ecs150 Spring 2006 : Operating System #1: OS Architecture, Kernel, & Process

transcript

03/30/2006 ecs150 Spring 2006 1

ecs150 Spring 2006:Operating SystemOperating System#1: OS Architecture, Kernel, & Process

Dr. S. Felix Wu

Computer Science Department

University of California, Davishttp://www.cs.ucdavis.edu/~wu/

sfelixwu@gmail.com

03/30/2006 ecs150 Spring 2006 2

VM/MVS, DOS, Win95/98/ME/2000/XP, Freebsd/Linux, MacOS-10, Mach, Minix, PalmOS, uCOS, TinyOS, …

03/30/2006 ecs150 Spring 2006 3

Applications……..

Hardware: CPU/Memory/HD/DVD/Wireless…

….where applications meet Hardware!!!

03/30/2006 ecs150 Spring 2006 4

““Information Router”Information Router”

One NIC a process’s user-level memory One file another file

– OS kernel layer– Hardware layer

03/30/2006 ecs150 Spring 2006 5

Applications……..

Hardware: CPU/Memory/HD/DVD/Wireless…

….where applications meet Hardware!!!

03/30/2006 ecs150 Spring 2006 6

Standard Full Virtualization e.g.,

Unmodified OS (XP, Linux, Solaris, or, FreeBSD)

Unmodified Applications

Hardware

VirtualPCWindowXP

virtualizationvirtualization

03/30/2006 ecs150 Spring 2006 7

03/30/2006 ecs150 Spring 2006 8

“Programmable” Full Virtualization

Hardware

Programmable VirtualizationProgrammable Virtualization

03/30/2006 ecs150 Spring 2006 9

Virtual PC or VMware

Hardware

FreeBSDFreeBSD

03/30/2006 ecs150 Spring 2006 10

This quarter….This quarter….

The internals of OS The basic design principles of OS The skills to modify or implement an OS.

03/30/2006 ecs150 Spring 2006 11

Operating SystemOperating System

An interesting balance between:– Theories and Practical Experiences/Experiments– Architectural Concept and Detailed Design– Formal Verification and Empirical Validation

03/30/2006 ecs150 Spring 2006 12

About the InstructorAbout the Instructor

S. Felix Wu – sfelixwu@gmail.com, x4-7070

Office: 3057 Engineering II Office Hours:

– 1-2 p.m. on Tuesday and Friday– by appointment

03/30/2006 ecs150 Spring 2006 13

About the TAAbout the TA

TA Valerie Szudziejka (szudziej@cs.ucdavis.edu)

– Office Hours: TBA– Discussion:

03/30/2006 ecs150 Spring 2006 14

about Web siteabout Web site

http://www.cs.ucdavis.edu/~wu/ecs150/ all lectures, notes, announcements,

homework assignments, tools, papers will be there.

03/30/2006 ecs150 Spring 2006 15

TextbookTextbook

http://www.freebsd.org/

"The Design and Implementation of the FreeBSD Operating Systems" by Marshall Kirk McKusick and George V. Neville-Neil

Addison Wesley Professional, 2005, ISBN 0-201-70245-2.

Reading this book itself is a major challenge!!But, you really learn when you go through this process!

03/30/2006 ecs150 Spring 2006 16

PrerequisitesPrerequisites

Programming Languages: C and assembly (ecs50)

Date Structure (ecs110) and basic Computer Architecture (ecs154a/eec70).

ecs40 Please talk to me if you have any concern.

03/30/2006 ecs150 Spring 2006 17

SyllabusSyllabus

Process/Kernel (09) Memory Management (06) midterm IO & File Systems (10) Others (03) final

03/30/2006 ecs150 Spring 2006 18

OS Principles/ConceptsOS Principles/Concepts

What is “kernel”?What is the difference between a process and a thread?What is the difference between user-level and kernel-level threads?What is the difference between a system call and a library function call?What are SJF, RR, Lottery, LRU, TLB, Second Chance?How to do Mutual Exclusion?What is the difference between deadlock prevention and avoidance?What are the differences among hardware interrupt, hardware trap, and software trap?

03/30/2006 ecs150 Spring 2006 19

Let’s examine OS concepts in a realistic context: “FreeBSD”

Then, we can re-think those concepts….– And, maybe you will realize later that some of

the concepts are either “misleading” or “irrelevant” in certain context.

