Messages in this thread | | | Date | Thu, 11 Aug 2022 11:19:35 -0400 | From | Peter Xu <> | Subject | Re: [PATCH v3 5/7] mm: Remember young/dirty bit for page migrations |
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On Tue, Aug 09, 2022 at 06:00:58PM -0400, Peter Xu wrote: > diff --git a/mm/migrate_device.c b/mm/migrate_device.c > index 27fb37d65476..699f821b8443 100644 > --- a/mm/migrate_device.c > +++ b/mm/migrate_device.c > @@ -221,6 +221,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > else > entry = make_readable_migration_entry( > page_to_pfn(page)); > + if (pte_young(pte)) > + entry = make_migration_entry_young(entry); > + if (pte_dirty(pte)) > + entry = make_migration_entry_dirty(entry); > swp_pte = swp_entry_to_pte(entry); > if (pte_present(pte)) { > if (pte_soft_dirty(pte))
This change needs to be wrapped with pte_present() at least..
I also just noticed that this change probably won't help anyway because:
(1) When ram->device, the pte will finally be replaced with a device private entry, and device private entry does not yet support A/D, it means A/D will be dropped again,
(2) When device->ram, we are missing information on either A/D bits, or even if device private entries start to suport A/D, it's still not clear whether we should take device read/write into considerations too on the page A/D bits to be accurate.
I think I'll probably keep the code there for completeness, but I think it won't really help much until more things are done.
-- Peter Xu
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