Building Efficient Software

T3chFest, 2018-03-02

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What We Will Cover

• Slow and Fast Software


• Finding Hot Spots


• Load Testing
  


• Micro Profiling


• Benchmarking


• Conclusions
  

Slow and Fast Software

The day comes when some client tells you:

Your Software Is Slow

Well, it happens to everyone

Web developers

Backend developers

Chuck Norris

MY SOFTWARE IS NOT SLOW, COLONEL!
(BONES CRUNCHING)

But is it slow?

What is it doing?

Can it be made faster?

Can you distract the user?

Can you avoid doing some things?

What Is Your Software Doing...

...with all those CPU cycles?

Each second has ~4·10⁹ cycles

Each toolchain has a max efficiency

Node.js: interpreter + compiler

Algorithmic efficiency

Premature Optimization

The real problem is that programmers

have spent far too much time

worrying about efficiency

in the wrong places and at the wrong times;

premature optimization is the root of all evil

(or at least most of it) in programming.

— Donald Knuth, computer scientist

Fast Software

... is not written fast

Which is faster?

• 2016: Lenovo X1 Carbon 4g (Windows)
• 2016: Samsung Galaxy S7
• 2002: Apple iMac G4
• 1993: Mac Color Classic
• 2017: Apple iPhone X
• 1998: Nintendo Gameboy Color
  
• 2017: Lenovo ThinkPad 13 (ChromeOS)
• 2017: Apple iPad Pro 10.5"
• 1977: Commodore Pet 4016
• 2017: Apple iPad Pro 10.5" pencil
• 1983: Apple 2e

Computer Latency

Source: Dan Luu

Finding Hot Spots

Pareto Rule

80% of the effects come

from 20% of the causes

— Vilfredo Pareto, Italian Sociologist*

*Not known for his many catchy quotes

Pareto Principle

Worry about the most relevant causes

Used in many engineering areas

Can be used recursively!

64% of the effects come
from 4% of the causes

Power Laws

... and the long tail

Use Sampling

It’s this simple: if you don’t sample,
you don’t scale.

If you think this is even a controversial statement,
you have never dealt with observability at scale OR you have done it wastefully and poorly.

— Charity Majors, computer engineer

Load Testing

Design Load Tests

Bring the problem to the laboratory

Reproducible environment

Iterate faster

Load Test Demo

Micro Profiling

Nanoseconds

— Grace Hopper, computer engineer

Profiler Granularity

Time to measure matters

Max resolution depends on measure

Measurement noise can kill you!

Microprofiler Demo

Sidebar: 32-bit Multiplication

Benchmarking

Lies, damn lies

and benchmarks

There are three gradations of inveracity:

there are lies, there are damned lies

and there are statistics

— Arthur James Balfour, UK Prime Minister

( probably)

Precision

Usually can get any precision desired

Your mileage may vary — wildly!

Handle with care

Iterate

Once the hot spot is replicated you can optimize it

It is usually harder than solving a regular bug

Work through the layers: interpreter, optimizer...

Benchmarking Demo

Conclusions

Don't Micro-optimize

Until you need to

And even then...

Don't micro-optimize blindly

Keep your target in sight

Persist

There are multiple obstacles on any path

Performance work requires perseverance

There are no magic bullets

Embrace Change

Results are likely to change

Every V8 version brings changes

Performance varies wildly across versions

Embrace Uncertainty

Religion is a culture of faith;
science is a culture of doubt.

— Richard Feynman?, physicist.

True Science teaches, above all,
to doubt and to be ignorant.

— Miguel de Unamuno, philosopher.

Thanks! We're Hiring!

@pinchito