linux-kernel - Re: [PATCH v2 3/4] mm, shmem: Add shmem resident memory accounting

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Date:	Thu, 14 May 2015 13:17:35 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	linux-mm@...ck.org, Jerome Marchand <jmarchan@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-doc@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Michal Hocko <mhocko@...e.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	linux-s390@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] mm, shmem: Add shmem resident memory accounting

On 03/27/2015 06:09 PM, Konstantin Khlebnikov wrote:
> On 27.03.2015 19:40, Vlastimil Babka wrote:
>> From: Jerome Marchand <jmarchan@...hat.com>
>>
>> Currently looking at /proc/<pid>/status or statm, there is no way to
>> distinguish shmem pages from pages mapped to a regular file (shmem
>> pages are mapped to /dev/zero), even though their implication in
>> actual memory use is quite different.
>> This patch adds MM_SHMEMPAGES counter to mm_rss_stat to account for
>> shmem pages instead of MM_FILEPAGES.
>>
>> Signed-off-by: Jerome Marchand <jmarchan@...hat.com>
>> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
>> ---
>
>
>> --- a/include/linux/mm_types.h
>> +++ b/include/linux/mm_types.h
>> @@ -327,9 +327,12 @@ struct core_state {
>>    };
>>
>>    enum {
>> -	MM_FILEPAGES,
>> -	MM_ANONPAGES,
>> -	MM_SWAPENTS,
>> +	MM_FILEPAGES,	/* Resident file mapping pages */
>> +	MM_ANONPAGES,	/* Resident anonymous pages */
>> +	MM_SWAPENTS,	/* Anonymous swap entries */
>> +#ifdef CONFIG_SHMEM
>> +	MM_SHMEMPAGES,	/* Resident shared memory pages */
>> +#endif
>
> I prefer to keep that counter unconditionally:
> kernel has MM_SWAPENTS even without CONFIG_SWAP.

Hmm, so just for consistency? I don't see much reason to make life 
harder for tiny systems, especially when it's not too much effort.

>
>>    	NR_MM_COUNTERS
>>    };
>>
>
> --
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