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  • Reverting a single file to a previous version in git

    - by georgeliquor
    Is there a way to go through different commits on a file. Say I modified a file 5 times and I want to go back to change 2, after I already committed and pushed to a repository. In my understanding the only way is to keep many branches, have I got that right? If I'm right I'm gonna have hundreds of branches in a few days, so I'm probably not understanding it really. Could anyone clear that up please?

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  • Coding without Grock. Is it wrong?

    - by OldCurmudgeon
    Should a professional programmer allow themselves to write code without completely understanding the requirements? In my 30+ years as a programmer I must have written many thousands of lines of code without completely understanding what is required of me at the time. In most cases the results were rubbish that should have been discarded. Every other industry that employs professionals has systems to root out such behavior. Ours does not. Is this right?

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  • Naive question of memory references in Operating system

    - by darkie15
    Hi All, I am learning memory references pertaining to Operating systems and don't seem to get to the crux of understanding it. For example, I am not able to visualize this scenario properly: "A 36 bit address employs both paging and segmentation. Both PTE and STE are 4 bytes each". How are they related? I can guess that this question might be too simple for many. But any help understanding the above basic concept would be appreciable. Regards, darkie15

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  • Why are enums considered compound types?

    - by FredOverflow
    Arrays, functions, pointers, references, classes, unions, enumerations and pointers to members are compound types. My understanding of a compound type is that is based on other type(s). For example, T[n], T* and T& are all based on T. Then what other type(s) is an enumeration based on? Or if my understanding of compound types is incorrect, what exactly is it about a type that makes it a compound type? Is compound simply a synonym for user-defined?

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  • Learning to read GCC assembler output

    - by porgarmingduod
    I'm considering picking up some very rudimentary understanding of assembly. My current goal is simple: VERY BASIC understanding of GCC assembler output when compiling C/C++ with the -S switch. Just enough to do simple things such as looking at a single function and verifying whether GCC optimizes away things I expect to disappear. Does anyone have/know of a truly concise introduction to assembly, relevant to GCC and specifically for the purpose of reading, and a list of the most important instructions anyone casually reading assembly should know?

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  • When should I use Yield in c#?

    - by Steve
    I have a vage understanding of the Yield keyword in c#, but I haven't yet seen the need to use it in my code. This probably comes from a lack of understanding of it.. So; What are some typical good usages of Yield?

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  • fetchBatchSize to be same as fetchLimit

    - by user1730622
    What does it mean to have fetchBatchSize to be the same as fetchLimit, say both are set to be 5. My understanding is that, with the fetchLimit, then only 5 records will be in the fetch result set; and additionally with the fetchBatchSize, only the ids/identities of the records will be read to the memory, and then the full records won't be retrieved until they are accessed. Is that a correct understanding?

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  • Can you suggest some UI related flex 3 interview questions for a senior pos?

    - by mohan talluri
    Our Company is looking for a sr.flex developer. As part of interview process customized UI understanding and implementation is also included. I am Usability&design Lead for the same product team have some understanding of flex 3 but am not sure if pure UI/usability questions can be answered by flex developer. So can you suggest some UI related questions to see if he/she has competency to refer a prototype(html/mockup's) and build the same UI in flex.

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  • A nuts and bolts reference to C# performance and memory use

    - by phil
    I wonder if anyone could point me in the direction where I can read about the nuts and bolts of C#. What I'm interested in learning are method call costs, what it costs to create objects and such. My aim of learning this is to get a better understanding of how increase the performance of an application and get a better understanding of how the C# language works. The reference should preferable be a book, a book that I can read cover to cover.

