[CS61C FA20] Lecture 28.1 - OS & Virtual Memory Intro: Intro — Transcript

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1. 0:00[Music]
2. 0:11hello there
3. 0:12welcome back to a new module in 61c in
4. 0:16which we are going to cover
5. 0:18the basics of operating systems and
6. 0:21understand how does the virtual memory
7. 0:23work
8. 0:24okay so let's get into it and orient
9. 0:28ourselves
10. 0:29in the traditional picture of machine
11. 0:31structures
12. 0:32we have been dealing with the
13. 0:34instruction set architecture and we
14. 0:36approached it with both sides from the
15. 0:37software side
16. 0:38and from the hardware side most recently
17. 0:41we understood how does the processor
18. 0:43work and how does it work
19. 0:45with the on-chip cache
20. 0:50what we are going to do now we are going
21. 0:52to add some more stuff around it
22. 0:54first we are going to add the operating
23. 0:56system
24. 0:58like what we will see function basic
25. 1:01functions that terminator on linux or
26. 1:02mac os or
27. 1:04windows and then talk about the
28. 1:08input and output to our computer and
29. 1:11then we are going to extend that to
30. 1:13cover how do we work with the memory
31. 1:16um especially how does the main memory
32. 1:19work together with the storage
33. 1:23okay so if you take a look into our
34. 1:25picture
35. 1:26of new school machine structures we are
36. 1:29now dealing
37. 1:30with the way how we would support
38. 1:32parallel threads
39. 1:33in our computers as well as
40. 1:37with the topics that are related to the
41. 1:40main memory
42. 1:42and also very importantly now we are
43. 1:44revealing the complete
44. 1:46picture of the locality and memory
45. 1:49hierarchy
46. 1:50so we see the whole pyramid now so we're
47. 1:54going to fill it in
48. 1:56we are going to look into our we looked
49. 1:58in in our caches
50. 2:00and now you're going to really
51. 2:01understand how does the physical memory
52. 2:04in this case dram work with ssds and
53. 2:07magnetic disks
54. 2:08to implement the virtual memory
55. 2:12when we are done with that we'll have
56. 2:14this complete illusion
57. 2:16of infinitely fast and infinitely large
58. 2:18memory
59. 2:20so let's recap one more time where we
60. 2:22are so far
61. 2:23in 61c so far we started with c
62. 2:27and in project one we built a relatively
63. 2:30small but fun and effective c program
64. 2:34then in project 2
65. 2:38in this course we started risk 5
66. 2:40assembly and we built
67. 2:42another project
68. 2:45in there in project 2 we built a risk 5
69. 2:48assembly a functionality five assembly
70. 2:50program then in project three
71. 2:52we built the data path for a risk five
72. 2:56processor
73. 2:57and now conceivably
74. 3:00pretty much any of these c programs that
75. 3:02we have written
76. 3:03or the assembly programs can run on this
77. 3:05data path we have extended that
78. 3:07to add the cache to improve the
79. 3:10performance and be able to
80. 3:12run fairly complex programs on our data
81. 3:16path
82. 3:17and then we conceptually introduced
83. 3:19memory but we didn't really go
84. 3:21in depth of the memory that's what we
85. 3:23are going to do now
86. 3:27but we have built a lot of really cool
87. 3:30components
88. 3:31but we really haven't built a computer
89. 3:34um
90. 3:34i mean let's take a look at a real
91. 3:36computer like a laptop
92. 3:38how is a laptop different than what we
93. 3:40have built so far well the
94. 3:41laptop surely does have a processor
95. 3:45and has a memory and has cache
96. 3:49but it has a few other things
97. 3:53that makes it a lot easier to run a c
98. 3:56program
99. 3:57uh to enter a c program and to see the
100. 3:59results well namely it does have a
101. 4:01screen display where we it can
102. 4:04output the results such that we can
103. 4:06conveniently view them
104. 4:08it has a keyboard that enables us to
105. 4:10enter things to input things into our
106. 4:13computer and has storage it has
107. 4:17disks inside in more modern computers it
108. 4:19is typically a solid-state drive
109. 4:22in some more older ones um we will
110. 4:25typically encounter
111. 4:27magnetic hard disk drives
112. 4:30so what do we need to do in this module
113. 4:32are a few steps
114. 4:35you know the most importantly we're
115. 4:36going to take a picture that we are
116. 4:38reasonably familiar with now
117. 4:39and we need to add input output first
118. 4:43to that so we are going to study
119. 4:47relatively briefly but hopefully
120. 4:49effectively how do we add
121. 4:51input output devices to our computer and
122. 4:54that will provide a uniform way to hook
123. 4:57up our screens
124. 4:59keyboards and storage
125. 5:04so that's what is going to happen here
126. 5:06we are going to see how does the memory
127. 5:08dram work and then how do we add storage
128. 5:11and how do we work with the i o
129. 5:15besides full fledged laptops
130. 5:18there are many other simpler computers
131. 5:22that are around us there is a number of
132. 5:24them that are called
133. 5:25single bore computers and one of them
134. 5:28that is particularly popular
135. 5:31that really opened up this space of
136. 5:34single board computers
137. 5:35is the raspberry pi so you can buy a
138. 5:37raspberry pi i have a
139. 5:38very many of them here is a raspberry pi
140. 5:424 that you can buy for
141. 5:4635 this one has a little bit more dram
142. 5:49on it so it's a little bit more
143. 5:52expensive you know 40 something dollars
144. 5:55and you'll
145. 5:56start noticing familiar things on it
146. 6:00there is a processor on it and i'll
