Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> writes:
> Now there are 3 places will validate if a page can mirate or not, and
> some validations are performed later, which will waste some CPU to call
> numa_migrate_prep().
>
> Thus we can move all the migration validation into numa_migrate_prep(),
> which is more maintainable as well as saving some CPU resources. Another
> benefit is that it can serve as a preparation for supporting batch migration
> in do_numa_page() in future.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
> mm/memory.c | 19 +++++++++++++++++++
> mm/migrate.c | 19 -------------------
> 2 files changed, 19 insertions(+), 19 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index d003076b218d..bee9b1e86ef0 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4747,6 +4747,25 @@ int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
> *flags |= TNF_FAULT_LOCAL;
> }
>
> + /*
> + * Don't migrate file pages that are mapped in multiple processes
> + * with execute permissions as they are probably shared libraries.
> + */
> + if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
> + (vma->vm_flags & VM_EXEC))
> + return NUMA_NO_NODE;
> +
> + /*
> + * Also do not migrate dirty pages as not all filesystems can move
> + * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
> + */
> + if (page_is_file_lru(page) && PageDirty(page))
> + return NUMA_NO_NODE;
> +
> + /* Do not migrate THP mapped by multiple processes */
> + if (PageTransHuge(page) && total_mapcount(page) > 1)
> + return NUMA_NO_NODE;
> +
> return mpol_misplaced(page, vma, addr);
In mpol_misplaced()->should_numa_migrate_memory(), accessing CPU and PID
will be recorded. So the code change above will introduce some behavior
change.
How about move these checks into a separate function which is called
between numa_migrate_prep() and migrate_misplaced_page() after unlocking
PTL?
--
Best Regards,
Huang, Ying
> }
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index e21d5a7e7447..9cc98fb1d6ec 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2485,10 +2485,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>
> VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
>
> - /* Do not migrate THP mapped by multiple processes */
> - if (PageTransHuge(page) && total_mapcount(page) > 1)
> - return 0;
> -
> /* Avoid migrating to a node that is nearly full */
> if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
> int z;
> @@ -2533,21 +2529,6 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
> LIST_HEAD(migratepages);
> int nr_pages = thp_nr_pages(page);
>
> - /*
> - * Don't migrate file pages that are mapped in multiple processes
> - * with execute permissions as they are probably shared libraries.
> - */
> - if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
> - (vma->vm_flags & VM_EXEC))
> - goto out;
> -
> - /*
> - * Also do not migrate dirty pages as not all filesystems can move
> - * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
> - */
> - if (page_is_file_lru(page) && PageDirty(page))
> - goto out;
> -
> isolated = numamigrate_isolate_page(pgdat, page);
> if (!isolated)
> goto out;
