difference between 96 threads and 6500 threads?

I recently read in a post that I can run 96 threads. However, when I look at my PC’s performance, and posts like this, I see thousands of threads being able to run.

I assume the word thread is being used for two different things here (correct me if I’m wrong and explain). I want to know what the difference between the two “thread”s are. Why is one post saying 92 but another saying 6500?

Answer

The answer is: both links “talk” about the same thread.

The major difference is: the first is effectively asking about the number of threads that a given CPU can really execute in parallel.

The other link talks about the fact how many threads you can coexist within a certain scope (for example one JVM).

In other words: the major “idea” behind threads is that … most of the time, they are idle! So having 6400 threads can work out – assuming that your workload is such, that 99.9% of the time, each thread is just doing nothing (like: waiting for something to happen). But of course: such a high number is probably not a good idea, unless we are talking about a really huge server that has zillions of cores to work with. One has to keep in mind that threads are also a resource, owned by the operating system, and many problems that you did solve using “more threads” in the past have no different answers (like using nio packages and non-blocking io instead of having zillions of threads waiting for responses for example).

Meaning: when you write example code where each thread just computes something (so, if run alone, that thread would consume 100% of the available CPU cycles) – then adding more threads just creates more load on the system.

Typically, a modern day CPU has c cores. And each cores can run t threads in parallel. So, you got often like 4 x 2 threads that can occupy the CPU in parallel. But as soon as your threads spent more time doing nothing (waiting for a disk read or network request to come back), you can easily create, manage, and utilize hundreds or even thousands of threads.

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