Embed Size (px)
Citation preview
09/27/2007 ecs150 Fall 2007 1
ecs150 Fall 2007:Operating SystemOperating System#1: OS Architecture, Kernel, & Process
Dr. S. Felix Wu
Computer Science Department
University of California, Davishttp://www.cs.ucdavis.edu/~wu/
09/27/2007 ecs150 Fall 2007 2
VM/MVS, DOS, Win95/98/ME/2000/XP, Freebsd/Linux, MacOS-10, Mach, Minix, PalmOS, uCOS, TinyOS, …
09/27/2007 ecs150 Fall 2007 3
Applications……..
Hardware: CPU/Memory/HD/DVD/Wireless…
OS
….where applications meet Hardware!!!
09/27/2007 ecs150 Fall 2007 4
““Information Router”Information Router”
One NIC a process’s user-level memory One file another file
– OS kernel layer– Hardware layer
09/27/2007 ecs150 Fall 2007 5
Applications……..
Hardware: CPU/Memory/HD/DVD/Wireless…
OS
….where applications meet Hardware!!!
09/27/2007 ecs150 Fall 2007 6
This quarter….This quarter….
The internals of OS The basic design principles of OS The skills to modify or implement an OS.
09/27/2007 ecs150 Fall 2007 7
Operating SystemOperating System
An interesting balance between:– Theories and Practical Experiences/Experiments– Architectural Concept and Detailed Design– Formal Verification and Empirical Validation
09/27/2007 ecs150 Fall 2007 8
About the InstructorAbout the Instructor
S. Felix Wu – [email protected] – Facebook group (under UCD network): ecs150
Office: 3057 Engineering II Phone: 530-754-7070 Office Hours:
– 1-2 p.m. on Tuesday and Friday– by appointment
09/27/2007 ecs150 Fall 2007 9
09/27/2007 ecs150 Fall 2007 10
Why 3 email addresses?Why 3 email addresses?
09/27/2007 ecs150 Fall 2007 11
Why 3 email addresses?Why 3 email addresses?
– [email protected]– My main email contact for everything all the time.
09/27/2007 ecs150 Fall 2007 12
Why 3 email addresses?Why 3 email addresses?
– [email protected]– My main email contact for everything all the time.
– [email protected]– Read only once in the past three months…
09/27/2007 ecs150 Fall 2007 13
Why 3 email addresses?Why 3 email addresses?
read/response during the quarters, especially before the homework deadlines.
– [email protected]– My main email contact for everything all the time.
– [email protected]– Read only once in the past three months…
09/27/2007 ecs150 Fall 2007 14
Anti-SpamAnti-Spam
[email protected] subject: [ecs150 f2007]…
[ecs150 2007]is the cyber social link between the instructor and the students in ecs150, fall 2007.
09/27/2007 ecs150 Fall 2007 15
Anti-SpamAnti-Spam
[email protected] subject: [ecs150 f2007]… [ecs150 f2007] is the cyber social link
between the instructor and the students in ecs150, fall 2007.
Let’s see by the end of quarter whether this little secret will be known to the spammers…
09/27/2007 ecs150 Fall 2007 16
About the TAAbout the TA
TA Sean Whalen ([email protected])– Office Hours: TBA– Discussion: Mon 4:10~5:00 (146 Olson)
09/27/2007 ecs150 Fall 2007 17
about Web siteabout Web site
http://www.cs.ucdavis.edu/~wu/ecs150/ Also the Facebook group all lectures, notes, announcements,
homework assignments, tools, papers will be there.
09/27/2007 ecs150 Fall 2007 18
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 may be a major challenge.But, you really learn when you go through this process!
09/27/2007 ecs150 Fall 2007 19
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.
09/27/2007 ecs150 Fall 2007 20
SyllabusSyllabus
Process/Kernel (09) Memory Management (06) Midterm (11/01/2007, in class) IO & File Systems (10) Others (03) Final (12/13/2007, 8~10 a.m.)
09/27/2007 ecs150 Fall 2007 21
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?
09/27/2007 ecs150 Fall 2007 22
OSOS
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.
09/27/2007 ecs150 Fall 2007 23
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.