03/30/2006 ecs150 Spring 2006 20

Principles vs. PracticePrinciples vs. Practice

Ideas and Theories first, then we will go over some FreeBSD code segments.

You will need to learn FreeBSD internals for programming assignments!!

The first few discussion sessions will be dedicated to FreeBSD internals.– Most of the discussion sessions are very important and

they will appear in the exams and homeworks.

03/30/2006 ecs150 Spring 2006 21

Course RequirementsCourse Requirements

48%: Programming Assignments– teamwork: 1~3 students– 3 Programming Assignments (12%, 18%, 18%)– HW#1 is out (check the website).

16%: In-class open-book midterm 32%: open-book final 04%: Participation of Lectures and Discussion

sessions.– Deducted if missed more than three sessions.

03/30/2006 ecs150 Spring 2006 22

GradingGrading

I will give +/- grades. possible grading (not finalized):

– A: >= 93 A-: >= 90 B+: >= 87– B: >= 84 B-: >= 81 C+: >= 78– C: >= 75 C-: >= 72 D : > 60

03/30/2006 ecs150 Spring 2006 23

FreeBSDFreeBSD

Your team need to have access to a FreeBSD environment– I386, VMware, VirtualPC

03/30/2006 ecs150 Spring 2006 24

The Structure of OSThe Structure of OS

The Kernel Processes and Threads The System Call Interface

03/30/2006 ecs150 Spring 2006 25

What is “kernel”?What is “kernel”?

03/30/2006 ecs150 Spring 2006 26

KernelKernel

The basic OS services Which services? What is it doing? Let’s check a couple examples

03/30/2006 ecs150 Spring 2006 27

….what are the basic services?

03/30/2006 ecs150 Spring 2006 28

FreeBSD Kernel: FreeBSD Kernel: ServicesServices

Timer/clock, descriptor, process Memory Management: paging/swapping I/O control and terminal File System Inter-process communication Networking

03/30/2006 ecs150 Spring 2006 29

03/30/2006 ecs150 Spring 2006 30

Kernel of SVR2 of AT&T UnixKernel of SVR2 of AT&T Unix

hardware

System Call Interface

LibrariesUser programs

trapuser

File subsys

Buffer cache

Hardware Control

Character blockdevice drivers

ProcessControlSubsys.

Inter-ProcessCommunication

Scheduler

MemoryManagement

kernel

03/30/2006 ecs150 Spring 2006 31

Kernel & ProcessesKernel & Processes

The concept of “application process”

03/30/2006 ecs150 Spring 2006 32

Kernel and User SpaceKernel and User Space

Process FOOFOOMemoryspace for thisprocess

System call(or trap into the kernel)

program

System Call

conceptually

Kernel Resources(disk or IO devices)

Process FOOFOOin the Kernel

03/30/2006 ecs150 Spring 2006 33

ProcessesProcesses

> ps PID TTY TIME CMD 2910 pts/4 0:00 tcsh> ps -ef UID PID PPID C STIME TTY TIME CMD root 0 0 0 Sep 25 ? 0:01 sched root 1 0 0 Sep 25 ? 0:00 /etc/init - root 2 0 0 Sep 25 ? 0:00 pageout root 3 0 0 Sep 25 ? 0:01 fsflush root 223 1 0 Sep 25 ? 0:00 /usr/lib/utmpd root 179 1 0 Sep 25 ? 0:00 /usr/sbin/cron root 273 1 0 Sep 25 ? 0:00 /usr/lib/saf/sac -t 300 root 56 1 0 Sep 25 ? 0:00 /usr/lib/devfsadm/devfseventd root 58 1 0 Sep 25 ? 0:00 /usr/lib/devfsadm/devfsadmd root 106 1 0 Sep 25 ? 0:00 /usr/sbin/rpcbind root 197 1 0 Sep 25 ? 0:01 /usr/sbin/nscd root 108 1 0 Sep 25 ? 0:00 /usr/sbin/keyserv root 168 1 0 Sep 25 ? 0:00 /usr/sbin/syslogd root 118 1 0 Sep 25 ? 0:00 /usr/lib/netsvc/yp/ypbind root 159 1 0 Sep 25 ? 0:00 /usr/lib/autofs/automountd