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  • SQL SERVER – Faster SQL Server Databases and Applications – Power and Control with SafePeak Caching Options

    - by Pinal Dave
    Update: This blog post is written based on the SafePeak, which is available for free download. Today, I’d like to examine more closely one of my preferred technologies for accelerating SQL Server databases, SafePeak. Safepeak’s software provides a variety of advanced data caching options, techniques and tools to accelerate the performance and scalability of SQL Server databases and applications. I’d like to look more closely at some of these options, as some of these capabilities could help you address lagging database and performance on your systems. To better understand the available options, it is best to start by understanding the difference between the usual “Basic Caching” vs. SafePeak’s “Dynamic Caching”. Basic Caching Basic Caching (or the stale and static cache) is an ability to put the results from a query into cache for a certain period of time. It is based on TTL, or Time-to-live, and is designed to stay in cache no matter what happens to the data. For example, although the actual data can be modified due to DML commands (update/insert/delete), the cache will still hold the same obsolete query data. Meaning that with the Basic Caching is really static / stale cache.  As you can tell, this approach has its limitations. Dynamic Caching Dynamic Caching (or the non-stale cache) is an ability to put the results from a query into cache while maintaining the cache transaction awareness looking for possible data modifications. The modifications can come as a result of: DML commands (update/insert/delete), indirect modifications due to triggers on other tables, executions of stored procedures with internal DML commands complex cases of stored procedures with multiple levels of internal stored procedures logic. When data modification commands arrive, the caching system identifies the related cache items and evicts them from cache immediately. In the dynamic caching option the TTL setting still exists, although its importance is reduced, since the main factor for cache invalidation (or cache eviction) become the actual data updates commands. Now that we have a basic understanding of the differences between “basic” and “dynamic” caching, let’s dive in deeper. SafePeak: A comprehensive and versatile caching platform SafePeak comes with a wide range of caching options. Some of SafePeak’s caching options are automated, while others require manual configuration. Together they provide a complete solution for IT and Data managers to reach excellent performance acceleration and application scalability for  a wide range of business cases and applications. Automated caching of SQL Queries: Fully/semi-automated caching of all “read” SQL queries, containing any types of data, including Blobs, XMLs, Texts as well as all other standard data types. SafePeak automatically analyzes the incoming queries, categorizes them into SQL Patterns, identifying directly and indirectly accessed tables, views, functions and stored procedures; Automated caching of Stored Procedures: Fully or semi-automated caching of all read” stored procedures, including procedures with complex sub-procedure logic as well as procedures with complex dynamic SQL code. All procedures are analyzed in advance by SafePeak’s  Metadata-Learning process, their SQL schemas are parsed – resulting with a full understanding of the underlying code, objects dependencies (tables, views, functions, sub-procedures) enabling automated or semi-automated (manually review and activate by a mouse-click) cache activation, with full understanding of the transaction logic for cache real-time invalidation; Transaction aware cache: Automated cache awareness for SQL transactions (SQL and in-procs); Dynamic SQL Caching: Procedures with dynamic SQL are pre-parsed, enabling easy cache configuration, eliminating SQL Server load for parsing time and delivering high response time value even in most complicated use-cases; Fully Automated Caching: SQL Patterns (including SQL queries and stored procedures) that are categorized by SafePeak as “read and deterministic” are automatically activated for caching; Semi-Automated Caching: SQL Patterns categorized as “Read and Non deterministic” are patterns of SQL queries and stored procedures that contain reference to non-deterministic functions, like getdate(). Such SQL Patterns are reviewed by the SafePeak administrator and in usually most of them are activated manually for caching (point and click activation); Fully Dynamic Caching: Automated detection of all dependent tables in each SQL Pattern, with automated real-time eviction of the relevant cache items in the event of “write” commands (a DML or a stored procedure) to one of relevant tables. A default setting; Semi Dynamic Caching: A manual cache configuration option enabling reducing the sensitivity of specific SQL Patterns to “write” commands to certain tables/views. An optimization technique relevant for cases when the query data is either known to be static (like archive order details), or when the application sensitivity to fresh data is not critical and can be stale for short period of time (gaining better performance and reduced load); Scheduled Cache Eviction: A manual cache configuration option enabling scheduling SQL Pattern cache eviction based on certain time(s) during a day. A very useful optimization technique when (for example) certain SQL Patterns can be cached but are time sensitive. Example: “select customers that today is their birthday”, an SQL with getdate() function, which can and should be cached, but the data stays relevant only until 00:00 (midnight); Parsing Exceptions Management: Stored procedures that were not fully parsed by SafePeak (due to too complex dynamic SQL or unfamiliar syntax), are signed as “Dynamic Objects” with highest transaction safety settings (such as: Full global cache eviction, DDL Check = lock cache and check for schema changes, and more). The SafePeak solution points the user to the Dynamic Objects that are important for cache effectiveness, provides easy configuration interface, allowing you to improve cache hits and reduce cache global evictions. Usually this is the first configuration in a deployment; Overriding Settings of Stored Procedures: Override the settings of stored procedures (or other object types) for cache optimization. For example, in case a stored procedure SP1 has an “insert” into table T1, it will not be allowed to be cached. However, it is possible that T1 is just a “logging or instrumentation” table left by developers. By overriding the settings a user can allow caching of the problematic stored procedure; Advanced Cache Warm-Up: Creating an XML-based list of queries and stored procedure (with lists of parameters) for periodically automated pre-fetching and caching. An advanced tool allowing you to handle more rare but very performance sensitive queries pre-fetch them into cache allowing high performance for users’ data access; Configuration Driven by Deep SQL Analytics: All SQL queries are continuously logged and analyzed, providing users with deep SQL Analytics and Performance Monitoring. Reduce troubleshooting from days to minutes with database objects and SQL Patterns heat-map. The performance driven configuration helps you to focus on the most important settings that bring you the highest performance gains. Use of SafePeak SQL Analytics allows continuous performance monitoring and analysis, easy identification of bottlenecks of both real-time and historical data; Cloud Ready: Available for instant deployment on Amazon Web Services (AWS). As you can see, there are many options to configure SafePeak’s SQL Server database and application acceleration caching technology to best fit a lot of situations. If you’re not familiar with their technology, they offer free-trial software you can download that comes with a free “help session” to help get you started. You can access the free trial here. Also, SafePeak is available to use on Amazon Cloud. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Making user input/math on data fast, unlike excel type programs

