Introduction to Lab 2
EDA092 – Operating Systems
2008-02-18
Wolfgang John
Slides by Magnus Almgren
Overview of OSP
• An Environment for
Operating System Projects
• Simulates an operating system (surprise!)
• Consists of modules that executes
different operating system functions, such
as
– Scheduling of CPU
– Virtual Memory Management
– File Access
(lab 2.1)
(lab 2.2)
(lab 2.3)
Slides by Magnus Almgren
OSP Modules: Overview
CPU
MEMORY
SIMCORE
DIALOG
FILES
INTER
DEVINT
PAGEINT
TIMEINT
DEVICES
Slides by Magnus Almgren
OSP Modules: Overview
Lab 2.1
CPU
Lab 2.2
MEMORY
SIMCORE
DIALOG
FILES
INTER
DEVINT
PAGEINT
TIMEINT
DEVICES
Slides by Magnus Almgren
OSP Modules: Overview
CPU
MEMORY
CPU
MEMORY
SIMCORE
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
DIALOG
DIALOG
FILES
DEVICES
FILES
INTER
DEVINT
PAGEINT
TIMEINT
DEVICES
Slides by Magnus Almgren
OSP Modules: Overview
CPU
MEMORY
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
DIALOG
FILES
DEVICES
CPU
MEMORY
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
DIALOG
FILES
DEVICES
Slides by Magnus Almgren
OSP Modules: Misc
•
•
•
•
RESOURCES – resource management
DEVICES
– disk access
SOCKETS – process communication
PROTOCOLS – protocols used for the
SOCKET module
CPU
MEMORY
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
DIALOG
FILES
DEVICES
Slides by Magnus Almgren
OSP Modules: SimCore
• SimCore – Main Part of System
– Generates events
•
•
•
•
•
Start and termination of processes
Virtual memory references
Timer interrupts
Read/write to external devices
Interrupts from external devices
– Parameters of the simulation controls the simulation
– Collects statistics about resource allocation
CPU
MEMORY
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
DIALOG
FILES
DEVICES
Slides by Magnus Almgren
OSP Modules: SimCore
• Hardware of OSP CPU
–
–
–
–
–
Interval Timer
Clock
Interrupt vector
Base register for page tables
Disk access
• Memory
– Virtual memory with paging: PAGE_TBL
CPU
MEMORY
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
DIALOG
FILES
DEVICES
Slides by Magnus Almgren
OSP Modules: CPU
• Lab 2.1: CPU Scheduling
• Three Process States
blocked
(+done:zombie)
sleep
wakeup
ready
timer
dispatch
interrupt
running
• Each process has a
Process Control Block
CPU
MEMORY
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
DIALOG
FILES
DEVICES
Slides by Magnus Almgren
struct pcb_node { /* from cpu.c */
int pcb_id;
/*
PCB id
*/
int size;
/*
process size in bytes; assigned by SIMCORE
*/
int creation_time;
/*
assigned by SIMCORE
*/
int last_dispatch;
/*
last time the process was dispatched
*/
int last_cpuburst;
/*
length of the previous CPU burst
*/
int accumulated_cpu; /*
accumulated CPU time
*/
PAGE_TBL *page_tbl;
/*
page table associated with the PCB
*/
STATUS status;
/*
status of process: running, ready, waiting, done
*/
EVENT *event;
/*
event upon which process may be suspended
*/
int priority;
/*
user-defined priority; used for scheduling
*/
PCB *next;
/*
next PCB in whatever queue
*/
PCB *prev;
/*
previous PCB in whatever queue
*/
int *hook;
/*
can hook up anything here
*/
};
Slides by Magnus Almgren
Lab 2.1:
Round Robin Scheduling
• Round Robin = Signing petitions w/out
showing who signed first
• Circular queue of processes ready to
execute
• No priority (regular RR)
• Each process executes until it
– Terminates
– Waits (for a resource)
– Runs out of time quanta (‘timer interrupt’)
Slides by Magnus Almgren
CPU
Ready Queue
1
2
3
4
Disk Queue
Slides by Magnus Almgren
CPU
Out of time
Ready Queue
1
2
3
4
Disk Queue
Slides by Magnus Almgren
CPU
Ready Queue
2
3
4
1
Disk Queue
Slides by Magnus Almgren
CPU
Out of time
Ready Queue
2
3
4
1
Disk Queue
Slides by Magnus Almgren
CPU
Ready Queue
3
4
1
2
Disk Queue
Slides by Magnus Almgren
CPU
Wait for disk access
Ready Queue
3
Disk Queue
3
4
1
2
Slides by Magnus Almgren
CPU
Wait for disk access
Ready Queue
4
1
Disk Queue
3
4
2
Slides by Magnus Almgren
CPU
Interrupt: Disk access
Ready Queue
1
2
Disk Queue
3
4
Slides by Magnus Almgren
CPU
Interrupt: Disk access
Ready Queue
2
3
Disk Queue
3
4
Slides by Magnus Almgren
CPU
Interrupt:
Process
Termination
Disk access
Ready Queue
2
Disk Queue
4
3
Slides by Magnus Almgren
Lab 2.1
Requirements?
