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SubjectRe: [RFC PATCH] Add /proc/<pid>/numa_vamaps for numa node information
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On 09/12/2018 01:42 PM, prakash.sangappa wrote:
>
>
> On 05/09/2018 04:31 PM, Dave Hansen wrote:
>> On 05/07/2018 06:16 PM, prakash.sangappa wrote:
>>> It will be /proc/<pid>/numa_vamaps. Yes, the behavior will be
>>> different with respect to seeking. Output will still be text and
>>> the format will be same.
>>>
>>> I want to get feedback on this approach.
>> I think it would be really great if you can write down a list of the
>> things you actually want to accomplish. Dare I say: you need a
>> requirements list.
>>
>> The numa_vamaps approach continues down the path of an ever-growing list
>> of highly-specialized /proc/<pid> files. I don't think that is
>> sustainable, even if it has been our trajectory for many years.
>>
>> Pagemap wasn't exactly a shining example of us getting new ABIs right,
>> but it sounds like something along those is what we need.
>
> Just sent out a V2 patch. This patch simplifies the file content. It
> only provides VA range to numa node id information.
>
> The requirement is basically observability for performance analysis.
>
> - Need to be able to determine VA range to numa node id information.
> Which also gives an idea of which range has memory allocated.
>
> - The proc file /proc/<pid>/numa_vamaps is in text so it is easy to
> directly view.
>
> The V2 patch supports seeking to a particular process VA from where
> the application could read the VA to numa node id information.
>
> Also added the 'PTRACE_MODE_READ_REALCREDS' check when opening the
> file /proc file as was indicated by Michal Hacko
>
I meant Michal Hocko
Sorry misspelled the name.


> The VA range to numa node information from this file can be used by pmap.
>
> Here is a sample from a prototype change to pmap(procps) showing
> numa node information, gathered from the new 'numa_vamaps' file.
>
> $ ./rpmap -L -A 00000000006f8000,00007f5f730fe000 31423|more
> 31423: bash
> 00000000006f8000 16K N1 rw--- bash
> 00000000006fc000 4K N0 rw--- bash
> 00000000006fd000 4K N0 rw--- [ anon ]
> 00000000006fe000 8K N1 rw--- [ anon ]
> 0000000000700000 4K N0 rw--- [ anon ]
> 0000000000701000 4K N1 rw--- [ anon ]
> 0000000000702000 4K N0 rw--- [ anon ]
> 0000000000ce8000 52K N0 rw--- [ anon ]
> 0000000000cf5000 4K N1 rw--- [ anon ]
> 0000000000cf6000 28K N0 rw--- [ anon ]
> 0000000000cfd000 4K N1 rw--- [ anon ]
> 0000000000cfe000 28K N0 rw--- [ anon ]
> 0000000000d05000 504K N1 rw--- [ anon ]
> 0000000000d83000 8K N0 rw--- [ anon ]
> 0000000000d85000 932K N1 rw--- [ anon ]
> 0000000000e6e000 4K - rw--- [ anon ]
> 0000000000e6f000 168K N1 rw--- [ anon ]
> 00007f5f72ef4000 4K N2 r-x-- libnss_files-2.23.so
> 00007f5f72ef5000 40K N0 r-x-- libnss_files-2.23.so
> 00007f5f72eff000 2044K - ----- libnss_files-2.23.so
> 00007f5f730fe000 4K N0 r---- libnss_files-2.23.so
> total 3868K
>
> -Prakash.

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