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Date:   Thu, 9 Jun 2022 11:18:38 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Christian =?iso-8859-1?Q?K=F6nig?= 
        <ckoenig.leichtzumerken@gmail.com>
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        andrey.grodzovsky@amd.com
Subject: Re: [PATCH 03/13] mm: shmem: provide oom badness for shmem files
Message-ID: <YqG67sox6L64E6wV@dhcp22.suse.cz>
References: <20220531100007.174649-1-christian.koenig@amd.com>
 <20220531100007.174649-4-christian.koenig@amd.com>
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In-Reply-To: <20220531100007.174649-4-christian.koenig@amd.com>
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On Tue 31-05-22 11:59:57, Christian K?nig wrote:
> This gives the OOM killer an additional hint which processes are
> referencing shmem files with potentially no other accounting for them.
> 
> Signed-off-by: Christian K?nig <christian.koenig@amd.com>
> ---
>  mm/shmem.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 4b2fea33158e..a4ad92a16968 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2179,6 +2179,11 @@ unsigned long shmem_get_unmapped_area(struct file *file,
>  	return inflated_addr;
>  }
>  
> +static long shmem_oom_badness(struct file *file)
> +{
> +	return i_size_read(file_inode(file)) >> PAGE_SHIFT;
> +}

This doesn't really represent the in memory size of the file, does it?
Also the memcg oom handling could be considerably skewed if the file was
shared between more memcgs.

-- 
Michal Hocko
SUSE Labs