1. Advanced Mobile Optimizations How to go to 60 fps after you have removed all Sleep calls ;-)

2. Disclaimer

The views expressed here are my personal views and do not necessarily reflect the thoughts, opinions, intentions, plans or strategies ofUnity

3. Optimization Mindset

you can't just make your game faster

• there is no magic bullet

• very specific stuff

• • not the same as scripting charachter

4. Optimization Mindset

not in specific order

know

think

measure

5. Optimization Mindset

You can't avoid any of that

• no, really

6. Optimization Mindset

know + think = shoot in the dark

• you just write code hoping for the best

know + measure = shoot in the dark

• you are missing "understand" part

think + measure = shoot in the dark

• you solve abstract problem, not real

7. Optimization Mindset:know + think

hardware is more complex then you think

• highly parallel

• deep pipelining

• when you write asm - high-level already

8. Optimization Mindset:know + measure

knowledge is static

knowledge comes from the past

knowledge is general

9. Optimization Mindset:know + measure

qsort vs bubble sort

• sure, qsort is faster

but you are missing the point

• maybe radix?

• maybe no need to sort?

• maybe insertion?

• parallel sorting network?

10. Optimization Mindset:think + measure

solving abstract problem

• example: GPU

• • optimizing for RIVA TNT and GTX is different

11. Optimization Mindset

well, if you are missing two from the three

• no comments

12. Know

your hardware

your data

• knowing data is interleaved with think

• we will talk more of it in "think"

13. Know your hardware

GPU

CPU

whatever

• e.g. disk load speed

14. Know your hardware: GPU

Pipeline

• meaning - slow step = slow everything

• you are as slow as your bottleneck

Know your pipeline

Won't go into full pipeline spec

• Resources section

Just common/biggest problems

15. Know your hardware:GPU Geometry

pre/post tnl cache

• should use indexed geometry or not

cache hit rate

• strips vs tri list

memory throughput

• vertex size

fetch cost (memory)

• pack attributes or not

16. Know your hardware:GPU Textures

Texture Cache

• swizzle

• compression

• mip-maps

Biggest memory hog

17. Know your hardware:GPU Shaders

VertexProgram vs FragmentShader

• balancing

• attributes

Unified Shaders

• load balancing

Precision

• gles: highp/mediump/lowp

• CG: float/half/fixed (iirc)

18. Know your hardware:GPU Rasterization

Fillrate (memory speed)

• alpha

2x2 samples (or more)

• why GometryLOD matters

19. Know your hardware: CPU

Mobile = in-order RISC

• for stupid code far worse than CISC

2 main issues:

• Memory speed

• Computation speed

20. Know your hardware:CPU Memory

This is single most important factor

• memory access far slower then computation

Latency vs Throughput

Caches

• fast memory

• your best friend

• L1/L2/whatever

LHS

21. Know your hardware:CPU Computations

SIMD

• better memory usage

• better arithmetic usage (4 vals instead of 1)

22. Know your target hardware

There were general rules

But you are running on that particular piece of sh... hardware

23. Know your target hardware: PowerVR

TBDR

• perfect hidden surface removal

• Alpha-Test/discard

shader precision

unified shaders

Tegra / ATI-AMD / Adreno more common

24. Know your target hardware: ARM

VFP = FPU on steroids (not real SIMD)

• scalar instructions at same speed as vectorized

NEON = SIMD

• more registers

• awesome load/store instructions

• not as cool as Altivec but cool enough for mobiles

25. Know your target hardware: ARM

Conditional execution of most instructions

Fold shifts and rotates into the "data processing" instructions

• load structure from array by index

Thumb + float = disaster

• switch back and forth between Thumb mode and regular 32-bit mode

26. Know your hardware: Resources

RTR

lots of whitepapers:

• powerVR (imgtech) tegra (nvidia) adreno (qualcomm)

• AMD/ATI - basically the same as X360, but much smaller tiles

ARM dev center

27. Think

Think about your data

Think about your algorithms

Think about your constraints

Think about your hardware

28. Think Basics

CPU vs GPU

• e.g. draw calls

• • pure CPU cost

CPU:

• memory vs arithmetic

• • memory slower

GPU:

• vprog vs fshader

• memory vs arithmetic

29. Think Memory

fragmentation

data organization

• AOS vs SOA

• hot/cold split

data structures

• linear vs random

• array vs list

• map vs hashtable

• allocators

30. Think Constraints

GPU: will you see the difference?

• really?

• on mobile screen?

• on that one small thingy in the corner?

CPU: will you need that?

• e.g. physics in casual game?

Memory: will you need that?

• will you need more then XXX actors?

31. Measure

you didn't optimize anything if you didn't measure difference

you can't optimize if you don't know what needs to be optimized

• if you can't measure what takes time

32. Measure Tools

there are lots of tools

• instruments (ios)

• perfhud (tegra)

• adreno profiler (qualcomm)

• some more probably

Poor-man profiler

• timers

33. Unity use case: random bits

Mobile shaders

• specialized of usual built-ins

Skinning

• full NEON/VFP impl

• • usually 10-15% of c-code time

• • • and we are not done optimizing it ;-)

Rej's baking material to texture and coming soon BRDF baking to texture

34. Unity use case: random bits

Remote Profiler

• run on target hw, data is transferred over wifi

• collect in Editor and show pretty graphs ;-)

Sort alpha-test *after* opaque

check *lots* of extensions

LODs - almost done

Vertex Cache optimization - after LODs ;-)

35. Closing Words

Know hardware

Know data

Think data

Think constraints

Measure always

• You better know earlier

You should be always optimizing

36. Questions