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COSC 6360 Operating Systems - September_17_2018_Lecture
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00:18 Okay. Okay. Well, I have two minutes to tell you the
00:27 news. First values, I've almost all the queen. And the results
00:33 very my Some people live very well many people. New standard should be
00:44 from. Thank you. The same details you. But first of,
00:55 you should be a wake up it could also be that some of
01:00 first semester we're not gonna or So that that's only the first bad
01:14 . The second bad news is that be discourse. Pope. Okay,
01:23 group Don't worry too much. Remember we five there is a total of
01:29 quizzes or more creases. Mhm. won't be great for everybody. What
01:37 would like to do today is to about the first assignment and for that
01:52 have a PowerPoint presentation. The first was posted on Friday night because some
02:00 wanted it to have it for the . And, you know, I
02:05 they were right. And I did . Yeah. So what? Do
02:11 have the purpose off? The first is to uh huh is to
02:21 right are very simply speak shell. me go backward. Yes, I
02:33 . We'll call it my shell should able to do ls minus. It
02:40 also be able to, uh, something like being a Jew. This
02:46 easier. This can be done directly using exactly If you do ls
02:52 you have to do you pet search because the specification tell you you can't
02:58 exactly p will be too Are all arguments are separated by space or redirection
03:07 people who do the class last semester a much harder assignment They were supposed
03:13 implement Pikes Unlimited number of pipes and fact, the best implement. These
03:21 recursive implementation of pipes And you realize problem. Of course you know,
03:27 something recursive with forks in it. a big chance, you know,
03:31 run over your limit. And so he added something. And look
03:37 for instance, work out minus the Councilor words from the fight text.
03:44 here you know the greater than sign , which means input, redirection,
03:50 a separator. There is no space the value and the greater than this
03:56 and your space When those abandoned that means you know, if you
04:01 to recycle could of somebody else, know you will have to modify the
04:06 to start. So let me let review how well do that process
04:13 And so far, by the the reference for the assignment is
04:19 Always hand up, hand out as what to do. And he had
04:25 explained things. But it's not as because this creation for exactly argument vector
04:33 saw that in class is repeated. basic system calls for creates a carbon
04:41 of a calling process. Sharing it's five. That's the only thing the
04:48 and a child share, who they . A code segment that nobody speaks
04:54 . That is done haven. But know, the child doodle shared address
05:01 of its parents. Everything the parent is not reflected in the child.
05:09 could prepare little demo for Wednesday. will be exit V overrides the contents
05:16 process outer space and creates an executable . So what about fork?
05:26 every UNIX process has apparent, except first process we should create by brute
05:35 . You know, when the system ? No, no, it Where
05:43 the first human. The first human had a her parents. They were
05:49 human in some way. So So happening when you have a fork?
06:01 look at the tax skier, but more interesting to look at the drawings
06:07 . Parents in China are different address . This address space is the code
06:16 the address states of the parent, they include. It's not sharing honey
06:25 in my pocket. A $20 It could be a clone off a
06:32 bill that you may have, but not sharing it. They're different.
06:42 for returns process idea of child The Return zero. So first example.
06:55 . Seabrook program includes Ustream. They've Standard Fork. I do see out
07:02 offline. This will print two lights after the four, because we run
07:09 the parent and by the child. way to look at it is the
07:17 world. We have a fork for a child parent and child run the
07:22 code waiting for child completion. Wait zero wait for the completion of any
07:33 . Now what's happening is defined as the child sorry has already complete that
07:40 have some kind of error? No. In fact, it returns
07:48 . This is because, as most you now unique keeps track off the
07:55 that have completed and have not been by the pound. Yeah, any
08:03 or all Children. But I need . So he returns any child.
08:09 . So let me this way. suppose you're president. 4 to 20
08:14 to wait for the completion. You a loop and you do wait 20
08:20 . You will see things will be little bit different when we'll we'll go
08:25 be friends in p threat. You , the snow wage called a joint
08:31 the joint is is specific to a threat you are waiting for. Anybody
08:36 already program with the French? they are fun. Except the call
08:43 creating a threat is and passing arguments the parent and child. You have
08:51 . You only pass only one argument it has a type voice. So
08:57 you have to pass, then you pass them instruct or even a
09:01 . They're all the same time. other example here. You know,
09:05 have the cease types this rage can't . If KP I'd resolve before
09:18 That means I am in. The is on child. I am the
09:21 process. The child process here executes in original program. So here we
09:31 one program creating two processes and we underscore exit zero, which is abnormal
09:41 . Some of you may be tempted use exit instead of underscore Exit
09:49 It's not a system call. It a function that calls underscore, exit
09:56 do a lot of crazy things before that, including rewinding input Far,
10:03 , in most program will have to . The results you will get will
10:07 fun but unpredictable. So you Exit off the faith y zero.
