A question about the calculation of the number of cpu

[beita1]

Hello, I was reading tinypool's source code and had two questions in the src/physicalCpuCount.ts. I don't understand the logic for counting cpu number , could you help me with it?

questions

• question 1: Why not just use os.cpus().length to get cpu count instead of doing special logic for different plaforms？
• question 2: Why does the Linux platform get the physical cpu cores by the command cat /proc/cpuinfo | grep "physical id" | sort | wc -l instead of the logical cpu's number by the command cat /proc/cpuinfo| grep "processor"| wc -l?

[Aslemammad]

Hey, Thank you for asking the question! Sure! for the first question, the answer is in the second one! it's because we want to spawn workers based on physical cores, not logical ones!
And why physical cores? Read this

[beita1]

These two articles may be helpful:

• https://www.howtogeek.com/194756/cpu-basics-multiple-cpus-cores-and-hyper-threading-explained/
• https://superuser.com/questions/740611/what-is-the-difference-between-multithreading-and-hyperthreading

And I think the physical core can be calculated like this

    const output = exec('cat /proc/cpuinfo | grep "physical id" | sort | wc -l'); 
    const cpuNum = parseInt(output.trim(), 10);

    const output2 = exec('cat /proc/cpuinfo| grep "cpu cores"| uniq');
    const coreNum = parseInt(output2.trim(), 10);
    const count = cpuNum * coreNum;

== edit
something is wrong

    const output = exec('cat /proc/cpuinfo | grep "physical id" | sort |uniq | wc -l'); 
    const cpuNum = parseInt(output.trim(), 10);

    const output2 = exec('cat /proc/cpuinfo| grep "cpu cores"| uniq');
    const coreNum = parseInt(output2.trim(), 10);
    const count = cpuNum * coreNum;

[Aslemammad]

I get it now! That's reasonable! one thing, can we count the coreNum with

cat /proc/cpuinfo | grep "core id" | uniq | wc -l

let me know if you think this works for (physical) cores!

[beita1]

• It can alos work: realCpuCount = cat /proc/cpuinfo | grep "physical id" | sort |uniq | wc -l * cat /proc/cpuinfo | grep "core id" | sort | uniq | wc -l
  `

• cat /proc/cpuinfo | grep "core id" | uniq | wc -l can't work because core id may be same in the different physical id. For example:
  

• Otherwise, we can get physical cores by lscpu: https://unix.stackexchange.com/questions/468766/understanding-output-of-lscpu

[Aslemammad]

That's great, could you please try sending a PR?

[beita1]

With pleasure, I will send a PR tonight

== edit

This pr has been created: #34