linux-kernel - Re: [PATCH] tmpfs: Insert tmpfs cache pages to inactive list at first

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Date:	Wed, 19 May 2010 23:51:45 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Shaohua Li <shaohua.li@...el.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] tmpfs: Insert tmpfs cache pages to inactive list at first

On Wed, May 19, 2010 at 05:44:49PM +0900, KOSAKI Motohiro wrote:
> Shaohua Li reported parallel file copy on tmpfs can lead to
> OOM killer. This is regression of caused by commit 9ff473b9a7
> (vmscan: evict streaming IO first). Wow, It is 2 years old patch!
> 
> Currently, tmpfs file cache is inserted active list at first. It
> mean the insertion doesn't only increase numbers of pages in anon LRU,
> but also reduce anon scanning ratio. Therefore, vmscan will get totally
> confusion. It scan almost only file LRU even though the system have
> plenty unused tmpfs pages.
> 
> Historically, lru_cache_add_active_anon() was used by two reasons.
> 1) Intend to priotize shmem page rather than regular file cache.
> 2) Intend to avoid reclaim priority inversion of used once pages.
> 
> But we've lost both motivation because (1) Now we have separate
> anon and file LRU list. then, to insert active list doesn't help
> such priotize. (2) In past, one pte access bit will cause page
> activation. then to insert inactive list with pte access bit mean
> higher priority than to insert active list. Its priority inversion
> may lead to uninteded lru chun. but it was already solved by commit
> 645747462 (vmscan: detect mapped file pages used only once).
> (Thanks Hannes, you are great!)
> 
> Thus, now we can use lru_cache_add_anon() instead.
> 
> Reported-by: Shaohua Li <shaohua.li@...el.com>
> Cc: Wu Fengguang <fengguang.wu@...el.com>
> Cc: Johannes Weiner <hannes@...xchg.org>

Reviewed-by: Johannes Weiner <hannes@...xchg.org>

> Cc: Rik van Riel <riel@...hat.com>
> Cc: Minchan Kim <minchan.kim@...il.com>
> Cc: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> ---
>  mm/filemap.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index b941996..023ef61 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -452,7 +452,7 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
>  		if (page_is_file_cache(page))
>  			lru_cache_add_file(page);
>  		else
> -			lru_cache_add_active_anon(page);
> +			lru_cache_add_anon(page);

Looks like the active_anon and active_file versions have no users
anymore..
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