10:14 can explain to me why we have zero. Sorry. It was
10:22 but what? Zero doesn't mean No error, no error there Tradition
10:31 the eunuchs world and I've been explored many or others is that there shall
10:38 no completion messages if things happen So you now UNIX. It's not
10:46 your grandmother. Are you happy to a grandmother make a good test cocoa
10:50 you? Are you not happy of ? And the world. Yes,
10:54 , yes, yes. You if you have to thank you for
10:58 with my mother, how I learned sue my buttons myself, it was
11:03 with myself. Then you have to so many. Thank you.
11:08 Okay. Well, this gave a nice picture of my personality, but
11:13 not right. So what you have is the error code. Everything is
11:21 different ways for the child does our for any process. The process,
11:28 course. Big. You will need use code like this because in your
11:35 program, you will have to wait the completion of the task created by
11:42 . Exactly. Exactly. Exactly. . P Exactly. While does the
11:51 search for you for both. And cannot use other thing. You cannot
11:56 it system. Why? Because if were writing your program with system is
12:02 simple. You will read one line system with that line. Go to
12:08 next line. And so far, system essentially takes a string of
12:16 Interpret them by, like a comment the shell. Exactly. Exit v
12:25 path. A argument vector in the vector. This scripture will be
12:32 Argument Vector is the first argument is short name off comment, though the
12:43 buffet and then the other arguments. you program with our CSI, our
12:49 , you say, Well, there argument vector on argument count here there
12:53 no argument. Count its simplicity by and no. So here we have
13:01 description off exactly with an argument count to name of the name of the
13:08 executed and the and the argument. the way, the shell is not
13:16 flags in UNIX flags with the minus They are. They are things which
13:24 specifying options for the command. They're names of FARC's. The shelters,
13:29 process them is of each program, that? So it happened. Ls
13:36 the convention that the flag start by . You will not this end.
13:41 modern programs the flag start by minus and other stuff. There is no
13:48 . People just, you know, the convention because off social pressure.
13:54 the system doesn't have any way to deal with flax, which gives the
13:57 simple, exact the exact VP we You cannot use them. So
14:06 You will expect here is to have like this for the dynamic creating
14:15 If process idea off. If the pages off our problems and presidents,
14:21 I should have better. So my there I will take XXV p My
14:28 argument I had working to with finding . Exit one here is different.
14:37 code is not zero. It's one . Why? Because normally the underscore
14:44 be executed. Exact will take place over that, if you want to
14:51 about it exactly. It's like programming learning in a different way. Thing
15:01 that let's suppose that when we're arriving at the University of Houston, they
15:06 a big helmet on your head. you learned before coming to Texas will
15:11 removed and replaced by new stuff. , for instance, you learned engineering
15:21 with the metric system. Forget about . We go back to the British
15:25 here, and, of course, program you to to drive the right
15:32 of the road. So when you that here and here with a pound
15:42 , so yeah, we'll show you very basic shell, and you will
15:47 once you look at the shell It give you a picture of how your
15:52 should be. Some details have been , for instance, from the problems
16:01 , the handoff subjects that use my as the problem. Why? Because
16:09 you shall will be working, he look very, very close to the
16:14 shell. The big difference would be special character here. We know to
16:21 characters Greater van unless of them. else. Vertical bar for pipes normal
16:33 star Normal corrector So my column normal Everything is just normal. It's wonderful
16:42 you. If you ask you To treat all those special corrective letter
16:47 does it will not be after It will be a semester project for
16:53 people maybe an extension for next Now what you will notice also is
17:01 you can, if you want, five school. It's semi colons,
17:05 colons X y z. Now the problem with those fives they're not that
17:12 to remove with a normal shop. we prefer you to thio to know
17:18 you are into your shell, my and nothing the normal Shanteau avoid doing
17:24 Surprised? So what we do here lie italics. Iconix means that it's
17:34 you have to write yourself part of input line, and to get the
17:38 vector, you parse. Er is straightforward part, sir. Remember,
17:43 needs to stop for consecutive blanks and detect greater than less, less less
17:53 that. Once you have that, have essentially a list off arguments on
18:02 life you need immediately to extract the after the lesser Dan. And after
18:11 greater than we do, So I direction. You will never pass them
18:15 the program, then up. Then know when you have done that,
18:20 built in argument. Vector zero sum are built in, for instance,
18:28 . Commit to terminate the shell You call a program to do that.
18:32 shell terminates itself after taking care killing the the background processes that's specifying
18:40 hand up. Well, you have a commerical of BG for background,
18:47 I've created for you own fun. means the process is to be sent
18:53 the background. What follows So those two, uh, two built in
19:01 . This a third one change directory . It's not a program that shall
19:09 that. The shelter do itself because , the shell changes default directory.
