On 06.06.24 11:38, Lance Yang wrote:
On Thu, Jun 6, 2024 at 4:06 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
On 06.06.24 10:01, David Hildenbrand wrote:
On 06.06.24 05:55, Lance Yang wrote:
On Wed, Jun 5, 2024 at 10:28 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
On 05.06.24 16:20, Lance Yang wrote:
Hi David,
On Wed, Jun 5, 2024 at 8:46 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
On 21.05.24 06:02, Lance Yang wrote:
In preparation for supporting try_to_unmap_one() to unmap PMD-mapped
folios, start the pagewalk first, then call split_huge_pmd_address() to
split the folio.
Since TTU_SPLIT_HUGE_PMD will no longer perform immediately, we might
encounter a PMD-mapped THP missing the mlock in the VM_LOCKED range during
the page walk. It’s probably necessary to mlock this THP to prevent it from
being picked up during page reclaim.
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Suggested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
---
[...] again, sorry for the late review.
No worries at all, thanks for taking time to review!
diff --git a/mm/rmap.c b/mm/rmap.c
index ddffa30c79fb..08a93347f283 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1640,9 +1640,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
if (flags & TTU_SYNC)
pvmw.flags = PVMW_SYNC;
- if (flags & TTU_SPLIT_HUGE_PMD)
- split_huge_pmd_address(vma, address, false, folio);
-
/*
* For THP, we have to assume the worse case ie pmd for invalidation.
* For hugetlb, it could be much worse if we need to do pud
@@ -1668,20 +1665,35 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(&pvmw)) {
- /* Unexpected PMD-mapped THP? */
- VM_BUG_ON_FOLIO(!pvmw.pte, folio);
-
/*
* If the folio is in an mlock()d vma, we must not swap it out.
*/
if (!(flags & TTU_IGNORE_MLOCK) &&
(vma->vm_flags & VM_LOCKED)) {
/* Restore the mlock which got missed */
- if (!folio_test_large(folio))
+ if (!folio_test_large(folio) ||
+ (!pvmw.pte && (flags & TTU_SPLIT_HUGE_PMD)))
mlock_vma_folio(folio, vma);
Should we still keep the '!pvmw.pte' here? Something like:
if (!folio_test_large(folio) || !pvmw.pte)
mlock_vma_folio(folio, vma);
I was wondering the same the whole time ...
We can mlock the THP to prevent it from being picked up during page reclaim.
David, I’d like to hear your thoughts on this ;)
but I think there is no need to for now, in the context of your patchset. :)
--
Cheers,
David / dhildenb
