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Re: Non-working CPU cores showing up

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> On Nov 30, 2021, at 8:18 AM, Paul M. Foster <paulf@quillandmouse.com> wrote:
> 
> On 11/30/21 6:24 AM, Dan Ritter wrote:
>> Paul M. Foster wrote:
>>> Folks:
>>> 
>>> Here's a curious thing. I have a 10th gen Intel i3 CPU with four cores. When
>>> I look at /proc/cpuinfo, it actually shows eight cores. There's a line in
>>> the output of each core which is
>>> 
>>> cpu cores       : 4
>>> 
>>> But there are outputs for each of eight cores, numbered 0 through 7.
>>> 
>>> Is it possible that there were eight cores on this CPU, and four of them
>>> were non-working (I know it's typical to have non-working cores on a die),
>>> and this file shows all the original cores?
>>> 
>>> Or does someone have a better explanation?
>>> 
>> Try lscpu. Useful lines:
>> CPU(s):                          12
>> On-line CPU(s) list:             0-11
>> Thread(s) per core:              2
>> Core(s) per socket:              6
>> Socket(s):                       1
>> So this machine has one socket, 6 cores in the socket, 2 threads
>> per core, which looks like 12 CPUs.
>> You should find that your has one socket, 4 cores in the socket,
>> 2 threads per core, which looks like 8 CPUs.
>> -dsr-
> 
> It appears you are correct. lscpu shows this CPU has 4 cores, and 2 threads per core. But it shows 8 CPUs. Silly.
> 
> Paul
> 

Some software, like ninja etc, use that information to decide how many parallel jobs to set up. On my systems (2 processors, 6 CPUs on each, each with two threads per core = 12 parallel build processes) that works out well it seems.

Ken

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Thread

Non-working CPU cores showing up "Paul M. Foster" <paulf@quillandmouse.com> - 2021-11-30 08:40 +0100
  Re: Non-working CPU cores showing up Kenneth Parker <sea7kenp@gmail.com> - 2021-11-30 08:50 +0100
  Re: Non-working CPU cores showing up Tixy <tixy@yxit.co.uk> - 2021-11-30 08:50 +0100
  Re: Non-working CPU cores showing up Felix Miata <mrmazda@earthlink.net> - 2021-11-30 09:40 +0100
  Re: Non-working CPU cores showing up piorunz <piorunz@gmx.com> - 2021-11-30 12:00 +0100
  Re: Non-working CPU cores showing up Eric S Fraga <e.fraga@ucl.ac.uk> - 2021-11-30 12:10 +0100
  Re: Non-working CPU cores showing up Dan Ritter <dsr@randomstring.org> - 2021-11-30 12:50 +0100
    Re: Non-working CPU cores showing up "Paul M. Foster" <paulf@quillandmouse.com> - 2021-11-30 17:30 +0100
      Re: Non-working CPU cores showing up Ken Cunningham <ken.cunningham.webuse@gmail.com> - 2021-11-30 18:00 +0100
        Re: Non-working CPU cores showing up Dirk Neumann <neum_d@yahoo.de> - 2021-12-01 08:40 +0100
          Re: Non-working CPU cores showing up Ken Cunningham <ken.cunningham.webuse@gmail.com> - 2021-12-01 09:40 +0100
      Re: Non-working CPU cores showing up Tixy <tixy@yxit.co.uk> - 2021-11-30 18:20 +0100

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