chuong07 memory management
DESCRIPTION
Quản lý bộ nhớTRANSCRIPT
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Khoa KTMT 1
Chng 7. Quan ly bo nh
Khai niem c s
Cac kieu a ch nh (physical address , logical
address)
Chuyen oi a ch nh
Overlay va swapping
Mo hnh quan ly bo nh n gian
Fixed partitioning
Dynamic partitioning
C che phan trang (paging)
C che phan oan (segmentation)
Segmentation with paging
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Khoa KTMT 2
Khai niem c s
Chng trnh phai c mang vao trong bo nh va at
no trong mot tien trnh e c x ly
Input Queue Mot tap hp cua nhng tien trnh tren a ma ang ch e c mang vao trong bo nh e thc
thi.
User programs trai qua nhieu bc trc khi c x ly.
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Khoa KTMT 3
Khai niem c s
Quan ly bo nh la cong viec cua he ieu hanh vi s ho
tr cua phan cng nham phan phoi, sap xep cac process
trong bo nh sao cho hieu qua.
Muc tieu can at c la nap cang nhieu process vao bo
nh cang tot (gia tang mc o a chng)
Trong hau het cac he thong, kernel se chiem mot phan co
nh cua bo nh; phan con lai phan phoi cho cac process.
Cac yeu cau oi vi viec quan ly bo nh
Cap phat bo nh cho cac process
Tai nh v (relocation): khi swapping,
Bao ve: phai kiem tra truy xuat bo nh co hp le khong
Chia se: cho phep cac process chia se vung nh chung
Ket gan a ch nh luan ly cua user vao a ch thc
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Khoa KTMT 4
Cac kieu a ch nh
a ch vat ly (physical address) (a ch thc) la mot v
tr thc trong bo nh chnh.
a ch luan ly (logical address) la mot v tr nh c
dien ta trong mot chng trnh ( con goi la a ch ao
virtual address)
Cac trnh bien dch (compiler) tao ra ma lenh chng trnh ma trong o moi tham chieu bo nh eu la a ch luan ly
a ch tng oi (relative address) (a ch kha tai nh v, relocatable address) la mot kieu a ch luan ly trong o cac a
ch c bieu dien tng oi so vi mot v tr xac nh nao o
trong chng trnh.
V du: 12 byte so vi v tr bat au chng trnh,
a ch tuyet oi (absolute address): a ch tng ng vi a ch thc.
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Khoa KTMT 5
Nap chng trnh vao bo nh
Bo linker: ket hp cac object module thanh mot file nh
phan kha thc thi goi la load module.
Bo loader: nap load module vao bo nh chnh
System
library
System
library
static linking
dynamic linking
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Khoa KTMT 6
C che thc hien linking
Module A
CALL B
Return
length L
Module B
CALL C
Return
length M
Module C
Return
length N
0
L 1
Module A
JMP L
Return
Module B
JMP L+M
Return
Module C
Return
L
L M 1
L M
L M N 1
relocatable
object modules
load module
0
L 1
0
M 1
0
N 1
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Khoa KTMT 7
Chuyen oi a ch
Chuyen oi a ch: qua trnh anh xa mot a ch t khong
gian a ch nay sang khong gian a ch khac.
Bieu dien a ch nh
Trong source code: symbolic (cac bien, hang, pointer,)
Thi iem bien dch: thng la a ch kha tai nh v
V du: a v tr 14 bytes so vi v tr bat au cua module.
Thi iem linking/loading: co the la a ch thc. V du: d lieu nam tai a ch bo nh thc 2030
0
250
2000
2250
relocatable addressphysical memory
symbolic address
int i;goto p1;
p1
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Khoa KTMT 8
Chuyen oi a ch (tt)
a ch lenh (instruction) va d lieu (data) c chuyen oi
thanh a ch thc co the xay ra tai ba thi iem khac nhau
Compile time: neu biet trc a ch bo nh cua chng trnh th
co the ket gan a ch tuyet oi luc bien dch.
V du: chng trnh .COM cua MS-DOS
Khuyet iem: phai bien dch lai neu thay oi a ch nap chng trnh
Load time: Vao thi iem loading, loader phai chuyen oi a ch
kha tai nh v thanh a ch thc da tren mot a ch nen (base
address).
a ch thc c tnh toan vao thi iem nap chng trnh phai
tien hanh reload neu a ch nen thay oi.
