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From: Oscar Salvador <osalvador@suse.de>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: akpm@linux-foundation.org, ying.huang@intel.com,
	songmuchun@bytedance.com, hch@infradead.org, willy@infradead.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/9] mm/vmscan: remove unneeded can_split_huge_page check
Date: Tue, 12 Apr 2022 10:59:51 +0200	[thread overview]
Message-ID: <YlU/h0fdE1L846Bd@localhost.localdomain> (raw)
In-Reply-To: <20220409093500.10329-3-linmiaohe@huawei.com>

On Sat, Apr 09, 2022 at 05:34:53PM +0800, Miaohe Lin wrote:
> We don't need to check can_split_folio() because folio_maybe_dma_pinned()
> is checked before. It will avoid the long term pinned pages to be swapped
> out. And we can live with short term pinned pages. Without can_split_folio
> checking we can simplify the code. Also activate_locked can be changed to
> keep_locked as it's just short term pinning.

What do you mean by "we can live with short term pinned pages"?
Does it mean that it was not pinned when we check
folio_maybe_dma_pinned() but now it is?

To me it looks like the pinning is fluctuating and we rely on
split_folio_to_list() to see whether we succeed or not, and if not
we give it another spin in the next round?

> Suggested-by: Huang, Ying <ying.huang@intel.com>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  mm/vmscan.c | 22 ++++++++--------------
>  1 file changed, 8 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 4a76be47bed1..01f5db75a507 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1711,20 +1711,14 @@ static unsigned int shrink_page_list(struct list_head *page_list,
>  					goto keep_locked;
>  				if (folio_maybe_dma_pinned(folio))
>  					goto keep_locked;
> -				if (PageTransHuge(page)) {
> -					/* cannot split THP, skip it */
> -					if (!can_split_folio(folio, NULL))
> -						goto activate_locked;
> -					/*
> -					 * Split pages without a PMD map right
> -					 * away. Chances are some or all of the
> -					 * tail pages can be freed without IO.
> -					 */
> -					if (!folio_entire_mapcount(folio) &&
> -					    split_folio_to_list(folio,
> -								page_list))
> -						goto activate_locked;
> -				}
> +				/*
> +				 * Split pages without a PMD map right
> +				 * away. Chances are some or all of the
> +				 * tail pages can be freed without IO.
> +				 */
> +				if (PageTransHuge(page) && !folio_entire_mapcount(folio) &&
> +				    split_folio_to_list(folio, page_list))
> +					goto keep_locked;
>  				if (!add_to_swap(page)) {
>  					if (!PageTransHuge(page))
>  						goto activate_locked_split;
> -- 
> 2.23.0
> 
> 

-- 
Oscar Salvador
SUSE Labs

  parent reply	other threads:[~2022-04-12 10:14 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-09  9:34 [PATCH v2 0/9] A few cleanup and fixup patches for vmscan Miaohe Lin
2022-04-09  9:34 ` [PATCH v2 1/9] mm/vmscan: add a comment about MADV_FREE pages check in folio_check_dirty_writeback Miaohe Lin
2022-04-11 11:50   ` ying.huang
2022-04-12  3:07     ` Miaohe Lin
2022-04-11 14:16   ` Christoph Hellwig
2022-04-12  3:15     ` Miaohe Lin
2022-04-12  8:44   ` Oscar Salvador
2022-04-09  9:34 ` [PATCH v2 2/9] mm/vmscan: remove unneeded can_split_huge_page check Miaohe Lin
2022-04-11 14:18   ` Christoph Hellwig
2022-04-12  3:14     ` Miaohe Lin
2022-04-12  0:52   ` ying.huang
2022-04-12  8:59   ` Oscar Salvador [this message]
2022-04-12 13:42     ` Miaohe Lin
2022-04-12 14:59       ` David Hildenbrand
2022-04-13  1:26         ` ying.huang
2022-04-13  2:17           ` Miaohe Lin
2022-04-15  3:07           ` ying.huang
2022-04-16  2:34             ` Miaohe Lin
2022-04-09  9:34 ` [PATCH v2 3/9] mm/vmscan: introduce helper function reclaim_page_list() Miaohe Lin
2022-04-09 13:44   ` Matthew Wilcox
2022-04-11  1:53     ` Miaohe Lin
2022-04-11  3:17       ` Matthew Wilcox
2022-04-11  3:26         ` Miaohe Lin
2022-04-09  9:34 ` [PATCH v2 4/9] mm/vmscan: save a bit of stack space in shrink_lruvec Miaohe Lin
2022-04-12  0:57   ` ying.huang
2022-04-12  3:13     ` Miaohe Lin
2022-04-09  9:34 ` [PATCH v2 5/9] mm/vmscan: activate swap-backed executable folios after first usage Miaohe Lin
2022-04-12  0:59   ` ying.huang
2022-04-09  9:34 ` [PATCH v2 6/9] mm/vmscan: take all base pages of THP into account when race with speculative reference Miaohe Lin
2022-04-09  9:34 ` [PATCH v2 7/9] mm/vmscan: take min_slab_pages into account when try to call shrink_node Miaohe Lin
2022-04-12  1:36   ` ying.huang
2022-04-09  9:34 ` [PATCH v2 8/9] mm/vmscan: remove obsolete comment in kswapd_run Miaohe Lin
2022-04-09  9:35 ` [PATCH v2 9/9] mm/vmscan: use helper folio_is_file_lru() Miaohe Lin

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