feature request: Cpus_allowed

[LXYan2333]

Dear maintainer:

I read this line:

pfs/include/pfs/types.hpp

Line 301 in 0d835d1

// Cpus_allowed[_list] will be added upon request.

Honestly speaking, I really do not want to parse this line by myself. On my laptop, it outputs:

$ cat /proc/self/status
……
Cpus_allowed:   ff
Cpus_allowed_list:      0-7
……

but on a server with 40 cores, it outputs:

$ cat /proc/self/status
……
Cpus_allowed:   ff,ffffffff
Cpus_allowed_list:      0-39
……

I guess parse it is bug prone. The document about it is very brief:

Cpus_allowed
        Hexadecimal mask of CPUs on which this process may
        run (since Linux 2.6.24, see [cpuset(7)](https://man7.org/linux/man-pages/man7/cpuset.7.html)).

Cpus_allowed_list
        Same as previous, but in "list format" (since Linux
        2.6.26, see [cpuset(7)](https://man7.org/linux/man-pages/man7/cpuset.7.html)).

[dtrugman]

Thanks for the request @LXYan2333,
I will try and implement this next week.

[dtrugman]

@LXYan2333, sorry, didn't have the time to get to it yet.
What is your use case? Is it enough to parse the Cpus_allowed_list?

[LXYan2333]

Hello:

I wrote a program using OpenMPI, which will restrict allowed cpu by default. https://stackoverflow.com/questions/61009618/openmp-threads-not-activating-when-run-with-mpirun

So I want to check the allowed cpu list to warn user they forget to configure OpenMPI if the allowed cpu is restricted. As an alternative, I read the https://github.com/coreutils/gnulib/blob/master/lib/nproc.c and found another api to get the allowed cpu list.