linux-kernel - Re: [PATCH] mm/migrate: Continue to migrate for small pages

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Message-ID: <875ycqcad0.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Sun, 29 Jan 2023 11:01:31 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Chen Wandun <chenwandun@...wei.com>
Cc:     <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/migrate: Continue to migrate for small pages

Chen Wandun <chenwandun@...wei.com> writes:

> migrate_hugetlbs returns -ENOMEM when no enough huge page,
> however maybe there are still free small pages, so continue
> to migrate for small pages.

Better to replace "page" with "folio", and "small" with "non-hugetlb".

> Signed-off-by: Chen Wandun <chenwandun@...wei.com>
> ---
>  mm/migrate.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index b971edbf32fc..c9d0d2058036 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1939,7 +1939,12 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  
>  	rc_gather = migrate_hugetlbs(from, get_new_page, put_new_page, private,
>  				     mode, reason, &stats, &ret_folios);
> -	if (rc_gather < 0)
> +	/* Maybe there are free small pages, continue to migrate.

There may be free non-hugetlb folios available, continue to migrate.

> +	 * Nowdays the only negtive return value of migrate_hugetlbs
> +	 * is -ENOMEM, keep compatible for coming negtive return
> +	 * value instead of ignore return value.

This can be moved to patch description.

> +	 */
> +	if (rc_gather < 0 && rc_gather != -ENOMEM)
>  		goto out;
>  again:
>  	nr_pages = 0;

Best Regards,
Huang, Ying