09/27/2007 ecs150 Fall 2007 24
Course RequirementsCourse Requirements
48%: Programming Assignments– teamwork: 1~2 students (no more than 2!)– 4 Assignments (10%, 18%, 12%, 8%)– HW#1 is out.
16%: In-class open-book midterm 32%: open-book final 04%: Participation of Lectures and
Discussion sessions.– Deducted if missed more than TWO sessions.
09/27/2007 ecs150 Fall 2007 25
GradingGrading
I will give +/- grades. possible grading :
– A: >= 92 A-: >= 89 B+: >= 85– B: >= 82 B-: >= 79 C+: >= 75– C: >= 72 C-: >= 69 D+: >= 65– D: >= 62 D-: >= 59
09/27/2007 ecs150 Fall 2007 26
FreeBSDFreeBSD
You need to have access to a FreeBSD environment– I386, QEMU, VMware, VirtualPC, Parallel
09/27/2007 ecs150 Fall 2007 27
Standard Full Virtualization e.g.,
Unmodified OS (XP, Linux, Solaris, or, FreeBSD)
Unmodified Applications
Hardware
VirtualPCWindowXP
virtualizationvirtualization
09/27/2007 ecs150 Fall 2007 28
09/27/2007 ecs150 Fall 2007 29
Virtual PC or VMware
Unmodified OS (XP, Linux, Solaris, or, FreeBSD)
Unmodified Applications
Hardware
AP
I
FreeBSDFreeBSD
09/27/2007 ecs150 Fall 2007 30
“Programmable” Full Virtualization
Unmodified OS (XP, Linux, Solaris, or, FreeBSD)
Unmodified Applications
Hardware
AP
I
DLVM
Programmable VirtualizationProgrammable Virtualization
DLVM
09/27/2007 ecs150 Fall 2007 31
The Structure of OSThe Structure of OS
The Kernel Processes and Threads The System Call Interface
09/27/2007 ecs150 Fall 2007 32
What is “kernel”?What is “kernel”?
09/27/2007 ecs150 Fall 2007 33
KernelKernel
The basic OS services Which services? What is it doing? Let’s check a couple examples
09/27/2007 ecs150 Fall 2007 34
OS
….what are the basic services?
09/27/2007 ecs150 Fall 2007 35
FreeBSD Kernel: FreeBSD Kernel: ServicesServices
Timer/clock, descriptor, process Memory Management: paging/swapping I/O control and terminal File System Inter-process communication Networking
09/27/2007 ecs150 Fall 2007 36
09/27/2007 ecs150 Fall 2007 37
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
09/27/2007 ecs150 Fall 2007 38
Kernel & ProcessesKernel & Processes
The concept of “application process”
09/27/2007 ecs150 Fall 2007 39
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
09/27/2007 ecs150 Fall 2007 40
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
09/27/2007 ecs150 Fall 2007 41
09/27/2007 ecs150 Fall 2007 42
09/27/2007 ecs150 Fall 2007 43
Memory StructureMemory StructureHigh
LowStack Growth
String Growth
Arguments
Return address
Prev. frame pointer
Local variables
Stack Pointer
09/27/2007 ecs150 Fall 2007 44
Memory StructureMemory StructureHigh
LowStack Growth
String Growth
Arguments
Return address
Prev. frame pointer
Local variables
Stack Pointer
bar( ){……}
foo( ){ …… call bar( ); ……}
foo
bar
09/27/2007 ecs150 Fall 2007 45
Procedure CallProcedure Call on the same on the same
User StackUser Stack
Per-processKernel Stack
User-stack
Heap
Initialized data Initialized data
text text
a.out header
a.out magic numberMemory
Disk
09/27/2007 ecs150 Fall 2007 46
System CallSystem Call on a different stack on a different stack
Per-processKernel Stack
User-stack
Heap
Initialized data Initialized data
text text
a.out header
a.out magic numberMemory
Disk
09/27/2007 ecs150 Fall 2007 47
System CallsSystem Calls
Not a “normal” procedure call
It is a software trap “into” the kernel– Hardware interrupt– Hardware trap– Software trap
09/27/2007 ecs150 Fall 2007 48
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
09/27/2007 ecs150 Fall 2007 49
System Entry VectorSystem Entry Vector
fork()
::
Trap
09/27/2007 ecs150 Fall 2007 50
System Entry VectorSystem Entry Vector
fork()
::
TrapReserved forloadable system calls
XYZ()
09/27/2007 ecs150 Fall 2007 51
kldloadkldload
fork()
::
Trap
XYZ()
09/27/2007 ecs150 Fall 2007 52
OS ArchitectureOS Architecture
09/27/2007 ecs150 Fall 2007 53
ProcessProcess
Process – a program in execution A process includes:
– program counter – stack– data section
09/27/2007 ecs150 Fall 2007 54
Context SwitchingContext Switching
09/27/2007 ecs150 Fall 2007 55
Running
Blocked Ready
Running
Blocked Ready
Running
Blocked Ready
Running
Blocked Ready
Scheduling &Context Switching
09/27/2007 ecs150 Fall 2007 56
States of a ProcessStates of a Process
Running, Blocked, and Ready
Running
Waiting Ready
09/27/2007 ecs150 Fall 2007 57
09/27/2007 ecs150 Fall 2007 58
1
0
0
1
0
1
::.