    - by proGrammar
    I'm creating a research platform solely for myself to do some research on data. Programs like excel are terribly slow for me so I'm trying to come up with another solution. Originally I used excel. A1 was the cell that contained the data and all other cells in use calculated something on A1, or on other cells, that all could be in the end traced to A1. A1 was like an element of an array, I then I incremented it to go through all my data. This was way too slow. So the only other option I found originally was to hand code in c# the calculations inside a loop. Then I simply recompiled each time I changed my math. This was terribly slow to do and I had to order everything correctly so things would update correctly (dependencies). I could have also used events, but hand coding events for each cell like calculation would also be very slow. Next I created an application to read Excel and to perfectly imitate it. Which is what I now use. Basically I write formulas onto a fraction of my data to get live results inside excel. Then my program reads excel, writes another c# program, compiles it, and runs that program which runs my excel created formulas through a lot more data a whole lot faster. The advantage being my application dependency sorts everything (or I could use events) so I don't have to (like excel does) And of course the speed. But now its not a single application anymore. Instead its 2 applications, one which only reads my formulas and writes another program. The other one being the result which only lives for a short while before I do other runs through my data with different formulas / settings. So I can't see multiple results at one time without introducing even more programs like a database or at least having the 2 applications talking to each other. My idea was to have a dll that would be written, compiled, loaded, and unloaded again and again. So a self-updating program, sort of. But apparently that's not possible without another appdomain which means data has to be marshaled to be moved between the appdomains. Which would slow things down, not for summaries, but for other stuff I need to do with all my data. I'm also forgetting to mention a huge problem with restarting an application again and again which is having to reload ALL my data into memory again and again. But its still a whole lot faster than excel. I'm really super puzzled as to what people do when they want to research data fast. I'm completely unable to have a program accept user input and having it fast. My understanding is that it would have to do things like excel which is to evaluate strings again and again. So my only option is to repeatedly compile applications. Do I have a correct understanding on computer science? I've only just began programming, and didn't think I would have to learn much to do some simple math on data. My understanding is its either compiling my user defined stuff to a program or evaluating them from a string or something stupid again and again. And my only option is to probably switch operating systems or something to be able to have a program compile and run itself without stopping (writing/compiling dll, loading dll to program, unloading, and repeating). Can someone give me some idea on how computers work? Is anything better possible? Like a running program, that can accept user input and compile it and then unload it later? I mean heck operating systems dont need to be RESTARTED with every change to user input. What is this the cave man days? Sorry, it's just so super frustrating not knowing what one can do, and can't do. If only I could understand and learn this stuff fast enough.

