Overview

MentaAffinity is a Java library for setting thread affinity in Linux. That means you can pin a thread to a single logical processor in order to avoid interrupts, context switches and cpu cache misses. It also allows you to distribute your threads through the cpu architecture, so you can run them in different physical processors, in different cores or in the same core if the processor has hyper-threading. Depending on what your threads are doing and on what kind of information they are sharing that can have a big impact on performance.

CPU Architecture

MentaAffinity parses the /proc/cpuinfo file to understand the machine cpu architecture so it can distribute threads across processing units:

• Chip: The physical processor you can hold in your hands. Some people call it socket but it can generate confusion with network programming. Different chips usually share the same L3 cache.
• Core: A chip can have multiple cores (multi-core processor). Each core usually has its own L1 cache, which is the fastest in-chip cache. Different cores usually share the same L2 cache.
• Processor: A *logical* processor which is the smallest processing unit that can execute only one thread at a time. If the chip supports hyper-threading, then each core will have two logical processors. Otherwise each core will only be able to execute one thread through a single logical processor.

Just keep in mind that for MentaAffinity the Processor object is the logical processor and NOT the physical processor. The physical processor is the Chip object.

The Basics

The basics of MentaAffinity is to allow you to pin a thread to a logical processor:

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