256 different priorities64 scheduling classes
RR
0~63 bottom-half kernel (interrupt)64~127 top-half kernel128~159 real-time user160~223 timeshare224~255 idle
09/27/2007 ecs150 Fall 2007 59
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
09/27/2007 ecs150 Fall 2007 60
09/27/2007 ecs150 Fall 2007 61
1
0
0
1
0
1
::.
256 different priorities64 scheduling classes
RR
0~63 bottom-half kernel (interrupt)64~127 top-half kernel128~159 real-time user160~223 timeshare224~255 idle
09/27/2007 ecs150 Fall 2007 62
Running
Waiting Ready
09/27/2007 ecs150 Fall 2007 63
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
09/27/2007 ecs150 Fall 2007 64
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 */
}
09/27/2007 ecs150 Fall 2007 65
5.x Kernel
09/27/2007 ecs150 Fall 2007 66
1
0
0
1
0
1
::.
256 different priorities64 scheduling classes
RR
0~63 bottom-half kernel (interrupt)64~127 top-half kernel128~159 real-time user160~223 timeshare224~255 idle
KSE:Kernel Scheduling Entity kernel-level thread
09/27/2007 ecs150 Fall 2007 67
09/27/2007 ecs150 Fall 2007 68
What is a thread?What is a thread?
09/27/2007 ecs150 Fall 2007 69
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.
09/27/2007 ecs150 Fall 2007 70
A Program and ThreadsA Program and Threads
(shared)variables
J=0;
If (j==0)
J=100
09/27/2007 ecs150 Fall 2007 71
ThreadsThreads
Heavy-weight Process versus Light-weight Thread
User-level versus Kernel-level
09/27/2007 ecs150 Fall 2007 72
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
09/27/2007 ecs150 Fall 2007 73
Process and ThreadsProcess and Threads
A Process can contain more than one threads sharing the resources (user or kernel).
Resources
09/27/2007 ecs150 Fall 2007 74
ThreadsThreads
User-level Kernel-level
09/27/2007 ecs150 Fall 2007 75
ThreadsThreads
Blocking/Synchronous I/O– One thread blocks all others???– “Block one block all”
09/27/2007 ecs150 Fall 2007 76
mainmemory
I/O bridge
bus interface
ALU
register file
CPU chip
system bus memory bus
disk controller
graphicsadapter
USBcontroller
mousekeyboard monitor
disk
I/O bus Expansion slots forother devices suchas network adapters.
09/27/2007 ecs150 Fall 2007 77
mainmemory
ALU
register file
CPU chip
disk controller
graphicsadapter
USBcontroller
mousekeyboard monitor
disk
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.
09/27/2007 ecs150 Fall 2007 78
mainmemory
ALU
register file
CPU chip
disk controller
graphicsadapter
USBcontroller
mousekeyboard monitor
disk
I/O bus
bus interface
Disk controller reads the sector and performs a direct memory access (DMA) transfer into main memory.
09/27/2007 ecs150 Fall 2007 79
mainmemory
ALU
register file
CPU chip
disk controller
graphicsadapter
USBcontroller
mousekeyboard monitor
disk
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)
09/27/2007 ecs150 Fall 2007 80
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 */ };
09/27/2007 ecs150 Fall 2007 81
/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
09/27/2007 ecs150 Fall 2007 82
Security Problem!!
