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To implement memory ballooning, the virtual machine's kernel implements a "balloon driver" that allocates unused memory within the VM's address space into a pool of memory (the "balloon"), which makes that memory unavailable to other processes on that VM.
This driver provides support for four kinds of memory backed virtual disks: malloc, preload, vnode, swap. Disks may be created with the next command line tools: mdconfig and mdmfs. An example of how to use these programs follows. [3] To create and mount memory disk with mdmfs: # mdmfs -F newimage -s 5m md0 /mnt
Virtual memory combines active RAM and inactive memory on DASD [a] to form a large range of contiguous addresses.. In computing, virtual memory, or virtual storage, [b] is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" [3] which "creates the illusion to users of a very large (main) memory".
RAM drives use normal system memory as if it were a partition on a physical hard drive rather than accessing the data bus normally used for secondary storage. Though RAM drives can often be supported directly in the operating system via special mechanisms in the OS kernel, it is generally simpler to access a RAM drive through a virtual device ...
A modern computer operating system usually uses virtual memory to provide separate address spaces or separate regions of a single address space, called user space and kernel space. [1] [a] Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour.
Virtual memory systems abstract between physical RAM and virtual addresses, assigning virtual memory addresses both to physical RAM and to disk-based storage, expanding addressable memory, but at the cost of speed. NUMA and SMP architectures optimize memory allocation within multi-processor systems. While these technologies dynamically manage ...
Full virtualization requires that every salient feature of the hardware be reflected into one of several virtual machines – including the full instruction set, input/output operations, interrupts, memory access, and whatever other elements are used by the software that runs on the bare machine, and that is intended to run in a virtual machine.
Virtual memory in the 8088 and 8086 was not supported by the processor hardware, and disk technology of the time would make it too slow and cumbersome to be practical. Expanded memory was a system that allowed application programs to access more RAM than directly visible to the processor's address space. The process was a form of bank switching.