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Khoa KTMT 9
Sinh a ch tuyet oi vao thi iem dch
Symbolic
addresses
PROGRAM
JUMP i
LOAD j
DATA
i
j
Source code
Absolute
addresses
1024
JUMP 1424
LOAD 2224
1424
2224
Absolute load module
Compile Link/Load
Physical memory
addresses
1024
JUMP 1424
LOAD 2224
1424
2224
Process image
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Khoa KTMT 10
Sinh a ch thc vao thi iem nap
Relative
(relocatable)
addresses
0
JUMP 400
LOAD 1200
400
1200
Relative
load module
Symbolic
addresses
PROGRAM
JUMP i
LOAD j
DATA
i
j
Source code
Compile Link/Load
Physical memory
addresses
1024
JUMP 1424
LOAD 2224
1424
2224
Process image
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Khoa KTMT 11
Chuyen oi a ch (tt)
Execution time: khi trong qua trnh
thc thi, process co the c di
chuyen t segment nay sang
segment khac trong bo nh th qua
trnh chuyen oi a ch c tr
hoan en thi iem thc thi
Can s ho tr cua phan cng cho viec anh xa a ch.
V du: trng hp a ch luan ly la relocatable th co the dung
thanh ghi base va limit,
S dung trong a so cac OS a dung (general-purpose) trong o
co cac c che swapping, paging,
segmentation
Relative (relocatable)
addresses
0
JUMP 400
LOAD 1200
400
1200
MAX = 2000
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Khoa KTMT 12
Khong gian a ch
a ch c tao bi CPU a ch logic (logical address). Tap hp a ch logic goi la khong gian a ch logic
a ch nap vao MAR a ch vat ly (physical address). Tap hp a ch vat ly goi la khong gian a ch vat ly
compile-time and load-time:
a ch Logical va physical la xac nh
Tai thi iem thc thi:
a ch logic khac vat ly, thng goi la a ch ao
Viec anh xa gia hai a ch c thc thi bi Memory Management
Unit (MMU)
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Khoa KTMT 13
MMU
Tai nh v s dung relocation register
memoryCPU
relocation
register
+logical
address
642
physical
address
7642
7000
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Khoa KTMT 14
Lien ket ong(Dynamic linking)
Qua trnh link en mot module ngoai (external module)
c thc hien sau khi a tao xong load module (i.e. file
co the thc thi, executable)
V du trong Windows: module ngoai la cac file .DLL con trong Unix, cac module ngoai la cac file .so (shared library)
Load module cha cac stub tham chieu (refer) en
routine cua external module.
Luc thc thi, khi stub c thc thi lan au (do process goi routine lan au), stub nap routine vao bo nh, t thay the bang
a ch cua routine va routine c thc thi.
Cac lan goi routine sau se xay ra bnh thng
Stub can s ho tr cua OS (nh kiem tra xem routine a
c nap vao bo nh cha).
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Khoa KTMT 15
u iem cua dynamic linking
Thong thng, external module la mot th vien cung cap
cac tien ch cua OS. Cac chng trnh thc thi co the
dung cac phien ban khac nhau cua external module ma
khong can sa oi, bien dch lai.
Chia se ma (code sharing): mot external module ch can
nap vao bo nh mot lan. Cac process can dung external
module nay th cung chia se oan ma cua external
module tiet kiem khong gian nh va a.
Phng phap dynamic linking can s ho tr cua OS
trong viec kiem tra xem mot thu tuc nao o co the c
chia se gia cac process hay la phan ma cua rieng mot
process (bi v ch co OS mi co quyen thc hien viec
kiem tra nay).
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Khoa KTMT 16
Nap ong(Dynamic loading)
C che: ch khi nao can c goi en th mot thu tuc mi
c nap vao bo nh chnh tang o hieu dung cua bo
nh (memory utilization) bi v cac thu tuc khong c
goi en se khong chiem cho trong bo nh
Rat hieu qua trong trng hp ton tai khoi lng ln ma
chng trnh co tan suat s dung thap, khong c s
dung thng xuyen (v du cac thu tuc x ly loi)
Ho tr t he ieu hanh
Thong thng, user chu trach nhiem thiet ke va hien thc cac chng trnh co dynamic loading.
He ieu hanh chu yeu cung cap mot so thu tuc, th vien ho tr, tao ieu kien de dang hn cho lap trnh vien.
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Khoa KTMT 17
C che phu lap (overlay)
Tai moi thi iem, ch gi lai trong bo nh nhng
lenh hoac d lieu can thiet, giai phong cac
lenh/d lieu cha hoac khong can dung en.