09/27/2007 ecs150 Fall 2007 83
User-Level ThreadsUser-Level Threads
Now, you should get the basic idea about how to avoid “block one block all”….
09/27/2007 ecs150 Fall 2007 84
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”.
09/27/2007 ecs150 Fall 2007 85
User and Kernel ThreadsUser and Kernel Threads One thread per process or multiple thread per
process
KernelTsUserLevelTs
Which approach is better???
UTS
KTS KTS
09/27/2007 ecs150 Fall 2007 86
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.
09/27/2007 ecs150 Fall 2007 87
09/27/2007 ecs150 Fall 2007 88
Why Multiple Threads??Why Multiple Threads??
09/27/2007 ecs150 Fall 2007 89
Responsiveness Resource Sharing Economy Utilization of MP Architectures
09/27/2007 ecs150 Fall 2007 90
fork()
fork()fork()Process A
GlobalVariables
Code
Stack
Process B
GlobalVariables
Code
Stack
09/27/2007 ecs150 Fall 2007 91
fork()Parent
GlobalVariables
Code
Stack
Child
GlobalVariables
Code
Stack
Child
GlobalVariables
Code
Stack
execve()
09/27/2007 ecs150 Fall 2007 92
pthread_create()pthread_create()Process AThread 1
GlobalVariables
Code
Stack
Process AThread 2
Stack
pthread_create()
09/27/2007 ecs150 Fall 2007 93
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)
09/27/2007 ecs150 Fall 2007 94
09/27/2007 ecs150 Fall 2007 95
User ThreadsUser Threads
Thread management done by user-level threads library
Examples
- POSIX Pthreads
- Mach C-threads
- Solaris threads
09/27/2007 ecs150 Fall 2007 96
Kernel ThreadsKernel Threads Supported by the Kernel Examples
- Windows 95/98/NT/2000
- Solaris
- Linux
09/27/2007 ecs150 Fall 2007 97
Solaris 2 ThreadsSolaris 2 Threads
09/27/2007 ecs150 Fall 2007 98
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)
09/27/2007 ecs150 Fall 2007 99
Operating System(Linux Native Thread)
Programming Library(POSIX thread)
Programming Language(Java)
Application(Web Server)
System call: Clone
Thread class: run
Lib call:
pthread_create
Open new connection
09/27/2007 ecs150 Fall 2007 100
KT vs. UTKT vs. UT
pros and cons?
BTW, how about FreeBSD?
Threads
09/27/2007 ecs150 Fall 2007 101
09/27/2007 ecs150 Fall 2007 102
UTS + KTSUTS + KTS Two independent schedulers:
processor processor processor
OS Kernel
Process Process Process
Scheduler
User Space
Scheduler Scheduler
09/27/2007 ecs150 Fall 2007 103
KTSKTS One single scheduler:
processor processor processor
OS Kernel
Process Process Process
Scheduler
User Space
09/27/2007 ecs150 Fall 2007 104
KT vs. UTKT vs. UT
Kernel Interface
UTS
KTS
09/27/2007 ecs150 Fall 2007 105
Solaris 2 ThreadsSolaris 2 Threads
mapping but NOT coordinating
09/27/2007 ecs150 Fall 2007 106
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)
09/27/2007 ecs150 Fall 2007 107
Kernel
Library
KTS
Notify I/O
events
UTS
Notify new
decision
09/27/2007 ecs150 Fall 2007 108
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?
09/27/2007 ecs150 Fall 2007 109
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?
