* [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
@ 2016-03-22 13:55 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2016-03-22 13:55 UTC (permalink / raw)
To: Linux MM, LKML
[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
^ permalink raw reply [flat|nested] 7+ messages in thread
* [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
@ 2016-03-22 13:55 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2016-03-22 13:55 UTC (permalink / raw)
To: Linux MM, LKML
[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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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
2016-03-22 13:55 ` Xishi Qiu
(?)
@ 2016-03-22 14:47 ` Shakeel Butt
2016-03-30 7:16 ` Xishi Qiu
-1 siblings, 1 reply; 7+ messages in thread
From: Shakeel Butt @ 2016-03-22 14:47 UTC (permalink / raw)
To: Xishi Qiu; +Cc: Linux MM, LKML
[-- Attachment #1: Type: text/plain, Size: 869 bytes --]
On Tue, Mar 22, 2016 at 6:55 AM, Xishi Qiu <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
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
2016-03-22 14:47 ` Shakeel Butt
@ 2016-03-30 7:16 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2016-03-30 7:16 UTC (permalink / raw)
To: Shakeel Butt; +Cc: Linux MM, LKML
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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
@ 2016-03-30 7:16 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2016-03-30 7:16 UTC (permalink / raw)
To: Shakeel Butt; +Cc: Linux MM, LKML
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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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
2016-03-30 7:16 ` Xishi Qiu
@ 2016-03-30 9:39 ` Xishi Qiu
-1 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2016-03-30 9:39 UTC (permalink / raw)
To: Shakeel Butt; +Cc: Linux MM, LKML
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
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm?
@ 2016-03-30 9:39 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2016-03-30 9:39 UTC (permalink / raw)
To: Shakeel Butt; +Cc: Linux MM, LKML
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
>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2016-03-30 9:44 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-03-22 13:55 [RFC] mm: why cat /proc/pid/smaps | grep Rss is different from cat /proc/pid/statm? Xishi Qiu
2016-03-22 13:55 ` Xishi Qiu
2016-03-22 14:47 ` Shakeel Butt
2016-03-30 7:16 ` Xishi Qiu
2016-03-30 7:16 ` Xishi Qiu
2016-03-30 9:39 ` Xishi Qiu
2016-03-30 9:39 ` Xishi Qiu
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