Zi Yan <ziy@xxxxxxxxxx> writes:
> do_numa_page() and do_huge_pmd_numa_page() share a lot of common code. To
> reduce redundancy, move common code to numa_migrate_prep() and rename
> the function to numa_migrate_check() to reflect its functionality.
>
> Now do_huge_pmd_numa_page() also checks shared folios to set TNF_SHARED
> flag.
>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> ---
> mm/huge_memory.c | 14 ++-------
> mm/internal.h | 5 ++--
> mm/memory.c | 76 ++++++++++++++++++++++++------------------------
> 3 files changed, 44 insertions(+), 51 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index a3c018f2b554..9b312cae6775 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1699,18 +1699,10 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
> if (!folio)
> goto out_map;
>
> - /* See similar comment in do_numa_page for explanation */
> - if (!writable)
> - flags |= TNF_NO_GROUP;
> -
> nid = folio_nid(folio);
NITPICK: It appears that we can remove "nid" local variable.
> - /*
> - * For memory tiering mode, cpupid of slow memory page is used
> - * to record page access time. So use default value.
> - */
> - if (!folio_use_access_time(folio))
> - last_cpupid = folio_last_cpupid(folio);
> - target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags);
> +
> + target_nid = numa_migrate_check(folio, vmf, haddr, &flags, writable,
> + &last_cpupid);
> if (target_nid == NUMA_NO_NODE)
> goto out_map;
> if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) {
> diff --git a/mm/internal.h b/mm/internal.h
> index 52f7fc4e8ac3..fb16e18c9761 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1191,8 +1191,9 @@ void vunmap_range_noflush(unsigned long start, unsigned long end);
>
> void __vunmap_range_noflush(unsigned long start, unsigned long end);
>
> -int numa_migrate_prep(struct folio *folio, struct vm_fault *vmf,
> - unsigned long addr, int page_nid, int *flags);
> +int numa_migrate_check(struct folio *folio, struct vm_fault *vmf,
> + unsigned long addr, int *flags, bool writable,
> + int *last_cpupid);
>
> void free_zone_device_folio(struct folio *folio);
> int migrate_device_coherent_page(struct page *page);
> diff --git a/mm/memory.c b/mm/memory.c
> index 503d493263df..b093df652c11 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5368,16 +5368,43 @@ static vm_fault_t do_fault(struct vm_fault *vmf)
> return ret;
> }
>
> -int numa_migrate_prep(struct folio *folio, struct vm_fault *vmf,
> - unsigned long addr, int page_nid, int *flags)
> +int numa_migrate_check(struct folio *folio, struct vm_fault *vmf,
> + unsigned long addr, int *flags,
> + bool writable, int *last_cpupid)
> {
> struct vm_area_struct *vma = vmf->vma;
>
> + /*
> + * Avoid grouping on RO pages in general. RO pages shouldn't hurt as
> + * much anyway since they can be in shared cache state. This misses
> + * the case where a mapping is writable but the process never writes
> + * to it but pte_write gets cleared during protection updates and
> + * pte_dirty has unpredictable behaviour between PTE scan updates,
> + * background writeback, dirty balancing and application behaviour.
> + */
> + if (!writable)
> + *flags |= TNF_NO_GROUP;
> +
> + /*
> + * Flag if the folio is shared between multiple address spaces. This
> + * is later used when determining whether to group tasks together
> + */
> + if (folio_likely_mapped_shared(folio) && (vma->vm_flags & VM_SHARED))
> + *flags |= TNF_SHARED;
> + /*
> + * For memory tiering mode, cpupid of slow memory page is used
> + * to record page access time. So use default value.
> + */
> + if (folio_use_access_time(folio))
> + *last_cpupid = (-1 & LAST_CPUPID_MASK);
> + else
> + *last_cpupid = folio_last_cpupid(folio);
> +
> /* Record the current PID acceesing VMA */
> vma_set_access_pid_bit(vma);
>
> count_vm_numa_event(NUMA_HINT_FAULTS);
> - if (page_nid == numa_node_id()) {
> + if (folio_nid(folio) == numa_node_id()) {
> count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
> *flags |= TNF_FAULT_LOCAL;
> }
> @@ -5442,13 +5469,13 @@ static void numa_rebuild_large_mapping(struct vm_fault *vmf, struct vm_area_stru
> static vm_fault_t do_numa_page(struct vm_fault *vmf)
> {
> struct vm_area_struct *vma = vmf->vma;
> + pte_t old_pte = vmf->orig_pte;
The usage of old_pte is different from other use cases. Where,
old_pte = *pte;
check old_pte and orig_pte
generate new_pte from old_pte
set new_pte
We have used this before in do_numa_page(), but not do that now. But I
still think that it's better to follow the convention partly if
possible. This makes code easier to be read. I notices that we don't
follow it in do_huge_pmd_numa_page(), we may change that?
> + pte_t pte;
> struct folio *folio = NULL;
> int nid = NUMA_NO_NODE;
> bool writable = false, ignore_writable = false;
> bool pte_write_upgrade = vma_wants_manual_pte_write_upgrade(vma);
> - int last_cpupid;
> - int target_nid;
> - pte_t pte, old_pte;
> + int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
Because we will initialize last_cpupid in numa_migrate_check(), we don't
need to initialize it here?
> int flags = 0, nr_pages;
>
> /*
> @@ -5456,10 +5483,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
> * table lock, that its contents have not changed during fault handling.
> */
> spin_lock(vmf->ptl);
> - /* Read the live PTE from the page tables: */
> - old_pte = ptep_get(vmf->pte);
> -
> - if (unlikely(!pte_same(old_pte, vmf->orig_pte))) {
> + if (unlikely(!pte_same(old_pte, ptep_get(vmf->pte)))) {
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> goto out;
> }
[snip]
--
Best Regards,
Huang, Ying
