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1 files changed, 396 insertions, 398 deletions
diff --git a/en_US.ISO8859-1/captions/2006/mckusick-kernelinternals/mckusick-kernelinternals-1.sbv b/en_US.ISO8859-1/captions/2006/mckusick-kernelinternals/mckusick-kernelinternals-1.sbv index 7f564d1d33..8d3b93ab6d 100644 --- a/en_US.ISO8859-1/captions/2006/mckusick-kernelinternals/mckusick-kernelinternals-1.sbv +++ b/en_US.ISO8859-1/captions/2006/mckusick-kernelinternals/mckusick-kernelinternals-1.sbv @@ -9,8 +9,8 @@ and mainframes have ruled the world which is to say the sixties and seventies 0:00:18.429,0:00:22.460 -however by 1970s a new breed of mammals had began to show up on -the scene, +however by 1970s a new breed of mammals had begun to show up +on the scene 0:00:22.460,0:00:24.240 known as mini computers @@ -35,11 +35,11 @@ UNIX operating system Ken Thompson who had been an alumnus at Berkeley 0:00:42.040,0:00:46.100 -came back on a sabbotical in 1975 bringing UNIX +came back on a sabbatical in 1975 bringing UNIX with him 0:00:46.100,0:00:47.539 -In the he was there +In the year that he was there 0:00:47.539,0:00:51.330 he managed to get a number of graduate students interested @@ -56,21 +56,21 @@ Bill Joy has taken over in running the UNIX system and in fact continuing to develop software for it. 0:01:00.470,0:01:04.339 -Bill began packaging up the software that have +Bill began packaging up the software that had been developed under Berkeley UNIX and 0:01:04.339,0:01:05.779 and distributing it 0:01:05.779,0:01:08.040 -as the Berkeley Software Distribution +as the Berkeley Software Distributions 0:01:08.040,0:01:12.310 whose name was quickly shortened to simply BSD 0:01:12.310,0:01:16.330 BSD continued to be distributed with -yearly distribution for almost fifteen +yearly distributions for almost fifteen 0:01:16.330,0:01:17.490 years @@ -127,7 +127,7 @@ two groups sprung up to continue supporting BSD 0:02:03.600,0:02:08.080 -the first of this is the NetBSD whose primary +the first of this was the NetBSD whose primary goal was to support 0:02:08.080,0:02:10.459 @@ -146,27 +146,27 @@ The other group that sprang up was FreeBSD. 0:02:22.419,0:02:28.239 Their goal was to bring up BSD and support -as wide set of devices as possible on the +as wide a set of devices as possible on the 0:02:28.239,0:02:29.719 PC architecture. 0:02:29.719,0:02:36.549 They also had a goal of trying to make the -the system as easy to install as possible to + system as easy to install as possible to 0:02:36.549,0:02:39.309 attract by a wide group of developers 0:02:39.309,0:02:42.319 -I chose to primarily work with the FreeBSD +I chose to work primarily with the FreeBSD group 0:02:42.319,0:02:43.740 both doing software 0:02:43.740,0:02:46.140 -and also together with George Neville +and also together with George Neville Neil 0:02:46.140,0:02:51.069 writing this book ""The Design and Implementation @@ -216,7 +216,7 @@ that's what I know best and that's what the textbook is organized around 0:03:26.379,0:03:29.979 -but the fact that the matter is back it's really +but the fact of the matter is that it's really 0:03:29.979,0:03:32.339 a class about your UNIX and that @@ -289,7 +289,7 @@ in that, it has to have the same effect 0:04:23.909,0:04:27.319 -and so until you get down to the really niddy +and so until you get down to the really nitty details 0:04:27.319,0:04:29.600 @@ -327,7 +327,7 @@ that. Okay so 0:04:54.569,0:04:59.279 -the other thing is I'm going to assume that +the other thing is that I'm going to assume that all of you have used the system. I get 0:04:59.279,0:05:00.910 @@ -338,7 +338,7 @@ you know raise the hands and ""Hey, what's a Shell?"" 0:05:04.249,0:05:07.990 or I don't -put a lot of code up but a small piece of code and someone said ""Why +put a lot of code up but a one piece of code and someone said ""Why 0:05:07.990,0:05:11.819 are there two pipe symbols in the middle of @@ -353,7 +353,7 @@ So hopefully you can tell the difference between Shell scripts and C code. 0:05:19.970,0:05:21.990 -okay but I am but am gonna assume +so okay but I am but am gonna assume 0:05:21.990,0:05:24.610 you haven't really looked inside the system. @@ -379,7 +379,7 @@ levels of knowledge and so 0:05:37.900,0:05:42.620 -the way that I find works best the sort of +the way that I find works best to sort of be useful to everybody is that three pass 0:05:42.620,0:05:43.860 @@ -400,23 +400,23 @@ same material again but at a lower level of detail 0:05:55.300,0:05:59.939 -then i finally go back and go through a very neatly +then i finally go back and go through a very nittily low-level of detail 0:05:59.939,0:06:04.649 -and the fact that is if you are learning new stuff +and the fact of this is if you are learning new stuff as I'm doing the high-level thing 0:06:04.649,0:06:08.649 you are gonna be utterly washed by the time I get to -low level nearly details +low level niggly details 0:06:08.649,0:06:10.699 but since I'm going to do it topic by topic 0:06:10.699,0:06:14.190 when I get to the end of one of those nearly -low level details +low level niggly details 0:06:14.190,0:06:17.900 i'll give you a clue as i will say ""Brain @@ -426,7 +426,7 @@ reset, I'm starting a new topic"" so even if you're completely lost 0:06:19.330,0:06:23.530 -you can now start listening again plus am gonna get +you can now start listening again plus I'm gonna get the broad brush up again. 0:06:23.530,0:06:27.059 @@ -437,7 +437,7 @@ this stuff already you'll probably find the broad brush rather boring 0:06:31.770,0:06:35.759 -but by the time i get down nearly low level +but by the time we get down to nearly low level details I think you'll actually 0:06:35.759,0:06:37.860 @@ -460,14 +460,14 @@ I am gonna start out by just walking through and giving you the 0:06:53.089,0:06:56.919 -outline of what we're going to try and do +outline of what we're going to try and do here here 0:06:56.919,0:07:01.169 As i said we're going to go roughly 0:07:01.169,0:07:03.270 -about two-and-an-half hours of lecture +just about two-and-an-half hours of lecture 0:07:03.270,0:07:04.729 about two hours forty minutes @@ -486,7 +486,7 @@ This is as I said we're going to start from the top 0:07:13.860,0:07:15.749 -and just start working our way down +and then just start working our way down 0:07:15.749,0:07:19.350 so the general thing I'm going to do is @@ -503,7 +503,7 @@ you've worked with that system and then 0:07:27.249,0:07:29.739 -sort of layout terminology +you have to sort of layout terminology 0:07:29.739,0:07:32.080 although we use normal english words @@ -519,7 +519,7 @@ common usage and 0:07:39.220,0:07:42.330 -I will just sort of lay out the terminology +so I will just sort of lay out the terminology lay out the 0:07:42.330,0:07:45.750 @@ -543,10 +543,10 @@ that is done so here in 0:07:59.970,0:08:01.400 -Week 2 +Week number 2 0:08:01.400,0:08:05.450 -%uh we're gonna look at the system from the +we're gonna look at the system from the perspective of 0:08:05.450,0:08:07.039 @@ -556,19 +556,19 @@ something that manages processes. 0:08:08.720,0:08:12.170 -One way of looking at the kernel it's really +One way of looking at the kernel is it's really just a 0:08:12.170,0:08:16.440 the resource manager and the resource that -is managing are things going to do with processes +its managing are things going to do with processes 0:08:16.440,0:08:19.460 So we'll look at a process, what the structure of it is 0:08:19.460,0:08:20.649 -%uh and +and 0:08:20.649,0:08:23.559 talk about the different ways that they can @@ -582,7 +582,7 @@ and can have one thread running in it can have multiple threads running in it. 0:08:29.749,0:08:34.620 -we'll talk about the different ways +so we'll talk about the different ways that we think a process is. 0:08:34.620,0:08:38.480 @@ -597,7 +597,7 @@ to lay out the bits and pieces that need to be managed 0:08:42.020,0:08:44.660 -%uh and then talk about +and then talk about 0:08:44.660,0:08:47.190 how we do that. @@ -613,18 +613,18 @@ hasn't made it into Linux yet although 0:08:56.320,0:09:01.630 -%uh the concept is %uh being actively worked +the concept is being actively worked on so my guess is that you'll see that 0:09:01.630,0:09:03.500 -%uh fairly soon. +fairly soon. 0:09:03.500,0:09:06.360 -%uh will also then talk about scheduling +we'll also then talk about scheduling 0:09:06.360,0:09:10.579 which is in essence how we decide what gets -to run, when it gets to run, how long it takes +to run, when it gets to run, how long it gets 0:09:10.579,0:09:13.500 to run, etc. @@ -641,7 +641,7 @@ Signals aren't really part of virtual memory but they didn't fit into next week's 0:09:23.800,0:09:26.400 -material so I just would drop that at the +material so I just would dropped that at the beginning 0:09:26.400,0:09:29.850 @@ -662,7 +662,7 @@ trying to use their address spaces and we will talk about 0:09:39.590,0:09:41.410 -essentially how you will make all that work +essentially how you will make that all work 0:09:41.410,0:09:43.510 It's called a virtual memory because it's @@ -683,15 +683,15 @@ get us through looking at the world as if it was all 0:09:58.340,0:10:00.560 -all about processes +all about processes. 