19:17 if your modified the state of the , you don't execute a program and
19:21 system called to use its CHD ir supposed to find that on your
19:27 But still you are here in I will tell you to you.
19:33 you know that you have the catchall . Do it Implement that handles the
19:39 off BG Seed you on here. we sort of built in command.
19:53 thing fine path Find Pan is not extremely simple program. Find Pat reads
20:04 path and breaks the path into that off possible directory names. So find
20:21 path essentially start by parsing. The difference here is that you parse stopping
20:30 columns. There are no tricks. , you know they So you get
20:37 list off the directory So I should like this like this. And for
20:42 of them, you have to check there is a binary that's execute herbal
20:51 . To do that, you have use a command called access and you
20:56 for X underscore. Okay, Then when we have found that you
21:09 . Uhh ! You have found the name of the command to execute for
21:14 it will be slash being such a so far for all the conventional take
21:18 time. So it's only you iterative trying all the director is the right
21:23 . That means that essential to the being played by, uh by the
21:33 list is the order in which each center because you search in that
21:46 No, What do you do? a you fogged the process You do
21:53 your direction in the Iot process mawr the EU redirection That's very easy is
22:03 few lines of code. Then you the exact with the full path name
22:10 their agreement factor that you have Remember the argument vector. It's simply
22:17 on your input line and you remove it. You know the redirection code
22:23 part of the command is um then know either processes interactive, which is
22:29 before you have the apparent waiting for child because so, yeah, finding
22:38 right execute hable, you do a in your path. My but its
22:47 your local is being used uncle being ? Uh huh. And you
22:52 how do you get that? You it like string copy into a
22:57 get environment. And then, you , the backer gives you the whole
23:06 . Then I told you, you it into a directory on Max in
23:13 campaigns one one directory that you can and you try them successively. What
23:21 do, for instance, suppose that program that you have to execute it's
23:29 bozo. Then you spite slash user local slash has been slash Bozo,
23:37 it execute herbal? Yes. A founded. Otherwise it slash use
23:42 following balls. Oh, no, , no. And at the
23:46 you can have a good program of on. Then you paint a message
23:52 or fun. Are you sure this explained? Here, look here.
24:01 I'm doing is oh, I need to I I'm not sure I do
24:10 to have a flash here. here I show my I like to
24:20 print spring we that brings in the string directory, string argument vector.
24:30 a few things. Let me see I need to add this slash or
24:39 . Probably Yes, I by the . Yeah, as sprinter. And
24:52 scan it are you friend, because can do a lot of things.
24:56 with them. There are some So the last thing I need to explain
25:06 you is input Redirection. I have shall construct here, work out from
25:19 . What does it mean? the static input off word count is
25:25 by content with five other ranks so getting its input from summit input
25:32 for the country, this is a powerful construct because when you write
25:40 you know, tech space programs in shuttle environment rather than opening fires,
25:47 know I use are your redirection It's much more flexible. Let me
25:55 you a new example. Thinking about off the graduate students we like to
26:03 our first assignment simulation off process, through pews in a computer, you
26:14 , to process arrived, going to , you the game Really CPU go
26:19 the dish or there's a way to for the disk and so far,
26:23 you know, of course, the A s want to test the assignments
26:27 not exactly the input that was sampling given by the students would like Thio
26:33 try something else to prevent people to a program that will just bought that
26:39 . That means you know, that would like to ta to be able
26:42 have different far input input five with system is very simple. You to
26:49 changed that. But what if you a hard wired named for the
26:55 Fine. It was the work then right thing to do is okay.
27:00 know, at the argument vector off program. You have the name on
27:05 fire. You check your argument. is correct. You reject if people
27:11 to put it. And then you you read the staying your opening
27:16 And so far, this is a of work for nothing. So I
27:19 to do that. So how do do? The are you redirect First
27:26 opened the fight and he opened in only by doing almost all right declared
27:38 the proper includes So it's a responsibility addle. The program includes So your
27:45 How do you which includes to use instance, I will type man open
27:51 man too you give me a description what opens Supposed This description is not
27:58 user friendly, but has in the although includes a need to being
28:10 Then what I do, I clues . Why do hello? Matching?