C che nay rat hu dung khi kch thc mot
process ln hn khong gian bo nh cap cho
process o.
C che nay c ieu khien bi ngi s dung
(thong qua s ho tr cua cac th vien lap trnh)
ch khong can s ho tr cua he ieu hanh
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Khoa KTMT 18
Pass 1 70K
Pass 2 80K
Symbol table 20K
Common routines 30K
Assembler
Total memory
available = 150KB
C che overlay (tt)
symbol
table20K
common
routines30K
overlay
driver10K
pass 1 pass 2
80K70K
n v: byte
nap va thc thi
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Khoa KTMT 19
C che hoan v (swapping)
Mot process co the tam thi b swap ra khoi bo nh
chnh va lu tren mot he thong lu tr phu. Sau o,
process co the c nap lai vao bo nh e tiep tuc qua
trnh thc thi.
Swapping policy: hai v du
Round-robin: swap out P1
(va tieu thu het quantum cua no),
swap in P2 , thc thi P
3,
Roll out, roll in: dung trong c che nh thi theo o u tien (priority-based scheduling)
Process co o u tien thap hn se b swap out nhng cho cho process co o u tien cao hn mi en c nap vao bo
nh e thc thi
Hien nay, t he thong s dung c che swapping tren
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Khoa KTMT 20
Minh hoa c che swapping
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Khoa KTMT 21
Mo hnh quan ly bo nh
Trong chng nay, mo hnh quan ly bo nh la mot mo
hnh n gian, khong co bo nh ao.
Mot process phai c nap hoan toan vao bo nh th
mi c thc thi (ngoai tr khi s dung c che overlay).
Cac c che quan ly bo nh sau ay rat t (hau nh
khong con) c dung trong cac he thong hien ai
Phan chia co nh (fixed partitioning)
Phan chia ong (dynamic partitioning)
Phan trang n gian (simple paging)
Phan oan n gian (simple segmentation)
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Khoa KTMT 22
Phan manh (fragmentation)
Phan manh ngoai (external fragmentation)
Kch thc khong gian nh con trong u e thoa man mot yeu cau cap phat, tuy nhien khong gian nh nay khong
lien tuc co the dung c che ket khoi (compaction) e gom lai thanh vung nh lien tuc.
Phan manh noi (internal fragmentation)
Kch thc vung nh c cap phat co the hi ln hn vung nh yeu cau.
V du: cap mot khoang trong 18,464 bytes cho mot process yeu cau 18,462 bytes.
Hien tng phan manh noi thng xay ra khi bo nh thc c chia thanh cac khoi kch thc co nh (fixed-sized
block) va cac process c cap phat theo n v khoi. V
du: c che phan trang (paging).
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Khoa KTMT 23
Phan manh noi
operating
system
(used)
yeu cau ke tiep la
18,462 bytes !!!
hole kch thc
18,464 bytescan quan ly khoang
trong 2 bytes !?!
OS se cap phat han khoi 18,464 bytes
cho process d ra 2 bytes khong dung!
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Khoa KTMT 24
Fixed partitioning
Khi khi ong he thong, bo nh chnh
c chia thanh nhieu phan ri nhau
goi la cac partition co kch thc bang
nhau hoac khac nhau
Process nao co kch thc nho hn
hoac bang kch thc partition th co
the c nap vao partition o.
Neu chng trnh co kch thc ln
hn partition th phai dung c che
overlay.
Nhan xet
Khong hieu qua do b phan manh noi: mot chng trnh du ln hay nho eu
c cap phat tron mot partition.
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Khoa KTMT 25
Chien lc placement (tt)
Partition co kch thc bang nhau
Neu con partition trong process mi se c nap vao partition o
Neu khong con partition trong, nhng trong o co process ang b
blocked swap process o ra bo
nh phu nhng cho cho process
mi.
