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

[Konstantin Khlebnikov]

On Thu, May 14, 2015 at 2:17 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote:
> On 03/27/2015 06:09 PM, Konstantin Khlebnikov wrote:
>>
>> On 27.03.2015 19:40, Vlastimil Babka wrote:
>>>
>>> From: Jerome Marchand <jmarchan@xxxxxxxxxx>
>>>
>>> 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@xxxxxxxxxx>
>>> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
>>> ---
>>
>>
>>
>>> --- 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.

Profit is vague, I guess slab anyway will round size to the next
cacheline or power-of-two.
That conditional (non)existence just adds unneeded code lines.

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