147. 6:02click here
148. 6:03processor is the silver thing in the
149. 6:05middle
150. 6:06there is a dram chip next to it and i
151. 6:08put some thermal glue on it
152. 6:10uh because i was using this one this
153. 6:12black chip
154. 6:13is the dram and that's our
155. 6:16our main memory that's you know that
156. 6:19that
157. 6:20rectangle that we've been showing so far
158. 6:22that's our memory we're going to see
159. 6:23how do we work with that um then
160. 6:26um our storage is going to be a flash
161. 6:29card here we don't really have a solid
162. 6:31state drive although we could hook up a
163. 6:33solid state
164. 6:34drive to it but the main memory here is
165. 6:35a flash card like the one
166. 6:37that we use in in
167. 6:41cameras or music players
168. 6:44and so on um then you know it's called a
169. 6:48secure digital card or sd card in this
170. 6:51case it's based on a
171. 6:52so-called flash memory we'll talk a
172. 6:54little bit more about that
173. 6:56um then there is a
174. 7:00screen i o we can hook up screens
175. 7:03to these two hdmi ports we can
176. 7:06add io in the form of a serial bus
177. 7:10there are four um serial ios of
178. 7:13in your universal serial bus type we can
179. 7:16get
180. 7:17add wired ethernet to it
181. 7:20this thing supports wired ethernet and
182. 7:22finally the silver chip
183. 7:24is essentially wi-fi so we have wi-fi
184. 7:28and bluetooth connectivity
185. 7:29as other types of ios so we're going to
186. 7:33take a look into the ways how these
187. 7:35things
188. 7:35actually do hook up to our processor
189. 7:38and the picture is going to be fairly
190. 7:40straightforward hopefully
191. 7:42and uniform but when we do that when we
192. 7:45add our i o to this fairly simple single
193. 7:48board computer
194. 7:50we have a real computer i mean you can
195. 7:52actually
196. 7:53run this class learn this class just by
197. 7:55using a raspberry pi
198. 7:58in this setup what we have we have a
199. 8:00raspberry pi
200. 8:01[Music]
201. 8:02with two screens a keyboard
202. 8:05and a mouse connected to it and it runs
203. 8:09unix linux a form of linux
204. 8:12and it and a whole bunch of applications
205. 8:15that go with that
206. 8:18even more than that you can actually
207. 8:21learn
208. 8:22computer architecture by examining
209. 8:24things and running all the labs
210. 8:26or many of the labs on raspberry pi
211. 8:28there is actually a really good textbook
212. 8:30that i really like that goes
213. 8:32slightly below the level of what we
214. 8:34cover in 61c
215. 8:35um this is the the the book that is
216. 8:39learning computer architecture with
217. 8:40raspberry pi and by the way
218. 8:42you can if you're a cal student you can
219. 8:46download it for free from this address
220. 8:47we are subscribed
221. 8:49uh our library has infinite number of
222. 8:51online copies of that book
223. 8:53so feel free to take a look at it and
224. 8:54browse to it
225. 8:56we are not using it in this class
226. 8:58because again conceptually it's a bit
227. 9:02lower level and
228. 9:05it is arm based so it's not as open as
229. 9:09we would like it to be it's a little bit
230. 9:11harder to build
231. 9:12your arm type of processors
232. 9:16um our labs would have been a lot more
233. 9:18complicated will not have been able to
234. 9:20accomplish
235. 9:20as much but it has a really good
236. 9:23treatment the book has really good
237. 9:24treatment of how do you deal with these
238. 9:27ios and memories and so on
239. 9:29and how do you see the computer
240. 9:33from the applications point of view
241. 9:36os's point of view and how do you run
242. 9:39things how do you hook up these input
243. 9:41and output devices
244. 9:43and there is a number of cool simple
245. 9:44experiments that are in there
246. 9:47one day when the single board computers
247. 9:50they're based on risk five
248. 9:52um are more affordable and more
249. 9:54widespread there are some but
250. 9:55they're a bit expensive if they're in
251. 9:58this class
252. 9:59or um if there are a lower class
253. 10:02they don't just support exactly what we
254. 10:04need beyond what we are doing in this
255. 10:05class
256. 10:06when these become a little bit more
257. 10:07widespread i'm sure we are going to see
258. 10:10um labs that are based on that
259. 10:14so check it out for now so
260. 10:19but there's another glitch here another
261. 10:22quirk
262. 10:23that we didn't quite cover um
263. 10:27it's you know what we have done so far
264. 10:29it's not really quite the same
265. 10:31with what we are seeing on a raspberry
266. 10:33pi computer or any other computer
267. 10:36the screen in raspberry pi looks a lot
268. 10:38different than what we get
269. 10:40out of our venus in venus we just
270. 10:43ran relatively short programs but we
271. 10:46always ran
272. 10:47a single program we could make it a lot
273. 10:49bigger a lot more complicated but it was
274. 10:50always just one computer
275. 10:53but our computer runs many programs at
276. 10:56the time a real computer runs many
277. 10:57programs over time
278. 10:59and what we'll do to try to convince you
279. 11:01that changes to the hardware
280. 11:03are minimal to be able to do this
281. 11:07this whole thing is just software
282. 11:11hardware is pretty much there you know a
283. 11:13few minor things that need to be added
284. 11:14but here and there
285. 11:16and that magical software that does that
286. 11:18is the operating system
287. 11:20so you're going to get into the
288. 11:21functions of the operating system just
289. 11:23after a quick break see you then