03/30/2006 ecs150 Spring 2006 34

03/30/2006 ecs150 Spring 2006 35

03/30/2006 ecs150 Spring 2006 36

Memory StructureMemory StructureHigh

LowStack Growth

String Growth

Arguments

Return address

Prev. frame pointer

Local variables

Stack Pointer

03/30/2006 ecs150 Spring 2006 37

Memory StructureMemory StructureHigh

LowStack Growth

String Growth

Arguments

Return address

Prev. frame pointer

Local variables

Stack Pointer

bar( ){……}

foo( ){ …… call bar( ); ……}

03/30/2006 ecs150 Spring 2006 38

Procedure CallProcedure Call on the same on the same

User StackUser Stack

Per-processKernel Stack

User-stack

Initialized data Initialized data

text text

a.out header

a.out magic numberMemory

03/30/2006 ecs150 Spring 2006 39

System CallSystem Call on a different stack on a different stack

Per-processKernel Stack

User-stack

Initialized data Initialized data

text text

a.out header

a.out magic numberMemory

03/30/2006 ecs150 Spring 2006 40

System CallsSystem Calls

Not a “normal” procedure call

It is a software trap “into” the kernel– Hardware interrupt– Hardware trap– Software trap

03/30/2006 ecs150 Spring 2006 41

System EntrySystem Entry

Hardware interrupt– Asynchronous, might not relate to the context

of the executing process Hardware trap

– Related to the current executing process, e.g., divided by zero

Software-initiated trap– Instructions, int

03/30/2006 ecs150 Spring 2006 42

System Entry VectorSystem Entry Vector

fork()

03/30/2006 ecs150 Spring 2006 43

System Entry VectorSystem Entry Vector

fork()

TrapReserved forloadable system calls

03/30/2006 ecs150 Spring 2006 44

kldloadkldload

fork()

03/30/2006 ecs150 Spring 2006 45

ProcessProcess

Process – a program in execution A process includes:

– program counter – stack– data section

03/30/2006 ecs150 Spring 2006 46

Context SwitchingContext Switching

03/30/2006 ecs150 Spring 2006 47

Running

Blocked Ready

Running

Blocked Ready

Running

Blocked Ready

Running

Blocked Ready

Scheduling &Context Switching

03/30/2006 ecs150 Spring 2006 48

States of a ProcessStates of a Process

Running, Blocked, and Ready

Running

Waiting Ready

03/30/2006 ecs150 Spring 2006 49

03/30/2006 ecs150 Spring 2006 50

256 different priorities64 scheduling classes

0~63 bottom-half kernel (interrupt)64~127 top-half kernel128~159 real-time user160~223 timeshare224~255 idle

03/30/2006 ecs150 Spring 2006 51

Kernel ProcessesKernel Processes

idle, swapper, vmdaemon, pagedaemon, pagezero, bufdaemon, syncer, ktrace, vnlru, random, g_event, g_up, g_down

/usr/src/sys/kern/kern_idle.c/usr/src/sys/kern/init_main.c/usr/src/sys/vm/vm_zeroidle.c/usr/src/sys/kern_ktrace.c/usr/src/sys/dev/random/randomsoft_dev.c

03/30/2006 ecs150 Spring 2006 52

03/30/2006 ecs150 Spring 2006 53

03/30/2006 ecs150 Spring 2006 54

Running

Waiting Ready

03/30/2006 ecs150 Spring 2006 55

4.4BSD Process Structure4.4BSD Process Structure(/usr/src/sys/sys/proc.h)(/usr/src/sys/sys/proc.h)

ProcessStructure

machine-dependentprocess information

process group

process credential

VM space

file descriptors

resource limits

statistics

signal actions

process control blockprocess kernel stack

session

user credential

region list

file entries

} user structure

03/30/2006 ecs150 Spring 2006 56

FreeBSD User StructureFreeBSD User Structure/*

* Per process structure containing data that isn’t needed in core when the

* process isn’t running (esp. when swapped out). This structure may or may not

* be at the same kernel address in all processes.

struct user {

struct pcb u_pcb;

struct sigacts u_sigacts; /* p_sigacts points here (use it!) */

struct pstats u_stats; /* p_stats points here (use it!) */

/* Remaining fields only for core dump and/or ptrace—

not valid at other times! */

struct kinfo_proc u_kproc; /* proc + eproc */

struce md_coredump u_md; /* machine dependent glop */

03/30/2006 ecs150 Spring 2006 57

5.x Kernel

03/30/2006 ecs150 Spring 2006 58

KSE:Kernel Scheduling Entity kernel-level thread

03/30/2006 ecs150 Spring 2006 59

03/30/2006 ecs150 Spring 2006 60

What is a thread?What is a thread?