Partition co kch thc khong bang
nhau: giai phap 1
Gan moi process vao partition nho nhat phu hp vi no
Co hang i cho moi partition
Giam thieu phan manh noi
Van e: co the co mot so hang i trong khong (v khong co process
vi kch thc tng ng) va hang
i day ac
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Khoa KTMT 26
Chien lc placement (tt)
Partition co kch thc khong
bang nhau: giai phap 2
Ch co mot hang i chung cho moi partition
Khi can nap mot process vao bo nh chnh chon partition
nho nhat con trong
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Khoa KTMT 27
Dynamic partitioning
So lng partition khong co nh va partition co the co
kch thc khac nhau
Moi process c cap phat chnh xac dung lng bo nh
can thiet
Gay ra hien tng phan manh ngoai
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Khoa KTMT 28
Chien lc placement
Dung e quyet nh cap phat
khoi bo nh trong nao cho
mot process
Muc tieu: giam chi ph
compaction
Cac chien lc placement
Best-fit: chon khoi nh trong nho nhat
First-fit: chon khoi nh trong phu hp au tien ke t au
bo nh
Next-fit: chon khoi nh trong phu hp au tien ke t v tr
cap phat cuoi cung
Worst-fit: chon khoi nh trong ln nhat
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Bi Tp
Gi s b nh chnh c phn thnh cc phn vng c kch
thc l 600K, 500K, 200K, 300K ( theo th t ), cho bit cc tin
trnh c kch thc 212K, 417K, 112K v 426K ( theo th t ) s
c cp pht b nh nh th no, nu s dng :
a) Thut ton First fit
b) Thut ton Best fit
c) Thut ton Worst fit
d) Thut ton Next fit
Thut ton no cho php s dng b nh hiu qa nht trong trng
hp trn ?
Khoa KTMT 29
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Khoa KTMT 30
Cap phat khong lien tuc
1.C che phan trang (paging)
Bo nh vat ly khung trang (frame). Kch thc cua frame la luy tha cua 2, t khoang 512 byte en
16MB.
Bo nh luan ly (logical memory) hay khong gian a ch
luan ly la tap moi a ch luan ly ma mot chng trnh
bat ky co the sinh ra page. V du
MOV REG,1000 //1000 la mot a ch luan ly
Bang phan trang (page table) e anh xa a ch luan ly
thanh a ch thc
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Khoa KTMT 31
1.C che phan trang (tt)
logical memory
1
4
3
5
0
1
2
3
page table
page 0
page 2
physical memory
framenumber
0
1
2
3
page 14
5 page 3
pagenumber
0
1
2
3
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Khoa KTMT 32
1.C che phan trang (tt)
A) Chuyen oi a ch trong paging
a ch luan ly gom co:
So hieu trang (Page number) p
a ch tng oi trong trang (Page offset) d
Neu kch thc cua khong gian a ch luan ly la 2m, va kch
thc cua trang la 2n
(n v la byte hay word tuy theo kien truc
may) th
Bang phan trang se co tong cong 2m/2
n= 2
m nmuc (entry)
p d
page number page offset
m n bits
(nh v t 0 2m n 1)
n bits
(nh v t 0 2n 1)
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Khoa KTMT 33
1.C che phan trang (tt)
CPU p d f d
f
p
page table
logical
address
physical
address
physical
memory
f 0000
f 1111
f framesA) Chuyen oi a ch trong paging
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Khoa KTMT 34
1.C che phan trang (tt)
V du: Chuyen oi a ch nh trong paging
-
V d
Xt mt khng gian a ch c 8 trang, mi
trang c kch thc 1KB. nh x vo b nh
vt l c 32 khung trang
a) a ch logic gm bao nhiu bit ?
b) a ch physic gm bao nhiu bit ?
c) Bng trang c bao nhiu mc?Mi mc
trong bng trang cn bao nhiu bit?
Khoa KTMT 35
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Khoa KTMT 36
1.C che phan trang (tt)
Trc khi va sau khi cap phat cho Process mi
-
Khoa KTMT 37
B) Cai at bang trang (Paging hardware)
Bang phan trang thng c lu gi trong bo nh chnh
Moi process c he ieu hanh cap mot bang phan trang
Thanh ghi page-table base (PTBR) tro en bang phan trang
Thanh ghi page-table length (PTLR) bieu th kch thc cua bang phan trang (co the c dung trong c che bao ve bo nh)
Thng dung mot bo phan cache phan cng co toc o
truy xuat va tm kiem cao, goi la thanh ghi ket hp
(associative register) hoac translation look-aside buffers
(TLBs)
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Khoa KTMT 38
B) Cai at bang trang (Paging hardware)
Dung thanh ghi Page-Table Base Register (PTBR)
p
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Khoa KTMT 39
Paging hardware vi TLB
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Khoa KTMT 40
C) Effective access time (EAT)
Tnh thi gian truy xuat hieu dung (effective access time,
EAT)
Thi gian tm kiem trong TLB (associative lookup):
Thi gian mot chu ky truy xuat bo nh: x
Hit ratio: t so gia so lan ch so trang c tm thay (hit)
trong TLB va so lan truy xuat khi nguon t CPU
K hieu hit ratio:
Thi gian can thiet e co c ch so frame
Khi ch so trang co trong TLB (hit) + x
Khi ch so trang khong co trong TLB (miss) + x + x
Thi gian truy xuat hieu dung
EAT = ( + x) + ( + 2x)(1 )
= (2 )x +
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Khoa KTMT 41
C) Effective access time (EAT)
V du 1: n v thi gian
nano giay
Associative lookup = 20
Memory access = 100
Hit ratio = 0.8
EAT = (100 + 20) 0.8 +
(200 + 20) 0.2
= 1.2 100 + 20
= 140
V du 2
Associative lookup = 20
Memory access = 100
Hit ratio = 0.98
EAT = (100 + 20) 0.98 +
(200 + 20) 0.02
= 1.02 100 + 20
= 122
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V d
Xt mt h thng s dng k thut phn trang, vi
bng trang c lu tr trong b nh chnh.