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  • How you would you describe the Observer pattern in beginner language?

    - by Sheldon
    Currently, my level of understanding is below all the coding examples on the web about the Observer Pattern. I understand it simply as being almost a subscription that updates all other events when a change is made that the delegate registers. However, I'm very unstable in my true comprehension of the benefits and uses. I've done some googling, but most are above my level of understanding. I'm trying to implement this pattern with my current homework assignment, and to truly make sense on my project need a better understanding of the pattern itself and perhaps an example to see what its use. I don't want to force this pattern into something just to submit, I need to understand the purpose and develop my methods accordingly so that it actually serves a good purpose. My text doesn't really go into it, just mentions it in one sentence. MSDN was hard for me to understand, as I'm a beginner on this, and it seems more of an advanced topic. How would you describe this Observer pattern and its uses in C# to a beginner? For an example, please keep code very simple so I can understand the purpose more than complex code snippets. I'm trying to use it effectively with some simple textbox string manipulations and using delegates for my assignment, so a pointer would help!

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  • Properties vs. Fields: Need help grasping the uses of Properties over Fields.

    - by pghtech
    First off, I have read through a list of postings on this topic and I don't feel I have grasped properties because of what I had come to understand about encapsulation and field modifiers (private, public..ect). One of the main aspects of C# that I have come to learn is the importance of data protection within your code by the use of encapsulation. I 'thought' I understood that to be because of the ability of the use of the modifiers (private, public, internal, protected). However, after learning about properties I am sort of torn in understanding not only properties uses, but the overall importance/ability of data protection (what I understood as encapsulation) within C#. To be more specific, everything I have read when I got to properties in C# is that you should try to use them in place of fields when you can because of: 1) they allow you to change the data type when you can't when directly accessing the field directly. 2) they add a level of protection to data access However, from what I 'thought' I had come to know about the use of field modifiers did #2, it seemed to me that properties just generated additional code unless you had some reason to change the type (#1) - because you are (more or less) creating hidden methods to access fields as opposed to directly. Then there is the whole modifiers being able to be added to Properties which further complicates my understanding for the need of properties to access data. I have read a number of chapters from different writers on "properties" and none have really explained a good understanding of properties vs. fields vs. encapsulation (and good programming methods). Can someone explain: 1) why I would want to use properties instead of fields (especially when it appears I am just adding additional code 2) any tips on recognizing the use of properties and not seeing them as simply methods (with the exception of the get;set being apparent) when tracing other peoples code? 3) Any general rules of thumb when it comes to good programming methods in relation to when to use what? Thanks and sorry for the long post - I didn't want to just ask a question that has been asked 100x without explaining why I am asking it again.

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  • Is there really such a thing as "being good at math"?

