STM, dev,clojure,

1. STM
@diego_pacheco
Software Architect | Agile Coach

2. Moore's law (Number os Transistors double ~2 years)

3. AMD Athlon 64 FX-53 CPU 2.4 GHz - Single CORE - 2005

4. Single Thread App: It’s ALL OVER !!!

5. More Than one CORE: Dual, Quad, etc..

6. Concurrent Threads == Challenges

7. Order of operations is not fixed…

8. Difficult to repeat failures…

9. WE often don’t think this way…

10. Testing effort is bigger…

11. Multithreaded: 2 General Categories
JOB JOB
Group
P1 P3
J1
P2 J2
J3
P4 P5 J4 J5
JOB JOB Group
DONE DONE

12. Current Models
Locks
Actors
STM

13. Current Models - LOCKS
Locks
Shared-Memory
OO
Surreal

14. Current Models - Actors
Actors
NO Shared Data
Async Messages Lightweight Threads

15. Current Models - STM
STM
ACID

16. STM Implementations Guarantee NO:
Dead Locks
Livelock
Race Conditions

17. STM Issues:
Retry Waste: Lots of transactions retry
Overhead: Transaction Bookkeeping
Lack of Tools: Identify, learn, tunning, etc...

18. Clojure/Haskell: All Immutable
Everything is immutable!
Change: Always
Inside a Transaction.

19. Clojure: Persistent Data Structures

20. Clojure STM Implementation
Multi-Version Concurrency Control (MVCC) + Snapshot isolation
Databases (Mysql, Postgress & Oracle),
Subversion,
EhCache, JBoss Cache
Clojure and several other solutions…

21. STM
Thank You!
@diego_pacheco
Software Architect | Agile Coach