a) Nu thi gian cho mt ln truy xut b nh bnh
thng l 200nanoseconds, th mt bao nhiu thi
gian cho mt thao tc truy xut b nh trong h
thng ny ?
b) Nu s dng TLBs vi hit-ratio ( t l tm thy)
l 75%, thi gian tm trong TLBs xem nh bng
0, tnh thi gian truy xut b nh trong h thng (
effective memory reference time)
Khoa KTMT 42
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Khoa KTMT 43
D) To chc bang trang - Phan trang a cap
Cac he thong hien ai eu ho tr khong gian a ch ao
rat ln (232
en 264
), ay gia s la 232
Gia s kch thc trang nh la 4KB (= 212)
bang phan trang se co 232/212 = 220 = 1M muc.
Gia s moi muc gom 4 byte th moi process can 4MB cho bang
phan trang
VD: Phan trang hai cap
P2 d
So trang o di trang
P1
10 bit 10 bit 12
-
Phn trang a cp (tt)
Khoa KTMT 44
-
Khoa KTMT 45
D) To chc bang trang
Phan trang a cap
-
Khoa KTMT 46
D) To chc bang trang
Bang trang nghch ao: s dung cho tat ca cac Process
i
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Khoa KTMT 47
E) Bao ve bo nh
Viec bao ve bo nh c hien thc bang cach gan vi
frame cac bit bao ve (protection bits) c gi trong
bang phan trang. Cac bit nay bieu th cac thuoc tnh sau
read-only, read-write, execute-only
Ngoai ra, con co mot valid/invalid bit gan vi moi muc
trong bang phan trang
valid: cho biet la trang cua process, do o la mot trang hp le.
invalid: cho biet la trang khong cua process, do o la mot trang
bat hp le.
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Khoa KTMT 48
Bao ve bang valid/invalid bit
Moi trang nh co kch thc 2K = 2048
Process co kch thc 10,468 phan manh noi frame 9 (cha page 5), cac a ch ao > 12287 la cac a ch invalid.
Dung PTLR e kiem tra truy xuat en bang phan trang co nam trong bang hay khong.
00000
10468
12287
2 v
3 v
4 v
7 v
8 v
9 v
0 i
0 i
frame
number
valid/
invalid bit
0
1
2
3
4
5
6
7
0
1
2 page 0
3 page 1
4 page 2
5
6
7 page 3
8 page 4
9 page 5
...
page n
16383
14 bit
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Khoa KTMT 49
F) Chia se cac trang nh
Process 1
ed 1
ed 2
ed 3
data 1
ed 1
ed 2
ed 2
data 3
Process 3
3
4
6
2
0
1
2
3
3
4
6
1
0
1
2
3
Process 2
ed 1
ed 2
ed 3
data 2
3
4
6
7
0
1
2
3
0
1 data 1
2 data 3
3 ed 1
4 ed 2
5
6 ed 3
7 data 2
8
9
10
Bo nh thc
-
Khoa KTMT 50
2.Phan oan (segmentation)
Nhn lai c che phan trang
user view (khong gian a ch ao) tach biet vi khong gian bo nh thc. C che phan trang thc hien phep anh xa user-view
vao bo nh thc.
Trong thc te, di goc nhn cua user, mot chng trnh
cau thanh t nhieu oan (segment). Moi oan la mot n
v luan ly cua chng trnh, nh
main program, procedure, function
local variables, global variables, common block, stack, symbol table, arrays,
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Khoa KTMT 51
User view cua mot chng trnh
Thong thng, mot chng trnh
c bien dch. Trnh bien dch
se t ong xay dng cac
segment.
