linux-kernel - Re: why the count nr_file_pages is not equal to nr_inactive_file + nr_active

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Date:	Fri, 13 May 2016 15:31:42 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Aaron Lu <aaron.lu@...el.com>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: why the count nr_file_pages is not equal to nr_inactive_file
 + nr_active_file ?

On 2016/5/13 15:00, Aaron Lu wrote:

> On 05/13/2016 11:58 AM, Xishi Qiu wrote:
>> I find the count nr_file_pages is not equal to nr_inactive_file + nr_active_file.
>> There are 8 cpus, 2 zones in my system.
>>
>> I think may be the pagevec trigger the problem, but PAGEVEC_SIZE is only 14.
>> Does anyone know the reason?
> 
> One thing I can see is the ram backed filesystem where the page is
> counted as NR_FILE_PAGE but go into the anonymous LRU list instead of
> the file LRU list.
> 
> See function shmem_getpage_gfp.
> 
> An example:
> [aaron@...onlu ~]$ head -11 /proc/vmstat 
> nr_free_pages 194472
> nr_alloc_batch 58
> nr_inactive_anon 483386
> nr_active_anon 298161
> nr_inactive_file 452791
> nr_active_file 1942376
> nr_unevictable 84
> nr_mlock 84
> nr_anon_pages 445332
> nr_mapped 93553
> nr_file_pages 2731481
> [aaron@...onlu ~]$ fallocate -l 400M /dev/shm/test
> [aaron@...onlu ~]$ head -11 /proc/vmstat 
> nr_free_pages 94808
> nr_alloc_batch 838
> nr_inactive_anon 582385
> nr_active_anon 298371
> nr_inactive_file 452795
> nr_active_file 1942380
> nr_unevictable 84
> nr_mlock 84
> nr_anon_pages 445543
> nr_mapped 93658
> nr_file_pages 2830488
> 
> The nr_file_pages increased with nr_inactive_anon while the
> nr_{in}active_file don't see much change.
> 
> Regards,
> Aaron
> 

Hi Aaron,

Thanks for your reply, but I find the count of nr_shmem is very small
in my system.

root@...650:/ # cat /proc/vmstat 
nr_free_pages 54192
nr_inactive_anon 39830
nr_active_anon 28794
nr_inactive_file 432444
nr_active_file 20659
nr_unevictable 2363
nr_mlock 0
nr_anon_pages 65249
nr_mapped 19742
nr_file_pages 462723
nr_dirty 20
nr_writeback 0
nr_slab_reclaimable 259333
nr_slab_unreclaimable 33463
nr_page_table_pages 3456
nr_kernel_stack 892
nr_unstable 0
nr_bounce 11
nr_vmscan_write 292032
nr_vmscan_immediate_reclaim 47204474
nr_writeback_temp 0
nr_isolated_anon 0
nr_isolated_file 0
nr_shmem 128
nr_dirtied 69574
nr_written 356299
nr_anon_transparent_hugepages 0
nr_free_cma 7519
nr_swapcache 41972
nr_dirty_threshold 6982
nr_dirty_background_threshold 99297