Thinking About Performance - Notes

I gave an internal presentation at Dropbox (sorry, video is not sharable publicly) about engineering software for performance. Here are a bunch of resources that went into the presentation.

Similar Presentations

• Professor Bill Gropp
• I wrote a related article before joining Dropbox
• Rico Mariani (Microsoft)'s performance blog
• Typical C++ Bullshit - A hilarious presentation by Mike Acton (Insomniac Games) about how OOP and C++ are not a good fit for high-performance code.
• Dan Luu

The Economics of Performance

• The Economic Value of Rapid Response Time
• Latency is Everywhere and it Costs You Sales - How to Crush it - many supporting links in here

Humans

Vision

• The Illusion of Motion

Touch

• Tactile vibration
• Human sensor for light touch (wikipedia)
• Human tactile detection thresholds: modification by inputs from specific tactile receptor classes

Reaction Times

• Reaction times benchmark
  • Take the test yourself!
• Beating the Gun or Running Fast

Response Time

• System Response Time and User Satisfaction: An Experimental Study of Browser-based Applications
• Response Time and Display Rate in Human Performance with Computers
• Response Times: The 3 Important Limits
• Typing with Pleasure

Perception of Time

• Actual Performance, Perceived Performance
• Mental chronometry
• Manipulating perceived duration in progress bars
  • more

Computers

Latency

• Byuu's awesome discussion of latency in emulators
• Operation Costs in CPU Clock Cycles
  • HN discussion
• Geostationary satellite latency
• Latency and the Quest for Interactivity
• Latency numbers every programmer should know

Examples of High-Performance Code

• SpookyHash - V2 inner hash body
  • Aras's @ Unity3D excellent hash function benchmarks
• Cal3D skeletal animation skinning loop - fits in registers
• CellPerformance

CPU architecture

In the talk I intentionally left out some detail - technically the branch predictor and branch target predictor are different things.

• Reservation station
• Branch predictor
• Branch target predictor

Agner Fog has amazing resources for CPU optimization, including his famous x86 instruction tables. It's helpful to scan the latencies and reciprocal throughputs of common instructions.

• Instruction tables
• Microarchitecture guide contains details on branch predictors, memory access, caching, the instruction decoder, etc.

Haswell

• Architecture details
• Anandtech 1
• Anandtech 2
• Architecture diagram (and other things)
• Wikipedia entry)
• realworldtech.com overview

Apple A9

• A9 Twister architecture
• Ars Technica A9 Review
• iPhone 6s RAM speed discussion

Caches, Memory, and Atomics

• rygorous's excellent cache coherency primer
• rygorous's explanation of the workings and costs of atomics
• Evaluating the cost of atomic operations on modern architectures
• Atomics: Odds & Ends
• What is the true cost/performance of atomic operations?
• Nonblocking algorithms and scalable multicore programming
• CAS latency

Memory Bandwidth

• Intel Iris Pro 5200 Memory Bandwidth
• 2012 MacBook Pro Memory Bandwidth

Branch Prediction

• Fast and slow if-statements: branch prediction in modern processors
• Branch prediction class notes from UWash
• Great example of improving speed by sorting the data
• Binary Search eliminates Branch Mispredictions by Paul Khuong

Miscellaneous

• CPU performance over time
• Premature optimization is the root of all evil
• Interactive visualization
• Modern Microprocessors - a 90 minute guide
• The Fallacy of Premature Optimization