28:20 have the five, the scripture for five and I do pit Make a
28:25 it where I would have to create new file Descriptor pointing to the fight
28:33 scripture there Which new? Five of ? Oh eunuchs always speaks the first
28:42 entry in the find The script of Yes, normal. If I use
28:50 the next five open be five I that will be six and so
28:54 But here rigged the game I closed So what's the first five descriptor
29:02 Zero Because it makes available. So what? After this thing here I
29:13 redirected the input in such a way where the program we'll try to read
29:22 zero senate if he will really stand the fighter scripture. Bingo. I
29:28 almost up. Why almost now? have the Paris staying here. I
29:37 need FD anymore. And after a to get rid of so very bad
29:48 . Yeah, you were in the . First three prepared. It's not
29:55 fault. Yeah, this is good but we want the That's transparent.
30:07 . Take care. The other Yeah, I need to. They
30:16 funding view, activism rule Frankfort First I opened, uh, five
30:30 read A remote I closed Stand Create a duplicate of the five descriptor
30:38 will be extended in. And then , the final scripter. My work
30:43 done. Officer direction here. What have is that you know, I
30:50 to make a listing. What's in directory minus l long listing. That
30:56 that I d list the culture of directory and I supplement each entering by
31:01 fetch from the i note of the . So access control list, you
31:07 , Name of the owner name of group. Last time it waas
31:14 And you know, the thing thinks like it like that. And then
31:18 I would like to do is the here should be redirected to this
31:25 So the speed is very simple. know, I opened fire directory takes
31:37 right, always. But in many you were direct the output into a
31:46 that doesn't exist. You wanted to creative. And then, you know
31:52 open system called has an option. , underscore. Creates. They
31:59 you know, when you try to the fight for writing into it.
32:03 the five doesn't exist, created by the way, it's interesting to
32:14 how those options are. Who represented ? Essentially, it's a macro for
32:29 big map Means you and the 32 word and you want it up saying
32:34 option time, Look at all good exclusive or so We're whoring all the
32:43 maps to say all the flags being raised. No, The last thing
32:48 is the little mystery stuff. Why we have that? That somebody explain
32:52 me what it means? I yeah, okay. You create a
33:01 five, you have to give some full permission here. You know,
33:07 use a crass method to described it octo. When I was in school
33:17 just a long time ago, Octel the barricade. Why? Because when
33:22 have a bite, architectures is easier do it in Exodus symbol, but
33:29 started before I became very motivated to something in computer science. They were
33:35 doctor. Article six, 44 It's There's six is 11010 while for
33:49 let's restart 110 year old 10010 That I created five, which is right
33:59 by Neo Lee and readable by me everybody else. All the five
34:04 I don't know if I care about . I could put a better protection
34:08 be five months. There are Stand out to eat a duplicate of
34:14 five at the first available space. this the first available space is what
34:24 I redirected here and that close. marvel that you have is that everything
34:32 is very basic UNIX is in simple. When a assignment repeat threats
34:39 synchronization purpose, you will see the calls for patriots are long. But
34:47 now we have. We are living the real off simplicity, which is
34:57 , so I will end. It's show the questions I give you until
35:11 tend to do the assignment. The will require some work to decide how
35:18 use the system calls. Otherwise it's a hard assignment. The key thing
35:25 to ride good partial. You have have one part for the scanning
35:34 One part sir, for breaking into fine names into You know, the
35:43 names the path strange, but that's . You can even, you
35:52 try to do one scanner doing That, except that the scanner for
35:59 import has to recognize security for That's for that. So it's a
36:04 between duplicate to duplicate simple program or more complex program doing both. If
36:13 have questions, you know, in . Also, keep in mind that
36:18 have Ah, you know this guy by the way, I still have
36:28 issues with the way the system recovered the big crash, when I lost
36:34 all my data. The system only the data for my W W.
36:41 directory, which is the one visible the outside world. But everything I've
36:47 , um, this system is lost . The good news is that I
36:58 that because starting a long time I decided that the system of the
37:05 was not trustworthy and I shall be on my own data, Which means
37:13 , you know, I'm very sorry lost all this stuff, but it's
37:16 contain anything interesting relief. Who this ? I lost data from before I
37:26 here and I was a Purdue. I still have probably some old
37:32 Uh, you know, whenever You. So what I did is
37:40 I and that posting everything off, some low pizza, has now a
37:51 entry called papers with the pdf off papers and also the Paul Paul representation
37:59 will use for this lecture. And the next lecture, I will start
38:06 presentations about, you know, more memory. And this time I need
38:17 talk to you about a very nice . Sorry. Yeah. You submitted
38:31 Blackboard. And what? I want to explain your assignment to the why
38:38 do that too. She their shells around Hi. A few things to
38:51 them less off this off. But you have to explain what you do
38:59 . So I Hi. Maybe raise hands high, in fact.
39:18 Okay. Hey. Yeah. stop signaling well. The third Society
39:47 For they from that? My Some old computer. Okay.
40:07 Yeah, very good. Well, when you don't exactly one himself.
