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SubjectRe: [PATCH v2 2/4] mm: migrate: move the numamigrate_isolate_page() into do_numa_page()
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On 8/22/2023 5:02 PM, Bharata B Rao wrote:
> On 22-Aug-23 6:23 AM, Baolin Wang wrote:
>> Move the numamigrate_isolate_page() into do_numa_page() to simplify the
>> migrate_misplaced_page(), which now only focuses on page migration, and
>> it also serves as a preparation for supporting batch migration for
>> migrate_misplaced_page().
>>
>> While we are at it, change the numamigrate_isolate_page() to boolean
>> type to make the return value more clear.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> ---
>> include/linux/migrate.h | 6 ++++++
>> mm/huge_memory.c | 7 +++++++
>> mm/memory.c | 7 +++++++
>> mm/migrate.c | 22 +++++++---------------
>> 4 files changed, 27 insertions(+), 15 deletions(-)
>>
>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
>> index 711dd9412561..ddcd62ec2c12 100644
>> --- a/include/linux/migrate.h
>> +++ b/include/linux/migrate.h
>> @@ -144,12 +144,18 @@ const struct movable_operations *page_movable_ops(struct page *page)
>> #ifdef CONFIG_NUMA_BALANCING
>> int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>> int node);
>> +bool numamigrate_isolate_page(pg_data_t *pgdat, struct page *page);
>> #else
>> static inline int migrate_misplaced_page(struct page *page,
>> struct vm_area_struct *vma, int node)
>> {
>> return -EAGAIN; /* can't migrate now */
>> }
>> +
>> +static inline bool numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>> +{
>> + return false;
>> +}
>> #endif /* CONFIG_NUMA_BALANCING */
>>
>> #ifdef CONFIG_MIGRATION
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 4a9b34a89854..07149ead11e4 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -1496,6 +1496,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
>> int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
>> bool migrated = false, writable = false;
>> int flags = 0;
>> + pg_data_t *pgdat;
>>
>> vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
>> if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
>> @@ -1545,6 +1546,12 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
>> goto migrate_fail;
>> }
>>
>> + pgdat = NODE_DATA(target_nid);
>> + if (!numamigrate_isolate_page(pgdat, page)) {
>> + put_page(page);
>> + goto migrate_fail;
>> + }
>> +
>> migrated = migrate_misplaced_page(page, vma, target_nid);
>> if (migrated) {
>> flags |= TNF_MIGRATED;
>> diff --git a/mm/memory.c b/mm/memory.c
>> index fc6f6b7a70e1..4e451b041488 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -4769,6 +4769,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
>> int target_nid;
>> pte_t pte, old_pte;
>> int flags = 0;
>> + pg_data_t *pgdat;
>>
>> /*
>> * The "pte" at this point cannot be used safely without
>> @@ -4844,6 +4845,12 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
>> goto migrate_fail;
>> }
>>
>> + pgdat = NODE_DATA(target_nid);
>> + if (!numamigrate_isolate_page(pgdat, page)) {
>> + put_page(page);
>> + goto migrate_fail;
>> + }
>> +
>> /* Migrate to the requested node */
>> if (migrate_misplaced_page(page, vma, target_nid)) {
>> page_nid = target_nid;
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 9cc98fb1d6ec..0b2b69a2a7ab 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -2478,7 +2478,7 @@ static struct folio *alloc_misplaced_dst_folio(struct folio *src,
>> return __folio_alloc_node(gfp, order, nid);
>> }
>>
>> -static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>> +bool numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>> {
>> int nr_pages = thp_nr_pages(page);
>> int order = compound_order(page);
>> @@ -2496,11 +2496,11 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>> break;
>> }
>
> There is an other s/return 0/return false/ changed required here for this chunk:
>
> if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING))
> return 0;

Good catch.

>
>> wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE);
>> - return 0;
>> + return false;
>> }
>
> Looks like this whole section under "Avoiding migrating to a node that is nearly full"
> check could be moved to numa_page_can_migrate() as that can be considered as one more
> check (or action to) see if the page can be migrated or not. After that numamigrate_isolate_page()
> will truly be about isolating the page.

Good idea. Will do. Thanks.

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