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From: Kirill A. Shutemov <kirill.shutemov <at> linux.intel.com>
Subject: [PATCHv3, RFC 00/34] Transparent huge page cache
Newsgroups: gmane.linux.kernel
Date: Friday 5th April 2013 11:59:24 UTC (over 3 years ago)
From: "Kirill A. Shutemov" 

Here's third RFC. Thanks everybody for feedback.

The patchset is pretty big already and I want to stop generate new
features to keep it reviewable. Next I'll concentrate on benchmarking and

Therefore some features will be outside initial transparent huge page
cache implementation:
 - page collapsing;
 - migration;
 - tmpfs/shmem;

There are few features which are not implemented and potentially can block

1. Currently we allocate 2M page even if we create only 1 byte file on
ramfs. I don't think it's a problem by itself. With anon thp pages we also
try to allocate huge pages whenever possible.
The problem is that ramfs pages are unevictable and we can't just split
and pushed them in swap as with anon thp. We (at some point) have to have
mechanism to split last page of the file under memory pressure to reclaim
some memory.

2. We don't have knobs for disabling transparent huge page cache per-mount
or per-file. Should we have mount option and fadivse flags as part of
initial implementation?

Any thoughts?

The patchset is also on git:


 - set RADIX_TREE_PRELOAD_NR to 512 only if we build with THP;
 - rewrite lru_add_page_tail() to address few bags;
 - memcg accounting;
 - represent file thp pages in meminfo and friends;
 - dump page order in filemap trace;
 - add missed flush_dcache_page() in zero_huge_user_segment;
 - random cleanups based on feedback.
 - mmap();
 - fix add_to_page_cache_locked() and delete_from_page_cache();
 - introduce mapping_can_have_hugepages();
 - call split_huge_page() only for head page in filemap_fault();
 - wait_split_huge_page(): serialize over i_mmap_mutex too;
 - lru_add_page_tail: avoid PageUnevictable on active/inactive lru lists;
 - fix off-by-one in zero_huge_user_segment();

Kirill A. Shutemov (34):
  mm: drop actor argument of do_generic_file_read()
  block: implement add_bdi_stat()
  mm: implement zero_huge_user_segment and friends
  radix-tree: implement preload for multiple contiguous elements
  memcg, thp: charge huge cache pages
  thp, mm: avoid PageUnevictable on active/inactive lru lists
  thp, mm: basic defines for transparent huge page cache
  thp, mm: introduce mapping_can_have_hugepages() predicate
  thp: represent file thp pages in meminfo and friends
  thp, mm: rewrite add_to_page_cache_locked() to support huge pages
  mm: trace filemap: dump page order
  thp, mm: rewrite delete_from_page_cache() to support huge pages
  thp, mm: trigger bug in replace_page_cache_page() on THP
  thp, mm: locking tail page is a bug
  thp, mm: handle tail pages in page_cache_get_speculative()
  thp, mm: add event counters for huge page alloc on write to a file
  thp, mm: implement grab_thp_write_begin()
  thp, mm: naive support of thp in generic read/write routines
  thp, libfs: initial support of thp in
  thp: handle file pages in split_huge_page()
  thp: wait_split_huge_page(): serialize over i_mmap_mutex too
  thp, mm: truncate support for transparent huge page cache
  thp, mm: split huge page on mmap file page
  ramfs: enable transparent huge page cache
  x86-64, mm: proper alignment mappings with hugepages
  mm: add huge_fault() callback to vm_operations_struct
  thp: prepare zap_huge_pmd() to uncharge file pages
  thp: move maybe_pmd_mkwrite() out of mk_huge_pmd()
  thp, mm: basic huge_fault implementation for generic_file_vm_ops
  thp: extract fallback path from do_huge_pmd_anonymous_page() to a
  thp: initial implementation of do_huge_linear_fault()
  thp: handle write-protect exception to file-backed huge pages
  thp: call __vma_adjust_trans_huge() for file-backed VMA
  thp: map file-backed huge pages on fault

 arch/x86/kernel/sys_x86_64.c   |   12 +-
 drivers/base/node.c            |   10 +
 fs/libfs.c                     |   48 +++-
 fs/proc/meminfo.c              |    6 +
 fs/ramfs/inode.c               |    6 +-
 include/linux/backing-dev.h    |   10 +
 include/linux/huge_mm.h        |   36 ++-
 include/linux/mm.h             |    8 +
 include/linux/mmzone.h         |    1 +
 include/linux/pagemap.h        |   33 ++-
 include/linux/radix-tree.h     |   11 +
 include/linux/vm_event_item.h  |    2 +
 include/trace/events/filemap.h |    7 +-
 lib/radix-tree.c               |   33 ++-
 mm/filemap.c                   |  298 ++++++++++++++++++++-----
 mm/huge_memory.c               |  474
 mm/memcontrol.c                |    2 -
 mm/memory.c                    |   41 +++-
 mm/mmap.c                      |    3 +
 mm/page_alloc.c                |    7 +-
 mm/swap.c                      |   20 +-
 mm/truncate.c                  |   13 ++
 mm/vmstat.c                    |    2 +
 23 files changed, 902 insertions(+), 181 deletions(-)


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