40:25 , Poor. You see there. ? Yeah. Oh, for
40:36 of course. Experience was likely Right? Fight of available to
40:51 Yeah, no problem. Uh Fine. Right. Are you?
41:20 . Holding for right people, want to Valley software people?
41:39 Ray. Parole. Yeah. Time . I understand. Maybe by the
41:49 . Yeah, the doctor. People here, the book, all
42:04 Yeah, Yeah. Mhm. Or before these scores. Space
42:29 Sure. And army. Nothing The problem? Horrible. But,
42:50 know, we need to embrace the and realizing that that's the way to
43:00 that. So I need That's a bad idea of going there, but
43:11 happened there. So what I will instead, I will go to directory
43:21 and go to the directory of a point because I want to talk to
43:28 about Mac trying to do that Okay, So is recording beginning?
44:50 , go and get block in the . And it's important because you find
45:08 off it in, Of course, ah, Mac os Stan Mac,
45:19 next step in France and also you know, in the in the
45:29 virtual memory to speak of the Pema I will show you there. But
45:35 me, the most interesting stuff is they explain to you how really to
45:39 the virtual memory outside of the confines what Berkeley UNIX did, and they
45:46 here three important new issues. Extra . Concept of inheritance. Copy
45:54 The paper is horrible. Good. to read it. It's a short
46:00 off other disturb Indians dissertation at Kennedy . The Mac team is really
46:09 This macron's developed in academic environment. you know both the adviser and you
46:15 he went to the industry regression. went to Microsoft in a have a
46:23 of Banyan went to Apple. First went to next, and then we
46:28 to our and evidence. Dominion is guy who brought Mac OS that as
46:36 way to get out of the old systems. They were basically a glorified
46:43 , but very little things for providing from modern computers. So show the
46:50 very poorly done. What I did that I don't know it a long
46:55 ago. I have a list of , exhortation. I read it and
47:00 the paper start to make sense with . And I wrote a little one
47:04 summary off it, and I put name on it because normally when you
47:10 a summary, it's just, you , a hack. But I believe
47:15 making sense off that paper wasa creative . I'm proud of it. So
47:23 general objectives to be exportable as UNIX memory system while supporting more functionality match
47:35 explain to you why my prize are , why we should embrace them and
47:41 through page inheritance. In fact, beauty off the skin of Mac proposes
47:50 to save the lightweight processes. And processes are just a special case off
47:57 way you do the form nothing more that. Also, they want to
48:04 multi processing distributed systems and large address is supporting multi processing waas. That
48:13 something that was dated in the sense you know, in the eighties,
48:20 believe that the future will be taking lot of cheap microprocessors putting them together
48:26 say, Oh, no fast you start a simple as that.
48:31 when you put together several multi processors a problem cash consistency. And this
48:39 a message item. So, you , for most of the nineties and
48:44 first use of this century Okay. processor. Yes, they are
48:49 Okay, yes. Forget about Now we have multi car architectures which
48:55 basically built in microprocessors and is yet . If you're BMB, If you
49:02 armed now, cash consistency issues are for you. So let's try to
49:09 by looking back to virtual memory and you buffering? And we look here
49:16 this picture and how do we Are you posted compared virtual memory on
49:26 left, you have virtual memory, essentially you have the process memory and
49:32 have a swept area. And when get expelled, if they are
49:38 you can record them from somewhere. they're dirty, they put back in
49:42 swamp area and they recovered Lee. the whole thing you realize because you
49:50 those transfers are transparent to the Those things they happen, you
50:00 by magic. And that's the beauty virtual memory. Your address space of
50:07 program is managed for you with some of the space in main memory,
50:13 parts elsewhere. Now let's talk about system courts. Remember that any system
50:21 will use, we'll use some card attracts. That means the transfer during
50:26 audio buffer and that this drives are to you. You do know what
50:32 will happen or a reasonable amount of . A few seconds. You can
50:38 them to happen by doing a And so far, nobody. You
50:41 this what the user controls of the calls between. Are you a buffer
50:49 made member? So essentially your vision when you do a read or write
50:56 your program is that you're just specifying between the main memory of your program
51:03 above. Right. Good. The spell so far as being This is
51:15 because you read and your rights do result into a disk Access. This
51:23 are very slow. Do you have there very, very fast.
51:32 but was the cost of transferring something the main memory in a buffer?
