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Groups > linux.kernel > #1362749 > unrolled thread
| Started by | Xishi Qiu <qiuxishi@huawei.com> |
|---|---|
| First post | 2016-03-22 15:00 +0100 |
| Last post | 2016-03-30 11:50 +0200 |
| Articles | 3 — 1 participant |
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[RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? Xishi Qiu <qiuxishi@huawei.com> - 2016-03-22 15:00 +0100
Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? Xishi Qiu <qiuxishi@huawei.com> - 2016-03-30 09:20 +0200
Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? Xishi Qiu <qiuxishi@huawei.com> - 2016-03-30 11:50 +0200
| From | Xishi Qiu <qiuxishi@huawei.com> |
|---|---|
| Date | 2016-03-22 15:00 +0100 |
| Subject | [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? |
| Message-ID | <rfv0K-5cK-11@gated-at.bofh.it> |
[root@localhost c_test]# cat /proc/3948/smaps | grep Rss
Rss: 4 kB
Rss: 4 kB
Rss: 4 kB
Rss: 796 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: 12 kB
Rss: 0 kB
Rss: 4 kB
Rss: 0 kB
[root@localhost c_test]# cat /proc/3948/statm
1042 173 154 1 0 48 0
173 means Rss is 173*4kb=692kb, right?
so why it is different from the sum(1020kb) of "cat /proc/pid/smaps | grep Rss"?
my test code is
...
int main()
{
sleep(1000);
return 0;
}
the kernel version is v4.1
Thanks,
Xishi Qiu
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| From | Xishi Qiu <qiuxishi@huawei.com> |
|---|---|
| Date | 2016-03-30 09:20 +0200 |
| Subject | Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? |
| Message-ID | <riiA3-1Vf-35@gated-at.bofh.it> |
| In reply to | #1362749 |
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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| From | Xishi Qiu <qiuxishi@huawei.com> |
|---|---|
| Date | 2016-03-30 11:50 +0200 |
| Subject | Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? |
| Message-ID | <rikVb-3my-7@gated-at.bofh.it> |
| In reply to | #1366946 |
On 2016/3/30 15:16, Xishi Qiu wrote: > 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 misunderstand your meaning before. I know the reason now. Thanks, Xishi Qiu > Hi Shakeel, > > I malloc and memset 10M, then sleep. It seems that the problem is still exist, > the kernel version is v4.1 >
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