03/30/2006 ecs150 Spring 2006 61

Process and ThreadProcess and Thread(abstraction and abstraction)

An execution instance of a program. Threads and resources

– a thread is a control entity of the logical flow in the program.

– A sequential program needs only one single thread because it only need to be controlled by one entity.

– Can you distinguish a process and a thread?

User mode versus (trap into the) Kernel mode.

03/30/2006 ecs150 Spring 2006 62

A Program and ThreadsA Program and Threads

(shared)variables

If (j==0)

03/30/2006 ecs150 Spring 2006 63

ThreadsThreads

Heavy-weight Process versus Light-weight Thread

User-level versus Kernel-level

03/30/2006 ecs150 Spring 2006 64

a Process and a Threada Process and a Thread A tradition process contains one thread (i.e,

one flow of control) and the resources (user or kernel).

Resources

No obvious concurrency within a process

03/30/2006 ecs150 Spring 2006 65

Process and ThreadsProcess and Threads

A Process can contain more than one threads sharing the resources (user or kernel).

Resources

03/30/2006 ecs150 Spring 2006 66

ThreadsThreads

User-level Kernel-level

03/30/2006 ecs150 Spring 2006 67

ThreadsThreads

Blocking/Synchronous I/O– One thread blocks all others???– “Block one block all”

03/30/2006 ecs150 Spring 2006 68

mainmemory

I/O bridge

bus interface

register file

CPU chip

system bus memory bus

disk controller

graphicsadapter

USBcontroller

mousekeyboard monitor

I/O bus Expansion slots forother devices suchas network adapters.

03/30/2006 ecs150 Spring 2006 69

mainmemory

register file

CPU chip

disk controller

graphicsadapter

USBcontroller

I/O bus

bus interface

CPU initiates a disk read by writing a command, logical block number, and destination memory address to a port (address) associated with disk controller.

03/30/2006 ecs150 Spring 2006 70

mainmemory

register file

CPU chip

disk controller

graphicsadapter

USBcontroller

I/O bus

bus interface

Disk controller reads the sector and performs a direct memory access (DMA) transfer into main memory.

03/30/2006 ecs150 Spring 2006 71

mainmemory

register file

CPU chip

disk controller

graphicsadapter

USBcontroller

I/O bus

bus interface

When the DMA transfer completes, the disk controller notifies the CPU with an interrupt (i.e., asserts a special “interrupt” pin on the CPU)

03/30/2006 ecs150 Spring 2006 72

Asynchronous I/OAsynchronous I/O

How to deal with multiple I/O operations concurrently? For example: wait for a keyboard input, a mouse click and

input from a network connection.

Select system call

Poll system call (same idea, different implementation)

For more info see http://www.kegel.com/c10k.html

int select(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);

int poll(struct pollfd *ufds, unsigned int nfds, int timeout);

struct pollfd { int fd; /* file descriptor */ short events; /* requested events */ short revents; /* returned events */ };

03/30/2006 ecs150 Spring 2006 73

/usr/src/sys/kern/vfs_aio.c/usr/src/sys/kern/vfs_aio.c

POSIX P1003.4 Asynchronous I/O interface functions:– aio_cancel:cancel asynchronous read and/or write

requests – aio_error:retrieve Asynchronous I/O error status – aio_fsync:asynchronously force I/O completion, and sets

errno to ENOSYS – aio_read:begin asynchronous read – aio_return:retrieve return status of Asynchronous I/O

operation – aio_suspend:suspend until Asynchronous I/O Completes – aio_write:begin asynchronous write – lio_listio:issue list of I/O requests

Solaris, Linux 2.6, FreeBSD pp230~231

03/30/2006 ecs150 Spring 2006 74

Security Problem!!

