Re: [PATCH v3 00/14] mm: page migration enhancement for thp
From: Zi Yan
Date: Thu Feb 23 2017 - 11:12:56 EST
Just want to get comments on THP migration part (Patch 4-14). If they
look OK, I can rebase THP migration part on mmotm-2017-02-22-16-28 and
send them out for merging.
Zi Yan wrote:
> From: Zi Yan <ziy@xxxxxxxxxx>
> Hi all,
> The patches are rebased on mmotm-2017-02-01-15-35 with feedbacks from
> Naoya Horiguchi's v2 patches.
> I fix a bug in zap_pmd_range() and include the fixes in Patches 1-3.
> The racy check in zap_pmd_range() can miss pmd_protnone and pmd_migration_entry,
> which leads to PTE page table not freed.
> In Patch 4, I move _PAGE_SWP_SOFT_DIRTY to bit 1. Because bit 6 (used in v2)
> can be set by some CPUs by mistake and the new swap entry format does not use
> bit 1-4.
> I also adjust two core migration functions, set_pmd_migration_entry() and
> remove_migration_pmd(), to use Kirill A. Shutemov's page_vma_mapped_walk()
> function. Patch 8 needs Kirill's comments, since I also add changes
> to his page_vma_mapped_walk() function with pmd_migration_entry handling.
> In Patch 8, I replace pmdp_huge_get_and_clear() with pmdp_huge_clear_flush()
> in set_pmd_migration_entry() to avoid data corruption after page migration.
> In Patch 9, I include is_pmd_migration_entry() in pmd_none_or_trans_huge_or_clear_bad().
> Otherwise, a pmd_migration_entry is treated as pmd_bad and cleared, which
> leads to deposited PTE page table not freed.
> I personally use this patchset with my customized kernel to test frequent
> page migrations by replacing page reclaim with page migration.
> The bugs fixed in Patches 1-3 and 8 was discovered while I am testing my kernel.
> I did a 16-hour stress test that has ~7 billion total page migrations.
> No error or data corruption was found.
> General description
> This patchset enhances page migration functionality to handle thp migration
> for various page migration's callers:
> - mbind(2)
> - move_pages(2)
> - migrate_pages(2)
> - cgroup/cpuset migration
> - memory hotremove
> - soft offline
> The main benefit is that we can avoid unnecessary thp splits, which helps us
> avoid performance decrease when your applications handles NUMA optimization on
> their own.
> The implementation is similar to that of normal page migration, the key point
> is that we modify a pmd to a pmd migration entry in swap-entry like format.
> Any comments or advices are welcomed.
> Best Regards,
> Yan Zi
> Naoya Horiguchi (11):
> mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1
> mm: mempolicy: add queue_pages_node_check()
> mm: thp: introduce separate TTU flag for thp freezing
> mm: thp: introduce CONFIG_ARCH_ENABLE_THP_MIGRATION
> mm: thp: enable thp migration in generic path
> mm: thp: check pmd migration entry in common path
> mm: soft-dirty: keep soft-dirty bits over thp migration
> mm: hwpoison: soft offline supports thp migration
> mm: mempolicy: mbind and migrate_pages support thp migration
> mm: migrate: move_pages() supports thp migration
> mm: memory_hotplug: memory hotremove supports thp migration
> Zi Yan (3):
> mm: thp: make __split_huge_pmd_locked visible.
> mm: thp: create new __zap_huge_pmd_locked function.
> mm: use pmd lock instead of racy checks in zap_pmd_range()
> arch/x86/Kconfig | 4 +
> arch/x86/include/asm/pgtable.h | 17 ++
> arch/x86/include/asm/pgtable_64.h | 2 +
> arch/x86/include/asm/pgtable_types.h | 10 +-
> arch/x86/mm/gup.c | 4 +-
> fs/proc/task_mmu.c | 37 +++--
> include/asm-generic/pgtable.h | 105 ++++--------
> include/linux/huge_mm.h | 36 ++++-
> include/linux/rmap.h | 1 +
> include/linux/swapops.h | 146 ++++++++++++++++-
> mm/Kconfig | 3 +
> mm/gup.c | 20 ++-
> mm/huge_memory.c | 302 +++++++++++++++++++++++++++++------
> mm/madvise.c | 2 +
> mm/memcontrol.c | 2 +
> mm/memory-failure.c | 31 ++--
> mm/memory.c | 33 ++--
> mm/memory_hotplug.c | 17 +-
> mm/mempolicy.c | 124 ++++++++++----
> mm/migrate.c | 66 ++++++--
> mm/mprotect.c | 6 +-
> mm/mremap.c | 2 +-
> mm/page_vma_mapped.c | 13 +-
> mm/pagewalk.c | 2 +
> mm/pgtable-generic.c | 3 +-
> mm/rmap.c | 21 ++-
> 26 files changed, 770 insertions(+), 239 deletions(-)
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