lkml.org 
[lkml]   [2016]   [Mar]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
On 2016/3/22 22:47, Shakeel Butt wrote:

>
> On Tue, Mar 22, 2016 at 6:55 AM, Xishi Qiu <qiuxishi@huawei.com <mailto:qiuxishi@huawei.com>> wrote:
>
> [root@localhost c_test]# cat /proc/3948/smaps | grep Rss
>
> The /proc/[pid]/smaps read triggers the traversal of all of process's vmas and then page tables and accumulate RSS on each present page table entry.
>
> [root@localhost c_test]# cat /proc/3948/statm
> 1042 173 154 1 0 48 0
>
> The files /proc/[pid]/statm and /proc/[pid]/status uses the counters (MM_ANONPAGES & MM_FILEPAGES) in mm_struct to report RSS of a process. These counters are modified on page table modifications. However the kernel implements an optimization where each thread keeps a local copy of these counters in its task_struct. These local counter are accumulated in the shared counter of mm_struct after some number of page faults (I think 32) faced by the thread and thus there will be mismatch with smaps file.
>
> Shakeel

Hi Shakeel,

I malloc and memset 10M, then sleep. It seems that the problem is still exist,
the kernel version is v4.1

[root@localhost c_test]# cat /proc/13746/statm
3603 2767 250 1 0 2609 0
[root@localhost c_test]# cat /proc/13746/smaps | grep Rss
Rss: 4 kB
Rss: 4 kB
Rss: 4 kB
Rss: 10244 kB
Rss: 924 kB
Rss: 0 kB
Rss: 16 kB
Rss: 8 kB
Rss: 12 kB
Rss: 132 kB
Rss: 12 kB
Rss: 4 kB
Rss: 4 kB
Rss: 4 kB
Rss: 4 kB
Rss: 8 kB
Rss: 0 kB
Rss: 4 kB
Rss: 0 kB

\
 
 \ /
  Last update: 2016-03-30 10:01    [W:0.034 / U:0.684 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site