linux-kernel - Re: [RFC PATCH 2/3] mm: migrate: Correct the hugetlb migration stats

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Message-ID: <A3211A4F-361E-4049-932F-6ED01D5EAD37@nvidia.com>
Date:   Thu, 04 Nov 2021 11:35:50 -0400
From:   Zi Yan <ziy@...dia.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, rostedt@...dmis.org, mingo@...hat.com,
        shy828301@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/3] mm: migrate: Correct the hugetlb migration stats

On 3 Nov 2021, at 6:51, Baolin Wang wrote:

> Correct the migration stats for hugetlb with using compound_nr() instead
> of thp_nr_pages(), meanwhile change 'nr_failed_pages' to record the
> number of normal pages failed to migrate, including THP and hugetlb,
> and 'nr_succeeded' will record the number of normal pages migrated
> successfully.
>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  mm/migrate.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 00b8922..00e231c 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1436,7 +1436,8 @@ static inline int try_split_thp(struct page *page, struct page **page2,
>   * It is caller's responsibility to call putback_movable_pages() to return pages
>   * to the LRU or free list only if ret != 0.
>   *
> - * Returns the number of {normal page, THP} that were not migrated, or an error code.
> + * Returns the number of {normal page, THP, hugetlb} that were not migrated,
> + * or an error code.
>   */
>  int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  		free_page_t put_new_page, unsigned long private,
> @@ -1476,7 +1477,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  			 * during migration.
>  			 */
>  			is_thp = PageTransHuge(page) && !PageHuge(page);
> -			nr_subpages = thp_nr_pages(page);
> +			nr_subpages = compound_nr(page);
>  			cond_resched();
>
>  			if (PageHuge(page))
> @@ -1523,6 +1524,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  				}
>
>  				/* Hugetlb migration is unsupported */
> +				nr_failed_pages++;
>  				nr_failed++;
>  				break;
>  			case -ENOMEM:
> @@ -1541,6 +1543,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  					nr_failed_pages += nr_subpages;
>  					goto out;
>  				}
> +				nr_failed_pages += nr_subpages;
>  				nr_failed++;
>  				goto out;
>  			case -EAGAIN:
> @@ -1551,12 +1554,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  				retry++;
>  				break;
>  			case MIGRATEPAGE_SUCCESS:
> +				nr_succeeded += nr_subpages;
>  				if (is_thp) {
>  					nr_thp_succeeded++;
> -					nr_succeeded += nr_subpages;
>  					break;
>  				}
> -				nr_succeeded++;
>  				break;
>  			default:
>  				/*
> @@ -1565,9 +1567,9 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  				 * removed from migration page list and not
>  				 * retried in the next outer loop.
>  				 */
> +				nr_failed_pages += nr_subpages;
>  				if (is_thp) {
>  					nr_thp_failed++;
> -					nr_failed_pages += nr_subpages;
>  					break;
>  				}
>  				nr_failed++;
> @@ -1576,7 +1578,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  		}
>  	}
>  	nr_failed += retry + thp_retry;
> -	nr_failed_pages += nr_failed;
>  	nr_thp_failed += thp_retry;
>  	rc = nr_failed + nr_thp_failed;
>  out:
> -- 
> 1.8.3.1

LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>

--
Best Regards,
Yan, Zi

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