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Processes without Partitions Matthew Flatt University of Utah Adam - - PowerPoint PPT Presentation

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Processes without Partitions Matthew Flatt University of Utah Adam Wick Robert Bruce Findler University of Utah University of Chicago 1 This talk has been modified from its original version. It has been edited for content and formatted to

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Processes without Partitions

Matthew Flatt

University of Utah Adam Wick

University of Utah

Robert Bruce Findler

University of Chicago

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SLIDE 2

This talk has been modified from its original

  • version. It has been edited for content and

formatted to fit your screen.

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SLIDE 3

Machines and Processes

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Machines and Processes

101010 010101

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SLIDE 5

Machines and Processes

101010 010101

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SLIDE 6

Machines and Processes

λ λ

101010 010101

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Machines and Processes

λ λ

OS

101010 010101

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SLIDE 8

Machines and Processes

λ λ

VM

101010 010101

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SLIDE 9

Process Examples

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Process Examples

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Process Examples

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Process Examples

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Process Examples

λ

DrScheme user's program

λ

Run DrScheme

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SLIDE 14

Languages with Termination

Pilot [Redell80] SPIN [Bershad95] JKernel [Hawblitzel98] Alta [Tullman99] KaffeOS [Back00] JSR-121 [Soper03] .NET application domains ...

λ λ

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Languages with Termination

PLT Scheme

λ λ

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Motivation and Approach Processes in PLT Scheme

  • Threads
  • Parameters
  • Eventspaces
  • Custodians

Memory Accounting

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SLIDE 17

Threads

Concurrent execution

(require "spin-display.scm")

eval

(define (spin) (rotate-a-little) (sleep 0.1) (spin)) (define spinner (thread spin))

eval

(kill-thread spinner)

eval

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SLIDE 18

Parameters (a.k.a. Fluid Variables)

Thread-local state

(printf "Hello\n") (fprintf (current-output-port) "Hola\n") (fprintf (current-error-port) "Goodbye\n") (error "Ciao")

eval

(parameterize ((current-error-port (current-output-port))) (error "Au Revoir"))

eval

(parameterize ((current-error-port (current-output-port))) (thread (lambda () (error "Zai Jian"))))

eval

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SLIDE 19

Eventspaces

Concurrent GUIs

(thread (lambda () (message-box "One" "Hi"))) (thread (lambda () (message-box "Two" "Bye")))

eval

(thread (lambda () (message-box "One" "Hi"))) (parameterize ((current-eventspace (make-eventspace))) (thread (lambda () (message-box "Two" "Bye"))))

eval

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SLIDE 20

Custodians

Termination and clean-up

(define c (make-custodian)) (parameterize ((current-custodian c)) ...)

eval

(custodian-shutdown-all c)

eval

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Etc.

  • Security Guards

Resource access control

  • Namespaces

Global bindings

  • Will Executors

Timing of finalizations

  • Inspectors

Debugging access

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SLIDE 22

Building a Programming Environment

SchemeEsq, a mini DrScheme [ICFP 99]

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GUI - Frame

(define frame (new frame% [label "SchemeEsq"] [width 400] [height 175])) (send frame show #t)

eval

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GUI - Reset Button

(new button% [label "Reset"] [parent frame] [callback (lambda (b e) (reset-program))])

eval

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GUI - Interaction Area

(define repl-display-canvas (new editor-canvas% [parent frame]))

eval

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GUI - Interaction Buffer

(define esq-text% (class text% ... (evaluate str) ...)) (define repl-editor (new esq-text%)) (send repl-display-canvas set-editor repl-editor)

eval

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Evaluator

(define (evaluate expr-str) (thread (lambda () (print (eval (read (open-input-string expr-str)))) (newline) (send repl-editor new-prompt))))

eval

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Evaluator Output

(define user-output-port (make-output-port ... repl-editor ...)) (define (evaluate expr-str) (parameterize ((current-output-port user-output-port)) (thread (lambda () ...))))