51:40 to context switches. The big rule you should be aware is that anytime
51:47 ask the colonel to do something trivial a program. The most important component
51:56 the cost is the cost of context . You are the example in real
52:01 , The example in real life is simple. You call the plumber you
52:08 call the plumber because you know, need to in style something new and
52:12 far. Or but sometimes you call atomic I'm a dripping faucet deployment,
52:21 . Cut the water and screw something , but a newly little piece of
52:28 or whatever back it will take exactly minutes. You get the bill from
52:34 plumber won the $20 Why? The was dominated by the cross of bringing
52:42 plumber to your home house. Call for the house girl and then peanuts
52:50 once we have the same situation But what I want you to notice
52:58 we have experts transfers here controlled by programmer. We had implicit transfers here
53:05 there. This implicit transfer make me that maybe there are more similarities between
53:16 fights. Have managing the virtual memory we're willing to accept. So we
53:25 the next slide, saying that in English, my partner. My friends
53:36 say Okay, unless you the virtual for everything. So when I open
53:43 file, I will associate with Manu , some range of address and my
53:49 memory, and then it will try access it. Fold, fold,
53:55 , fold, fold. I bring in so my read still exists.
54:01 they read inside my program. I get rid off the reeds completely and
54:09 Just, you know, my client honoree advice and access it using c++
54:16 for for by Tory's I could also I know I want to keep the
54:22 function, but those becoming the every extremely, extremely cheap now, what
54:28 the rights? Well, when I things, I just modified the bytes
54:34 memory and then, you know something the external page. Here, we'll
54:40 track off them till we need to something with that. When I modified
54:49 in my memory, corresponding to a off my father, you know,
54:54 be explored, why do we call pagers? Because they're not normal
55:01 Noble virtual memory system. When you your program bagels your memory here.
55:08 , When you close your program things thinks that to be saved. And
55:14 far so what we do here when process opens, a five full five
55:23 into the process, no data and then we bring the things on
55:27 man. What if you want to the five, you're going to share
55:34 . Second, So the Mac implementation to say, Well, okay,
55:41 have the usual virtue already paid. disrupt area. And this is responsible
55:48 one address free. Here I have not filed, and I use on
55:58 pager in the park system and this different rules. The biggest difference is
56:04 everything being modified needs to be saved , rather than being wiped out in
56:10 front. Do remarks there first. is a strong motivation to have larger
56:24 space. 32 bit address space works . Provide You don't open too many
56:33 files. Otherwise, for gigabytes is a bit tight. So we moved
56:45 64 date address spaces realize that 60 be to virtual memory is way too
56:53 . And then we settled for 48 ad and this already create some problems
57:02 the page table because we have, , several levels off page of pages
57:13 for you, the programmer. Nothing to change even though into address
57:20 you can still use all the system used to accept that their library function
57:27 the benefit is that library functions are . It will be different from scripting
57:36 . But you know, you program Java c++ or even the old see
57:43 function calls are very optimized. Some you have been in school for a
57:49 time, and I'm sure none off got a note on a program great
57:57 ta. You have too many function . Make your program ma analytics or
58:03 fashion? No. So it's wonderful . Little problems, which is my
58:14 worry here. How do you know exercise off a five before all the
58:20 were done through system problems. Now receive pages you find a tricky all
58:27 problems. The right I've done in speaks being guarantees they are coming.
58:37 means that multiple writers accessing the same will be even less reform. The
58:46 to that. It's a very simple . Unique fives are rarely shared,
58:55 when they're shared, Ihsan read all . If you want to share five
59:01 write mode and you know basic locks not are not sufficient, call it
59:08 database. They're essentially, you multiple conquer and writing to a
59:15 It's a database with data base base people they killed that French or lightweight
59:28 shared with her space on their parents be kernels supported or implemented user
59:35 The trend started to be implemented at level. I know they are hybrid
59:40 where they are half wish Colonel supported . I'm trying to use argument for
59:48 level. Something worked very well, for girls supported. This is essential
59:55 you want to do multitasking inside a . Now that we have all Tyco
60:02 , we like for some programs to able work and several course at the
60:06 time. Mark Virtual Inter Fix. Mike was designed, there was not
60:17 simple uniformed model of virtual memory. was quite the opposite, you
60:27 as the youth of the sixties experimented several ways. The architects of the
60:35 experiment with different multi processors pictures, so far, in this sense,
60:43 you look at architectures off computers. living now in a boring world where
60:49 is marriage with intel architectures, you a magic it Intel chips inside.
60:57 that's a real problem about, you , giving a user interface and be
61:01 for think and everything. They decided it will be consistent and even
61:09 even though some of the features will participle by some machine, the future
61:18 be present. But if you're around machine X, you go to a
61:25 . Full support for multi processing support and everything. Modular paging means
61:32 essentially we do mapping by giving external that mapping to the five system some
61:41 and also recoverable virtual memory. Everybody about recoverable virtual memory. This is
61:49 atomic transaction atomic transaction. He's that bring or system one state A to
62:00 B, and either it's successful or to state A. The best example
62:08 the atomic transaction is when you purchase on one hand, you you have
62:18 money and you have promised off alone hand. You have the owner,
62:26 is probably a alone, too, reimburse and expect some cash and a
62:32 of face could go around now the will be patients and so forth.