03/30/2006 ecs150 Spring 2006 75

User-Level ThreadsUser-Level Threads

Now, you should get the basic idea about how to avoid “block one block all”….

03/30/2006 ecs150 Spring 2006 76

ThreadsThreads

User-level– Kernel is unaware of multiple threading within

the same process. (Conceptually, the kernel pretends one “kernel” thread per process.)

Kernel-level– Kernel is fully aware of multiple kernel threads

within the same process, and therefore, it will provide “related kernel services”.

03/30/2006 ecs150 Spring 2006 77

User and Kernel ThreadsUser and Kernel Threads One thread per process or multiple thread per

process

KernelTsUserLevelTs

Which approach is better???

KTS KTS

03/30/2006 ecs150 Spring 2006 78

User-Level ThreadsUser-Level Threads

A small OS in the user-space to manage the threads.

The kernel is totally unaware how many threads the process currently has.

03/30/2006 ecs150 Spring 2006 79

03/30/2006 ecs150 Spring 2006 80

Why Multiple Threads??Why Multiple Threads??

03/30/2006 ecs150 Spring 2006 81

Responsiveness Resource Sharing Economy Utilization of MP Architectures

03/30/2006 ecs150 Spring 2006 82

fork()

fork()fork()Process A

GlobalVariables

Process B

GlobalVariables

03/30/2006 ecs150 Spring 2006 83

fork()Parent

GlobalVariables

execve()

03/30/2006 ecs150 Spring 2006 84

pthread_create()pthread_create()Process AThread 1

GlobalVariables

Process AThread 2

pthread_create()

03/30/2006 ecs150 Spring 2006 85

Creation Time DifferenceCreation Time Difference Because threads are by definition lightweight, they can be created

more quickly that “heavy” processes:

– Sun Ultra5, 320 Meg Ram, 1 CPU 94 forks()/second 1,737 threads/second (18x faster)

– Sun Sparc Ultra 1, 256 Meg Ram , 1 CPU 67 forks()/second 1,359 threads/second (20x faster)

– Sun Enterprise 420R, 5 Gig Ram, 4 CPUs 146 forks()/second 35,640 threads/second (244x faster)

– Linux 2.4 Kernel, .5 Gig Ram, 2 CPUs 1,811 forks()/second 227,611 threads/second (125x faster)

03/30/2006 ecs150 Spring 2006 86

03/30/2006 ecs150 Spring 2006 87

User ThreadsUser Threads

Thread management done by user-level threads library

Examples

- POSIX Pthreads

- Mach C-threads

- Solaris threads

03/30/2006 ecs150 Spring 2006 88

Kernel ThreadsKernel Threads Supported by the Kernel Examples

- Windows 95/98/NT/2000

- Solaris

- Linux

03/30/2006 ecs150 Spring 2006 89

Solaris 2 ThreadsSolaris 2 Threads

03/30/2006 ecs150 Spring 2006 90

Linux ThreadsLinux Threads

Linux refers to them as tasks rather than threads.

Thread creation is done through clone() system call.

clone() allows a child task to share the address space of the parent task (process)

03/30/2006 ecs150 Spring 2006 91

O p era tin g S ys tem(L in u x N ative Th read )

P rog ram m in g L ib ra ry(P O S IX th read )

P rog ram m in g L an g u ag e(Java)

A p p lica tion(W eb S erver)

System call: Clone

Thread class: run

Lib call:

pthread_create

Open new connection

03/30/2006 ecs150 Spring 2006 92

KT vs. UTKT vs. UT

pros and cons?

BTW, how about FreeBSD?

Threads

03/30/2006 ecs150 Spring 2006 93

03/30/2006 ecs150 Spring 2006 94

UTS + KTSUTS + KTS Two independent schedulers:

processor processor processor

OS Kernel

Process Process Process

Scheduler

User Space

Scheduler Scheduler

03/30/2006 ecs150 Spring 2006 95

KTSKTS One single scheduler:

processor processor processor

OS Kernel

Process Process Process

Scheduler

User Space

03/30/2006 ecs150 Spring 2006 96

KT vs. UTKT vs. UT

Kernel Interface

03/30/2006 ecs150 Spring 2006 97

Solaris 2 ThreadsSolaris 2 Threads

mapping but NOT coordinating

03/30/2006 ecs150 Spring 2006 98

Questions to askQuestions to ask Why do we need “coordination”?