eval

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Evaluating GUIs

(define user-eventspace (make-eventspace)) (define (evaluate expr-str) (parameterize ((current-output-port user-output-port) (current-eventspace user-eventspace)) (thread (lambda () ...)))

eval

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Custodian for Evaluation

(define user-custodian (make-custodian)) (define user-eventspace (parameterize ((current-custodian user-custodian)) (make-eventspace))) (define (evaluate expr-str) (parameterize ((current-output-port user-output-port) (current-eventspace user-eventspace) (current-custodian user-custodian)) (thread (lambda () ...))))

eval

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Reset Evaluation

(define (reset-program) (custodian-shutdown-all user-custodian) (set! user-custodian (make-custodian)) (parameterize ((current-custodian user-custodian)) (set! user-eventspace (make-eventspace))) (send repl-editor reset))

eval

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Motivation and Approach Processes in PLT Scheme Memory Accounting

  • Without partitions

[ISMM 04]

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Resource Consumption

λ

DrScheme user's program

λ

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Resource Consumption

λ

DrScheme user's program

λ

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Resource Consumption

λ

DrScheme user's program

λ

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SLIDE 36

Resource Consumption

λ

DrScheme user's program

λ

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Resource Consumption

λ

DrScheme user's program

λ

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SLIDE 38

Resource Consumption

λ

DrScheme user's program

λ

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SLIDE 39

Resource Accounting

  • Conventional OS: process memory use = size of partition

λ λ

Accounting is easy Trading data is difficult

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Resource Accounting

  • Language as OS: process memory use = size of owned data

λ λ

Trading data is easy Accounting appears difficult: sharing, real-time tracking

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Resource Accounting

Our strategy: compute accounting charges during GC

λ λ

See also [Price03]

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Basic Accounting

λ

= custodian A

λ

= custodian B

thread 1 thread 2 thread 3

x y z q r s

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SLIDE 43

Basic Accounting

λ

= custodian A

λ

= custodian B

thread 1 thread 2 thread 3

x A y A z B q A r A s B

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Basic Accounting

λ

= custodian A

λ

= custodian B

thread 1 thread 2 thread 3

x A y A z B, A q A r A s B, A

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Sharing

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x y z

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Sharing

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x A y B z A or B

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Sharing: Charge the Child

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x A y B z B, A

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Threads, Custodians, and Weak References

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x

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Threads, Custodians, and Weak References

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x B

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Threads, Custodians, and Weak References

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x B

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Threads, Custodians, and Weak References

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x B

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Why Charge the Child?

λ

= custodian A

λ

= custodian B

thread 1 thread 2

x A y B z B, A

  • Parent is responsible for children
  • Parent may allocate for children

GUI objects File descriptors ...

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Initial Experience: DrScheme

Bad Loop Normal Normal

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Initial Experience: DrScheme

Bad Loop Normal Shut Down

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DrScheme Bug

λ

= DrScheme

λ

= User1

λ

= User2

thread 0 thread 1 thread 2

x y z

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SLIDE 56

DrScheme Repair

λ

= DrScheme

λ

= User1

λ

= User2

thread 0 thread 1 thread 2

x y z

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SLIDE 57

DrScheme Repair

λ

= DrScheme

λ

= User1

λ

= User2

thread 0 thread 1 thread 2

x y z Changed 5 references:

  • Weakened 2
  • Removed 2
  • Moved 1 into child

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Current Experience: DrScheme

Bad Loop Normal Normal

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Current Experience: DrScheme

Shut Down Normal Normal

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Accounting without Partitions

Useful accounting

  • Doesn't need partitions
  • Does need hierarchy

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Conclusion

λ λ

  • Programmers need OS-like constructs in languages

concurrency adjust run-time environment easy termination

  • Multiple language constructs for “process”

programmer can mix and match to balance isolation and cooperation

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