Advanced Topics in Programming Languages: A Lock-Free Hash Table
Why Hacker News recommends it
HN regards it as one of the best technical talks, a deep and clear walkthrough of scalable lock-free hash tables built on compare-and-swap.
What it is
A 2007 Google Tech Talk in which Cliff Click of Azul Systems presents a lock-free concurrent hash table that scales to 768 CPUs. He explains why it is correct by reasoning in a different way than usual happens-before and memory-order arguments.
Recommended by 4 HN commenters across 5 different months, 2013 to 2024.
What Hacker News said
Strong rec qznc · 2013-04 · on “Ask HN: What's the best technical talk you've heard?”
Probably this one: [this video] Anything from Cliff Click is quite good. This guy has a very deep understanding of compilers, virtual-machines, CPUs, and their interactions. A JVM does that? [LINK] Java on a 1000 Cores [LINK]
Strong rec benreesman · 2024-09 · on “Build a serverless ACID database with this one neat trick (atomic PutIfAbsent)”
For folks interested in this topic I highly recommend this talk by Cliff Click about building highly scalable hash tables via Compare And Swap: [this video]
Recommends ignoramous · 2016-02 · on “A resizable concurrent map”
Dr. Cliff Click's Google talk on Lock-Free Hashtable is here: [this video] Acc to Dr. Click, if you do not have 30+ CPUs in a single machine, ConcurrentHashMap (built-in to the JDK) will do the trick more often than not. The talk is really worth it, if you're curious about the design, esp. Dr. Click also had memorable debate with Rich Hickey over STMs. He works at h2o.ai and wrote about building a Key-Value store two years ago: [LINK]
Recommends eternalban · 2017-05 · on “An Atomic Hash Table”
I've always admired the wizardry of Cliff Click's concurrent hash: [LINK] [this video] I'm not sure what to make of an "atomic" hash. I don't think OP does as well: "Doesn't this kind of defeat the point of concurrent algorithms? Well, in a sense, it does make it non-atomic, but it isn't really a spin-lock or anything like that, even though it can seem like that:" Concurrent hash seems to be more correct and clear.
Recommends benreesman · 2022-08 · on “C++ Concurrency Model on x86 for Dummies (2020)”
It's worth noting that for a lot of people for a long time, Intel TSO was the memory model in practice (which IIRC makes `std::memory_order_seq_cst` pretty much free on Intel). Many clothes have been torn and many teeth gnashed porting C++ from Intel to more relaxed architectures. Back in the day that usually meant like SPARC, today that usually means ARM. "Acquire" and "Release" are relatively comprehensible in isolated examples, but the intuitions don't compose well. It's realllly easy to end up with an ABA type issue or an architecture dependency even with the simplest lock-free primitives like CAS. Combine that with how cheap `std::mutex` is on most platforms and it's just really a last