CilkSilk : An Efficient Multithreaded Runtime System

1
Cilk(Silk) An Efficient Multi-threaded Runtime
System

• Robert D. blumofe Christopher F.joerg etc
• MIT Laboratory for Computer Science _at_1995 ACM
• / Seminar by copyleft yi_sang /

2
Abstract

• Cilk is C-based runtime system for multithreaded
  parallel programming.
• Combined by work critical path
• On this idea, we can predict the runtime
  accurately.
• It can make efficient parallel processing by
  non-blocking thread function.

3
Cilks properties

• Support non-blocking Thread model (in C code)
• Schedule by work stealing scheduler
• multithreaded computation can be viewed a DAG
• Finally it gains Tp T1 / P s running time.

4
Thread model of Cilk (1)
5
Thread model of Cilk (2)

• Basically, its using Continuation method. Thus
  args sending/receiving is easy and fast.
• Continuation method is not sending total memory
  contest, but just sending the datas pointer.
• So, it is fast.
• thread T (arg-decls ) stmts
• Thread definition
• spawn T (args )
• When calling Child thread
• spawn_next T (args )
• When calling Successor thread
• send_argunemt (k, value)
• Sending value to its waiting parent thread

6
Thread model of Cilk (3)

• Figure 3 Example program of computing
  nth-Fibonacci number

7
Work Stealing Scheduler(assumption of multi
processor system)

• Flow of work-stealing process
• 1. Select a victim processor at random.
• 2. If the victims ready queue is empty, go to
  step 1.
• 3. Else, extract a thread from the tail of the
  list in the shallowest level o the ready queue,
  and invoke it.
• By ready queue and join counter, it can
  process the scheduler. (see Figure 2)

8
Performance of Cilk applications

• Tp T1/P Tinf gtgt we can predict the running
  time of program.
• And It provides good scheduling performance.

9
Conclusion Future work

• Cilk program can get two rabbits
• 1. High-performance
• 2. Easy to programming in programmers view
• Currently, Cilk runtime system runs on
• Connection Machine CM5 MPP
• Intel Paragon MPP
• Silicon Graphics Power Challenge SMP
• MIT Phish network of workstations
• But, it has limited points
• Capabilities are limited.
• Continuation passing style is burdensome
  slower!
• (worst 50 cycles are needed)