Ch'04 Outline

1
Ch.04 Outline

• Motivation
• Web browser, word processor
• Benefits
• Responsiveness, resource sharing, economy,
  utilization of multiprocessor
• User kernel threads

2
Ch.05 Outline (cont)

• Multithreading models
• Many-to-one
• One-to-one
• Many-to-many
• Threading issues
• Fork exec calls
• Duplication replacement

3
Ch.05 Outline (cont)

• Threading issues (cont)
• cancellation
• Asynchronous or deferred(cancellation pts)
• Signal handling
• Handling
• Default or user defined handler
• Signal delivery in multithreaded program
• Applied, every, certain, specific

4
Ch.05 Outline (cont)

• Threading issues (cont)
• Thread pools
• Time required for creation of threads
• Bound on number of threads
• Thread pools solves above problems
• Thread-specific data
• Thread examples

5
PRESENTATION

• Threading issues (?4.4)
• Fork exec calls
• Duplication replacement
• cancellation
• Asynchronous or deferred(cancellation pts)
• Signal handling
• Handling
• Default or user defined handler
• Signal delivery in multithreaded program

6
PRESENTATION

• Threading issues (cont)
• Thread pools
• Problems in multithreading
• Benefits
• Thread-specific data
• PP. 132 138 in the text

7
threads

• Motivation
• Context switching overhead in HWP
• Other benefits
• User vs kernel threads
• Efficient, fast, easy to manage
• A thread can block the entire threads

8
Threads (cont.)

• Many-to-one model
• User threads
• One-to-one model
• No entire blocking, MP utilization
• Overhead in kernel thread creation
• thus limit the of threads
• Many-to-many
• Strong points of above models

9
Threading issues

• Fork exec
• Fork either duplicates all threads or one
• Exec replaces entire process
• Cancellation (target thread)
• Asynchronous
• reclaim of resources can be faulty
• Deferred
• cancellation points

10
Threading issues(cont.)

• Signal handling
• Definition
• Asynchronous vs synchronous
• Default or user-defined signal handler
• Signal delivery
• one ( applied or specific), all, certain
• synchronous obvious

11
Threading issues(cont.)

• Signal handling (cont.)
• Signal delivery (cont.)
• Asynchronous signals
• ex. Process termination to all
• to non-blocking threads
• first one directly or thru a specific
• thread

12
Threading issues(cont.)

• Thread pools
• two problems
• time of threads
• Create a thread pool at start up time solves
  above problems
• Thread specific data
• Copy not sharing (eg. Transaction proc.)

13
homework

• What are the 5 issues in threading? List and
  explain them.
• Solve exercise 5.1.
• Solve exercise 5.2.
• Solve exercise 5.8.