PROCESS MANAGEMENT
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Transcript of PROCESS MANAGEMENT
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PROCESS MANAGEMENT
DEFN OF PROCESS – A PROGRAM UNDER EXECUTION, WHICH COMPETES FOR THE CPU TIME & OTHER RESOURCES
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CPU Switch From Process to Process
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Diagram of Process State
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PROCESS CONTROL BLOCK (PCB)
* OS MAINTAINS INFORMATION OF EACH PROCESS IN A RECORD OR DATA STRUCTURE CALLED PCB
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EACH USER PROCESS HAS A PCB. IT IS CREATED WHEN A USER CREATES
A PROCESS & IT IS REMOVED FROM THE SYSTEM WHEN THE PROCESS IS KILLED.
ALL THESE PCBs ARE KEPT IN MEM RESERVED FOR THE OS.
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PROCESS CONTROL BLOCK (PCB)
PROCESS – ID
PROCESS STATE
PROCESS PRIORITY
REG SAVE AREA FOR PC, IR, SP
PTR’ TO PROCESS MEM
PTR’ TO OTHER RESOURCES
LIST OF OPEN FILES
ACCOUNTING INFORMATION CPU TIME CONNECT TIME etc
OTHER INFORMATION IF REQUIRED BFD OF (CURRENT DIR etc)
PTR’ TO OTHER PCB’
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Ex: OS MAINTAINS 4 Q’ OR LISTS OF RUNNING PRS RDY PRS BLOCKED PRS & FREE PCB’
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PROCESS ID
PRIOR
PROCESS STATE
PSW
CPU REGS
EVENT INFORMATION
MEM ALLOCN
RESOURCES HELD
PCB PTR
DHAMDHARE
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OPERATIONS ON A PROCESS
CREATE A PROCESS
KILL A PROCESS
DISPATCH
CHANGE PRIORITY OF A PROCESS
BLOCK A PROCESS
TIME –UP
WAKE – UP
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CREATE A PROCESS
BEGIN 0 READ CUST – FILE ADD ….. 7 DIV…… 8 ………. 9 CALL “SORT” 10 ADD……….
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1 ALL CPU REGS ARE SAVED BEFORE A NEW CHILD PROCESS IS CREATED & A PCB IS ALLOCATED TO IT.
2 THE OS CONSULTS LIST OF FREE PCBs’ & ACQUIRES A FREE PCB. PCB NO 8 IN FIG.
3 ASSIGNS PID = 8 FOR NEW PROCESS
4 UPDATES FREE PCB HEADER
1 9
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5 OS COUSULTS IM FOR LOCN… OF SUB – PROGR.. ( STARTING ADDRS etc)
6 OS CONSULTS MM TO DET AVAIL ABILITY OF FREE MEM & ALLOCATES THOSE LOCNS
7 OS REQUESTS IM TO LOAD THE PROGR IN THE ALLOCATED MEM LOCNS
8 PRIORITY
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9 PCB FIELDS OF PCB 8 ARE INITIALIZED10 OS LINKS THIS PCB IN THE LIST OF RDY
PROCESSES. ROUND ROBIN (13,4,14,7,8)PRIORITY – etc
PRESUMING HIGHEST PRIORITY RDY- 8,13,4,14,7
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5 OS COUSULTS IM FOR LOCN… OF SUB – PROGR.. ( STARTING ADDRS etc)
6 OS CONSULTS MM TO DET AVAIL ABILITY OF FREE MEM & ALLOCATES THOSE LOCNS
7 OS REQUESTS IM TO LOAD THE PROGR IN THE ALLOCATED MEM LOCNS
8 PRIORITY
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