62:39 it's certainly what's happening is that you , you go to in this
62:46 officer, and essentially they decide to . Dozen of paper, literally.
62:52 bought the house, you know, spending time signing, signing and then
62:59 magic is Either everything goes through. have the house, give the guy
63:06 a cash the alone. It's paid . You have a new loan with
63:11 . Nothing happens. Then you go . How do you implement that?
63:18 great idea is recovered from virtual You start their transaction. You do
63:25 only operation in virtual memory. Special . That means that before you modify
63:31 , they have Old State. And started somewhere on this. Then they
63:37 , modifying, modifying, modified. yet everything is okay. Pass the
63:40 . Shave the old state, Save new state. Something is that Roll
63:45 to the Ulster and Mike was used in the eighties to do a very
63:53 and rather Slover transaction management system. memory made in place. Problem waas
64:04 incompatibilities? Yes, because they were on multiple machines. Culture is that
64:10 previously previously is designed for the Intel . So be is the virtual
64:17 the one that will know Berkeley essentially , assuming that everything will be like
64:25 . I heard a lot of stories that. Like I post classical Cirque
64:29 C is because all the PDP live then actually, so far. So
64:36 thou, uh, unique is architectures . They were influenced by what's happening
64:47 . So Mac designs won. The of the architectures need mutual.
64:54 So they did. The structures there a virtual memory were designed to be
65:04 independent off the system. And what they do? First, you have
65:11 realize most of the time the colonel's have to do anything with virtual the
65:19 main memory. And the only thing do is that is keeping the big
65:26 more about it. You'll be, went, so you know the big
65:35 to be dealt with. It is to do when there's a page fault
65:39 we have to bring a new and so otherwise nothing. So the
65:44 structures reason pH tape of memory object map their private to Mac. The
65:52 rate is not residents they stay track , which means that main memory memory
66:03 , a memory object is staying clean there. Area Are you backing story
66:13 area? I do like to stay object, but we'll start with address
66:21 . That's essential. And when I through the next slide, I want
66:26 to pay attention to it. Then . Sometimes the colonel has to interact
66:33 virtual memory. We're being paged limits and therefore there we have the
66:40 which is the memory of being the . There's a hard way if they
66:46 . And then, of course, interaction between those three day blocked while
66:50 is basically reporting. But all the dealing those three tapes is very
67:01 No, the address man. Let's it here. It's a circular.
67:11 know. It's a Double Inc Why do you go through a link
67:20 ? Essentially because they will not And because we use access them
67:27 The only exercise address map one of page. Hold on. When you
67:32 like what? Three pollinators? First working. Remember that what we saw
67:49 address ring the temptation to say, , we handle a code segment and
67:58 for five and so forth will will to use a segmented architect. Segmental
68:05 are pain in the neck. Use program because you cannot move large at
68:12 space. The segment boundaries do You know, Mike decided will be
68:19 . Race in virtual memory from this has this is marriage and what he
68:32 you Rachel address. It's not this so range here. It's supposed that
68:47 side object is the execute herbal somewhere the file system and we started
68:56 Zero For all this range of We get this protect and you
69:04 since he is a good segment, good segue, Monday's no right
69:09 maybe readable and surely exist pointers here for the nation. Now we have
69:19 specify the inheritance inheritance. Say, do we do when we create a
69:27 ? Using for the code segment can shared with parent and child. We
69:36 pretend they're totally different, but nobody see the day just like you
69:41 if you're around gcc um, Iran . We will fare the same code
69:47 and believing we have to some The truth is that read Onley data
69:53 be shared very easy. Then you he say Well, okay.
