linux-kernel - Re: [RFC] mm:change meminfo cached calculation

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Message-Id: <20150106164340.55e83f742d6f57c19e6500ff@linux-foundation.org>
Date:	Tue, 6 Jan 2015 16:43:40 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
Cc:	"'minchan@...nel.org'" <minchan@...nel.org>,
	"'Konstantin Khlebnikov'" <koct9i@...il.com>,
	"'Kirill A. Shutemov'" <kirill@...temov.name>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'linux-mm@...ck.org'" <linux-mm@...ck.org>,
	"'linux-arm-kernel@...ts.infradead.org'" 
	<linux-arm-kernel@...ts.infradead.org>,
	"'n-horiguchi@...jp.nec.com'" <n-horiguchi@...jp.nec.com>,
	"'pintu.k@...sung.com'" <pintu.k@...sung.com>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org
Subject: Re: [RFC] mm:change meminfo cached calculation

On Fri, 26 Dec 2014 19:56:49 +0800 "Wang, Yalin" <Yalin.Wang@...ymobile.com> wrote:

> This patch subtract sharedram from cached,
> sharedram can only be swap into swap partitions,
> they should be treated as swap pages, not as cached pages.
> 
> ...
>
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -45,7 +45,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  	committed = percpu_counter_read_positive(&vm_committed_as);
>  
>  	cached = global_page_state(NR_FILE_PAGES) -
> -			total_swapcache_pages() - i.bufferram;
> +			total_swapcache_pages() - i.bufferram - i.sharedram;
>  	if (cached < 0)
>  		cached = 0;

Documentation/filesystems/proc.txt says

:      Cached: in-memory cache for files read from the disk (the
:              pagecache).  Doesn't include SwapCached

So yes, I guess it should not include shmem.

And why not do this as well?


--- a/Documentation/filesystems/proc.txt~mm-change-meminfo-cached-calculation-fix
+++ a/Documentation/filesystems/proc.txt
@@ -811,7 +811,7 @@ MemAvailable: An estimate of how much me
      Buffers: Relatively temporary storage for raw disk blocks
               shouldn't get tremendously large (20MB or so)
       Cached: in-memory cache for files read from the disk (the
-              pagecache).  Doesn't include SwapCached
+              pagecache).  Doesn't include SwapCached or Shmem.
   SwapCached: Memory that once was swapped out, is swapped back in but
               still also is in the swapfile (if memory is needed it
               doesn't need to be swapped out AGAIN because it is already
_

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