V du, trnh bien dch Pascal se
tao ra cac segment sau:
Global variables
Procedure call stack
Procedure/function code
Local variable
Trnh loader se gan moi
segment mot so nh danh
rieng.
procedurestack
symbol
table
function
sqrt
main program
Logical address space
-
Khoa KTMT 52
Phan oan
Dung c che phan oan e quan ly bo nh co ho tr
user view
Khong gian a ch ao la mot tap cac oan, moi oan co ten va kch thc rieng.
Mot a ch luan ly c nh v bang ten oan va o di (offset) ben trong oan o (so sanh vi phan trang!)
-
Khoa KTMT 53
Phan oan (tt)
logical address space physical memory space
segment 1
segment 2
segment 3 segment 4
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Khoa KTMT 54
Cai at phan oan
a ch luan ly la mot cap gia tr
(segment number, offset)
Bang phan oan (segment table): gom nhieu muc, moi
muc cha
base, cha a ch khi au cua segment trong bo nh
limit, xac nh kch thc cua segment
Segment-table base register (STBR): tro en v tr bang
phan oan trong bo nh
Segment-table length register (STLR): so lng segment
cua chng trnh
Mot ch so segment s la hp le neu s < STLR
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Khoa KTMT 55
Mot v du ve phan oan
procedure
stack
symbol
table
function
sqrt
main program
segment 0
segment 3
segment 1segment 2
segment 4
procedure
stack
main
symbol table
function sqrt
limit base
0 1000 1400
1 400 6300
2 400 4300
3 1100 3200
4 1000 4700
segment
table
logical address spacephysical memory space
1400
2400
3200
4300
4700
5700
6300
-
Khoa KTMT 56
Phan cng ho tr phan oan
CPU
+physical
memory
no
trap; addressing error
limit base
s
s d
yes
segment
table
-
Khoa KTMT 57
Chuyen oi a ch trong c che phan oan
V du
-
Khoa KTMT 58
Chia se cac oan
editordata 1
segment 0segment 1
logical address space
process P1
editordata 2
segment 0segment 1
logical address space
process P2
limit base
0 25286 43062
1 4425 68348
segment table
process P1
limit base
0 25286 43062
1 8850 90003
segment table
process P2
editor
data 1
data 2
physical memory
43062
72773
68348
90003
98853
-
Khoa KTMT 59
3.Ket hp phan trang va phan oan
Ket hp phan trang va phan oan nham ket hp cac u
iem ong thi han che cac khuyet iem cua phan
trang va phan oan:
Van e cua phan oan: Neu mot oan qua ln th co the khong nap no c vao bo nh.
Y tng giai quyet: paging oan, khi o ch can gi trong bo nh cac page cua oan hien ang can.
Logic Addr =
-
Khoa KTMT 60
3.Ket hp phan trang va phan oan
-
Khoa KTMT 61
3.Ket hp phan trang va phan oan
-
Bi Tp
Xt mt khng gian c b nh lun l kch thc
1 trang l 1KB. Tnh s trang v di (offset)
ca tng a ch sau:
a) 2.375
b) 19.366
c) 30.000
d) 256
e) 16.385
Khoa KTMT 62
-
Bi Tp
Xt mt khng gian c b nh lun l c 64
trang, mi trang c 1024 t, mi t l 2 byte c
nh x vo b nh vt l c 32 trang:
a) a ch b nh vt l c bao nhiu bit?
b) a ch b nh lun l c bao nhiu bit?
c) C bao nhiu mc trong bng phn trang? Mi
mc cha bao nhiu bit?
Khoa KTMT 63
-
Bi tp
Xt mt h thng s dng k thut phn trang, vi
bng trang c lu tr trong b nh chnh.
a) Nu thi gian cho mt ln truy xut b nh bnh
thng l 100 nanoseconds, th mt bao nhiu thi
gian cho mt thao tc truy xut b nh trong h
thng ny ?
b) Nu s dng TLBs vi hit-ratio ( t l tm thy)
l 85%, thi gian tm trong TLBs l 20
nanosecond, tnh thi gian truy xut b nh trong
h thng ( effective memory reference time)
Khoa KTMT 64
-
Bi tp
Xt bng phn on sau y :
Cho bit a ch vt l tng ng vi cc a ch logic sau
y :
a. 0,430 b. 1,100 c. 2,500 d. 3,400 e. 4,112
Khoa KTMT 65
Segment Base Length
0 219 600
1 2300 14
2 90 100
3 1327 580
4 1952 96