70:08 I took you the semantics off the for the files. What's happening when
70:19 for you know, the charge in often find So basically I the range
70:26 reversal fights is shared because of this of a range of address I can
70:35 read only find I can access read finds for So I have all the
70:42 here to do two things first to memory in that trial and I also
70:52 on the have also that great processing Attribute here three value can be copy
71:06 . Don't do anything. Forget regular roots segment. We shared China copy
71:17 data segment and we we can modify evaluation Mark possible posed as much as
71:34 evaluation of tasks because we suppose that be unnecessary. So copying whole data
71:43 apparent process before what to do We use copyright. Sure, you
71:49 back. There were enforced all that . European writers are the present accent
71:56 so far I don't think I need explain that in too much. The
72:00 is getting close to the end I finish page replacement policy. They wanted
72:08 page of priests and policy that waas nude. The dummies will probably implemented
72:15 there any architectures. So they decided use a very simple one. What's
72:24 is that the memory is managed as large global fight for pool. Why
72:32 ft is very simple to implement does require any special hardware to do it
72:40 we can do on any machine. problem is that 5 ft does not
72:46 between pages that are being used repeatedly pays or used only once, so
72:54 pretty terrible. So what's happening here expelled ages go on a second chance
73:04 view and they can be reclaimed on you If you get access, then
73:11 know, when they moved to the que they find felt. I don't
73:18 a the slides. You think But, you know, they were
73:25 . What? Have a page reference available. And then they say,
73:30 we can refine these and minimizing the transfers. And so so the only
73:39 of policy is that it does not real time process. Advantage is very
73:49 . You could be tend to Hey, it looks like a little
73:51 like the Windows Policy is the ancestor policy. No, the Ancestor Windows
73:58 Waas, the VMS policy and this dated by several years. So it's
74:03 simplification we could think about locks and . Oh, deadlocks are a
74:18 We heard in any course supreme system section about that log prevention have Berman's
74:26 condition and then any good in You This is wonderful in theory,
74:31 in practice, you know any system you have exchanged messages car Vermant conditions
74:39 be Yeah, you read out. Here they were able to deadlock prevention
74:46 building system did not free from the . So this is interesting because this
74:51 a case of the theory. Works works absolute now total sized machine dependent
75:01 of 3rd 16 kilobytes. Do memorize the big for a copy and write
75:07 to implement efficient message passing between custom same machine you know normally, when
75:15 do, exchange of data between two in the same machine. You have
75:20 methods. The fast methods is shared to save Methodist Church. If message
75:29 nothing is shared, You know, are you data? You do whatever
75:34 want with them. Take damage so , Mark as accent was doing
75:41 Use copy and write to say, , this is shared. But I
75:46 see what you are doing, and can see what I'm doing. So
75:50 had the benefits of both shared What are shared library? When you
75:58 programs, you will notice that many those C programs and so forth use
76:03 same libraries the libraries air read Why not to share So essentially,
76:09 you do with shared libraries that when load the programming to main memory below
76:15 binary, you do know the libraries already two main memory them if need
76:23 , use them and very much more in doing. I want this list
76:28 being wasted by multiple copies Thieves, . And also, when you fetch
76:35 , you fish in the past come the market problems with inverted based able
76:47 rt The machine no, for forgot paid stables, but they were using
76:57 based tables. Also know a hash eight. They were one hashed paste
77:03 entry for memory frame in main memory the sister was designed to make it
77:13 to implement. Shared PhD. I . They've had to belong in one
77:18 or so the Mac implementation rt of based table means that, you
77:24 they changed the thing about it. page stages, like some of the
77:31 to passport in many case, is simple, very convenient. You gain
77:39 your nationality, you keep the previous and sometimes you know one passport gives
77:46 access to some countries or the other go. For instance, even American
77:51 is a visa to go to I am a Belgian citizen. European
78:00 . I enter with no problems that some cases impossible. So essentially,
78:07 way they do that here is you ? Okay, you want Texas saying
78:12 are Belgium, then you want to on your passport, OK, you
78:17 become friends, become belt. Mac offers the future. Wanting you
78:24 very bad comments paper. It's hard read but cover sort of ground.
78:36 the concepts, read my summary, by the power points line. You
78:48 it took me sometimes to make the with the with the page table handling
78:57 the address. Strange. I spent for a reason. This is fundamental
79:03 the way Mac work, so pay to it more about Mac. Toe
79:14 provides unique simulation through either unique simulator the kernel or are unique simulation server
79:22 use the space. So they tried do a micro Carla. Of
79:27 micro kernel introduced extra context, which they are not a good idea.
79:35 even try to emulate unique through a of specific servers, all the use
79:40 space, the loose project heard. think this is finished. The staff
79:50 stopped. Question for the for grace now Lennox is an accident. We
79:58 have a new operating system. The team and Richard Stallman wanted to write
80:07 whole upgrading system and they start. they use this hard approach because they
80:16 told by the smart people. That the way to do future. Belongs
80:21 micro kernels and micro kernels will have modules. And so forth was a
80:28 Stallman extended How it was making the complicated, difficult, and making you
80:35 fast was even more difficult. So happening is that the new project to
80:41 with a hard colonel went to nowhere you have this guy in Finland that
80:49 a colonel specifically tailored for the intel of the time. And he got
80:56 project on time and running with a performance. That's why you have this
81:01 slash no system. Which means that believing the gospel is not the rial
81:09 to do things right. In the designer off Lennox, the Linux
81:21 did the thing they were not supposed do, but it was successful and
81:26 the competition, so that should be little inspiration, So Okay,
81:44 with a
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