erlang:system_info(cpu_topology) strange behavior

[Rickard Green]

On Thu, Oct 8, 2020 at 7:36 PM Frank Muller <frank.muller.erl@REDACTED>
wrote:

> Answering my own question.
>
> The second attempt worked because I was under “root”.
>
> Attaching to the release with -remsh failed because the node was running
> under user “orca” which has less privileges.
>
> Is this an expected behavior?
>
> /Frank
>
>
The runtime system gets the information about cpu topology by reading files
under /sys/devices/system/. If it cannot read and parse the files there, it
will fail to detect the cpu topology. Seems like only root is allowed to
read that part of the file-system in your case.

Regards,
Rickard Green



> Frank<frank.muller.erl@REDACTED>
>
>> Hi guys,
>>
>> When I attached (-remsh) to my release application (/opt/orca), this call
>> returns undefined:
>>
>> (orca@REDACTED)1> erlang:system_info(cpu_topology).
>> undefined
>>
>> If try this instead, the call seems to work as expected:
>>
>> $ /opt/orca/erts-10.7.2.4/bin/erl
>> 1> erlang:system_info(cpu_topology).
>> [{processor,[{core,[{thread,{logical,0}},
>>                     {thread,{logical,4}}]},
>>              {core,[{thread,{logical,1}},{thread,{logical,5}}]},
>>              {core,[{thread,{logical,2}},{thread,{logical,6}}]},
>>              {core,[{thread,{logical,3}},{thread,{logical,7}}]}]}]
>>
>>
>> I’m on Ubuntu16 LTS kernel 4.4.0, Erlang 22.3.4.11.
>>
>> Help appreciated
>>
>> /Frank
>>
>

-- 
Rickard Green, Erlang/OTP, Ericsson AB
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20201008/b841bf21/attachment.htm>