...There are many benefits of using virtual memory; the most important part is memory management, Memory management is the process of managing computer memory. The memory management subsystem of the operating system carries out this duty. Because the beginning of calculating, there has always existed the need for more memory than the existing physical memory in the system. Surrounded by many important jobs an operating system does in a computer memory allocation to the processes being implemented is the most important one. Operating systems should have the capability to assign memory when available and clear to make room for data and instructions when the memory is full. The capability to recognize the location of an entire program or a particular location in the physical memory is another responsibility the operating system should be able to accommodate. Operating systems are designed to take benefit of file system conveniences and virtual memory to address the needs of memory management. Data stored in long-term memory is saved as named objects called files, and data and instructions stored in virtual memory is addressed in a logical point of view. Because of the small ability of the virtual memory, only a limited part of a program is kept in virtual memory. The ability to address memory both reasonably and physically enables the operating system to separate processes and run several programs run concomitantly. By using virtual addresses and real addresses, the operating...
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...The Virtual Memory Manager (VMM) The Difference between virtual memory and physical memory Physical memories are the RAM chips purchased and placed in a slot on the computer motherboard. The RAM is the first memory used when the computer requires memory usage, such as for loading an application or opening a document. Virtual Virtual memory is stored on the hard drive. Virtual memory is used when the RAM is filled. Virtual memory is slower than physical memory, so it can decrease the performance of applications. Allocation Physical memory allocates information in a "first in, last out" process. The information is placed on the stack. Virtual memory uses a process called paging. These pages are laid across the hard drive in fixed sizes. Size 1. Physical memory is limited to the size of the RAM chips installed in the computer. Virtual memory is limited by the size of the hard drive, so virtual memory has the capability for more STORAGE. 2. Virtual memory is a memory management technique developed for multitasking kernels. 3. In virtual memory Operating systems have memory areas that are pinned (never swapped to secondary storage). For example, interrupt mechanisms rely on an array of pointers to their handlers, such as I/O completion and page fault. If the pages containing these pointers or the code that they invoke were pageable, interrupt-handling would become far more complex and time-consuming, particularly in the case of page fault interruptions...
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... (a) Virtual memory can be based on Paging only, Segmentation only or a combination of the two. (i) With the help of a diagram, show how a virtual address is translated into a physical address in a paging-based memory management scheme OR in a segmentation-based memory management scheme. The mechanism used for reading a word from memory involves the translation of a virtual address consisting of page number and offset into a physical address, consisting of frame number and offset and this translation is done using a page table. Figure 1 shows the structure of paging mechanism. When a particular process is running, a register holds the starting address of the page table for that process. The page number of a virtual address is used to index that table and look up the corresponding frame number. This is combined with the offset portion of the virtual address to produce the desired physical address. Figure 1: Adress Translation in a paging-based memory management (ii) What is the memory management technique used in Linux? Demand paged virtual memory is used as memory management technique in Linux. It is a dynamic memory allocation technique that consists of deferring page frame allocation until the last possible moment which can be the moment when a process attempts to access a page that is not present in RAM. The basic unit of memory allocation for this technique is page and the page size is 212 (4096 bytes or 4KB). (iii) Every virtual memory reference...
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...The Benefits and Uses of Virtual Memory Marcia Amnay POS/355 Steven Kernan April 22nd, 2013 The Benefits and Uses of Virtual Memory This paper will discuss the benefits and uses of virtual memory. Programs require memory to start and run on computers. When several jobs are being processed at the same time, the operating system must keep track of how the computer’s memory and make sure there is enough. Computers come with a limited amount of random access memory which is known as RAM. RAM is the main memory on a computer. If a user is running multiple applications at the same time, the RAM on it will not be enough to execute the processes. This is when virtual memory comes in and balances the process. Virtual memory is a memory management technique. Virtual memory is secondary memory that can act as if it were part of the main memory. When the RAM is used up, virtual memory places data by using the hard disk or another disk of some kind for space. The hard disk is much slower then RAM so the more virtual memory used, the slower your computer will run. The computer will look for areas on the RAM that are not in use and copy it to the hard disk to free up space on the RAM. Virtual memory keeps ‘active’ process in the RAM and keeps the ‘inactive’ processes on the address space on the disk. When an ‘inactive’ process is needed, it will bring that process back to the RAM from the disk. This process is running in the background without the user being aware...
