However, CPU threads may only show physical performance boosts when being utilized for specific tasks. CPU cores are physical hardware components that are inside your computer. Threads are virtual components that help to manage workload and computer tasks efficiently. The CPU can interact with multiple threads at once if needed or if the first thread is unreliable or slow. However, multithreading and hyper-threading are slight variations of the same thing.
Intel owns the concept for hyper-threading, which allows Intel processing units to process threads more efficiently. Despite the futuristic name, hyper-threading came onto the commercial scene in in the form of Pentium 4. Essentially, hyper-threading tells your operating system that threads are actually physical CPU cores.
Therefore, information is shared fasted, and decoding is more streamlined. Hyper-threading is patented by Sun Microsystems.
A cache miss occurs when data requested is not found in the CPU cache memory. When this failure happen, the information has to be fetched from other cache levels or memory, like storage disks or RAM. The delayed fetch can cause latency which will end up hindering the performance of your CPU. Running multiple threads allows the CPU to schedule information beforehand, which minimizes down time. Regardless of the application running, reducing cache misses will improve performance and speed across the board.
Cores or CPUs are the physical elements of your computer that execute code. Usually, each core has all necessary elements to perform computations, register files, interrupt lines etc. Most operating systems represent applications as processes.
A process consists of one or more threads , which carry out the real work of an application by executing machine code on a CPU. The operating system determines, which thread executes on which CPU by using clever heuristics to improve load balance, energy consumption etc.
If your application consists only of a single thread, then your whole multi-CPU-system won't help you much as it will still only use one CPU for your application. However, overall performance may still improve as the OS will run other applications on the other CPUs so they don't intermingle with the first one. What OpenMP does is to generate code that spawns a certain amount of threads to distribute shared computational work from loops of your program in multiple threads.
It can use the OS's hint mechanism see: thread affinity to do so. However, OpenMP applications will still run concurrently to others and thus the OS is free to interrupt one of the threads and schedule other potentially unrelated work on a CPU. In reality, there are many different scheduling schemes you might want to apply depending on your situation, but this is highly specific and most of the time you should be able to trust your OS doing the right thing for you.
This comes a from the OS doing its job in the meantime and b from the fact that your application is never running alone -- each running system consists of a whole bunch of concurrently executing tasks. Note also that the OS doesn't much care which process the threads are from. This could lead to four threads from one process running at the same time, as easily as one thread from four processes running at the same time.
If your application consists only of a single thread, then your whole multi-CPU-system won't help you much as it will still only use one CPU for your application I think even if its a single threaded application, that application thread may be executed on different cores during its lifetime. On each preemption and later assignment to a CPU, a different core may get assigned to that thread.
Yes, threads and processes can run concurrently on multi-core CPUs, so this works as you describe regardless of how you create those threads and processes, OpenMP or otherwise. A single process or thread only runs on a single core at a time. If there are more threads requesting CPU time than available cores generally the case , the operating system scheduler will move threads on and off cores as needed.
The reason why single-threaded processes run on more than one CPU or core is related to your operating system, and not specifically any feature of the hardware.
Other than causing cache misses, this generally doesn't affect the performance of your process. Moving them out of the core is time consuming than their execution time.
If the threads need be run in a different core. I think one has to supply the affinity info to the thread. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
By submitting your email, you agree to the Terms of Use and Privacy Policy. The central processing unit CPU in your computer does the computational work—running programs, basically.
But modern CPUs offer features like multiple cores and hyper-threading. The clock speed for a CPU used to be enough when comparing performance. All of these features are designed to allow PCs to more easily run multiple processes at the same time—increasing your performance when multitasking or under the demands of powerful apps like video encoders and modern games.
Hyper-threading attempted to make up for that. While the operating system sees two CPUs for each core, the actual CPU hardware only has a single set of execution resources for each core. The CPU pretends it has more cores than it does, and it uses its own logic to speed up program execution. Hyper-threading allows the two logical CPU cores to share physical execution resources. This can speed things up somewhat—if one virtual CPU is stalled and waiting, the other virtual CPU can borrow its execution resources.
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