On Wed, 2 Jul 2025 15:13:36 -0500 Bijan Tabatabai <bijan311@xxxxxxxxx> wrote:
> From: Bijan Tabatabai <bijantabatab@xxxxxxxxxx>
>
> The paddr versions of migrate_{hot/cold} filter out folios from
> migration based on the scheme's filters. This patch does the same for
> the vaddr versions of those schemes.
>
> The filtering code is mostly the same for the paddr and vaddr versions.
> The exception is the young filter. paddr determines if a page is young
> by doing a folio rmap walk to find the page table entries corresponding
> to the folio. However, vaddr schemes have easier access to the page
> tables, so we add some logic to avoid the extra work.
>
> Co-developed-by: Ravi Shankar Jonnalagadda <ravis.opensrc@xxxxxxxxxx>
> Signed-off-by: Ravi Shankar Jonnalagadda <ravis.opensrc@xxxxxxxxxx>
> Signed-off-by: Bijan Tabatabai <bijantabatab@xxxxxxxxxx>
> ---
> mm/damon/vaddr.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
>
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index 5f230a427fdc..2a485bf19101 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -611,6 +611,62 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
> return max_nr_accesses;
> }
>
> +static bool damos_va_filter_young(struct damos_filter *filter,
> + struct folio *folio, struct vm_area_struct *vma,
> + unsigned long addr, pte_t *ptep, pmd_t *pmdp)
> +{
> + bool young;
> +
> + if (ptep) {
> + young = pte_young(*ptep);
Let's use ptep_get().
> + } else if (pmdp) {
> + young = pmd_young(*pmdp);
Let's use pmdp_get().
> + } else {
> + WARN_ONCE(1, "Neither ptep nor pmdp provided");
> + return false;
> + }
Can this really happen? If so, let's remove WARN_ONCE(). If not, let's drop
the entire else case.
> +
> + young = young || !folio_test_idle(folio) ||
> + mmu_notifier_test_young(vma->vm_mm, addr);
> +
> + if (young && ptep)
> + damon_ptep_mkold(ptep, vma, addr);
> + else if (young && pmdp)
> + damon_pmdp_mkold(pmdp, vma, addr);
> +
> + return young == filter->matching;
I now realize this function is not returning if the folio is young, but if the
youngness matches the filter. Let's rename, say,
damos_va_filter_young_match()?
> +}
> +
> +static bool damos_va_filter_out(struct damos *scheme, struct folio *folio,
> + struct vm_area_struct *vma, unsigned long addr,
> + pte_t *ptep, pmd_t *pmdp)
> +{
> + struct damos_filter *filter;
> + bool matched;
> +
> + if (scheme->core_filters_allowed)
> + return false;
> +
> + damos_for_each_ops_filter(filter, scheme) {
> + /*
> + * damos_folio_filter_match checks the young filter by doing an
> + * rmap on the folio to find its page table. However, being the
> + * vaddr scheme, we have direct access to the page tables, so
> + * use that instead.
> + */
> + if (filter->type == DAMOS_FILTER_TYPE_YOUNG) {
> + matched = damos_va_filter_young(filter, folio, vma,
> + addr, ptep, pmdp);
> + } else {
> + matched = damos_folio_filter_match(filter, folio);
> + }
Let's drop enclosing braces for single line if-esle statements.
> +
> + if (matched)
> + return !filter->allow;
> + }
> + return scheme->ops_filters_default_reject;
> +}
> +
> struct damos_va_migrate_private {
> struct list_head *migration_lists;
> struct damos *scheme;
> @@ -695,8 +751,12 @@ static int damos_va_migrate_pmd_entry(pmd_t *pmd, unsigned long addr,
> if (!folio)
> goto unlock;
>
> + if (damos_va_filter_out(s, folio, walk->vma, addr, NULL, pmd))
> + goto put_folio;
> +
> damos_va_migrate_folio(folio, walk->vma, addr, dests, migration_lists);
>
> +put_folio:
> folio_put(folio);
> unlock:
> spin_unlock(ptl);
> @@ -724,8 +784,12 @@ static int damos_va_migrate_pte_entry(pte_t *pte, unsigned long addr,
> if (!folio)
> return 0;
>
> + if (damos_va_filter_out(s, folio, walk->vma, addr, pte, NULL))
> + goto put_folio;
> +
> damos_va_migrate_folio(folio, walk->vma, addr, dests, migration_lists);
>
> +put_folio:
> folio_put(folio);
> return 0;
> }
> --
> 2.43.5
>
>
Thanks,
SJ
