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Subject[PATCH v7 0/4] THP aware uprobe
This set makes uprobe aware of THPs.

Currently, when uprobe is attached to text on THP, the page is split by
FOLL_SPLIT. As a result, uprobe eliminates the performance benefit of THP.

This set makes uprobe THP-aware. Instead of FOLL_SPLIT, we introduces
FOLL_SPLIT_PMD, which only split PMD for uprobe.

TODO (temporarily removed in v7):
After all uprobes within the THP are removed, regroup the PTE-mapped pages
into huge PMD.

This set (plus a few THP patches) is also available at

Changes v6 => v7:
1. Include Acked-by from Kirill A. Shutemov for the first 4 patches;
2. Keep only the first 4 patches (while I working on improving the last 2).

Changes v5 => v6:
1. Enable khugepaged to collapse pmd for pte-mapped THP
(Kirill A. Shutemov).
2. uprobe asks khuagepaged to collaspe pmd. (Kirill A. Shutemov)

Note: Theast two patches in v6 the set apply _after_ v7 of set "Enable THP
for text section of non-shmem files"

Changes v4 => v5:
1. Propagate pte_alloc() error out of follow_pmd_mask().

Changes since v3:
1. Simplify FOLL_SPLIT_PMD case in follow_pmd_mask(), (Kirill A. Shutemov)
2. Fix try_collapse_huge_pmd() to match change in follow_pmd_mask().

Changes since v2:
1. For FOLL_SPLIT_PMD, populated the page table in follow_pmd_mask().
2. Simplify logic in uprobe_write_opcode. (Oleg Nesterov)
3. Fix page refcount handling with FOLL_SPLIT_PMD.
4. Much more testing, together with THP on ext4 and btrfs (sending in
separate set).
5. Rebased.

Changes since v1:
1. introduces FOLL_SPLIT_PMD, instead of modifying split_huge_pmd*();
2. reuse pages_identical() from ksm.c;
3. rewrite most of try_collapse_huge_pmd().

Song Liu (4):
mm: move memcmp_pages() and pages_identical()
uprobe: use original page when all uprobes are removed
mm, thp: introduce FOLL_SPLIT_PMD
uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT

include/linux/mm.h | 8 +++++++
kernel/events/uprobes.c | 51 +++++++++++++++++++++++++++++++----------
mm/gup.c | 8 +++++--
mm/ksm.c | 18 ---------------
mm/util.c | 13 +++++++++++
5 files changed, 66 insertions(+), 32 deletions(-)


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