09/27/2007 ecs150 Fall 2007 110
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
09/27/2007 ecs150 Fall 2007 111
Kernel
Library
KTS – virtual CPU’s
Notify I/O
events
UTS - threads
Notify new
decision
SA SA
SA SA
One Model (FreeBSD 5.x)
09/27/2007 ecs150 Fall 2007 112
09/27/2007 ecs150 Fall 2007 113
I/O happens for ThreadI/O happens for Thread
(4)(3)(2)
(1)
User Program
User-LevelRuntime System
Operating System Kernel
Processors
AddProcessor
AddProcessor
(A) (B)
09/27/2007 ecs150 Fall 2007 114
A’s Thread has blocked on an I/O requestA’s Thread has blocked on an I/O request
(4)
(3)(2)(1)
User Program
User-LevelRuntime System
Processors
B
(A) (B) ( C )
A’s thread has blockedOperating System Kernel
09/27/2007 ecs150 Fall 2007 115
(4)(3)(2)
(1)
User Program
User-LevelRuntime System
Processors
(A) (B) ( C )Operating System Kernel
(1)
(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”
09/27/2007 ecs150 Fall 2007 116
A’s Thread resumes on Scheduler Activation D
(4)(3)(2)
User Program
User-LevelRuntime System
Processors
( C )Operating System Kernel
(1)
(D) A’s thread and B’s Thread can continue
(1)
09/27/2007 ecs150 Fall 2007 117
09/27/2007 ecs150 Fall 2007 118
Kernel
Library
KTS – virtual CPU’s
Notify I/O
events
UTS - threads
Notify new
decision
SA SA
SA SA
One Model (FreeBSD 5.x)
09/27/2007 ecs150 Fall 2007 119
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.
09/27/2007 ecs150 Fall 2007 120
09/27/2007 ecs150 Fall 2007 121
09/27/2007 ecs150 Fall 2007 122
#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);
09/27/2007 ecs150 Fall 2007 123
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];
};
09/27/2007 ecs150 Fall 2007 124
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];
};
09/27/2007 ecs150 Fall 2007 125
upcallsupcalls
ksec_new ksec_preempt ksec_block ksec_unblock
09/27/2007 ecs150 Fall 2007 126
Kernel
Library
KTS
UTS
ksec_new
ksec_preempt
ksec_block
ksec_unblock
kse_createkse_exitkse_releasekse_wakeupkse_thr_interrupt
09/27/2007 ecs150 Fall 2007 127
KSE InternalKSE Internal
KSE KSEG KSEC
09/27/2007 ecs150 Fall 2007 128
09/27/2007 ecs150 Fall 2007 129
09/27/2007 ecs150 Fall 2007 130
09/27/2007 ecs150 Fall 2007 131
09/27/2007 ecs150 Fall 2007 132
Linux VPILinux VPI(Virtual Processor Interface)
Experimental/Research Prototype– Benson/Butner/Padden/Fedosov– Scheduler activation in Linux Kernel 2.4.18
09/27/2007 ecs150 Fall 2007 133
09/27/2007 ecs150 Fall 2007 134
Kernel
Library
KTS – virtual CPU’s
Notify I/O
events
UTS - threads
Notify new
decision
SA SA
SA SA
One Model (FreeBSD 5.x)
09/27/2007 ecs150 Fall 2007 135
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.”
09/27/2007 ecs150 Fall 2007 136
FreeBSD KernelFreeBSD Kernel
09/27/2007 ecs150 Fall 2007 137
FreeBSD KernelFreeBSD Kernel
09/27/2007 ecs150 Fall 2007 138
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
09/27/2007 ecs150 Fall 2007 139
What is “micro-kernel”?What is “micro-kernel”?
09/27/2007 ecs150 Fall 2007 140
OS
….what are the basic services?
09/27/2007 ecs150 Fall 2007 141
An Alternative: Micro-Kernel
Message Passing versus Optimized Procedure Calls
09/27/2007 ecs150 Fall 2007 142
09/27/2007 ecs150 Fall 2007 143
System callsSystem calls
int 80h *.s (not in /usr/src/sys/kern/*) *.c (not in /usr/src/sys/kern/*) sysent/sysvec function pointer lkmnosys()
09/27/2007 ecs150 Fall 2007 144
/usr/src/sys/i386/i386/*.*
09/27/2007 ecs150 Fall 2007 145
Micro versus MonolithicMicro versus Monolithic
What is the real difference between these two models??
First Brainstorming!!
09/27/2007 ecs150 Fall 2007 146
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.
09/27/2007 ecs150 Fall 2007 147
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
09/27/2007 ecs150 Fall 2007 148
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).
09/27/2007 ecs150 Fall 2007 149
What is “Process”? What is “System Call”? What is “Kernel”?
