Re: git: 48bfd3597654 - main - Add nproc(1)

On 2/8/23, Steffen Nurpmeso <steffen@sdaoden.eu> wrote:
> Mateusz Guzik wrote in
>  <202302081947.318Jlbt6052826@gitrepo.freebsd.org>:
>  ...
>  |URL: https://cgit.FreeBSD.org/src/commit/?id=48bfd3597654490cdc43bf0f591\
>  |a539d3a28b590
>  ...
>  |    Add nproc(1)
>
> Hey!  Great.  (NPROC is mentioned in POSIX for environment
> variables, as well as a make macro that did not make it, ..  and
> nproc(1) is commonly used on Linux it seems.)  Thanks.
>
>  |    This program prints the number of CPU threads it can run on, while
>  |    respecting cpusets (or not, depending on switches).
>  |
>  |    It aims to be compatible with nproc as found in GNU coreutils.
>
> That, "however",
>
>   ...
>  |+     if (all_flag) {
>  |+             cpus = sysconf(_SC_NPROCESSORS_ONLN);
>
> is not compatible -- note i like the FreeBSD way better, and maybe
> someone should make a bug report even.
>
>   #?0|kent:$ getconf -a|grep NPROC
>   _NPROCESSORS_CONF                  8
>   _NPROCESSORS_ONLN                  4
>   #?0|kent:$ nproc
>   4
>   #?0|kent:$ nproc --all
>   8
>   #?0|kent:$
>

Is this from disabling hyperthreading?

I have a 40-way box, after doing it I see:
NPROCESSORS_CONF: 20
NPROCESSORS_ONLN: 20
_NPROCESSORS_CONF: 20
_NPROCESSORS_ONLN: 20

iow it wont make a difference.

I'm going to sleep on it, will probably add BUGS to the manpage.

I do think linux nproc behavior on this is one peculiar at best though.

Thanks for reporting.


>
>  |+             if (cpus == -1)
>  |+                     err(1, "sysconf");
>  |+     } else {
>  |+             CPU_ZERO(&mask);
>  |+             if (cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TID, -1,
>  |+                 sizeof(mask), &mask) != 0)
>  |+                     err(1, "cpuset_getaffinity");
>  |+             cpus = CPU_COUNT(&mask);
>
> That is the right thing to do, imho!
>
> Thank you.
>
> --steffen
> |
> |Der Kragenbaer,                The moon bear,
> |der holt sich munter           he cheerfully and one by one
> |einen nach dem anderen runter  wa.ks himself off
> |(By Robert Gernhardt)
>


-- 
Mateusz Guzik <mjguzik gmail.com>