Dragged, Kicking and Screaming: Multicore Architecture and Video Games.

Dragged,

Kicking and Screaming:

Multicore Architecture and Video Games

Summary of Topics:

Console Architecture

Meaning of Paper’s Title/Why the Video Game Developer HATED the new

Techniques/Problems

The Future

Video Game Architecture

For the most part, same as computer:

Very operating system-linked.

With PCs, almost always have been games.

Mac Gaming is sparse, recently increased.

Linux users have to compile/make their own.

Console Games = primarily single-core processors…until 2005.

XBOX 360• 3.2 GHz “Xenon” triple-core PowerPC, 2 hardware threads per processor

• 256 MB main RAM

• 500 MHz ATI “Xenos” GPU

-CPU accesses memory

through the GPU!

• GPU has 10 MB RAM embedded frame buffer

XBOX 360 vs. Playstation 3

Triple-Core PPC

• Xbox 360 - 512 MB, 700 MHz, GDDR3, shared by CPU and GPU

• CPU accesses memory through the GPU!

• GPU has 10 MB RAM embedded frame buffer

Multicore Cell Engine

PS3 - 512 MB total

256 MB 3.2 GHz XDR main RAM for the CPU

256 MB 700 MHz GDDR3 video RAM for the GPU

Multiple synergistic core units that attach to local stores, which then feed into DMAs going into the on-chip bus. One set-off PPE

(Power Processing Element), with an L1 and L2 cache. Developers are having some serious problems with this model.

Cell Architecture

Why So Unhappy?

Delays, setbacks, ecetera = unhappy fans.

Yu Suzuki; Saturn Virtua Fighter: “One very fast central processor would be preferable...I think that only one in 100 programmers are good enough to get this kind of speed out of the Saturn.”

Not implementing parallelism, use of multicore architecture, etc = unhappy fans.

If game developers utilize parallelism, the game will be delayed – 6 months, 1 year?

“I guess, if we have to.”

Multicore Parallelism

Implementations

Beginning Techniques

• Patches, so computers at least realize there’s multiple cores available.

• Intel releases several multicore assists; especially in the beginning (coaxing people into it)

• Building Blocks

• Codeplay’s sieve compilers

• Broke a program into “sieve blocks” where automatic parallelization could be utilized

What do we do today?

Multithreading from the ground up

Decent (and fast!) parallelization

One of two main ways:

Every process on a different thread

Dependencies galore~!

Main gaming thread, with branches coming off for specific parts of the game and splintering into other threads.

Particularly beastly programs get their own multithreading implementations.Networking and I/O get their own threads.

“Best” Multithreading Approach

CASE EXAMPLE: Kameo, which achieved 2.2~2.5 cores in 6mos.Rendering, decompression were on a separate thread

Latter saved space on the DVD and improved load times for the game. Additionally, file I/O was separated onto two threads – one for reading, and

one for decompressing.

CASE EXAMPLE: Kameo

Best Processes for MTFile decompression – improve load times.

Rendering – separate update and render; can be problematic

Physics Engine? – Physics/Update/Render, but latency issues.

Graphical Fluff – always and forever.

Artificial Intelligence - position independency of data, cache coherency

Cascade ProjectFix dataflow by sending data from the parent to the child before the parent had completed!

Respect dependencies, divided AI

Resulted in reducing “the average time per frame from 15.5ms using a single thread to 7.8ms using eight threads.”

51% Speedup!

Work in progress – CDML

List constraints in language instead of working out later.

Multithreading is Tricky

Threads can fight over the cache

Dependencies

Data corruption, deadlocks

Bugs might not be apparent right away

Debugging sets developers back

The Future

ARM’s GPU/CPU Chip

Intel’s Larrabee Chip

Mobile Gaming Platforms laugh for now…

Unreal 4 Engine – “We’re waiting for massively multicore processors.”

Thanks for watching!

It’s just not that easy anymore.