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Non-working CPU cores showing up

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  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

#242540 — Non-working CPU cores showing up

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?

Paul

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#242541

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On Tue, Nov 30, 2021, 2:30 AM Paul M. Foster <paulf@quillandmouse.com>
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?
>

Place Holders?

>
> Paul
>

Kenneth Parker

>

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#242542

On Tue, 2021-11-30 at 02:30 -0500, 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?

That each core supports Symmetric Multi-Threading (SMT), AKA
Hyperthreading, so appears to software as two CPUs. This is common for
most modern x86 CPUs. (Though the one I'm typing this on actual 8 CPUs
without hyper-threading).

-- 
Tixy

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#242543

Paul M. Foster composed on 2021-11-30 02:30 (UTC-0500):

> 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?
										
At least one 10th gen i3 has hyperthreading, so yours probably does too.
<https://www.intel.com/content/www/us/en/products/sku/199283/intel-core-i310100-processor-6m-cache-up-to-4-30-ghz/specifications.html>
Hyperthreading typically shows up in cpuinfo as twice as many software cores as
physical cores, two threads per core.
-- 
Evolution as taught in public schools is, like religion,
	based on faith, not based on science.

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata

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#242546

On 30/11/2021 07:30, Paul M. Foster wrote:
> Folks:
> 
> Here's a curious thing. I have a 10th gen Intel i3 CPU with four cores. 

What exact model do you have?

-- 
With kindest regards, Piotr.

⢀⣴⠾⠻⢶⣦⠀
⣾⠁⢠⠒⠀⣿⡁ Debian - The universal operating system
⢿⡄⠘⠷⠚⠋⠀ https://www.debian.org/
⠈⠳⣄⠀⠀⠀⠀

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#242547

On Tuesday, 30 Nov 2021 at 02:30, Paul M. Foster wrote:
> But there are outputs for each of eight cores, numbered 0 through 7.

You will find that these entries are allocated to 4 cores (look at core
id for each entry).  This is due to hyper-threading which essentially
provides two virtual processors for each core.

-- 
Eric S Fraga with org 9.5 in Emacs 29.0.50 on Debian 11.1

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#242549

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-

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#242551

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

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#242552

> 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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#242560

On Tue, 30 Nov 2021 08:52:59 -0800
Ken Cunningham <ken.cunningham.webuse@gmail.com> wrote:


> 
> 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.

I would have expected 24 parallel build processes on your machine....

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#242565

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hey, you're right!

free upgrade :)

K

On Tuesday, November 30, 2021, Dirk Neumann <neum_d@yahoo.de> wrote:

> On Tue, 30 Nov 2021 08:52:59 -0800
> Ken Cunningham <ken.cunningham.webuse@gmail.com> wrote:
>
>
> >
> > 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.
>
> I would have expected 24 parallel build processes on your machine....
>
>
>

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#242554

On Tue, 2021-11-30 at 11:18 -0500, Paul M. Foster wrote:
> It appears you are correct. lscpu shows this CPU has 4 cores, and 2 
> threads per core. But it shows 8 CPUs. Silly.

It may be not what you were expecting but that doesn't automatically
make it 'silly'. Your processor chip can execute 8 independent programs
simultaneously, so I would consider it more silly to report it only
having 4 CPUs (or one if that was what you were expecting - for one
chip).

-- 
Tixy 

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