linux-kernel - Re: [PATCH 03/13] mm: shmem: provide oom badness for shmem files

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Message-ID: <YqG67sox6L64E6wV@dhcp22.suse.cz>
Date:   Thu, 9 Jun 2022 11:18:38 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Christian König 
        <ckoenig.leichtzumerken@...il.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        christian.koenig@....com, alexander.deucher@....com,
        daniel@...ll.ch, viro@...iv.linux.org.uk,
        akpm@...ux-foundation.org, hughd@...gle.com,
        andrey.grodzovsky@....com
Subject: Re: [PATCH 03/13] mm: shmem: provide oom badness for shmem files

On Tue 31-05-22 11:59:57, Christian König 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 König <christian.koenig@....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