    - by thezhaba
    Aside from gifted individuals able to perform complex calculations in their head, I'm wondering if proficiency in mathematics, namely calculus and algebra, has really got to do with one's natural inclination towards sciences, if you can put it that way. A number of students in my calculus course pick up material in seemingly no time whereas I, personally, have to spend time thinking about and understanding most concepts. Even then, if a question that requires a bit more 'imagination' comes up I don't always recognize the concepts behind it, as is the case with calculus proofs, for instance. Nevertheless, I refuse to believe that I'm simply not made for it. I do very well in programming and software engineering courses where a lot of students struggle. At first I could not grasp what they found to be so difficult, but eventually I realized that having previous programming experience is a great asset -- once I've seen and made practical use of the programming concepts learning about them in depth in an academic setting became much easier as I have then already seen their use "in the wild". I suppose I'm hoping that something similar happens with mathematics -- perhaps once the practical idea behind a concept (which authors of textbooks sure do a great job of concealing..) is evident, understanding the seemingly dry and symbolic ideas and proofs would be more obvious? I'm really not sure. All I'm sure of is I'd like to get better at calculus, but I don't yet understand why some of us pick it up easily while others have to spend considerable amounts of time on it and still not have complete understanding if an unusual problem is given.

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  • Check packet vlan tag using Tap virtual interface

    - by ankit
    Hi all, I am trying to learn how to implement virtual interfaces using the Tap driver. So far my understanding is that using the tap driver I can create a virtual interface and then have a userspace program attach to this interface to analyse the data coming into this device. Now what if I attach a cisco switch to my LAN interface using a TRUNK link, forward all the packets coming into the LAN interface to the virtual tap interface and then in my program attached to this interface do some coding to analyze the vlan tag in the packet and only allow certain vlans to be forwarded to the WAN interface ? Does this sound plausible or is there is flaw in my basic understanding ? Thanks for the help! ankit

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  • Do i need a dedicated server for load balancing?

    - by Ben
    I'm completely new to the concept of load balancing so i hope this question isn't a "stupid question" because i've been searching around and im having a hard time understanding this. So to my understanding, in order to load balance, i need a separate machine with an ip address i can direct all traffic to. I initially thought i needed to rent 3 dedicated servers, one for load balancing and the other two as backend servers. Would a dedicated server be too much for a load balancer or do hosting companies have special types of computers for that process? Then i read somewhere else that i can install a load balance software in both of the two servers and configure it in a way that doesn't require me to rent another machine/dedicated server for load balancing. So im a bit confuse on how to actually implement a load balancer and whether or not i need a dedicated server for the sole purpose of acting as a load balancing machine. Also, i was recommended to use HAproxy so i'll be heading that direction for load balancing.

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  • How can I pass environment variables to a WSGI script, using uWSGI?

    - by orokusaki
    I've added the following line to /etc/environment: FOO_DEPLOYMENT_ENV="vbox" Upon logging in via SSH, I can echo $FOO_DEPLOYMENT_ENV and, of course, see vbox output to the shell. If I open a Python shell and run os.getenv('FOO_DEPLOYMENT_ENV'), it will return 'vbox', but the same code in my Python application, when run by uWSGI (as the www-data user), it does not see the environment variable. Clearly, this isn't a problem of uWSGI, and is rather a problem with my understanding of environment variables, or how they're properly set, and the contexts in which they can be retrieved. What am I doing or understanding incorrectly?

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  • What is the DNS root zone and domain?

    - by Nimmy Lebby
    This might seem like a silly question but I want to get my terminology correct. Please do not delete. I will be more than happy to delete the question myself once I (with the help of a few people I hope) get to a consensus: This was my understanding: DNS root zone = . DNS root domain = (nameless) However, after reading the Wikipedia article, I'm not so sure: A domain name consists of one or more parts, technically called labels, that are conventionally concatenated, and delimited by dots, such as example.com. So this would lead me to believe: DNS root zone = . DNS root domain = . DNS root label = (nameless) Does this make sense? What is your understanding?

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  • Is it possible to do a full Android backup without first rooting the phone?