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...Peoples had great expectations on windows mobile after the release of its first preview of mobile OS. Microsoft seems to be lost in mobile market today because lack of customizability, limited multitasking, device compatibility and so on. Certainly the idea behind one size fits all is to remove the big difference between ARM based PC and x86 or x64 based PC. Right now I see most disagreements over web on Microsoft’s new design which shows persuade of creating single platform for all type of hardwires like PDAs, Laptops, Palmtops, Desktops etc. But I think it’s a good idea to bring up in order to lead mobile market. Apple is already in a run to merge Mac OS and IOS together, to some extend that bought an extra ordinary feature for the organization to role the market. On the other hand companies like Google (Android), Canonical (Ubuntu) are also showing their efforts in bringing their products into a single universal OS. Mobiles are not less than a PC these days. An ARM based OSs like Debian, Android, Chrome OS, Firefox OS, Kali Linux are just the best examples running on PCs and PDAs. Although there can be some issues with the hardware and application support I do agree but someone (so why not Microsoft?) has to take a first step to lead and eventually that will be fruitful outcomes thereafter. But if this idea hits then developers need not to worry about writing same applications in multiple languages, overall it will be cost effective and so on. References: ...
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...What are some differences from the new version that make creation and deployments of VMs easier (or better)? The essential contrasts are STANDARD accompanies more predictable execution on the CPU and system, while likewise offering burden adjusting and auto-scaling though BASIC does not offer these components. A virtual machine format is a library resource that involves a hardware profile, a virtual hard plate, and an optional guest working structure profile. Formats give a regulated assembling of hardware and programming settings that you can use to make different new virtual machines organized with those settings. The essential contrasts are STANDARD accompanies more predictable execution on the CPU and system, while additionally offering burden adjusting and auto-scaling though BASIC does not offer these elements. Explain in detail some enhancements of the VMware tools device drivers? The VMware Tools establishment contains numerous gadget drivers which help to improve execution. It relies on upon the Operation System which ones get introduced, yet this is a rundown of what can be enhanced as * SVGA Driver – Enables 32-bit shows, high show determination and speedier design execution. On windows based frameworks who are vista or later the VMware SVGA 3D (WDDM) driver is introduced to bolster Aero. * SCSI Driver – If you determine to utilize a Bus Logic Adapter, the visitor OS utilizes this driver. Some late visitor OSes will contain LSI Logic Parallel or SAS...
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...Memory Hierarchy Chapter 2 Abdullah Muzahid Copyright Muzahid, Whaley 2010, 2012 1 45. Virtual Memory Managing mem needs in excess of physical mem automatically requires Virtual Memory. • Originally developed for single prog wt lrg mem needs • Now critical for multiprocessing/time sharing. • Divides physical memory into blocks and allocates these blocks to di↵erent processes • Allows a process to exec wt only part of process resident in memory. – Reduces startup/switch time! • Provides protection to prevent processes from accessing blocks inappropriately – Critical for multiprocessing Copyright Muzahid, Whaley 2010, 2012 2 46. Virtual Memory Terms • Page: virtual memory’s block. • Page fault: a main memory miss (page is on disk, not in memory). • Physical address: @ used to access main mem and typically cache as well • Page table: data structure that maps between virtual and physical addresses • Translation Lookaside Bu↵er : cache that contains a portion of the page table ‘@’ means address Copyright Muzahid, Whaley 2010, 2012 3 C-40 I is Virtually Contiguous, 47. Program Appendix C Review of Memory Hierarchy Not so Physically Physical Virtual • Small prog consumes minor address Comp Arch, Henn & Patt, Fig B.19, pg B-41 address A 0 0 amount of virtual space (virtual 4K B 4K C C 8K space bigger than physical on 8K 12K D 12K Physical...
