On Tue, Mar 22, 2016 at 6:55 AM, Xishi Qiu <qiuxishi@xxxxxxxxxx> 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