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Date: Fri, 2 Jul 2021 14:29:37 +0100
From: Vincent Donnefort <>
Subject: Re: Re: [PATCH v2] sysconf: add _SC_NPROCESSORS_CONF support

Hi James,

Here's a new thread as I never received your previous email and I just
noticed the answer today.

I'm not sure I understand why I can't use "present". As per the kernel

    possible:   CPUs that have been allocated resources and can be
                brought online if they are present. [cpu_possible_mask]

    present:    CPUs that have been identified as being present in the
                system. [cpu_present_mask]

    In this example, the NR_CPUS config option is 128, but the kernel was
    started with possible_cpus=144.  There are 4 CPUs in the system and cpu2
    was manually taken offline (and is the only CPU that can be brought
         kernel_max: 127
            offline: 2,4-127,128-143
             online: 0-1,3
           possible: 0-127
            present: 0-3

So indeed I could use "possible"... but there's a chance the two masks won't
be equal, and the sysfs entries are matching "present", not "possible".

"possible" is the CPUs that have allocated resources and can be physically
added to the system. "present" is the CPUs that are known as physically
present but might be offline.


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