0:10:00.560,0:10:03.880 -and in Week 4 we change gears. we say +Then in Week 4 we change gears. we say okay well you know 0:10:03.880,0:10:07.570 -the kernel isn't just about processes. You can sort of look at it orthogonally -and you can +the kernel isn't just all about processes. You can sort of +look at it orthogonally and you can 0:10:07.570,0:10:10.000 say it's really just a giant I/O switch @@ -713,8 +713,8 @@ so let's look at it from that perspective. And 0:10:19.310,0:10:24.740 -%uh we'll start with special files, again this -where the interface when you talk about UNIX +we'll start with special files, again this +sort of the interface when you talk about UNIX 0:10:24.740,0:10:25.880 systems, when you talk about @@ -731,14 +731,14 @@ and we'll look at how that's organized and the structure of it 0:10:37.220,0:10:41.840 -%uh which is to be fairly simple but in the +which used to be fairly simple but in the last decade has gotten 0:10:41.840,0:10:43.670 incredibly complicated. 0:10:43.670,0:10:48.540 -We will also talk about sudo terminals in +We will also talk about pseudo terminals in job control 0:10:48.540,0:10:53.330 @@ -761,14 +761,14 @@ Okay we will then continue in Week 5 with the kernel I/O structure, 0:11:11.430,0:11:16.090 -%uh We will start with multiplexing of I/O. The -kernel has done this +We will start with multiplexing of I/O. The +kernel of course has done this 0:11:16.090,0:11:17.360 always 0:11:17.360,0:11:22.110 -but we will really talking more about how do +but we're really talking more about how do we export I/O multiplexing to 0:11:22.110,0:11:25.970 @@ -784,7 +784,7 @@ Auto configuration is what happens 0:11:32.770,0:11:36.619 -and typically or historically I guess you +typically or historically I guess you could say as the system boots. 0:11:36.619,0:11:39.500 @@ -815,23 +815,23 @@ anytime you plug a new I/O device, a PCMCIA card, 0:12:00.550,0:12:03.680 -you remove a disk or you put in a new disk. +or you remove a disk or you put in a new disk. 0:12:03.680,0:12:07.010 -Any sort of activity that changes the the I/O +or any sort of activity that changes the I/O 0:12:07.010,0:12:08.360 structure of the machine 0:12:08.360,0:12:10.870 -auto configuration has to fired back up +auto configuration has to get fired back up 0:12:10.870,0:12:13.050 and figure out what's disappeared 0:12:13.050,0:12:18.330 and cleanup and figure out what new has arrived -to conongiure it in. +to configure it in. 0:12:18.330,0:12:19.320 and then we'll talk @@ -841,7 +841,7 @@ a little bit about the configuration of the device driver 0:12:23.870,0:12:27.390 -this actually gets into an area of that +this actually gets into an area that 0:12:27.390,0:12:28.660 is @@ -854,7 +854,7 @@ of advice to the class esspecially those of you who work in system administration. 0:12:36.780,0:12:42.010 -You'd really want to be careful that +You really want to be careful that you don't learn too much about device drivers 0:12:42.010,0:12:44.670 @@ -874,8 +874,8 @@ because if you become an expert or viewed as an expert in any of these areas 0:12:54.960,0:12:59.370 -you will become the designated stocky for -that and your psyche you'll never get to do +you will become the designated stuccy for +that and your site you'll never get to do 0:12:59.370,0:13:01.760 anything @@ -884,7 +884,7 @@ anything but that 0:13:02.610,0:13:07.360 -The three things that I highly +so The three things that I highly recommend not learning very much about are 0:13:07.360,0:13:09.060 @@ -901,7 +901,7 @@ with LDAP or anything in that general domain 0:13:19.350,0:13:22.660 -%uh because as I say +because as I say 0:13:22.660,0:13:24.900 that will become your life's work @@ -914,22 +914,22 @@ there's other things that you might find more interesting. ""Do you have a question?"" 0:13:33.870,0:13:36.659 -so one of my students empathized with my point +so one of my students empathizes with my point 0:13:36.659,0:13:39.640 I believe you said you worked on that mail system 0:13:39.640,0:13:43.120 -%uh so you you might know something about -Sum mail configuration files but you don't +so you you might know something about +Sendmail configuration files but you don't 0:13:43.120,0:13:47.850 have to answer that 0:13:47.850,0:13:52.100 -so we're going to talk about what a device -driver does and really just the entry +okay so we're going to talk about what a device +driver does and really just sort of the entry 0:13:52.100,0:13:53.170 points to it @@ -943,35 +943,35 @@ or much of anything about it. I actually used to teach an entire class believe it or not 0:14:01.490,0:14:02.720 -about the device drivers +about device drivers 0:14:02.720,0:14:05.849 -%uh but then I realized a year i waste +but then I realized the error of my ways and I have since 0:14:05.849,0:14:12.580 -i gone through and made a point of forgetting + gone through and made a point of forgetting every slide in that talk. 0:14:12.580,0:14:16.860 -so then we will move on to Filesystem +okay so then we will move on to File system 0:14:16.860,0:14:21.540 -and as always will start at the high level +and as always we'll start at the high level talk about the interface what is it that is 0:14:21.540,0:14:23.020 exported out of the system 0:14:23.020,0:14:27.840 -%uh and then we will start diving down in sea and +and then we will start diving down in the C and how do we go about implementing that 0:14:27.840,0:14:29.010 -%uh so +so 0:14:29.010,0:14:31.010 -we'll start with that +we'll start with the 0:14:31.010,0:14:32.560 so called @@ -984,11 +984,11 @@ it's historically been called buffer cache 0:14:36.140,0:14:38.590 -and it's still recalled that periodically +and you still hear it called that periodically 0:14:38.590,0:14:42.720 -and the fact that the matter is that there isn't really -about buffer cache anymore,thers is just one big +and the fact of the matter is that there isn't really +about buffer cache anymore, there is just one big 0:14:42.720,0:14:44.620 cache in it.Its the VM cache @@ -1012,15 +1012,15 @@ pages of memory because that just leads to trouble. 0:14:59.390,0:15:03.390 -But Filesystems think that they have buffers and so -there's been a year where we make +But Filesystems think they have buffers and so +there's this manouver where we make 0:15:03.390,0:15:06.149 these things that look like what historically were buffers 0:15:06.149,0:15:08.830 -that really just happened just really map into VM system +that really just map into VM system 0:15:08.830,0:15:11.720 but they're still managed in the way that @@ -1030,7 +1030,7 @@ they have been managed historically 0:15:15.020,0:15:20.670 -We will then get down into Filesystem implementation +okay We will then get down into Filesystem implementation the local file system if you will 0:15:20.670,0:15:23.400 @@ -1040,7 +1040,7 @@ and into also soft updates and snapshots. 0:15:25.730,0:15:26.440 -on this + this 0:15:26.440,0:15:31.100 for the time being is something that you see @@ -1054,18 +1054,18 @@ which is %uh more commonly used for example what is used by ext3 0:15:39.630,0:15:41.179 -so i'll go through soft updates and +and so i'll go through soft updates and 0:15:41.179,0:15:45.260 a lot of the issues in soft updates are the same issues that you have to deal with journalling 0:15:45.260,0:15:48.370 -what is it that we're protecting and how we +what is it that we're protecting and how do we go about doing that 0:15:48.370,0:15:51.150 -and the differences is in the detail. +and the difference is in the detail. 