Re: [PATCH v5 1/8] mm/huge_memory: only split PMD mapping when necessary in unmap_folio()

On 26.02.24 21:55, Zi Yan wrote:

From: Zi Yan ziy@nvidia.com

As multi-size THP support is added, not all THPs are PMD-mapped, thus during a huge page split, there is no need to always split PMD mapping in unmap_folio(). Make it conditional.

Signed-off-by: Zi Yan ziy@nvidia.com

mm/huge_memory.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 28341a5067fb..b20e535e874c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2727,11 +2727,14 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, static void unmap_folio(struct folio *folio) {

• enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |

• TTU_SYNC | TTU_BATCH_FLUSH;
  

• enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SYNC |

• TTU_BATCH_FLUSH;
  

VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);

• if (folio_test_pmd_mappable(folio))

• ttu_flags |= TTU_SPLIT_HUGE_PMD;
  

• /*
  • Anon pages need migration entries to preserve them, but file
  • pages can simply be left unmapped, then faulted back on demand.

Reviewed-by: David Hildenbrand david@redhat.com