– kernel-support user-level threads What do we need in this “K/U

coordination”?– extended system call API

Is this only good for SMP?– How about single processor?– How about NPU? (e.g., IXP-2400)

03/30/2006 ecs150 Spring 2006 99

Kernel

Library

Notify I/O

events

Notify new

decision

03/30/2006 ecs150 Spring 2006 100

Kernel Space

User Space

Hardware

syscall

I/O request interrupt

I don’t know how many UT’s you have up there?

I can guess but I am not sure that is exactly what you want!

Is this a problem?

03/30/2006 ecs150 Spring 2006 101

Scheduler ActivationsScheduler Activations

Kernel Space

User Space

Hardware

upcall upcall

Kernel Space

User Space

Hardware

syscall

I/O request interrupt

CPU time wasted

CPU used

I don’t know how many UT’s you have up there?

03/30/2006 ecs150 Spring 2006 102

Scheduler ActivationsScheduler Activations First proposed by [Anderson et al. 91] Idea: cooperation between schedulers should take place in

both directions User scheduler uses system calls Kernel scheduler should use upcalls!

Upcalls– Notify the user-level of kernel scheduling events

Activations– A new structure to support upcalls (~kernel thread)– As many running activations as processors– Kernel controls activation creation and destruction

03/30/2006 ecs150 Spring 2006 103

Kernel

Library

KTS – virtual CPU’s

Notify I/O

events

UTS - threads

Notify new

decision

One Model (FreeBSD 5.x)

03/30/2006 ecs150 Spring 2006 104

03/30/2006 ecs150 Spring 2006 105

I/O happens for ThreadI/O happens for Thread

(4)(3)(2)

User Program

User-LevelRuntime System

Operating System Kernel

Processors

AddProcessor

(A) (B)

03/30/2006 ecs150 Spring 2006 106

A’s Thread has blocked on an I/O requestA’s Thread has blocked on an I/O request

(3)(2)(1)

User Program

Processors

(A) (B) ( C )

A’s thread has blockedOperating System Kernel

03/30/2006 ecs150 Spring 2006 107

(4)(3)(2)

User Program

Processors

(A) (B) ( C )Operating System Kernel

(D) A’s thread and B’s Thread can continue

A’s Thread I/O completedA’s Thread I/O completed

“the upcall stack problem”

03/30/2006 ecs150 Spring 2006 108

A’s Thread resumes on Scheduler Activation D

(4)(3)(2)

User Program

Processors

( C )Operating System Kernel

(D) A’s thread and B’s Thread can continue

03/30/2006 ecs150 Spring 2006 109

03/30/2006 ecs150 Spring 2006 110

Kernel

Library

Notify I/O

events

UTS - threads

Notify new

decision

03/30/2006 ecs150 Spring 2006 111

FreeBSD 5.xFreeBSD 5.x

Kernel Scheduling Entity (KSE)– a virtual CPU– When “anything” changes regarding the service

of this KSE to the process, this KSE is “unassigned” as the kernel doesn’t know what other threads might be there!!

– Upcall to the UTS (via KSE mailbox).– UTS uses both KSE mailbox and Thread

mailbox to handle/decide.

03/30/2006 ecs150 Spring 2006 112

03/30/2006 ecs150 Spring 2006 113

03/30/2006 ecs150 Spring 2006 114

#include <sys/types.h>#include <sys/kse.h>

int kse_create(struct kse_mailbox *mbx, int newsgroup);int kse_exit(void);int kse_release(struct timespec *timeout);int kse_wakeup(struct kse_mailbox *mbx);int kse_thr_interrupt(struct kse_thr_mailbox *tmbx);

03/30/2006 ecs150 Spring 2006 115

struct kse_mailbox {int km_version;struct kse_thr_mailbox *km_curthread; struct kse_thr_mailbox *km_completed;sigset_t km_sigscaught;unsigned int km_flags;kse_func_t *km_func; /* UTS function */stack_t km_stack; /* UTS context */void *km_udata; /* For use by the UTS */struct timespec km_timeofday; /* Time of day */int km_quantum;int km_spare[8];

