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Memories
Published in Geoff Lewis, Communications Technology Handbook, 2013
Virtual memory. Large areas of addressable RAM space is costly: disk-based storage is very much cheaper. Therefore by using a disk system to support the memory, the processor can be made to cheat. The large part of the addressable memory on the disk is now known as a virtual memory. This is achieved because the processor has the ability to detect accesses to memory pages not currently being held in RAM. When virtual memory detects such an access, it then, independently of the program, automatically transfers the required new pages into RAM, storing the previous RAM contents as necessary in the process. To the user, all memory appears to be in RAM, but in fact only that part of the program currently being executed is in RAM, the rest is in the disk store.
Advances in Computing Infrastructure
Published in Siyong Kim, John Wong, Advanced and Emerging Technologies in Radiation Oncology Physics, 2018
Yulong Yan, Alicia Yingling, Steve Jiang
Virtual memory is a technique that uses slower storage (e.g., hard drives) to access and map memory for operating systems. Many operating systems have a swap area where memory can be stored on a drive. Ideally this memory would not be used to avoid any performance problems. The speed of memory is between 2 and 20 GB/s, and the fastest SSDs are still under 550 MB/s. Since many operations occur within memory, speed difference can be noticeable for a very large number of operations. When systems exhaust their physical memory and are forced to use their virtual memory frequently, the machine may become unresponsive, spoiling the user experience.
Evaluating the Performance of NT-Based Systems
Published in Steven F. Blanding, Enterprise Operations Management, 2020
Virtual memory is a term used to reference the use of disk storage as a temporary storage area for program code and other information normally stored in random access memory (RAM). When the RAM storage requirements of applications programs and various NT operating system modules exceed physical RAM, NT will temporarily swap data to virtual memory. When that information is required again, Windows NT will retrieve it from disk and, if necessary, swap other information to virtual memory. Although virtual memory swapping is transparent to the user, it has a significant effect on computer performance.
Integrating memory-mapping and N-dimensional hash function for fast and efficient grid-based climate data query
Published in Annals of GIS, 2021
Mengchao Xu, Liang Zhao, Ruixin Yang, Jingchao Yang, Dexuan Sha, Chaowei Yang
In LotDB, data are stored in the secondary storage system, and the access to it is done by utilizing memory-mapping technology and through page files. This technology is widely used in database systems like LMDB and MongoDB. Specifically, instead of loading the whole file into memory, the file handler maps the file to virtual memory as a big array and assign a virtual memory address to each page file without loading any actual data into the memory other than file’s metadata. When a data access call is made for a page file, it will cause a page fault and enable read/write of the secondary storage. In this way, bytes are copied to actual memory addresses directly, no need to go through disk caches as the standard open/write will do. In addition, by utilizing memory-mapping of arrays, LotDB could exceed the memory cap for accessing large data files and makes it possible for LotDB accessing big arrays without tiling. Meanwhile, when integrating with the n-dimensional hash function, the array indexes could be virtually calculated with low costs and could increase data retrieve speed exponentially when compared with traditional database solutions.
Iot based laundry services: an application of big data analytics, intelligent logistics management, and machine learning techniques
Published in International Journal of Production Research, 2020
Chang Liu, Yongfu Feng, Dongtao Lin, Liang Wu, Min Guo
On the other hand, cloud computing is an Internet-based infrastructure characterised by speediness and flexibility. Its main idea is to rely on resources sharing to achieve economies of scale. The intelligent laundry proposed in this study needs to store and process massive volumes of operational information such as customer information, clothing material coded information, and GPS information required for cloud laundry. The system is constantly under computing for scheduling, planning, coordinating, and reporting. The analytics is too complex for any SMEs to afford. Furthermore, the SMEs would encounter formidable costs involving implementing and maintaining the system. The virtual memory provided by cloud computing companies can quickly improve laundry data resources, reduce the marginal cost of the laundry industry, and expand the storage space for user information. Figure 7 presents the concept of the clouding computing.
The impacts of cloud computing architecture on cloud service performance
Published in Journal of Computer Information Systems, 2020
About Set 2, using cache or virtual memory is a way to improve a system’s performance, and this applies to cloud computing. For applications where the same sets of data are used frequently, a user’s data request may already be in the server’s cache or main memory. If we search the cache memory first and there is a hit, then there is no need to search the data on the hard drive or database servers. This will certainly improve data request and access performance. But, if there is a search miss in the cache memory, then the request will be re-sent to the hard drive or database servers for a search. This would create an additional communication delay overhead.