Re: git: d9d5f2c042a5 - main - cpuset: add --count

From: Jessica Clarke <jrtc27_at_freebsd.org>
Date: Thu, 16 Feb 2023 18:01:32 UTC
On 5 Feb 2023, at 17:28, Alexey Dokuchaev <danfe@freebsd.org> wrote:
> 
> On Sun, Feb 05, 2023 at 04:42:16PM +0100, Mateusz Guzik wrote:
>> On 2/5/23, Alexey Dokuchaev <danfe@freebsd.org> wrote:
>>> On Sat, Feb 04, 2023 at 05:51:27PM +0000, Mateusz Guzik wrote:
>>>> commit d9d5f2c042a51a9f0dd69eb1fc349efd81ffa483
>>>> 
>>>>  cpuset: add --count
>>>> 
>>>>  Can be used to count the number of hardware threads in the cpu set.
>>>> 
>>>>  For example: [...]
>>>> 
>>>>  The intent is to replace calls to sysctl hw.ncpu and kern.smp.cpus
>>> 
>>> Speaking of these two, do we really need both, unless they are not
>>> exactly the same?  (They do seem so, though.)
>> 
>> They are not, cpuset grabs a pid argument, while nproc only works on itself.
> 
> cpuset? pid argument?  But I was not asking about cpuset, I was wondering
> whether we need both of these sysctls:
> 
> $ sysctl hw.ncpu
> hw.ncpu: 2
> $ sysctl kern.smp.cpus
> kern.smp.cpus: 2

One prints mp_ncpus, the other smp_cpus. As far as I’m aware those two
are the same for as long as userspace is running, and only differ
during early boot before AP bringup (mp_ncpus is how many it will bring
up, and smp_cpus counts up as they come online until the two become
equal).

Jess