0:15:51.150,0:15:54.630 There is actually a paper in the back to your @@ -1075,7 +1075,7 @@ notes if this is something that interests you 0:15:55.240,0:15:59.930 -%uh it's a comparison of journalling versus +it's a comparison of journalling versus soft updates that was done 0:15:59.930,0:16:02.120 @@ -1086,7 +1086,7 @@ and not to spoil the punch line but the answers they both work about are the same 0:16:08.460,0:16:12.500 -Okay the snapshots again is something that +Okay snapshots again is something that if 0:16:12.500,0:16:15.920 @@ -1098,21 +1098,22 @@ aware of what snapshots are and how they do or don't work for you 0:16:19.640,0:16:21.959 -this is this the same functionality +this is the same functionality 0:16:21.959,0:16:27.380 -%uh in the Filesystem implemented in a +in the Filesystem implemented in a somewhat different way 0:16:27.380,0:16:28.449 -%uh so this +okay so this 0:16:28.449,0:16:31.940 -that Week 6 is really going to be the local +Week 6 is really going to be the local file system 0:16:31.940,0:16:34.750 -the disk connected to the machine you work. +the disk connected to the machine +that we are dealing with. 0:16:34.750,0:16:39.140 Week 7 then we get into multiple @@ -1140,7 +1141,7 @@ with a Linux machine you can run the ext2 or ext3 0:16:58.310,0:17:01.020 -%uh and it will perfectly happily do that +and it will perfectly happily do that 0:17:01.020,0:17:01.620 so @@ -1156,21 +1157,21 @@ Filesystems that we want to support another area of which there's been a great 0:17:12.250,0:17:15.309 -deal of growth at least in coding complexity +deal of growth at least in code complexity 0:17:15.309,0:17:17.840 is so-called Volume Management 0:17:17.840,0:17:19.370 -%uh so in the +so in the 0:17:19.370,0:17:24.480 good old days a Filesystem lived on a disk or piece of disk and that was that 0:17:24.480,0:17:26.130 -but this day and age +but in this day and age 0:17:26.130,0:17:31.150 that won't do any more so we aggregate disks @@ -1180,7 +1181,7 @@ together by striping them or RAID arraying them 0:17:31.980,0:17:33.380 -and we need such really things +or various other things 0:17:33.380,0:17:39.210 and we need a whole layer in the system just to @@ -1200,11 +1201,11 @@ but that's not because this is the world's best remote file system 0:17:51.090,0:17:55.240 -or the cleanest design or any of the thing +or the cleanest design or any of the properties you might hope that 0:17:55.240,0:17:57.049 -such a class is this one would have +such a class as this one would have 0:17:57.049,0:17:58.600 but it's ubiquitous @@ -1216,13 +1217,13 @@ very widely used and 0:18:01.350,0:18:06.850 -we're going to talk about that one +so we're going to talk about that one 0:18:06.850,0:18:07.740 -we'll +okay we'll 0:18:07.740,0:18:10.970 -then once again switch gears on Week 8 +then once again switch gears in Week 8 0:18:10.970,0:18:17.120 and turn our attention to of Networking and @@ -1239,18 +1240,18 @@ go through, we'll go with concepts, the terminology that gets used 0:18:24.450,0:18:30.230 -and what's difference between domain +and what's the difference between domain based addressing and an address domain you know 0:18:30.230,0:18:30.910 we'll go through 0:18:30.910,0:18:34.910 -well what the basic IPC services are, + what the basic IPC services are, 0:18:34.910,0:18:39.080 -essentially what all the system calls that -has anything to do with networking +essentially what are all the system calls that +have anything to do with networking 0:18:39.080,0:18:40.590 and @@ -1263,10 +1264,10 @@ and I'm going to go through a somewhat contrived example 0:18:45.830,0:18:49.840 -it makes use of every one of those interfaces +that makes use of every one of those interfaces 0:18:49.840,0:18:52.860 -and just to show how they all conected +and just to sort of show how they all connect together 0:18:52.860,0:18:54.169 @@ -1277,7 +1278,7 @@ in networking or had done any kind of network programming 0:18:57.400,0:19:00.480 -if you're looking for a week to miss and this +if you're looking for a week to miss and the Week 8 is the one to miss that's 'cause that's 0:19:00.480,0:19:02.780 @@ -1297,7 +1298,7 @@ one of the papers in the back it is an introduction to Interprocess communication 0:19:12.620,0:19:18.279 -%uh read that paper if you say yeah yeah yeah +read that paper if you say yeah yeah yeah yeah yeah you are done with Week 8. 0:19:18.279,0:19:20.590 @@ -1338,14 +1339,14 @@ we will spend a significant portion of that class talking about routing 0:19:48.330,0:19:50.230 -%uh routing +routing 0:19:50.230,0:19:53.610 for those of you that haven't had the pleasure of dealing with it 0:19:53.610,0:19:55.540 -is a black heart +is a black art 0:19:55.540,0:19:58.050 or at least a dark science @@ -1360,7 +1361,7 @@ so we'll talk about it 0:20:02.490,0:20:06.270 -from the perspective first of all to what +from the perspective first of all of what do we do locally within the machine 0:20:06.270,0:20:10.090 @@ -1368,26 +1369,24 @@ and then what are some of the bigger strategies that we can use for doing routing 0:20:10.090,0:20:11.910 -%uh enterprise +enterprise 0:20:11.910,0:20:14.840 wide routing or 0:20:14.840,0:20:20.190 -area wide routing some like throughout the -state of California or throughout US whatever +area wide routing something like throughout the +state of California or throughout the US whatever 0:20:20.190,0:20:25.379 this again like device drivers is really just sort of a nickel 0:20:25.379,0:20:26.480 -%uh throught the dark - -0:20:26.480,0:20:27.800 +tour through the 0:20:27.800,0:20:31.820 -what what the choices are what that the basic +what the choices are what that the basic strategies are that are used 0:20:31.820,0:20:33.989 @@ -1408,7 +1407,7 @@ of what the issues are and what the general solutions are 0:20:44.430,0:20:48.950 -then finally in Week 10 well not finally +okay then finally in Week 10 well not finally but next few weeks and 0:20:48.950,0:20:52.380 @@ -1436,8 +1435,8 @@ on changes that have been made in the protocols 0:21:07.730,0:21:14.310 -to deal with a lot of attacks that -we've been seeing SYN attacks and +to deal with a lot of the sort of attacks that +we've been seeing the SYN attacks and 0:21:14.310,0:21:16.880 that sort of thing @@ -1453,50 +1452,50 @@ are i'll talk primarily about IPv4 0:21:24.940,0:21:31.940 -%uh but I will also try and talk a bit about +but I will also try and talk a bit about IPv6 as well 0:21:33.510,0:21:35.850 -so the first ten weeks are +all right so the first ten weeks are 0:21:35.850,0:21:38.100 -sort of kernel course +sort of the kernel course 0:21:38.100,0:21:40.800 -now back with two weeks on at the end +now we attack two weeks at the end 0:21:40.800,0:21:42.010 to talk about 0:21:42.010,0:21:43.990 -through the bigger picture of +sort of the bigger picture of 0:21:43.990,0:21:48.240 System Tuning,Crash dump analysis that level of thing 0:21:48.240,0:21:52.940 -The idea is really to consolidate what +The idea is to really consolidate what we figured out or talked about in the first 0:21:52.940,0:21:54.710 ten weeks and 0:21:54.710,0:21:58.760 -how that applies to tools that are available +how that applies to tools that we have available to us to 0:21:58.760,0:22:00.760 look at what the system is doing, 0:22:00.760,0:22:02.649 -to analyze what the system is doing + analyze what the system is doing 0:22:02.649,0:22:03.650 and hopefully 0:22:03.650,0:22:04.720 -improves +improve 0:22:04.720,0:22:07.130 the performance of what the system is doing @@ -1505,7 +1504,7 @@ the performance of what the system is doing and 0:22:07.750,0:22:12.169 -for the most part the kind of tuning I'm +for the most part the kind of tuning that I'm talking about is not 0:22:12.169,0:22:14.740 @@ -1515,10 +1514,10 @@ going in and hack hack hacking your kernel because the fact that the matter is 0:22:16.510,0:22:18.600 -you can't do that anyway +most of the time you can't do that anyway 0:22:18.600,0:22:22.340 -%uh so it's more looking at it from the perspective +so it's more looking at it from the perspective of saying 0:22:22.340,0:22:26.390 @@ -1530,7 +1529,7 @@ or is it running badly because there isn't enough I/O capacity? 0:22:29.470,0:22:33.549 -or is it running badly because the it's got +or is it running badly because it's got enough I/O capacity but 0:22:33.549,0:22:35.940 @@ -1562,7 +1561,7 @@ and 0:22:55.120,0:22:58.750 essentially measure what it is and hopefully -then you will understand the context of what +then you will understand in the context of what 0:22:58.750,0:23:00.690 we talked about in the VM section @@ -1571,14 +1570,14 @@ we talked about in the VM section what that really means 0:23:03.990,0:23:07.460 -the Crash dump analysis is is one of these +the Crash dump analysis is one of these topics that 0:23:07.460,0:23:08.730 you are gonna love or hate 0:23:08.730,0:23:12.530 -%uh you actually have to deal with crashed +you actually have to deal with crashed dumps 0:23:12.530,0:23:13.679 @@ -1592,7 +1591,7 @@ it's an incredible mass of boring detail 0:23:18.790,0:23:23.240 the only good part of it is that that's the -whole session is only about an hour or long +whole session is only about an hour long 0:23:23.240,0:23:25.529 If it interests you, listen closely @@ -1601,11 +1600,11 @@ If it interests you, listen closely and if it bores you, well, its only an hour long 0:23:28.950,0:23:32.880 -okay up lastly we'll talk a little bit about +okay lastly we'll talk a little bit about security issues 0:23:32.880,0:23:36.250 -again this is really more of the tools that +again this is really more to the tools that are available 0:23:36.250,0:23:40.750 @@ -1617,11 +1616,11 @@ how to implement security so those of you that deal with security 0:23:45.120,0:23:48.400 -it's just gonna to be sort of security one on +this is just gonna to be sort of security one oh one 0:23:48.400,0:23:50.029 -%uh for those of you +for those of you 0:23:50.029,0:23:51.500 that have but @@ -1631,19 +1630,19 @@ you'll have to deal with it but haven't really thought about it 0:23:54.399,0:23:58.549 -%uh it'll probably scare you to death and -you wonder have to keep the machines from +it'll probably scare you to death and +you wonder how to keep the machines from 0:23:58.549,0:24:02.840 being hijacked everyday 0:24:02.840,0:24:08.030 -Okay that's in essence what we're going +Okay so that's in essence what we're going to try and do here 0:24:08.030,0:24:15.030 anybody have any comments, questions, thoughts. -Alright, no, well. +No? All right well. 0:24:16.130,0:24:17.840 Let's get started @@ -1656,7 +1655,7 @@ overview of the kernel. Hopefully nobody's lost yet. 0:24:26.040,0:24:29.310 -What's a kernel? Alright. +What's a kernel? All right. 