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...Abstract Memory management plays a key role for any multiprogramming operating system. Memory should be managed such that many processes can be in the memory at the same time .As the physical memory is limited , operating systems make use of virtual memory to run processes which are larger than the physical memory. Virtual memory is a technique using which processes can run even when they are not entirely in memory. Main memory is treated as an array of pages thus separating in to logical memory and physical memory, thus the size of the physical memory is not a limitation for the user. Memory management in Windows The physical memory in Windows is divided into a number of physical pages .If the pages are divided in to say 4KB size causes external fragmentation of memory. If the pages are divided into 2MB pages this causes internal fragmentation. Windows uses large pages to better the performance of translation look aside buffer TLB( is a cache used by memory management hardware to improve virtual address translation speed).The physical pages are in one of the following states free page, zeroed page, modified page, standby page ,bad page, transition page, valid page. Valid pages are in processes page tables ,while pages in other states are separated in to list based on their state. Virtual memory in Windows is implemented by demand paging with clustering. Demand paging is method in which the pages are loaded in to the memory as they are required in the course of the process’s...
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...Linux Memory Management: Its similarities and difference with Windows’ Memory Management specifically in Page swapping algorithms Abstract Memory management in all the operating system is important because it is crucial for both programming and system administration. In order to make the system faster is that to use an algorithm that saves the time for managing processes and jobs. The article stated the brief discussion on how the Linux memory management works and thus it states that it works almost the same as what the Windows operating system with 32-bit and 64-bit is using. All i/o Linux goes through the page cache and area that caches to improve disk i/o performance same as with the one used in Windows’ cache and Virtual Memory. The paper discussed the difference and similarities of Windows’ memory management and Linux’s Memory Management. It concludes that Linux’s memory management is simpler and easier to maintain compared to Windows’ though, thus Window’s memory management favors the performance and Linux’s having its operating system open sourced, needs improvement through some researches and open sourced programmers. Keywords: Linux, Unix, Page Swapping, Windows, Memory, Virtual Memory, Paging, Placement Policy, Least Recently Used (LRU), Not Recently Used (NRU) Linux Memory Management: Its similarities and difference with Windows’ Memory Management specifically in Page swapping algorithms Operating systems is the heart of all computers may it be...
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...Operating serves that are available to use. There are four main Operating systems that are used in today’s Technological world: UNIX, Linux, Mac, and Windows. Each one of these systems has its own unique aspects to offer users, while still sharing the same basics that an operating system needs. Memory Management UNIX/Linux In comparison to other operating systems, UNIX is quite different when it comes to managing its memory. It uses extremely sophisticated memory management algorithms to make the best use of memory resources. Though UNIX and Linux are extremely similar when it comes to how things work internally, there are slight differences that make UNIX distinct. One process that UNIX uses is Swapping; this is done by moving chunks of the Virtual Memory, known as pages, out of the main memory and moving others in. In order for this process to work at its best, those pages that are needed must be accessible in the Main Memory at the demand of the CPU. When a page is expected to be needed in the very near future it is called a resident set. This can lead to errors due to memory allocation issues. If the CPU attempts to access a page that is no longer available in the Main Memory, a page fault will occur, and the needed page will then have to be located, as the CPU...
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...Distributed Memory Management: Design Issues and Future Trends Ehab S. Al-Shaer College of Computer Science Northeastern University Boston, MA 02115 March 19, 1993 ABSTRACT In recent times the shared memory paradigm has received considerable attention in the realm of distributed systems. Distributed Shared Memory (DSM) is the abstraction for supporting the notion of shared memory in a physically non-shared (distributed) architecture. Issues to be addressed in the design and implementation of DSM include maintaining the consistency of the shared data across the network without incurring high overhead and integrating the DSM mechanisms with the local memory management. The consistency model provided by a given DSM implementation attempts to balance performance and ease of programming: while DSM provides the abstraction of shared memory, it is not true shared memory - both from the point of view of the semantics and the cost of shared memory access. The focus of this paper is to identify the issues involved in the design of DSM systems, briefly highlight the mechanisms in use by some current DSM implementations and propose some new DSM models for future distributed systems. I INTRODUCTION As computers become cheaper, there is increasing interest in using multiple CPUs to speed up individual applications. There are basically two design approaches to achieve this goal of high performance at low cost: multiprocessors and multicomputers. Multiprocessors contain...
