linux-kernel - Re: [PATCH 1/2] mm: add cond_resched to generic_swapfile

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Message-ID: <20160725072609.GB9401@dhcp22.suse.cz>
Date:	Mon, 25 Jul 2016 09:26:09 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Mikulas Patocka <mpatocka@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: add cond_resched to generic_swapfile_activate

On Fri 22-07-16 17:11:20, Mikulas Patocka wrote:
> The function generic_swapfile_activate can take quite long time, it iterates
> over all blocks of a file, so add cond_resched to it. I observed about 1 second
> stalls when activating a swapfile that was almost unfragmented - this patch
> fixes it.
> 
> Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> 
> ---
>  mm/page_io.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> Index: linux-4.7-rc7/mm/page_io.c
> ===================================================================
> --- linux-4.7-rc7.orig/mm/page_io.c	2016-05-30 17:34:37.000000000 +0200
> +++ linux-4.7-rc7/mm/page_io.c	2016-07-11 17:23:33.000000000 +0200
> @@ -166,6 +166,8 @@ int generic_swapfile_activate(struct swa
>  		unsigned block_in_page;
>  		sector_t first_block;
>  
> +		cond_resched();
> +
>  		first_block = bmap(inode, probe_block);
>  		if (first_block == 0)
>  			goto bad_bmap;

-- 
Michal Hocko
SUSE Labs