0:24:29.310,0:24:31.370 so starting at the very top @@ -1671,14 +1670,14 @@ what we have is a UNIX virtual machine and 0:24:38.330,0:24:41.660 -and virtual machines are actually something + virtual machines are actually something that has been around 0:24:41.660,0:24:44.539 as a concept since the sixties 0:24:44.539,0:24:48.919 -the diffrence is really just sort of the level + difference is really just sort of the level of the interface that people have dealt with 0:24:48.919,0:24:51.360 @@ -1692,7 +1691,7 @@ computers were these enormous things you would have 0:24:56.770,0:24:58.870 -your computer room would be something that be +your computer room would be something that'd be 0:24:58.870,0:25:01.909 three times the size of this conference @@ -1702,7 +1701,7 @@ room if you had a computer 0:25:03.230,0:25:05.530 -the computer itself was this +the computer itself was 0:25:05.530,0:25:07.840 tall as a refrigerator freezer @@ -1715,29 +1714,29 @@ five or eight or ten of these units side by side that itself made up the computer 0:25:13.909,0:25:16.080 -that would be one +that would be one big 0:25:16.080,0:25:20.030 for the core processor and the one which should be the floating point unit and several 0:25:20.030,0:25:24.080 -of them that would be the memory the core -literally +of them that would be the memory the core momory +literally the core memory 0:25:24.080,0:25:29.110 -%uh and then they'd be other rows of these -disk drives about the size of a washing +and then they'd be other rows of these +disk drives which were about the size of the washing 0:25:29.110,0:25:29.660 machine 0:25:29.660,0:25:34.169 -%then behind that since you couldn't store -everything on disk so +and then behind that since you couldn't store +everything on disks so 0:25:34.169,0:25:36.300 -that you had rows of tape drives +then you had rows of tape drives 0:25:36.300,0:25:37.880 and then you had this little @@ -1747,7 +1746,7 @@ set of sort of 0:25:39.610,0:25:43.330 munchkins that would run around and and tend -to the machine and they mount tapes and take +to the machine and they'd mount tapes and take 0:25:43.330,0:25:46.710 off tapes and mount disc packs and remove disc packs @@ -1772,7 +1771,7 @@ you could take out a set of platters and put in another 0:25:59.460,0:26:02.540 -hundred megabytes of platters and these are +hundred megabytes set of platters and these are platters that are 0:26:02.540,0:26:05.280 @@ -1780,7 +1779,7 @@ this big around and it's like six or eight of them and 0:26:05.280,0:26:09.140 -a giant head assemblies they comes rumbling in and + giant head assemblies they comes rumbling in and out 0:26:09.140,0:26:12.440 @@ -1797,14 +1796,14 @@ million instructions per second, 10 mips and 10 mips 0:26:21.630,0:26:28.330 -that's was more computing power than anybody + was more computing power than anybody could possibly imagine using in a single application 0:26:28.330,0:26:28.880 just 0:26:28.880,0:26:31.050 -by contrast this this +by contrast you know this 0:26:31.050,0:26:34.070 four-year-old laptop here is probably on @@ -1822,7 +1821,7 @@ do with a lot of computing power 0:26:40.760,0:26:44.640 and the other thing was that you didn't have -a notion of sort of operating system that had +a notion of sort of an operating system that had 0:26:44.640,0:26:45.890 applications running on it @@ -1838,7 +1837,7 @@ the raw hardware and so 0:26:51.750,0:26:55.900 -IBM who was a big manufacturer +what IBM who was a big manufacturer of machines in those days 0:26:55.900,0:26:59.060 @@ -1852,43 +1851,43 @@ and this was a little you'd call an operating system really 0:27:02.549,0:27:05.130 -but what it did is a cloned +but what it did is it cloned 0:27:05.130,0:27:09.270 -independent copies of the machine worked just -like the original machines you could boot +independent copies of the machine that worked just +like the original machines so you could boot 0:27:09.270,0:27:11.769 -something that thought it was an operating +something that you thought it was an operating system 0:27:11.769,0:27:13.380 on top of VM 0:27:13.380,0:27:16.750 -so you take one least ten that machines and +so you take one least ten mip machines and it would clone 0:27:16.750,0:27:20.050 six identical one mip copies 0:27:20.050,0:27:22.030 -%uh and then you could boot +and then you could boot 0:27:22.030,0:27:24.700 whatever you wanted on each one of those machines so 0:27:24.700,0:27:29.510 -if you were doing database that you do your -database because database cannot run on the raw hardware +if you were doing database stuff you would boot your +database because database cannot ran on the raw hardware 0:27:29.510,0:27:32.920 or if you're doing payroll who would boot up the payroll program 0:27:32.920,0:27:37.950 -%uh or if you actually tried to service the +or if you actually tried to service users you could boot a time sharing batch thing 0:27:37.950,0:27:40.790 @@ -1900,20 +1899,20 @@ or they even had TSO the Time Sharing Option where you could interactively sit 0:27:44.460,0:27:45.559 -and type send +and type and send 0:27:45.559,0:27:47.560 stuffs in and get answers back 0:27:47.560,0:27:48.570 -%uh and + and 0:27:48.570,0:27:51.429 -%uh also you could boot TSO so whatever set +also you could boot TSO so whatever set of 0:27:51.429,0:27:52.219 -%um + 0:27:52.219,0:27:55.339 things you need you could boot them and they ran @@ -1930,7 +1929,7 @@ raw copy of the hardware so when UNIX came along 0:28:04.529,0:28:07.350 -they sort of like the notion of +they sort of liked the notion of 0:28:07.350,0:28:11.509 providing the concept of independent @@ -1940,13 +1939,13 @@ things that you could operate in but they wanted it at a higher level 0:28:13.610,0:28:15.610 -so you're looking merely to do that +so you're looking really to do it 0:28:15.610,0:28:17.480 instead of at the raw hardware level 0:28:17.480,0:28:19.679 -to do it at a process well +to do it at a process level 0:28:19.679,0:28:23.799 and the idea that then was that the interface you @@ -1962,19 +1961,19 @@ and the idea then was that you would be given a process or set of processes 0:28:30.740,0:28:34.990 -and those were independent your process +and those were independent. your process couldn't affect 0:28:34.990,0:28:38.830 -the address space of another process reach -over and mess around with the addresses, +the address space of another processor. You couldn't reach +over and mess around with their addresses, 0:28:38.830,0:28:41.030 you couldn't mess around with their I/O channels 0:28:41.030,0:28:43.179 -%uh you could slow them down by +you could slow them down by 0:28:43.179,0:28:44.299 being a pig but @@ -1987,14 +1986,14 @@ other processes and 0:28:48.480,0:28:49.830 -%uh so +so 0:28:49.830,0:28:52.669 what the interfaces that they had there 0:28:52.669,0:28:58.660 -with one that had these characteristics -he had a a paged virtual address space +was one that had these characteristics + had a a paged virtual address space 0:28:58.660,0:29:02.980 so you din't have to know as in the old days how much physical @@ -2014,27 +2013,27 @@ hardware had segments or some other hardware brain damage 0:29:13.580,0:29:17.390 -it look to you like he just had a big uniform +it looked to you like he just had a big uniform address space and 0:29:17.390,0:29:21.070 -the size of the address space was independent -of the amount of memory that was on the machine +the size of your address space was independent +of the amount of memory that was on your machine 0:29:21.070,0:29:23.900 -your address space could be bigger than amount of +your address space couldn't be bigger than amount of physical memory 0:29:23.900,0:29:26.499 -cause we got to move pages around underneath +cause we sort of move pages around underneath 0:29:26.499,0:29:29.320 whatever part address space was actually active 0:29:29.320,0:29:34.260 -that is obviously do this if you if -you are trying to run 1 gigabyte of +and there's obviously limits to this if +you are trying to run a 1 gigabyte of 0:29:34.260,0:29:35.630 application on top of @@ -2054,32 +2053,32 @@ will eventually move the pages around and you will progress through getting your application run 0:29:49.740,0:29:53.890 -anothe thing was dealing with software +another thing was dealing with software interrupts 0:29:53.890,0:29:55.789 -%uh in the old days +in the old days 0:29:55.789,0:29:58.749 you had to understand how the hardware worked 0:29:58.749,0:30:03.900 in order to deal with exceptional conditions -so for example to did a divide by zero +so for example if you did a divide by zero 0:30:03.900,0:30:08.170 -the the hardware would have jumped to some +the hardware would jump through some vector location or 0:30:08.170,0:30:08.630 something 0:30:08.630,0:30:12.799 -and you had no khow how that worked and make +and you had know how that worked and make sure that you had your program 0:30:12.799,0:30:16.510 -use just a little bit of assembly language which +usually some little bit of assembly language set up to deal with that 0:30:16.510,0:30:19.870 @@ -2090,11 +2089,11 @@ from the hardware here and so they did this thing called signals 0:30:22.080,0:30:25.700 -the answer is, the finest of the signals is that +and so they just define a set of the signals is that if you do divide by zero 0:30:25.700,0:30:29.529 -%uh you simply register a routine you +you simply register a routine you want to have called you don't have to know 0:30:29.529,0:30:31.220 @@ -2125,7 +2124,7 @@ protection and scheduling and so on and one of the 0:30:55.820,0:31:00.320 -the early philosophies of UNIX was that to try +the early philosophies of UNIX was to try and keep it simple. 0:31:00.320,0:31:02.630 @@ -2139,11 +2138,11 @@ pre dated UNIX was a thing called Multix 0:31:07.350,0:31:12.820 -%uh Multix was was a joint project between +Multix was was a joint project between Honeywell, a big computer manufacturer of the 0:31:12.820,0:31:15.740 -time at +time 0:31:15.740,0:31:17.129 AT&T bell laboratories @@ -2161,7 +2160,7 @@ a big university then and still today 0:31:24.690,0:31:29.259 -%uh and that those three organizations got +and those three organizations got together to try and build this 0:31:29.259,0:31:31.400 @@ -2178,11 +2177,11 @@ more grandiose and more complex and never finished 0:31:37.160,0:31:38.979 -but as soon as that's what we see +because as soon as they sort of see 0:31:38.979,0:31:42.709 -although we know how to do that but also we could -do this other thing too and so then the teared it +oh we know how to do that but we could +do this other thing too and so then they would tear it 0:31:42.709,0:31:43.429 apart and @@ -2211,33 +2210,33 @@ the two of the people that had been working on that project, Ken Thompson and Dennis Richie 0:32:00.000,0:32:04.390 -%uh were sort of bound because they were now +were sort of bummed because they were now back to typing cards and putting them through 0:32:04.390,0:32:05.259 -card reader and +card readers and 0:32:05.259,0:32:07.960 -they are just used to the idea that you could +they had gotten used to the idea that you could actually 0:32:07.960,0:32:11.559 -sit at an ASSR teletype and interact +sit at an ASSR33 teletype and interact with your computer 0:32:11.559,0:32:13.440 and so 0:32:13.440,0:32:18.230 -they found an old %uh PDP-8 soon off in -the quarter that have been abandoned +they found an old %uh PDP-8 sitting off in +the corner that had been abandoned 0:32:18.230,0:32:22.120 and started working on this little tiny operating system which they called UNIX 0:32:22.120,0:32:26.549 -%uh which eventually moved to the PDP-11 and +which eventually moved to the PDP-11 and became what we have today 0:32:26.549,0:32:28.050 @@ -2251,8 +2250,8 @@ where everything had been done and in great grandiose detail 0:32:34.110,0:32:37.549 -and because they're fundamentally just two -the of them working on it and they wanted to get something +and because they're fundamentally were two + of them working on it and they wanted to get something 0:32:37.549,0:32:38.370 done and @@ -2264,14 +2263,14 @@ within a year or so one of their philosophies was 0:32:41.529,0:32:44.099 -let's find out one way of doing things +let's find the one way of doing things 0:32:44.099,0:32:48.180 let's not have eight ways from Sunday let's just get the one way 0:32:48.180,0:32:53.860 -and and that's what we will provide. So what is +and that's what we will provide. So what is the sort of core set of things that we need. 0:32:53.860,0:32:58.620 @@ -2289,8 +2288,8 @@ user identifier and at that time a single group identifier and later expanded 0:33:09.620,0:33:14.200 -and they used that sort of identifies for everything -so its used for counting, used for main +and they used that sort of identifiers for everything +so its used for counting, used for making 0:33:14.200,0:33:17.410 protection decisions, used for scheduling @@ -2304,17 +2303,17 @@ again it was the simplicity of thing which was what was driving their decision 0:33:24.279,0:33:28.840 -but they're really sort of true key idea +but they're really sort of two key ideas that they had 0:33:28.840,0:33:30.880 -that really made a difference that +that really made the difference that 0:33:30.880,0:33:32.539 -that's were set them up side +that's what set them up side 0:33:32.539,0:33:34.749 -from what everybody else done before them +from what everybody else had done before them 0:33:34.749,0:33:35.450 and which @@ -2327,24 +2326,24 @@ more or less ever since the first of these was the notion 0:33:41.869,0:33:44.840 -that we have a unique descriptive space +that we have a unique descriptor space 0:33:44.840,0:33:46.289 -%uh that is +that is 0:33:46.289,0:33:51.250 given a descriptor it can reference any I/O device 0:33:51.250,0:33:53.650 -or even any kind of I/O channel +so or even any kind of I/O channel 0:33:53.650,0:33:58.270 so you can have a descriptor for terminal -or descriptor for file or descriptive for +or descriptor for a file or descriptive for 0:33:58.270,0:34:02.240 -a disk or descriptor for pipe or descriptor +a disk or descriptor for a pipe or descriptor for a socket 0:34:02.240,0:34:03.500 @@ -2355,11 +2354,11 @@ you don't need to know 0:34:04.790,0:34:07.940 what it references in order to be able to read -and write on that thing +and write that thing 0:34:07.940,0:34:11.290 so if i hand you a descriptor -can read from that the descriptor or you can write +you can read from that the descriptor or you can write 0:34:11.290,0:34:13.259 to that descriptor @@ -2374,11 +2373,11 @@ the correct thing will happen and you'd say well 0:34:19.089,0:34:23.629 -that's obvious I mean how else could you -possibly think about doing it +that's so obvious I mean how else could you +possibly think of doing it? 0:34:23.629,0:34:25.179 -predating UNIX +well predating UNIX 0:34:25.179,0:34:28.059 everything was done with @@ -2392,10 +2391,10 @@ file, close a file 0:34:33.419,0:34:37.429 and there was another set of system calls which -would open a terminal,read a terminal, write terminal +would open a terminal,read a terminal, write terminal, 0:34:37.429,0:34:38.089 -,close terminal +close terminal 0:34:38.089,0:34:39.210 and yet another one @@ -2405,8 +2404,8 @@ which was create a pipe,read a pipe, write a pipe and so on. 0:34:42.409,0:34:47.699 -so if you are just dropped at a stupid -program like CAD +so if you are just a drop dead stupid +program like say CAD 0:34:47.699,0:34:51.579 you would have to have code in there and say was @@ -2436,7 +2435,7 @@ whereas when they went to the uniform descriptor space 0:35:07.159,0:35:09.630 -CAD doesn't know and doesn't need to know +CAD doesn't know it doesn't need to know it just says 0:35:09.630,0:35:10.819 @@ -2446,7 +2445,7 @@ read my input, write the output 0:35:13.979,0:35:17.059 -it works and we add a new type of descriptor +and it works and we add a new type of descriptor 0:35:17.059,0:35:17.600 and @@ -2463,7 +2462,7 @@ and pretty much every operating system after UNIX 0:35:27.019,0:35:28.659 -did that and there's +did that there's 0:35:28.659,0:35:30.210 one exception of %uh @@ -2488,7 +2487,7 @@ Longhorn will be here. and anyway 0:35:43.939,0:35:46.190 -this set of facilities +this set of facilities then 0:35:46.190,0:35:50.150 makes up the UNIX virtual machine @@ -2497,14 +2496,14 @@ makes up the UNIX virtual machine and 0:35:51.559,0:35:55.559 -in sometimes we still see virtual machines +in some sense we still see virtual machines being used today in fact we're seeing sort 0:35:55.559,0:35:56.749 of a reversion 0:35:56.749,0:36:01.429 -%uh back to some of the ideas stop in things +back to some of the IBM stuff in things like the VMware 0:36:01.429,0:36:03.079 @@ -2518,29 +2517,29 @@ native operating systems again so sort of interesting to watch 0:36:08.280,0:36:09.060 -that's the sort of +that the sort of 0:36:09.060,0:36:12.919 -%uh %uh pendulum of back going back and forth +pendulum of back going back