Process Creation | System Calls | Mode & Context Switching | Overhead | Easy Learning IT Classroom
• Process creation + System Calls
• Dual Mode Execution (Mode Switching)
• Processing a System Call
• Context Switching
• System calls allow processes running at the user mode to access kernel functions that run under the kernel mode
• Prevent processes from doing bad things, such as
• Halting the entire operating system
• Modifying the MBR
System Calls Contd.:
• Serve as an entry point to OS code
• Allows users to request OS services
• API’s/library functions usually provide an interface to system calls
• e.g, language-level I/O functions map user parameters into system-call format
• Thus, the run-time support system of a prog. language acts as an interface between programmer and OS interface
• In general-purpose systems, some way is needed to create processes as needed during operation. There are four principal events led to processes creation.
• System initialization.
• Execution of a process Creation System calls by a running process.
• A user request to create a new process.
• Initialization of a batch job.
Process Creation: Following are some reasons for creation of a process
• User logs on.
• User starts a program.
• Operating systems creates process to provide service, e.g., to manage printer.
• Some program starts another process, e.g., Netscape calls xv to display a picture.
• System calls allow boundary to be crossed
• System call initiates mode switch from user to kernel mode
• User Mode Kernel Mode
• Special instruction – “software interrupt” – calls the kernel function
• transfers control to a location in the interrupt vector table
• OS executes kernel code, mode switch occurs again when control returns to user process
Processing a System Call:
• Before we discuss processing of system call, one should know what is Context Switch and an Overhead
• Context switching is an Overhead.
• Overhead, time that doesn’t involve any user process execution, but it is needed to accomplish various important tasks.
Context Switching: Switching the CPU to another process requires saving the state of the old process and loading the saved state for the new process
Processing a System Call contd.:
• Switching between kernel and user mode is time consuming
• Kernel must
• Save registers so the executing process can resume execution
• Other overhead is involved; e.g. cache misses, & prefetch
• Verify system call name and parameters
• Call the kernel function to perform the service
• On completion, restore registers and return to caller
C++ tutorials playlist - https://www.youtube.com/playlist?list=PLhmA3HN6Mpp1Ab_MqrMljkkFVSz68-gzv
• Best from C++ Playlist
Lecture 1 - Introduction to C++ (HINDI/URDU) Part 1 | Easy Learning IT Classroom– https://youtu.be/pPd-aZT68n...
This site provides links to random videos hosted at YouTube, with the emphasis on random.
The original idea for this site actually stemmed from another idea to provide a way of benchmarking the popularity of a video against the general population of YouTube videos. There are probably sites that do this by now, but there wasn’t when we started out. Anyway, in order to figure out how popular any one video is, you need a pretty large sample of videos to rank it against. The challenge is that the sample needs to be very random in order to properly rank a video and YouTube doesn’t appear to provide a way to obtain large numbers of random video IDs.
Alternative random YouTube videos generator: YouTuBeRandom
Even if you search on YouTube for a random string, the set of results that will be returned will still be based on popularity, so if you’re using this approach to build up your sample, you’re already in trouble. It turns out there is a multitude of ways in which the YouTube search function makes it very difficult to retrieve truly random results.
So how can we provide truly random links to YouTube videos? It turns out that the YouTube programming interface (API) provides additional functions that allow the discovery of videos which, with the right approach, are much more random. Using a number of tricks, combined some subtle manipulation of the space-time fabric, we have managed to create a process that yields something very close to 100% random links to YouTube videos.
YouTube is an American video-sharing website headquartered in San Bruno, California. YouTube allows users to upload, view, rate, share, add to playlists, report, comment on videos, and subscribe to other users. It offers a wide variety of user-generated and corporate media videos. Available content includes video clips, TV show clips, music videos, short and documentary films, audio recordings, movie trailers, live streams, and other content such as video blogging, short original videos, and educational videos. Most content on YouTube is uploaded by individuals, but media corporations including CBS, the BBC, Vevo, and Hulu offer some of their material via YouTube as part of the YouTube partnership program. Unregistered users can only watch videos on the site, while registered users are permitted to upload an unlimited number of videos and add comments to videos. Videos deemed potentially inappropriate are available only to registered users affirming themselves to be at least 18 years old.
YouTube and selected creators earn advertising revenue from Google AdSense, a program which targets ads according to site content and audience. The vast majority of its videos are free to view, but there are exceptions, including subscription-based premium channels, film rentals, as well as YouTube Music and YouTube Premium, subscription services respectively offering premium and ad-free music streaming, and ad-free access to all content, including exclusive content commissioned from notable personalities. As of February 2017, there were more than 400 hours of content uploaded to YouTube each minute, and one billion hours of content being watched on YouTube every day. As of August 2018, the website is ranked as the second-most popular site in the world, according to Alexa Internet, just behind Google. As of May 2019, more than 500 hours of video content are uploaded to YouTube every minute.
YouTube has faced criticism over aspects of its operations, including its handling of copyrighted content contained within uploaded videos, its recommendation algorithms perpetuating videos that promote conspiracy theories and falsehoods, hosting videos ostensibly targeting children but containing violent and/or sexually suggestive content involving popular characters, videos of minors attracting pedophilic activities in their comment sections, and fluctuating policies on the types of content that is eligible to be monetized with advertising.