A CPU core is a hardware component that enables the greater CPU to process instructions received from applications, daemons, and other sources on the machine. Each CPU has a varying number of these individual cores — which together allow a computer to tackle multiple tasks simultaneously and provide seamless user experiences. Why does this matter? A CPU without cores is like a car without an engine. The platform is physically there, but you won't actually get anywhere (or be able to run anything).
Both consumer devices (personal computers, smartphones, etc.) and enterprise-grade server farms alike rely on multi-core CPUs to efficiently power through complex workloads.
How do CPU cores work?
The number of CPU cores has long differentiated one processor from the next. Theoretically, a system with a greater number of cores will have more processing power than one with fewer cores. Each core can support a varied number of threads, each of which represents a task or instruction assigned to the CPU. These cores work independently to get work done.
Given the trend of shrinking electronic components, the practice of squeezing more cores into a CPU package is evolving. Instead of commonly creating larger CPUs to accommodate additional cores (such as with AMD Threadripper), chip designers are working to reduce the size of each individual core (as with transistors) to fit more within the same CPU form factor. However, adding cores doesn't necessarily lead to massive, linear performance gains. The performance boost from moving to a higher core diminishes as the count increases — with each increase having less impact than the last. This practice is typically more beneficial for incredibly complex, data-intensive use cases than for consumer use cases.
Single core CPUs, though less common now than in years passed, consume less power overall. Meanwhile, newer multi-core and massively multi-core CPU designs are more power hungry and excel in situations where multitasking (or something close to it) and complex computation are required.
Modern CPUs are more intricate than their predecessors, possessing a higher number of cores on average. Each core may also be tuned for a specific purpose, such as high performance or efficiency. Chipmakers can intentionally design these individual cores for workloads of differing intensity and runtime while shifting lighter tasks away from performance cores.
The operating system's scheduler — part of the kernel space — decides which threads to run where based on internal algorithms and built-in logic. This is typically enforced at the OS level by default, but application developers can explicitly define which cores certain workloads will run on using mechanisms such as CPU affinity. This requires the developer to understand where other threads are running, meaning you get closer control over scheduling without some important guardrails (depending on your programming experience). It's possible to cause conflicts and bottlenecking if you don't manage threads carefully.
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Is HAProxy optimized to get the most performance from CPU cores?
Yes! HAProxy runs on machines with any number and arrangement of cores. It's built for optimized thread management and multithreading, intelligently organizing threads to prevent data transmission between CPU cores located far apart from one another.
This capability is bolstered by features such as automatic CPU binding and intelligently creating thread groups based on CPU mapping to reduce data sharing between threads, zero-copy forwarding (preventing L3 cache evictions by reducing unneeded buffering), load-balancing algorithms that scale with many threads, and more to boost application delivery performance.
To learn more about CPU core optimizations in HAProxy, check out our How HAProxy takes advantage of multi-core CPUs blog.