and forth of what's the correct layer 0:36:12.919,0:36:14.609 for for doing 0:36:14.609,0:36:18.890 -%uh virtual machines +virtual machines 0:36:18.890,0:36:22.499 -Okay. so far so good. +Okay? so far so good? 0:36:22.499,0:36:24.719 -all right i said there was +all right so i said that there were 0:36:24.719,0:36:27.160 two key ideas that UNIX had 0:36:27.160,0:36:30.279 -the first thing is uniform descriptor +the first of these being the uniform descriptor space 0:36:30.279,0:36:35.819 @@ -2551,7 +2550,7 @@ this notion of processes as a commodity item 0:36:37.309,0:36:40.220 -so here on Page 17 I tried to lay +so here on Page 17 I've tried to lay it out 0:36:40.220,0:36:41.090 @@ -2561,14 +2560,14 @@ the that the components that make up a process 0:36:44.159,0:36:45.759 -%uh and +and 0:36:45.759,0:36:50.359 what do I really mean when I say a process as a commodity item 0:36:50.359,0:36:53.650 -leading up to +okay leading up to 0:36:53.650,0:36:54.689 UNIX @@ -2580,7 +2579,7 @@ the systems that pre-dated it, processes were these very large 0:36:59.200,0:37:02.169 -heavyweight expensive thing +heavyweight expensive things 0:37:02.169,0:37:02.779 and @@ -2607,7 +2606,7 @@ to support so they'd say well 0:37:18.140,0:37:20.739 -well, let upto six things happen at once +well, we'll let upto six things happen at once 0:37:20.739,0:37:22.490 and so as part of booting up @@ -2623,13 +2622,13 @@ and now you as a user if you wanted to do something let's say you wanted to 0:37:30.059,0:37:32.009 -compile and ran a program +compile and run a program 0:37:32.009,0:37:34.960 -%uh you would be given a process +you would be given a process 0:37:34.960,0:37:36.019 -and it's up to you +and it was up to you 0:37:36.019,0:37:39.369 to figure out how to stage what you needed @@ -2639,7 +2638,7 @@ done and 0:37:39.819,0:37:43.930 -%uh that this was often fairly complex +that this was often fairly complex 0:37:43.930,0:37:47.880 and so you would have to write out all the @@ -2649,25 +2648,25 @@ steps that you wanted in this wonderful thing called JCL 0:37:50.300,0:37:52.259 -Job Control Language and +Job Control Language. 0:37:52.259,0:37:56.650 Job Control Language was send mail configuration file of the sixties 0:37:56.650,0:38:00.679 -other where people who sold job that the company +there where people whose sole job at the company was how to put this stuff together 'cause 0:38:00.679,0:38:04.189 -like to do is get what one extra space or -missing comma +all you had to do is get one extra space or +a missing comma 0:38:04.189,0:38:05.000 -something in their +something in there 0:38:05.000,0:38:08.630 -and I hope it would just blow up it would +and the whole thing would just blow up. it would just sort of spit the card deck back at 0:38:08.630,0:38:09.799 @@ -2675,7 +2674,7 @@ you and say well 0:38:09.799,0:38:13.500 somewhere in there is a mistake that's sort of -the general area of this card +in the general area of this card 0:38:13.500,0:38:15.549 and I can't deal with it. Fix it. @@ -2685,7 +2684,7 @@ and of course 0:38:16.489,0:38:20.550 in those days it wasn't just a matter of hitting -carriage when you know make cariage return you have to +carriage when you know make carriage return you have to 0:38:20.550,0:38:25.239 get your deck pull out the card, and type the @@ -2710,10 +2709,10 @@ if you were not lucky a few hours later you would get 0:38:37.849,0:38:39.570 -a print print out +a print out 0:38:39.570,0:38:43.419 -which was what it happened and then you could +which was what had happened and then you could look at it and you know 0:38:43.419,0:38:47.209 @@ -2724,23 +2723,22 @@ I get to do it all again so 0:38:49.930,0:38:54.940 -if you would need to do something -like compiling and running a program +the thing you would need to do there for compiling and running a program 0:38:54.940,0:38:59.579 was you'd have to break into these steps. well I need to run the the preprocessor 0:38:59.579,0:39:04.670 -and so us clean out whatever gump that was left +and so clean out whatever gump that was left over on that process from the previous user 0:39:04.670,0:39:06.240 put the preprocessor in there 0:39:06.240,0:39:10.530 -%uh and then read from this file here let's -say gotta put it somewhere so creative +and then read from this file here let's +say I gotta put it somewhere so creative 0:39:10.530,0:39:12.510 scratch file over on this disk and @@ -2768,7 +2766,7 @@ the output of the preprocessor and then you'd load the first pass of the compiler 0:39:33.100,0:39:36.930 -and lets now read from that scratch file +and you say now read from that scratch file and create this other scratch file over here and 0:39:36.930,0:39:39.450 @@ -2780,7 +2778,7 @@ and then load the second pass, put that back into another scratch file and then we run this 0:39:43.830,0:39:45.950 -assembler, optimizer then the +assembler, and the optimizer then the 0:39:45.950,0:39:47.750 loader this and that @@ -2789,13 +2787,13 @@ loader this and that finally run the program 0:39:49.410,0:39:50.900 -and %uh if all goes well +and if all goes well 0:39:50.900,0:39:57.029 you know at step sixteen out comes the answer 0:39:57.029,0:39:58.129 -fourty two. so UNIX +forty two. so UNIX 0:39:58.129,0:40:00.819 said, look this is silly @@ -2815,7 +2813,7 @@ all these cycles it's like 0:40:12.179,0:40:16.309 computers are supposed to be labor-saving -devices right so +devices right? so 0:40:16.309,0:40:20.150 they came up with this notion that they would @@ -2852,7 +2850,7 @@ executable and 0:40:40.030,0:40:42.880 -we simply create each of these processes +we will simply create each of these processes 0:40:42.880,0:40:44.650 and @@ -2861,7 +2859,7 @@ and so you as a user just 0:40:46.549,0:40:49.479 -type you know the C compiler just +type you know the C compiler and it just 0:40:49.479,0:40:52.429 fork these things pipe them together got the result @@ -2874,14 +2872,14 @@ then once it was done with this processes is just threw them away so any time you'd create a 0:40:57.509,0:41:00.479 -new process and it came to you christine clean +new process and it came to you pristine clean 0:41:00.479,0:41:04.239 and you needed a bunch of things it did put everything in intermediate files 0:41:04.239,0:41:07.549 -the fact that matter is in the early days +the fact of the matter is in the early days 0:41:07.549,0:41:08.129 those computers @@ -2895,15 +2893,15 @@ behind you those pipes were actually implemented as files 0:41:15.809,0:41:19.319 -you didn't have atleast to remember to create +but you didn't have atleast to remember to create them and delete them 0:41:19.319,0:41:20.200 and deal with them 0:41:20.200,0:41:24.020 -as far as you're concerned it just look stuff flowing through pipes -and of course today it +as far as you were concerned it just look stuff +flowing through pipes and of course today it 0:41:24.020,0:41:24.490 just @@ -2922,7 +2920,7 @@ create processes on the fly is needed and connect them together as needed 0:41:35.559,0:41:38.039 -and that was a novel concept +it was a novel concept 0:41:38.039,0:41:43.599 and it wasn't that somehow mysteriously figured @@ -2957,7 +2955,7 @@ so we have to create a process load the ls binary into it 0:42:04.259,0:42:06.180 -and it prints a line or two on your screen +it prints a line or two on your screen 0:42:06.180,0:42:10.609 and we tear the entire thing down and return @@ -2972,13 +2970,13 @@ a tiny fraction of it is actually running ls 0:42:19.239,0:42:24.259 -it goes so fast, who cares right +but it goes so fast, who cares right 0:42:24.259,0:42:25.749 -the point is that +so the point is that 0:42:25.749,0:42:30.039 -%uh that concept of just creating things as +that concept of just creating things as needed 0:42:30.039,0:42:31.780 @@ -2992,8 +2990,8 @@ okay so what is a process actually made up of 0:42:38.639,0:42:43.179 -%uh it gets some amount of CPU time or at -least we do really hope that it gets some +it gets some amount of CPU time or at +least we do dearly hope that it gets some 0:42:43.179,0:42:46.050 amount of CPU time, the lack of getting @@ -3003,7 +3001,7 @@ CPU time that makes it 0:42:46.670,0:42:47.979 -a pure so sluggish +a computer so sluggish 0:42:47.979,0:42:49.409 of course @@ -3024,26 +3022,26 @@ in a couple weeks time we have the asynchronous events 0:43:01.619,0:43:04.569 -%uh these are the external events that +these are the external events that 0:43:04.569,0:43:05.659 are coming in 0:43:05.659,0:43:07.679 -%uh so +so 0:43:07.679,0:43:10.169 they may be either things that 0:43:10.169,0:43:14.339 -we're coming in from the outside world like +were coming in from the outside world like start, stop and quit 0:43:14.339,0:43:15.279 -%uh oh +oh 0:43:15.279,0:43:18.170 -out-of-band arrival notification that kind +out-of-band data arrival notification that kind of thing 0:43:18.170,0:43:22.339 @@ -3051,7 +3049,7 @@ or it may in fact be things that the program is bringing down upon itself 0:43:22.339,0:43:25.590 -on such as a segment fault,a divide by zero +such as a segment fault,a divide by zero 0:43:25.590,0:43:26.910 and some other @@ -3061,14 +3059,14 @@ what would normally be viewed as incorrect operation 0:43:31.959,0:43:35.849 -and so will talk about that when we talk about +and so we'll talk about that when we talk about signals 0:43:35.849,0:43:37.039 every program 0:43:37.039,0:43:38.899 -get some amount of memory +gets some amount of memory 0:43:38.899,0:43:42.659 it gets an initial amount when it starts @@ -3078,7 +3076,7 @@ up injured generally allocates more as it goes along 0:43:45.229,0:43:49.429 -of course we will deal with up her extensively +this of course we will deal with very extensively will spend an entire week on it 0:43:49.429,0:43:54.249 @@ -3088,7 +3086,7 @@ when we talk about how virtual memory is implemented and 0:43:54.609,0:43:57.429 -%uh then we get I/O descriptors +then we get I/O descriptors 0:43:57.429,0:44:02.259 I used to say that every program had to have @@ -3105,7 +3103,7 @@ then it was sort of pointless 0:44:09.049,0:44:12.900 of course I had to have one of my students -come up and point out to me there is a +come up and point out to me there is an a 0:44:12.900,0:44:13.849 class of programs @@ -3120,7 +3118,7 @@ and that is these things called benchmarks 0:44:19.549,0:44:23.249 -the just compute something all we really care +it just compute something all we really care about is how long it takes them to compute 0:44:23.249,0:44:24.959 @@ -3130,7 +3128,7 @@ we dont actually care what the answer is In theory we dont 0:44:26.019,0:44:29.779 -I personally felt like my benchmark stop with +I personally like my benchmark stop with something so I can see it there 0:44:29.779,0:44:31.489 @@ -3153,7 +3151,7 @@ of course we'll talk about descriptors quite extensively 0:44:43.659,0:44:47.349 -%uh as we go through the I/O subsystem +as we go through the I/O subsystem 0:44:47.349,0:44:50.969 okay so the executive summary is that processes @@ -3193,14 +3191,14 @@ providing that bit of service 0:45:16.639,0:45:17.900 -the next thing that I +the next thing that I'm 0:45:17.900,0:45:22.210 going to do now is this go through and lay out some of the terminology that 0:45:22.210,0:45:23.239 -we have we when +we have when 0:45:23.239,0:45:25.130 we're talking about processes @@ -3220,7 +3218,7 @@ make up the system 0:45:36.640,0:45:39.029 -the currently running user process +we have the currently running user process 0:45:39.029,0:45:41.180 and then what we call the top half of the kernel @@ -3253,7 +3251,7 @@ but for any given CPU on a multiprocessor it is running exactly one process 0:46:05.709,0:46:09.309 -so you may think they were running for four-five +so you may think they we're running for four-five processes all at once 0:46:09.309,0:46:14.319 @@ -3267,7 +3265,7 @@ actually running and 0:46:18.609,0:46:21.429 -that is the one that we have within the system +that is the one that we have loaded in the system 0:46:21.429,0:46:25.199 now we give the illusion that were running @@ -3287,14 +3285,14 @@ but in reality that's not really happening 0:46:33.619,0:46:36.440 -okay there is a set of properties that I want to +okay so there is a set of properties that I want to look at 0:46:36.440,0:46:40.899 that had to do with each one of these parts here 0:46:40.899,0:46:44.359 -but that just to look at it from the +but just to sort of look at it from the big picture perspective 0:46:44.359,0:46:45.970 @@ -3319,7 +3317,7 @@ like calling strcat, strcpy or something like that 0:47:00.319,0:47:03.679 -%uh when you do a system call +when you do a system call 0:47:03.679,0:47:05.650 we take that same set of parameters @@ -3334,35 +3332,35 @@ brick Wall here if you will that is protecting 0:47:11.380,0:47:13.680 -the the top half of the kernel +the top half of the kernel 0:47:13.680,0:47:15.299 from the application 0:47:15.299,0:47:18.899 -I'm more go into some detail about how that +I'll go more into some detail about how that actually gets implemented 0:47:18.899,0:47:22.729 -but in a sense you can think of it -is is there sort of this whaling Wall with little +but in essense you can think of it +is is there sort of this whaling Wall and these little 0:47:22.729,0:47:24.990 -chinks there you can sort of push a request +chinks there and you can sort of push a request through 0:47:24.990,0:47:28.230 -and somebody other sites where polls that -looks at it and decide whether they're going +and somebody other sides sort of pulls that +looks at it and decides whether they're going 0:47:28.230,0:47:28.690 to 0:47:28.690,0:47:30.769 -dained to provide service to you +dain to provide service to you 0:47:30.769,0:47:34.229 -and if they do then they will send it back +and if they do then they sort of send it back 0:47:34.229,0:47:37.649 well like a library where you can just sort @@ -3389,7 +3387,7 @@ a lot like a big library 0:47:50.509,0:47:53.509 -%uh it just happens to be a library of +%uh it just happens to be a library routines 0:47:53.509,0:47:57.599 @@ -3404,7 +3402,7 @@ for what's the difference between the C library and the top half of the kernel 0:48:03.259,0:48:08.020 -%uh if it's something that you're doing that +if it's something that you're doing that no other process needs to know about 0:48:08.020,0:48:09.799 @@ -3445,11 +3443,11 @@ has to be done by the kernel because they can coordinate 0:48:33.120,0:48:37.189 -on the daemon processes that are trying to access +all the different processes that are trying to access that file. 0:48:37.189,0:48:40.529 -so the top of the kernel is pretty straightforward +so the top half of the kernel is pretty straightforward code 0:48:40.529,0:48:45.539 @@ -3465,20 +3463,20 @@ get some data that we put it in the buffer and we return back 0:48:53.719,0:48:57.470 -in fact writing code for the top half of +and in fact writing code for the top half of the kernel is 0:48:57.470,0:48:59.729 not all that difficult to do 0:48:59.729,0:49:00.989 -%uh it's +it's 0:49:00.989,0:49:01.959 you have 0:49:01.959,0:49:05.939 -for many the same properties that you would +for many of the same properties that you would when you're writing user level application 0:49:05.939,0:49:07.529 @@ -3489,7 +3487,7 @@ the bottom half of the kernel is where things start to get nasty 0:49:11.779,0:49:14.820 -thus the bottom half of the kernel is the part +because the bottom half of the kernel is the part of the system 0:49:14.820,0:49:18.769 @@ -3497,7 +3495,7 @@ that deals with all of the asynchronous events in the system 0:49:18.769,0:49:22.179 -%uh is things like device drivers, +is things like device drivers, 0:49:22.179,0:49:23.779 timers @@ -3515,7 +3513,7 @@ so for example a packet arrives on the network 0:49:31.459,0:49:33.670 -that causes and interrupt a command +that causes an interrupt to come and 0:49:33.670,0:49:36.729 that will be handled by the bottom half of @@ -3529,7 +3527,7 @@ when an interrupt came in it preempted whatever else was going on 0:49:43.079,0:49:45.400 -and it ran until it's finished and then return +and it ran until it finished and then it returned 0:49:45.400,0:49:46.539 and it could not @@ -3542,8 +3540,8 @@ things %uh in current systems 0:49:51.339,0:49:54.549 -you can actually go to sleep in a interrupt driver -and wait for +you can actually go to sleep in the interrupt driver +and waiting for 0:49:54.549,0:49:56.739 some other activity to complete @@ -3558,7 +3556,7 @@ not a good idea to do that because 0:50:01.909,0:50:06.739 -the usual case of most of device drivers is they +the usual case of most device drivers is they can finish whatever they're doing in an interrupt 0:50:06.739,0:50:08.579 @@ -3568,7 +3566,7 @@ without ever blocking and so 0:50:09.580,0:50:13.649 -when an interrupt comes in and we assume that you're +when an interrupt comes in we assume that you're not going to sleep 0:50:13.649,0:50:14.710 @@ -3579,7 +3577,7 @@ then go to sleep.oh man 0:50:17.219,0:50:20.469 you didnt tell us you're going to do this we -have to go off into a whole lot of other work +have to go off to do a whole lot of other work 0:50:20.469,0:50:23.029 that we had originally planned on doing @@ -3588,7 +3586,7 @@ that we had originally planned on doing so if you go to sleep in a device driver 0:50:25.460,0:50:28.209 -you are taking a very serious performance +you are taking a very serious performance hit 0:50:28.209,0:50:31.019 so it's highly recommended that you don't @@ -3606,10 +3604,10 @@ of not being able to sleep in the bottom half of the kernel 0:50:39.899,0:50:42.119 -certain properties that have +that you have certain properties that have 0:50:42.119,0:50:44.769 -%uh taken over in device drivers +taken over in device drivers 0:50:44.769,0:50:45.940 and that is @@ -3633,13 +3631,13 @@ Go read this particular block 0:50:59.410,0:51:02.650 here is a chunk of memory that I want that -my data to put in + data to put in 0:51:02.650,0:51:03.959 and 0:51:03.959,0:51:06.169 -no to find it when it's done +notify me when it's done 0:51:06.169,0:51:06.970 because @@ -3681,7 +3679,7 @@ you don't know when somebody's going to send packets to you 0:51:34.630,0:51:37.040 -you say well you're looking you're open connections +you say well you're looking to open connections 0:51:37.040,0:51:39.360 but if you're doing something like IP forwarding @@ -3710,7 +3708,7 @@ they need to allocate memory and 0:51:56.640,0:51:58.829 -it memory gets into short supply +if memory gets into short supply 0:51:58.829,0:52:01.689 and they try to allocate memory and it's not @@ -3735,14 +3733,14 @@ it's like well I didn't have any place to put it sorry oops 0:52:18.109,0:52:20.940 -now that doesn't called incorrect behavior +now that doesn't cause incorrect behavior 0:52:20.940,0:52:24.369 -because a higher level protocols what we transmit +because the higher level protocols will retransmit 0:52:24.369,0:52:29.140 but it does cause great performance problems -because we transmissions means that connections +because retransmission means that connections 0:52:29.140,0:52:29.879 stall @@ -3771,7 +3769,7 @@ pre allocate a certain amount of memory for the network drivers 0:52:46.499,0:52:48.299 -%uh and +and 0:52:48.299,0:52:52.169 we try very hard to make sure that we're not @@ -3782,7 +3780,7 @@ if packets come fast enough and we can't deal with them 0:52:54.869,0:52:57.940 -as quickly as they are arriving over short period +as quickly as they are arriving then over short period of time 0:52:57.940,0:53:03.489 @@ -3790,11 +3788,11 @@ we get to the point where we simply have to start dropping packets 0:53:03.489,0:53:07.649 -this is a part of kernel that you do not wish to +okay this is a part of kernel that you do not wish to write code for 0:53:07.649,0:53:10.919 -because it is extremely difficult +because it is extremely difficult to debug 0:53:10.919,0:53:12.759 @@ -3822,7 +3820,7 @@ and when all those things happened the system panics 0:53:32.719,0:53:37.380 -and of course there's like the panic +and of course there's like it panics cause you're following some bad pointer 0:53:37.380,0:53:40.969 @@ -3840,7 +3838,7 @@ try to debug things like that is extremely difficult 0:53:47.400,0:53:48.509 -mean you can +and you can 0:53:48.509,0:53:52.120 think well I think I found the problem but @@ -3858,7 +3856,7 @@ and 0:53:57.469,0:54:01.449 you know so you sort of statistically -gets that you fix that you know I was getting +guess that you fix that you know I was getting 0:54:01.449,0:54:03.510 this bug once every three days @@ -3876,11 +3874,11 @@ or if you've been lucky and and it's 0:54:10.459,0:54:14.349 -that that coupled with the fact that you're +that coupled with the fact that you're dealing with hardware 0:54:14.349,0:54:18.049 -and hardware really works the way it's documented +and hardware rarely works the way it's documented to work 0:54:18.049,0:54:21.770 @@ -3902,7 +3900,7 @@ not said it doesn't work occasionally 0:54:33.769,0:54:36.110 -this is another reason that you really want +so this is another reason that you really want of avoid 0:54:36.110,0:54:40.459 @@ -3910,14 +3908,14 @@ dealing with this part of the system if you can possibly help 0:54:40.459,0:54:44.369 -but lets go through and and look at some -of the properties here starting up with at +okay but lets go through and and look at some +of the properties here starting up at 0:54:44.369,0:54:45.789 the user process 0:54:45.789,0:54:47.980 -%uh we're running with +we're running with 0:54:47.980,0:54:51.449 preemptive scheduling @@ -3939,7 +3937,7 @@ schedulers like the real time scheduler where what I'm saying isnt that true 0:55:02.869,0:55:05.709 -%uh will talk about some of the schedulers was +we'll talk about some of the schedulers was later 0:55:05.709,0:55:09.930 @@ -3947,7 +3945,7 @@ but the usual scheduler that you're running on under UNIX is a shared scheduler 0:55:09.930,0:55:13.229 -and under the shared scheduler the user applications +and under the shared scheduler user applications 0:55:13.229,0:55:15.159 run with pre emptive scheduling @@ -3959,13 +3957,13 @@ and pre emptive scheduling means that you run at the whim of the system 0:55:20.019,0:55:21.420 -if they want you to run +if it wants you to run 0:55:21.420,0:55:22.140 you run 0:55:22.140,0:55:25.490 -once you start running you have no guarantee +once you to start running you have no guarantee of how long you're going to run 0:55:25.490,0:55:29.370 @@ -3976,11 +3974,11 @@ and then decide it doesn't like you many more it wants to run something else 0:55:31.150,0:55:35.920 -while you might get to run for several seconds +or you might get to run for several seconds and in a row with the with no intervening 0:55:35.920,0:55:37.469 -things interrupting +things interrupting you 0:55:37.469,0:55:39.719 you just don't know @@ -3995,7 +3993,7 @@ really all you know is that 0:55:43.569,0:55:48.239 -%uh they claim that they're using statistics +they claim that they're using statistics and that and that the statistics are fair 0:55:48.239,0:55:55.059 @@ -4013,7 +4011,7 @@ is that you don't have any way of creating a critical section 0:56:01.940,0:56:04.950 -you can say okay I don't want to be interrupted +you can't say okay I don't want to be interrupted 0:56:04.950,0:56:07.429 during this particular sequence of things @@ -4030,7 +4028,7 @@ okay 0:56:14.979,0:56:18.909 the next thing is that when you're running -in user process +in a user process 0:56:18.909,0:56:20.719 you are running in @@ -4051,7 +4049,7 @@ support privileged and unprivileged two different modes of operation 0:56:33.709,0:56:37.049 -in privilege mode which is what the kernel +in privileged mode which is what the kernel runs in 0:56:37.049,0:56:38.950 @@ -4061,21 +4059,21 @@ the entire repertoire of the hardware is available 0:56:40.869,0:56:45.339 -by this I mean you can set all the register -as you can fiddle with the memory management +by this I mean you can set all the registers +you can fiddle with the memory management 0:56:45.339,0:56:47.460 unit you can initiate I/O 0:56:47.460,0:56:50.519 -you can access any register anywhere +you can access any memory anywhere 0:56:50.519,0:56:51.919 etc 0:56:51.919,0:56:56.540 when you're running in unprivileged -mode which is what user process run in and +mode which is what user processes run in and 0:56:56.540,0:57:00.709 this a large subset of the instructions which @@ -4095,11 +4093,11 @@ you cannot access memory that's not part of your address space 0:57:10.209,0:57:13.299 -%uh you cannot execute certain instructions +you cannot execute certain instructions like halt 0:57:13.299,0:57:15.589 -%uh and +and 0:57:15.589,0:57:19.039 so in general you are protected @@ -4112,7 +4110,7 @@ address space this of course is desirable because 0:57:23.759,0:57:27.059 -%uh when you're running in this unprevileged +when you're running in this unprevileged mode 0:57:27.059,0:57:28.300 @@ -4169,7 +4167,7 @@ implement things like viruses and worms and other things because 0:58:05.459,0:58:09.619 -user application can we rewrite the boot +a user application can we rewrite the boot block on the disk they can just the write down 0:58:09.619,0:58:13.109 @@ -4184,7 +4182,7 @@ mode you cant write those kinds of of things 0:58:20.179,0:58:24.119 -modern versions of Windows from about +so modern versions of Windows anything from about 2000 on 0:58:24.119,0:58:26.630 @@ -4197,7 +4195,7 @@ but UNIX has always required that and so when you're running an 0:58:30.219,0:58:31.319 -the user process + user process 0:58:31.319,0:58:33.389 you cannot block i mean @@ -4221,7 +4219,7 @@ hey I've got nothing to do. pick somebody else to run 0:58:49.269,0:58:53.449 -the operating system is the think they can +and the operating system is the think they can then execute the instructions which cause 0:58:53.449,0:58:57.609 @@ -4235,7 +4233,7 @@ alright.finally while you're in a user application you're running on a user stack 0:59:03.400,0:59:06.410 -that's part of the user address space +that's part of the user's address space 0:59:06.410,0:59:07.889 so @@ -4256,13 +4254,13 @@ as big as you want it to be so if you are running on thirty two-bit processor 0:59:19.949,0:59:22.819 -you're stack can get 2 gigabytes +you're stack can get the 2 gigabytes 0:59:22.819,0:59:23.319 and 0:59:23.319,0:59:26.839 -%uh the what this means is that anytime you +the what this means is that anytime you allocate local variables 0:59:26.839,0:59:28.529 @@ -4290,7 +4288,7 @@ and it just decrements your stack pointer by hundred hundred thousand bytes 0:59:44.029,0:59:45.009 -a way to go +away you go 0:59:45.009,0:59:47.299 it's just virtual address space |