and 384 CPUs.
In the UnixBench tests, there is a test "execl" which tests
the execve system call.

  When we test our server with "./Run -c 384 execl",
the test result is not good enough. The i_mmap locks contended heavily on
"libc.so" and "ld.so". For example, the i_mmap tree for "libc.so" can have 
over 6000 VMAs, all the VMAs can be in different NUMA mode.
The insert/remove operations do not run quickly enough.

patch 1 & patch 2 are try to hide the direct access of i_mmap.
patch 3 splits the i_mmap into sibling trees, each tree has separate lock,
and we can get better performance with this patch set in our NUMA server:
    we can get over 400% performance improvement.

I did not test the non-NUMA case, since I do not have such server.    
    
v1 --> v2:
	Not only split the immap tree, but also split the lock.
	v1 : https://lkml.org/lkml/2026/4/13/199

Huang Shijie (4):
  mm: use mapping_mapped to simplify the code
  mm: use get_i_mmap_root to access the file's i_mmap
  mm/fs: split the file's i_mmap tree
  docs/mm: update document for split i_mmap tree

 Documentation/mm/process_addrs.rst |  63 +++++++---
 arch/arm/mm/fault-armv.c           |   3 +-
 arch/arm/mm/flush.c                |   3 +-
 arch/nios2/mm/cacheflush.c         |   3 +-
 arch/parisc/kernel/cache.c         |   4 +-
 fs/Kconfig                         |   8 ++
 fs/dax.c                           |   3 +-
 fs/hugetlbfs/inode.c               |  30 +++--
 fs/inode.c                         |  75 +++++++++++-
 include/linux/fs.h                 | 179 ++++++++++++++++++++++++++++-
 include/linux/mm.h                 |  81 +++++++++++++
 include/linux/mm_types.h           |   3 +
 kernel/events/uprobes.c            |   3 +-
 mm/hugetlb.c                       |   7 +-
 mm/internal.h                      |   3 +-
 mm/khugepaged.c                    |   6 +-
 mm/memory-failure.c                |   8 +-
 mm/memory.c                        |   8 +-
 mm/mmap.c                          |  11 +-
 mm/nommu.c                         |  28 +++--
 mm/pagewalk.c                      |   4 +-
 mm/rmap.c                          |   2 +-
 mm/vma.c                           |  74 +++++++++---
 mm/vma_init.c                      |   3 +
 24 files changed, 534 insertions(+), 78 deletions(-)

-- 
2.53.0