Messages in this thread | | | Date | Wed, 30 Mar 2016 15:16:07 +0800 | From | Xishi Qiu <> | Subject | Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? |
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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
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