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...Windows and Linux- Memory Management Marlana Muzny POS/355 May 13, 2013 Joe Fischer Windows and Linux- Memory Management Memory management is the process that the operating system takes to manage the computers processes and memory. This means that the operating system has to figure out what sections of the memory are free and are being used at the current time allocating and reallocating as needed. Memory management is extremely important in how a computer operates. In this paper, we will compare the new Windows 8 to the Linux operating system and describe the differences in the memory management. Windows 8, it is the newest product in operating systems for Microsoft. With enhancements from the previous version, Windows 8 makes better use of the memory management than the previous version Windows 7. In Windows 7, Microsoft started making changes to the operating system when it came to memory management; however, fell short compared to what was already being done in Linux operating system. With the previous versions, most of the memory management occurred upon login. This slowed the processor down taking up all the resources at one time using the system memory. To address this issue and correct it in Windows 8, Microsoft implemented a start on demand model. What this means is that processes that are needed are delayed until the process is needed verses having all the processes start automatically when the computer is started. This makes more run...
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...Memory Management Federico Torres POS 355 April 9, 2013 CASTLE W. PHELPS, ABD Memory Management “I cannot guarantee that I carry all the facts in my mind. Intense mental concentration has a curious way of blotting out what has passed. Each of my cases displaces the last…”(Doyle, 1901). The way the brain manages memory is metaphorically speaking very similar to the way computers today manage memory. A memory management unit takes a huge part in the speed at which computers can operate. The memory management unit works systematically with the operating system and computer processing unit. There are two different parts to types of memory, primary, also referred to as main, and secondary. The former has two parts, one part for the kernel, which is reserved for the operating system, and the other part for the programs currently being executed. Memory management units must work efficiently in transferring information between primary and secondary. In order for this to succeed, there are a few requirements that memory management units must meet in order to fulfill the demands of users. Memory management units require relocation, protection, sharing, both local and physical organization, among processes in both primary and secondary memory. Two examples of operating systems that meet these requirements, but yet both manage memory differently are Windows and OS X, which is used by Macintosh as an operating system. Since main memory is shared among different types of processes...
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...Option 2: The Differences in Memory Management between Windows® and Linux®. Linux and Windows are both operating systems for the everyday computers. They both do not require special hardware. Many claim one operating system is better than the other. Windows does something better than Linux and Linux does something’s better than Windows. How each of these handles memory is the key to understanding. Linux has the unique ability to virtually extend system RAM capabilities with another form of partitioning called SWAP space. SWAP space is used by Linux to add more virtual RAM to the system. Virtual memory sort of trick the system to think it has more memory that it actually has by sharing it between competing processes as they are desired. This speeds up the capability of Linux to operate faster and with less system resources than a Windows machine with similar RAM specs. This swap space is dedicated specifically for paging operations. Paging is the function of writing parts of memory chunks to temporary space on a hard disk. Windows commonly uses a dynamically allocated temporary space on a hard disk called a “page file” for memory management. A “page file” is allocated on disk, for less frequently accessed objects in memory; things that would not necessarily be needed to be constantly in the hard drive or RAM memory buffer. This leaves more RAM obtainable to aggressively used objects. Windows and Linux have modern memory management architecture that in reality have lot...
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...Chapter 03 – Memory management I. Problems 3.1. Consider a swapping system in which the memory consists of the following hole sizes: 10 K, 4 K, 20 K, 15 K, 9 K. Assume first fit/ next fit/ best fit algorithm is used. Which holes are taken for successive segment requests of 8 K, 12 K, 10 K? 3.2. Suppose a virtual address space of 2^28 words and the page size is 2^12 words. If the virtual address is 1234567 in Hexadecimal, what would be the page number in Hexadecimal? 3.3. A computer has four page frames. The time of loading, time of last access, and the R and M bits for each page are as shown below (the times are in clock ticks): Page Loaded Last ref. R M -----------------------------------------------------------------------------------------------------0 226 280 0 0 1 160 265 0 1 2 110 270 1 0 3 120 285 1 1 Which page will LRU replace? Which page will FIFO replace? Which page will NRU replace? Which page will Second chance method replace? 3.4. A machine with 512 MB memory has 64 bit memory word. If the frame size is 16 KB, how many bits are used to indicate the frame number? 3.5. If there are 64 pages and the page size is 2048 words, what is the length of logical address? 3.6. A computer with a 32-bit address uses a two-level page table. Virtual addresses are split into a 9-bit top-level page table field, an 11-bit second-level page table field, and an offset. How many pages are there in the address space? 3.7. A computer with a 32-bit...
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