UD II : Gerência de Processos – parte 2 Referências: • ASO – F. B. Machado – cap 5, 6, 8, 14 e 15 • SOM - A.S. Tanenbaum – cap 1, 2, 10 e 11 • SO com Java - Silberschatz – cap 7, 8, 20 e 21 • SO - Deitel - cap 3, 4, 8, 20 e 21 (Adaptado de Arquitetura de Sistemas Operacionais de F. B. Machado e Sistemas Operacionais Modernos de A. S. Tanenbaum)

1

Ambiente Monothread (ASO-M)

Thread

Thread

Thread

2

The Thread Model (SOM-TB)

3

Ambiente Multithread - 1(ASO-M)

Contexto de hardware

Contexto de hardware

Thread 1

Thread 2

Thread 3

Contexto de software

Contexto de hardware

Espaço de endereçamento

4

Threads: private and shared items (SOM-TB)

5

Each thread has its own stack (SOM-TB)

6

Ambiente multithread - 2 (ASO-M) Processo

Programa Principal

Thread_1 PC SP

Call Sub_1

Hardware

Variáveis

Contexto de

...

Espaço de endereçamento

Ret

Thread_3 PC SP

Sub_2

Hardware

PC SP

Sub_1

Contexto de

Thread_2

Hardware

Fim

Contexto de

Call Sub_2

...

Ret

7

Aplicação multithread - 1 (ASO-M)

T h r ea d d e en tr ada

B u f f er

T h r ea d d e exi bi ção

T h r ea d d e g r avaçã o

8

Aplicação multithread - 2 (ASO-M) Processo servidor

Solicitações

Thread

Thread

Thread

Processo cliente

Processo cliente

Processo cliente

9

A word processor with three threads (SOM-TB)

10

A multithreaded Web server (SOM-TB)

11

Rough outline of code for previous slide

(a) Dispatcher thread (b) Worker thread 12

Three ways to construct a server (SOM-TB)

13

Arquitetura e Implementação (ASO-M)

• • • •

Threads em modo usuário Threads em modo kernel Threads em modo híbrido Scheduler Activations

14

Thread 4

Thread 3

Thread 2

Thread 1

Thread 0

Threads em modo usuário

(ASO-M)

Modo usuário

Biblioteca Kernel

Modo kernel

15

Implementing Threads in User Space (SOM-TB)

16

Kernel

Th rea d 4

Th rea d 3

Th read 2

Thr ead 1

Thr ead 0

Threads em modo Kernel

(ASO-M)

Modo usuário

Modo kernel

17

Implementing Threads in the Kernel (SOM-TB)

18

TMU 5

TMU 4

TMU 3

TMU 2

TMU 1

TMU 0

Threads em modo híbrido

(ASO-M)

Modo usuário

Biblioteca

TMK 0

TMK 1

TMK 2

TMK 3 Modo kernel

Kernel

19

Hybrid Implementations (SOM-TB)

Multiplexing user-level threads onto kernel-level threads 20

Thread 4

Thread 3

Thread 2

Thread 1

Thread 0

Scheduler Activations: ED BIB Threads (ASO-M)

Modo usuário

Biblioteca

Kernel

Modo kernel

21

Scheduler Activations (SOM-TB) • Goal – mimic functionality of kernel threads – gain performance of user space threads

• Avoids unnecessary user/kernel transitions • Kernel assigns virtual processors to each process – lets runtime system allocate threads to processors

• Problem: Fundamental reliance on kernel (lower layer) Calling procedures in user space (higher layer)

22

Pop-Up Threads (SOM-TB)

• Creation of a new thread when message arrives (a) before message arrives (b) after message arrives 23

Making Single-Threaded Code Multithreaded (1)

Conflicts between threads over the use of a global variable 24

Making Single-Threaded Code Multithreaded (2)

Threads can have private global variables 25