linux-kernel - Re: [PATCH] mm/vmscan: drop checking if _deferred_list is empty before using TTU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <81d768d4-6d37-4d73-a1a4-39950a663105@redhat.com>
Date: Mon, 1 Jul 2024 10:51:08 +0200
From: David Hildenbrand <david@...hat.com>
To: Barry Song <21cnbao@...il.com>, akpm@...ux-foundation.org,
 linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org, Barry Song <v-songbaohua@...o.com>,
 Ryan Roberts <ryan.roberts@....com>
Subject: Re: [PATCH] mm/vmscan: drop checking if _deferred_list is empty
 before using TTU_SYNC

On 30.06.24 01:41, Barry Song wrote:
> From: Barry Song <v-songbaohua@...o.com>
> 
> The optimization of list_empty(&folio->_deferred_list) aimed to prevent
> increasing the PTL duration when a large folio is partially unmapped,
> for example, from subpage 0 to subpage (nr - 2).
> 
> But Ryan's commit 5ed890ce5147 ("mm: vmscan: avoid split during
> shrink_folio_list()") actually splits this kind of large folios. This
> makes the "optimization" useless.
> 
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Ryan Roberts <ryan.roberts@....com>
> ---
>   -v1
>   * I remember David and Ryan once suggested that this check could be dropped
>     while the patch was being pulled into mm-unstable. However, for some reason,
>     I forgot to request squashing this change.
> 
>   mm/vmscan.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 3d4c681c6d40..0761f91b407f 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
>   			 * try_to_unmap acquire PTL from the first PTE,
>   			 * eliminating the influence of temporary PTE values.
>   			 */
> -			if (folio_test_large(folio) && list_empty(&folio->_deferred_list))
> +			if (folio_test_large(folio))
>   				flags |= TTU_SYNC;
>   
>   			try_to_unmap(folio, flags);

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb