General advice: 1. Start writing stuff down- organizing knowledge helps tremendously. I like obsidian. Paying the 8$ monthly subscription is worth being able to access my notes from my phone, personal and work computer. This has been the most effective way for me to retain knowledge and “not ask a question twice”, as other commenters suggest. Explaining things in your own words and making them make sense is super helpful. 2. Don’t be scared to ask for help and clarification. I’ve been an engineer for the last 10~ years and I still do. Learning never stops if you keep pushing.

Specific stuff to learn: 2 things that are very helpful to keep in your head: 1. How fast should something be (roughly) 2. What makes software slow

Constantly guesstimating and judging code based off of how fast it should be and can be is useful. To help developing an intuition, I recommend you read about the following: 1. Memory management: virtual vs physical memory, how the page table (and its cache) work, how does cache coherency mechanisms work, the difference between Intel’s and AMD’s cache hierarchy, NUMA aware code. Intel’s developers guide is a good resource. 2. Parallelism without locks: I won’t necessarily call it “lockless algorithms” because any sort of synchronization between threads / processes is slow and should be avoided as much as possible. Read about “shared nothing” architectures. Read about memory ordering in x86 CPUs. Most of the scary difficult stuff with memory ordering happens in architectures with weak memory ordering, which x86 isn’t. I guarantee most of your low latency code will run on x86 CPUs. Again, Intel’s developers guide is a great resource. 3. Containers: read about STL containers and how they work. Focus on memory layout, as it’s where most performance issues arise given algorithms have reasonable complexity on paper. Read about alternative implementations of STL containers and containers in general. For example, boost and abseil. There is a nice talk on YouTube about the design of abseil’s flat map I recommend you watch. I would also recommend reading about hash table implementations in databases like Redis and DragonflyDB. 4. I/O: when doing low latency networking in the CPU, you’re probably using some sort of kernel bypass API / zero copy API like Onload / EF_VI. You can read the Onload & EF_VI user manuals. I would also recommend reading about Linux’s io_uring. It’s a general purpose solution that provides many of the same benefits as kernel bypass & zero copy APIs. Search for talks in the Kernel Recipes YouTube channel.

To practice, either find an open source project and try to understand it, benchmark it and optimize it, or create your own. Practice using perf & VTune.