03/30/2006 ecs150 Spring 2006 116

struct kse_thr_mailbox {ucontext_t tm_context; /* User and machine context */unsigned int tm_flags; /* Thread flags */struct kse_thr_mailbox *tm_next; /* Next thread in list */void *tm_udata; /* For use by the UTS */unsigned int tm_uticks;unsigned int tm_sticks;int tm_spare[8];

03/30/2006 ecs150 Spring 2006 117

upcallsupcalls

ksec_new ksec_preempt ksec_block ksec_unblock

03/30/2006 ecs150 Spring 2006 118

Kernel

Library

ksec_new

ksec_preempt

ksec_block

ksec_unblock

kse_createkse_exitkse_releasekse_wakeupkse_thr_interrupt

03/30/2006 ecs150 Spring 2006 119

KSE InternalKSE Internal

KSE KSEG KSEC

03/30/2006 ecs150 Spring 2006 120

03/30/2006 ecs150 Spring 2006 121

03/30/2006 ecs150 Spring 2006 122

03/30/2006 ecs150 Spring 2006 123

03/30/2006 ecs150 Spring 2006 124

Linux VPILinux VPI(Virtual Processor Interface)

Experimental/Research Prototype– Benson/Butner/Padden/Fedosov– Scheduler activation in Linux Kernel 2.4.18

03/30/2006 ecs150 Spring 2006 125

03/30/2006 ecs150 Spring 2006 126

Kernel

Library

Notify I/O

events

UTS - threads

Notify new

decision

03/30/2006 ecs150 Spring 2006 127

Kernel ProcessesKernel Processes((table 3.1 page 50)table 3.1 page 50)

idle, swapper, vmdaemon, pagedaemon, pagezero, bufdaemon, syncer, ktrace, vnlru, random, g_event, g_up, g_down

“Kernel processes execute code that is complied into the kernel’s load image and operate with the kernel’s privileged execution code.”

03/30/2006 ecs150 Spring 2006 128

FreeBSD KernelFreeBSD Kernel

03/30/2006 ecs150 Spring 2006 129

FreeBSD KernelFreeBSD Kernel

03/30/2006 ecs150 Spring 2006 130

Kernel and User SpaceKernel and User Space

Process FOOFOOMemoryspace for thisprocess

System call(or trap into the kernel)

program

System Call

conceptually

Kernel Resources(disk or IO devices)

Process FOOFOOin the Kernel

03/30/2006 ecs150 Spring 2006 131

What is “micro-kernel”?What is “micro-kernel”?

03/30/2006 ecs150 Spring 2006 132

….what are the basic services?

03/30/2006 ecs150 Spring 2006 133

An Alternative: Micro-Kernel

Message Passing versus Optimized Procedure Calls

03/30/2006 ecs150 Spring 2006 134

03/30/2006 ecs150 Spring 2006 135

Micro versus MonolithicMicro versus Monolithic

What is the real difference between these two models??

First Brainstorming!!

03/30/2006 ecs150 Spring 2006 136

Micro versus MonolithicMicro versus Monolithic

Is this really relevant? Advantages of Micro Kernels

– Modules (Architectural Cleanness), Adaptive, Small/Quick-to-Boot,…

We did learn some lessons– We have to consider the “users” &

“applications”, and make a new engineering design decision.

03/30/2006 ecs150 Spring 2006 137

FreeBSD Kernel: SizeFreeBSD Kernel: Size

689794 machine independent LOC 108346 machine dependent LOC 846525 device driver LOC

Comparing:– Windows 3.1 ~ 6M LOC– Windows 2000 ~ 30-50M LOC– Windows XP ~ 45M LOC– Netscape ~ 7M LOC

03/30/2006 ecs150 Spring 2006 138

OS DesignOS Design

Architectural Design– how to organize the user and kernel resources?

Module Control Design– how to design a control mechanism to protect the OS

resource integrity?

Interface Design– how to let user programs access the resources easier?

(e.g., system call interface, multi-threaded interface).

03/30/2006 ecs150 Spring 2006 139

What is “Process”? What is “System Call”? What is “Kernel”?

ecs150 Spring 2006 : Operating System #1: OS Architecture, Kernel, & Process

Documents