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From: SeongJae Park <sj@kernel.org>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Oscar Salvador <osalvador@suse.de>, SeongJae Park <sj@kernel.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	damon@lists.linux.dev, vishal.moola@gmail.com,
	willy@infradead.org
Subject: Re: [PATCH -next 2/8] mm: page_idle: Convert page idle to use folios
Date: Tue, 13 Dec 2022 19:14:22 +0000	[thread overview]
Message-ID: <20221213191422.138595-1-sj@kernel.org> (raw)
In-Reply-To: <20221213092735.187924-3-wangkefeng.wang@huawei.com>

On Tue, 13 Dec 2022 17:27:29 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote:

> This change and rename all page related function to use folio,
> which save many compound_head() calls and kernel text.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  mm/page_idle.c | 91 ++++++++++++++++++++++++--------------------------
>  1 file changed, 44 insertions(+), 47 deletions(-)
> 
> diff --git a/mm/page_idle.c b/mm/page_idle.c
> index bc08332a609c..38641f94cf49 100644
> --- a/mm/page_idle.c
> +++ b/mm/page_idle.c
> @@ -19,34 +19,33 @@
>  #define BITMAP_CHUNK_BITS	(BITMAP_CHUNK_SIZE * BITS_PER_BYTE)
>  
>  /*
> - * Idle page tracking only considers user memory pages, for other types of
> - * pages the idle flag is always unset and an attempt to set it is silently
> + * Idle folio tracking only considers user memory folios, for other types of
> + * folios the idle flag is always unset and an attempt to set it is silently
>   * ignored.

I think this might make future readers confused, as the code and comments will
call this subsystem as Idle _folio_ tracking while the user interface and the
document calls it as Idle _page_ tracking.

>   *
> - * We treat a page as a user memory page if it is on an LRU list, because it is
> - * always safe to pass such a page to rmap_walk(), which is essential for idle
> - * page tracking. With such an indicator of user pages we can skip isolated
> - * pages, but since there are not usually many of them, it will hardly affect
> + * We treat a folio as a user memory folio if it is on an LRU list, because it is
> + * always safe to pass such a folio to rmap_walk(), which is essential for idle
> + * folio tracking. With such an indicator of user folios we can skip isolated
> + * folios, but since there are not usually many of them, it will hardly affect
>   * the overall result.
>   *
> - * This function tries to get a user memory page by pfn as described above.
> + * This function tries to get a user memory folio by pfn as described above.
>   */
> -static struct page *page_idle_get_page(unsigned long pfn)
> +static struct folio *folio_idle_get_folio(unsigned long pfn)
>  {
> -	struct page *page = pfn_to_online_page(pfn);
> +	struct folio *folio = pfn_to_online_folio(pfn);
>  
> -	if (!page || !PageLRU(page) ||
> -	    !get_page_unless_zero(page))
> +	if (!folio || !folio_test_lru(folio) || !folio_try_get(folio))
>  		return NULL;

As Matthew also mentioned, you changed the behavior.  It looks like a right
behavior if we call this function folio_idle_get_folio(), but it shouldn't.
page_idle_get_folio() would be a better name in my humble opinion.

So, unless we're gonna change the behavior of this subsystem (which wouldn't be
the case as it would break users), I think it would be better to keep the name
of this subsystem as Idle page tracking and avoid unnecessary renaming changes.


Thanks,
SJ

  parent reply	other threads:[~2022-12-13 19:14 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-13  9:27 [PATCH -next 0/8] mm: converted page idle and damon to use folios Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 1/8] mm: memory_hotplug: add pfn_to_online_folio() Kefeng Wang
2022-12-13 11:13   ` kernel test robot
2022-12-13 11:36     ` Kefeng Wang
2022-12-13 11:23   ` kernel test robot
2022-12-13 11:40   ` David Hildenbrand
2022-12-13 12:13     ` Kefeng Wang
2022-12-13 14:42       ` David Hildenbrand
2022-12-13 14:47       ` Matthew Wilcox
2022-12-14  1:10         ` Kefeng Wang
2022-12-13 12:03   ` kernel test robot
2022-12-14  4:15   ` kernel test robot
2022-12-13  9:27 ` [PATCH -next 2/8] mm: page_idle: Convert page idle to use folios Kefeng Wang
2022-12-13 14:34   ` Matthew Wilcox
2022-12-13 19:14   ` SeongJae Park [this message]
2022-12-13  9:27 ` [PATCH -next 3/8] mm: huge_memory: convert split_huge_pages_all() " Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 4/8] mm: damon: add temporary damon_get_folio() Kefeng Wang
2022-12-13 14:40   ` Matthew Wilcox
2022-12-13 19:18     ` SeongJae Park
2022-12-13  9:27 ` [PATCH -next 5/8] mm: damon: convert damon_ptep/pmdp_mkold() to use folios Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 6/8] mm: damon: paddr: convert damon_pa_*() " Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 7/8] mm: damon: vaddr: convert damon_young_pmd_entry() to use folio Kefeng Wang
2022-12-13  9:27 ` [PATCH -next 8/8] mm: damon: remove unneed damon_get_page() Kefeng Wang
2022-12-13 19:26   ` SeongJae Park

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