linux-kernel - Re: Why is Shmem included in Cached in /proc/meminfo?

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Message-ID: <0d11f620-0562-e150-259d-85de8d10cd7a@infradead.org>
Date:   Mon, 30 Aug 2021 07:34:38 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Mikko Rantalainen <mikko.rantalainen@...a.net>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: Why is Shmem included in Cached in /proc/meminfo?

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On 8/30/21 12:44 AM, Mikko Rantalainen wrote:
> It's not immediately obvious from fs/proc/meminfo.c function
> meminfo_proc_show() but the output of Cached: field seems to always
> include all of Shmem: field, too.
> 
> Is this intentional? Usually cache is something that can be discarded if
> needed but shared memory (e.g. used to contain files in tmpfs) cannot be
> discarded without a data-loss. As such, I'd argue that it shouldn't be
> included in the Cached: output.
> 
> A simple fix could be
> 
> -	cached = global_node_page_state(NR_FILE_PAGES) -
> -			total_swapcache_pages() - i.bufferram;
> +	cached = global_node_page_state(NR_FILE_PAGES) -
> +			total_swapcache_pages()
> +			- i.bufferram - i.sharedram;
> 


-- 
~Randy