    - by Howiecamp
    I'm running stock 2.1 on my Moto Droid and am interested in rooting. My (admittedly weak at this point) understanding is that, in order to perform a backup[*], you need to root first. But in order to root, you've got to replace the 2.1 image with a rooted 2.0.1 or a stock 2.0.1 and then a rooted 2.1. So there's no CYA protection given that you've got to take the risk of replacing the image in order to get root and then do a backup. [*] Ideally, I'd like to backup the stock 2.1 image AND my apps. Am I understanding this correctly, or is there a way to do a backup without first replacing the image?

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  • Recommendations for managing dedicated server DNS

    - by KP Overflow
    I've rented a dedicated server for several years with a number of domains. I've got a coding background so am comfortable with that side of the tech, but I hate that I still don't truly understand DNS settings. Example: My provider (hostgator) just told me that my parent nameservers are not correctly configured as there is no A record for my primary nameserver. What book/link/tutorial should I read to go from kind of understanding that comment to really understanding it & knowing exactly what I need to do to fix it rather than trial & error which is what I usually do. Thanks BTW I'm using a WHM/cpanel linux setup at hostgator but am eager to learn the fundamentals.

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  • Possible to write an implement of RAIDZ or RAIDZ2 for the MD driver in the Linux kernel?

    - by Pharaun
    I am curious on if it is possible to have an implement of RAIDZ and/or RAIDZ2 in the MD driver in the Linux kernel? From my understanding of it is that the RAIDZ version is equivalent to a RAID 5, and that a RAIDZ2 is equivalent to a RAID 6. The main difference is that the stripe size can be variable for RAIDZ as opposite to RAID 5/6 from my understanding, which helps performance. So what I am wondering is would it be possible to add this performance enhancing technique to RAID 5 & 6 in the MD driver in the kernel? Or is it tied too closely to how the ZFS works?

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  • How to route all traffic over site to site VPN tunnel?

    - by Hutch
    I have a site to site VPN configured between our main site (Site A) and a remote site (Site B). Site A is 10.60.0.0/16 Site B is 192.168.99.0/24 The firewall in Site B is a Juniper SSG running ScreenOS 6.3 and I'm using a route based VPN. The tunnel works perfectly in that from Site A you can reach 192.168.99.0 via the tunnel, and from Site B you can reach 10.60.0.0 via the tunnel. However, we want it so that if you're in Site B and want the Internet it goes via the firewall at Site A, and right now on the Juniper 0.0.0.0 has the ISP router as next hop. My understanding is that on the Juniper, I can set a route for the /32 public IP at our main site that the VPN tunnel connects to to the ISP router via ethernet0/0 (the SSG's external interface), and then modify the 0.0.0.0 route to use our main site firewall via tunnel.1 (the VPN tunnel). Not sure I've explained that so well but is my understanding correct? Thanks

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  • What is Slotted and pure aloha?

    - by caspert
    So I am having a really hard time understanding slotted and pure aloha. I have understood CSMA/CD fairly well, but that is it. I have the book: Computer networking - a top down approach, but I find the explanation very cryptic and hard to understand. Wikipedia did not help me. Does anyone have a brief "aloha for dummies" explanation? or perhaps a video tutorial? I think I need something visual. I don't need to be able to create the protocol, I just need a general understanding of it.

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  • In a virtual machine monitor such as VMware’s ESXi Server, how are shadow page tables implemented?

    - by ali01
    My understanding is that VMMs such as VMware's ESXi Server maintain shadow page tables to map virtual page addresses of guest operating systems directly to machine (hardware) addresses. I've been told that shadow page tables are then used directly by the processor's paging hardware to allow memory access in the VM to execute without translation overhead. I would like to understand a bit more about how the shadow page table mechanism works in a VMM. Is my high level understanding above correct? What kind of data structures are used in the implementation of shadow page tables? What is the flow of control from the guest operating system all the way to the hardware? How are memory access translations made for a guest operating system before its shadow page table is populated? How is page sharing supported? Short of straight up reading the source code of an open source VMM, what resources can I look into to learn more about hardware virtualization?

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