[v2,0/2] khugepaged: collapse pmd for pte-mapped THP

Message

Song Liu July 31, 2019, 6:33 p.m. UTC

Changes v1 => v2:
1. Call collapse_pte_mapped_thp() directly from uprobe_write_opcode();
2. Add VM_BUG_ON() for addr alignment in khugepaged_add_pte_mapped_thp()
   and collapse_pte_mapped_thp().

This set is the newer version of 5/6 and 6/6 of [1]. Newer version of
1-4 of the work [2] was recently picked by Andrew.

Patch 1 enables khugepaged to handle pte-mapped THP. These THPs are left
in such state when khugepaged failed to get exclusive lock of mmap_sem.

Patch 2 leverages work in 1 for uprobe on THP. After [2], uprobe only
splits the PMD. When the uprobe is disabled, we get pte-mapped THP.
After this set, these pte-mapped THP will be collapsed as pmd-mapped.

[1] https://lkml.org/lkml/2019/6/23/23
[2] https://www.spinics.net/lists/linux-mm/msg185889.html

Song Liu (2):
  khugepaged: enable collapse pmd for pte-mapped THP
  uprobe: collapse THP pmd after removing all uprobes

 include/linux/khugepaged.h |  12 ++++
 kernel/events/uprobes.c    |   9 +++
 mm/khugepaged.c            | 138 +++++++++++++++++++++++++++++++++++++
 3 files changed, 159 insertions(+)

--
2.17.1

Comments

Kirill A. Shutemov Aug. 1, 2019, 11:19 a.m. UTC | #1

On Wed, Jul 31, 2019 at 11:33:29AM -0700, Song Liu wrote:
> Changes v1 => v2:
> 1. Call collapse_pte_mapped_thp() directly from uprobe_write_opcode();
> 2. Add VM_BUG_ON() for addr alignment in khugepaged_add_pte_mapped_thp()
>    and collapse_pte_mapped_thp().
> 
> This set is the newer version of 5/6 and 6/6 of [1]. Newer version of
> 1-4 of the work [2] was recently picked by Andrew.
> 
> Patch 1 enables khugepaged to handle pte-mapped THP. These THPs are left
> in such state when khugepaged failed to get exclusive lock of mmap_sem.
> 
> Patch 2 leverages work in 1 for uprobe on THP. After [2], uprobe only
> splits the PMD. When the uprobe is disabled, we get pte-mapped THP.
> After this set, these pte-mapped THP will be collapsed as pmd-mapped.
> 
> [1] https://lkml.org/lkml/2019/6/23/23
> [2] https://www.spinics.net/lists/linux-mm/msg185889.html
> 
> Song Liu (2):
>   khugepaged: enable collapse pmd for pte-mapped THP
>   uprobe: collapse THP pmd after removing all uprobes

Looks good for the start.

Acked-by: Kirill A. Shutemov <[e-mail]>