Round Robin Scheduling in OSP:
1.
Implement a ready queue, and move processes
from running and ready queue.
Key Information: OSP 1.6
(impossible to do lab without it!!!)
2. Main Working File: cpu.c
3. Need: Linked List for Round Robin …
Slides by Magnus Almgren
/*************************************************************/
/*
Module CPU
*/
/*
External Declarations
*/
/*************************************************************/
/* OSP constant */
#define
MAX_PAGE 16
/* max size of page tables */
/* OSP enumeration constants */
typedef enum {
false, true
} BOOL;
/* the boolean data type */
typedef enum {
running,ready,waiting,done
} STATUS;
/* types of status
*/
Slides by Magnus Almgren
/* external type definitions */
typedef
typedef
typedef
typedef
struct
struct
struct
struct
page_entry_node PAGE_ENTRY;
page_tbl_node PAGE_TBL;
event_node EVENT;
pcb_node PCB;
/* external data structures */
struct page_entry_node {
int
frame_id; /* frame id holding this page
BOOL
valid;
/* page in main memory : valid = true; not : false
BOOL
ref;
/* set to true every time page is referenced AD
int
*hook;
/* can hook up anything here
};
struct page_tbl_node {
PCB
*pcb;
/* PCB of the process in question
PAGE_ENTRY page_entry[MAX_PAGE];
int
*hook;
/* can hook up anything here
};
*/
*/
*/
*/
*/
*/
Slides by Magnus Almgren
struct pcb_node {
int pcb_id;
/*
PCB id
*/
int size;
/*
process size in bytes; assigned by SIMCORE
*/
int creation_time;
/*
assigned by SIMCORE
*/
int last_dispatch;
/*
last time the process was dispatched
*/
int last_cpuburst;
/*
length of the previous CPU burst
*/
int accumulated_cpu; /*
accumulated CPU time
*/
PAGE_TBL *page_tbl;
/*
page table associated with the PCB
*/
STATUS status;
/*
status of process
*/
EVENT *event;
/*
event upon which process may be suspended
*/
int priority;
/*
user-defined priority; used for scheduling
*/
PCB *next;
/*
next PCB in whatever queue
*/
PCB *prev;
/*
previous PCB in whatever queue
*/
int *hook;
/*
can hook up anything here
*/
};
Slides by Magnus Almgren
/* external variables */
extern PAGE_TBL *PTBR;
/* page table base register */
extern int Quantum;
/* global time quantum; contains the value
entered at the beginning or changed
at snapshot. Has no effect on timer
interrupts, unless passed to set_timer() */
/* external routines */
extern
extern
extern
extern
prepage(/* pcb */);
int start_cost(/* pcb */);
set_timer(/* time_quantum */);
int get_clock();
/* PCB *pcb; */
/* int time_quantum; */
Slides by Magnus Almgren
/*******************************************************/
/*
Module CPU
*/
/*
Internal Routines
*/
/*******************************************************/
void cpu_init() {
lots of smart code
Here is mostly where you add
your code for lab 2.1!
}
void dispatch() {
ready to run?
Important: Check the Intro to OSP
for all necessary steps.
}
void insert_ready(pcb)
PCB *pcb;
{
round robin
}
/*
end of module
*/
Slides by Magnus Almgren
Building a Linked List
• Assume that a list of positions (x,y) shall be
implemented in the C language using linked lists.
Determine a suitable type declaration and write
functions to do the following:
– Create an empty list
– Add an element (x,y) to a list
– Search for an element (x,y) in a list and remove it if
present in the list
Head:
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Slides by Magnus Almgren
Introduction to LL
• Double-linked, circular list
• Useful to have synonym for the last
element too
Head:
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tail: head->previous
Slides by Magnus Almgren
Lab 2.2
Memory Management
• OSP Modules
– MEMORY
– PAGEINT
• Carefully read OSP 1.4.3 and 1.5 !!!
• Experiment with parameters to
reduce the page faults
CPU
SIMCORE
INTER
DEVINT
PAGEINT
TIMEINT
MEMORY
DIALOG
FILES
DEVICES
Slides by Magnus Almgren
Memory Management
• Algorithms to replace pages
– FIFO
– Optimal Algorithm (Imaginary)
– LRU (Least Recently Used)
• Good but difficult to implement
• Second-Chance Algorithm, w/ reference bit
Slides by Magnus Almgren
2nd Chance Clock Algorithm
Page 337 in Operating System Concepts
reference pages
bits
next
victim
reference pages
bits
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Slides by Magnus Almgren